/*------------------------------------------------------------------------- * * xlog.c * PostgreSQL write-ahead log manager * * The Write-Ahead Log (WAL) functionality is split into several source * files, in addition to this one: * * xloginsert.c - Functions for constructing WAL records * xlogrecovery.c - WAL recovery and standby code * xlogreader.c - Facility for reading WAL files and parsing WAL records * xlogutils.c - Helper functions for WAL redo routines * * This file contains functions for coordinating database startup and * checkpointing, and managing the write-ahead log buffers when the * system is running. * * StartupXLOG() is the main entry point of the startup process. It * coordinates database startup, performing WAL recovery, and the * transition from WAL recovery into normal operations. * * XLogInsertRecord() inserts a WAL record into the WAL buffers. Most * callers should not call this directly, but use the functions in * xloginsert.c to construct the WAL record. XLogFlush() can be used * to force the WAL to disk. * * In addition to those, there are many other functions for interrogating * the current system state, and for starting/stopping backups. * * * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * src/backend/access/transam/xlog.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include #include #include #include #include #include #include #include "access/clog.h" #include "access/commit_ts.h" #include "access/heaptoast.h" #include "access/multixact.h" #include "access/rewriteheap.h" #include "access/subtrans.h" #include "access/timeline.h" #include "access/transam.h" #include "access/twophase.h" #include "access/xact.h" #include "access/xlog_internal.h" #include "access/xlogarchive.h" #include "access/xloginsert.h" #include "access/xlogprefetcher.h" #include "access/xlogreader.h" #include "access/xlogrecovery.h" #include "access/xlogutils.h" #include "backup/basebackup.h" #include "catalog/catversion.h" #include "catalog/pg_control.h" #include "catalog/pg_database.h" #include "common/controldata_utils.h" #include "common/file_utils.h" #include "executor/instrument.h" #include "miscadmin.h" #include "pg_trace.h" #include "pgstat.h" #include "port/atomics.h" #include "port/pg_iovec.h" #include "postmaster/bgwriter.h" #include "postmaster/startup.h" #include "postmaster/walwriter.h" #include "replication/logical.h" #include "replication/origin.h" #include "replication/slot.h" #include "replication/snapbuild.h" #include "replication/walreceiver.h" #include "replication/walsender.h" #include "storage/bufmgr.h" #include "storage/fd.h" #include "storage/ipc.h" #include "storage/large_object.h" #include "storage/latch.h" #include "storage/pmsignal.h" #include "storage/predicate.h" #include "storage/proc.h" #include "storage/procarray.h" #include "storage/reinit.h" #include "storage/smgr.h" #include "storage/spin.h" #include "storage/sync.h" #include "utils/guc_hooks.h" #include "utils/guc_tables.h" #include "utils/memutils.h" #include "utils/ps_status.h" #include "utils/relmapper.h" #include "utils/pg_rusage.h" #include "utils/snapmgr.h" #include "utils/timeout.h" #include "utils/timestamp.h" #include "utils/varlena.h" extern uint32 bootstrap_data_checksum_version; /* timeline ID to be used when bootstrapping */ #define BootstrapTimeLineID 1 /* User-settable parameters */ int max_wal_size_mb = 1024; /* 1 GB */ int min_wal_size_mb = 80; /* 80 MB */ int wal_keep_size_mb = 0; int XLOGbuffers = -1; int XLogArchiveTimeout = 0; int XLogArchiveMode = ARCHIVE_MODE_OFF; char *XLogArchiveCommand = NULL; bool EnableHotStandby = false; bool fullPageWrites = true; bool wal_log_hints = false; int wal_compression = WAL_COMPRESSION_NONE; char *wal_consistency_checking_string = NULL; bool *wal_consistency_checking = NULL; bool wal_init_zero = true; bool wal_recycle = true; bool log_checkpoints = true; int sync_method = DEFAULT_SYNC_METHOD; int wal_level = WAL_LEVEL_REPLICA; int CommitDelay = 0; /* precommit delay in microseconds */ int CommitSiblings = 5; /* # concurrent xacts needed to sleep */ int wal_retrieve_retry_interval = 5000; int max_slot_wal_keep_size_mb = -1; int wal_decode_buffer_size = 512 * 1024; bool track_wal_io_timing = false; #ifdef WAL_DEBUG bool XLOG_DEBUG = false; #endif int wal_segment_size = DEFAULT_XLOG_SEG_SIZE; /* * Number of WAL insertion locks to use. A higher value allows more insertions * to happen concurrently, but adds some CPU overhead to flushing the WAL, * which needs to iterate all the locks. */ #define NUM_XLOGINSERT_LOCKS 8 /* * Max distance from last checkpoint, before triggering a new xlog-based * checkpoint. */ int CheckPointSegments; /* Estimated distance between checkpoints, in bytes */ static double CheckPointDistanceEstimate = 0; static double PrevCheckPointDistance = 0; /* * Track whether there were any deferred checks for custom resource managers * specified in wal_consistency_checking. */ static bool check_wal_consistency_checking_deferred = false; /* * GUC support */ const struct config_enum_entry sync_method_options[] = { {"fsync", SYNC_METHOD_FSYNC, false}, #ifdef HAVE_FSYNC_WRITETHROUGH {"fsync_writethrough", SYNC_METHOD_FSYNC_WRITETHROUGH, false}, #endif {"fdatasync", SYNC_METHOD_FDATASYNC, false}, #ifdef O_SYNC {"open_sync", SYNC_METHOD_OPEN, false}, #endif #ifdef O_DSYNC {"open_datasync", SYNC_METHOD_OPEN_DSYNC, false}, #endif {NULL, 0, false} }; /* * Although only "on", "off", and "always" are documented, * we accept all the likely variants of "on" and "off". */ const struct config_enum_entry archive_mode_options[] = { {"always", ARCHIVE_MODE_ALWAYS, false}, {"on", ARCHIVE_MODE_ON, false}, {"off", ARCHIVE_MODE_OFF, false}, {"true", ARCHIVE_MODE_ON, true}, {"false", ARCHIVE_MODE_OFF, true}, {"yes", ARCHIVE_MODE_ON, true}, {"no", ARCHIVE_MODE_OFF, true}, {"1", ARCHIVE_MODE_ON, true}, {"0", ARCHIVE_MODE_OFF, true}, {NULL, 0, false} }; /* * Statistics for current checkpoint are collected in this global struct. * Because only the checkpointer or a stand-alone backend can perform * checkpoints, this will be unused in normal backends. */ CheckpointStatsData CheckpointStats; /* * During recovery, lastFullPageWrites keeps track of full_page_writes that * the replayed WAL records indicate. It's initialized with full_page_writes * that the recovery starting checkpoint record indicates, and then updated * each time XLOG_FPW_CHANGE record is replayed. */ static bool lastFullPageWrites; /* * Local copy of the state tracked by SharedRecoveryState in shared memory, * It is false if SharedRecoveryState is RECOVERY_STATE_DONE. True actually * means "not known, need to check the shared state". */ static bool LocalRecoveryInProgress = true; /* * Local state for XLogInsertAllowed(): * 1: unconditionally allowed to insert XLOG * 0: unconditionally not allowed to insert XLOG * -1: must check RecoveryInProgress(); disallow until it is false * Most processes start with -1 and transition to 1 after seeing that recovery * is not in progress. But we can also force the value for special cases. * The coding in XLogInsertAllowed() depends on the first two of these states * being numerically the same as bool true and false. */ static int LocalXLogInsertAllowed = -1; /* * ProcLastRecPtr points to the start of the last XLOG record inserted by the * current backend. It is updated for all inserts. XactLastRecEnd points to * end+1 of the last record, and is reset when we end a top-level transaction, * or start a new one; so it can be used to tell if the current transaction has * created any XLOG records. * * While in parallel mode, this may not be fully up to date. When committing, * a transaction can assume this covers all xlog records written either by the * user backend or by any parallel worker which was present at any point during * the transaction. But when aborting, or when still in parallel mode, other * parallel backends may have written WAL records at later LSNs than the value * stored here. The parallel leader advances its own copy, when necessary, * in WaitForParallelWorkersToFinish. */ XLogRecPtr ProcLastRecPtr = InvalidXLogRecPtr; XLogRecPtr XactLastRecEnd = InvalidXLogRecPtr; XLogRecPtr XactLastCommitEnd = InvalidXLogRecPtr; /* * RedoRecPtr is this backend's local copy of the REDO record pointer * (which is almost but not quite the same as a pointer to the most recent * CHECKPOINT record). We update this from the shared-memory copy, * XLogCtl->Insert.RedoRecPtr, whenever we can safely do so (ie, when we * hold an insertion lock). See XLogInsertRecord for details. We are also * allowed to update from XLogCtl->RedoRecPtr if we hold the info_lck; * see GetRedoRecPtr. * * NB: Code that uses this variable must be prepared not only for the * possibility that it may be arbitrarily out of date, but also for the * possibility that it might be set to InvalidXLogRecPtr. We used to * initialize it as a side effect of the first call to RecoveryInProgress(), * which meant that most code that might use it could assume that it had a * real if perhaps stale value. That's no longer the case. */ static XLogRecPtr RedoRecPtr; /* * doPageWrites is this backend's local copy of (fullPageWrites || * runningBackups > 0). It is used together with RedoRecPtr to decide whether * a full-page image of a page need to be taken. * * NB: Initially this is false, and there's no guarantee that it will be * initialized to any other value before it is first used. Any code that * makes use of it must recheck the value after obtaining a WALInsertLock, * and respond appropriately if it turns out that the previous value wasn't * accurate. */ static bool doPageWrites; /*---------- * Shared-memory data structures for XLOG control * * LogwrtRqst indicates a byte position that we need to write and/or fsync * the log up to (all records before that point must be written or fsynced). * LogwrtResult indicates the byte positions we have already written/fsynced. * These structs are identical but are declared separately to indicate their * slightly different functions. * * To read XLogCtl->LogwrtResult, you must hold either info_lck or * WALWriteLock. To update it, you need to hold both locks. The point of * this arrangement is that the value can be examined by code that already * holds WALWriteLock without needing to grab info_lck as well. In addition * to the shared variable, each backend has a private copy of LogwrtResult, * which is updated when convenient. * * The request bookkeeping is simpler: there is a shared XLogCtl->LogwrtRqst * (protected by info_lck), but we don't need to cache any copies of it. * * info_lck is only held long enough to read/update the protected variables, * so it's a plain spinlock. The other locks are held longer (potentially * over I/O operations), so we use LWLocks for them. These locks are: * * WALBufMappingLock: must be held to replace a page in the WAL buffer cache. * It is only held while initializing and changing the mapping. If the * contents of the buffer being replaced haven't been written yet, the mapping * lock is released while the write is done, and reacquired afterwards. * * WALWriteLock: must be held to write WAL buffers to disk (XLogWrite or * XLogFlush). * * ControlFileLock: must be held to read/update control file or create * new log file. * *---------- */ typedef struct XLogwrtRqst { XLogRecPtr Write; /* last byte + 1 to write out */ XLogRecPtr Flush; /* last byte + 1 to flush */ } XLogwrtRqst; typedef struct XLogwrtResult { XLogRecPtr Write; /* last byte + 1 written out */ XLogRecPtr Flush; /* last byte + 1 flushed */ } XLogwrtResult; /* * Inserting to WAL is protected by a small fixed number of WAL insertion * locks. To insert to the WAL, you must hold one of the locks - it doesn't * matter which one. To lock out other concurrent insertions, you must hold * of them. Each WAL insertion lock consists of a lightweight lock, plus an * indicator of how far the insertion has progressed (insertingAt). * * The insertingAt values are read when a process wants to flush WAL from * the in-memory buffers to disk, to check that all the insertions to the * region the process is about to write out have finished. You could simply * wait for all currently in-progress insertions to finish, but the * insertingAt indicator allows you to ignore insertions to later in the WAL, * so that you only wait for the insertions that are modifying the buffers * you're about to write out. * * This isn't just an optimization. If all the WAL buffers are dirty, an * inserter that's holding a WAL insert lock might need to evict an old WAL * buffer, which requires flushing the WAL. If it's possible for an inserter * to block on another inserter unnecessarily, deadlock can arise when two * inserters holding a WAL insert lock wait for each other to finish their * insertion. * * Small WAL records that don't cross a page boundary never update the value, * the WAL record is just copied to the page and the lock is released. But * to avoid the deadlock-scenario explained above, the indicator is always * updated before sleeping while holding an insertion lock. * * lastImportantAt contains the LSN of the last important WAL record inserted * using a given lock. This value is used to detect if there has been * important WAL activity since the last time some action, like a checkpoint, * was performed - allowing to not repeat the action if not. The LSN is * updated for all insertions, unless the XLOG_MARK_UNIMPORTANT flag was * set. lastImportantAt is never cleared, only overwritten by the LSN of newer * records. Tracking the WAL activity directly in WALInsertLock has the * advantage of not needing any additional locks to update the value. */ typedef struct { LWLock lock; XLogRecPtr insertingAt; XLogRecPtr lastImportantAt; } WALInsertLock; /* * All the WAL insertion locks are allocated as an array in shared memory. We * force the array stride to be a power of 2, which saves a few cycles in * indexing, but more importantly also ensures that individual slots don't * cross cache line boundaries. (Of course, we have to also ensure that the * array start address is suitably aligned.) */ typedef union WALInsertLockPadded { WALInsertLock l; char pad[PG_CACHE_LINE_SIZE]; } WALInsertLockPadded; /* * Session status of running backup, used for sanity checks in SQL-callable * functions to start and stop backups. */ static SessionBackupState sessionBackupState = SESSION_BACKUP_NONE; /* * Shared state data for WAL insertion. */ typedef struct XLogCtlInsert { slock_t insertpos_lck; /* protects CurrBytePos and PrevBytePos */ /* * CurrBytePos is the end of reserved WAL. The next record will be * inserted at that position. PrevBytePos is the start position of the * previously inserted (or rather, reserved) record - it is copied to the * prev-link of the next record. These are stored as "usable byte * positions" rather than XLogRecPtrs (see XLogBytePosToRecPtr()). */ uint64 CurrBytePos; uint64 PrevBytePos; /* * Make sure the above heavily-contended spinlock and byte positions are * on their own cache line. In particular, the RedoRecPtr and full page * write variables below should be on a different cache line. They are * read on every WAL insertion, but updated rarely, and we don't want * those reads to steal the cache line containing Curr/PrevBytePos. */ char pad[PG_CACHE_LINE_SIZE]; /* * fullPageWrites is the authoritative value used by all backends to * determine whether to write full-page image to WAL. This shared value, * instead of the process-local fullPageWrites, is required because, when * full_page_writes is changed by SIGHUP, we must WAL-log it before it * actually affects WAL-logging by backends. Checkpointer sets at startup * or after SIGHUP. * * To read these fields, you must hold an insertion lock. To modify them, * you must hold ALL the locks. */ XLogRecPtr RedoRecPtr; /* current redo point for insertions */ bool fullPageWrites; /* * runningBackups is a counter indicating the number of backups currently * in progress. lastBackupStart is the latest checkpoint redo location * used as a starting point for an online backup. */ int runningBackups; XLogRecPtr lastBackupStart; /* * WAL insertion locks. */ WALInsertLockPadded *WALInsertLocks; } XLogCtlInsert; /* * Total shared-memory state for XLOG. */ typedef struct XLogCtlData { XLogCtlInsert Insert; /* Protected by info_lck: */ XLogwrtRqst LogwrtRqst; XLogRecPtr RedoRecPtr; /* a recent copy of Insert->RedoRecPtr */ FullTransactionId ckptFullXid; /* nextXid of latest checkpoint */ XLogRecPtr asyncXactLSN; /* LSN of newest async commit/abort */ XLogRecPtr replicationSlotMinLSN; /* oldest LSN needed by any slot */ XLogSegNo lastRemovedSegNo; /* latest removed/recycled XLOG segment */ /* Fake LSN counter, for unlogged relations. Protected by ulsn_lck. */ XLogRecPtr unloggedLSN; slock_t ulsn_lck; /* Time and LSN of last xlog segment switch. Protected by WALWriteLock. */ pg_time_t lastSegSwitchTime; XLogRecPtr lastSegSwitchLSN; /* * Protected by info_lck and WALWriteLock (you must hold either lock to * read it, but both to update) */ XLogwrtResult LogwrtResult; /* * Latest initialized page in the cache (last byte position + 1). * * To change the identity of a buffer (and InitializedUpTo), you need to * hold WALBufMappingLock. To change the identity of a buffer that's * still dirty, the old page needs to be written out first, and for that * you need WALWriteLock, and you need to ensure that there are no * in-progress insertions to the page by calling * WaitXLogInsertionsToFinish(). */ XLogRecPtr InitializedUpTo; /* * These values do not change after startup, although the pointed-to pages * and xlblocks values certainly do. xlblocks values are protected by * WALBufMappingLock. */ char *pages; /* buffers for unwritten XLOG pages */ XLogRecPtr *xlblocks; /* 1st byte ptr-s + XLOG_BLCKSZ */ int XLogCacheBlck; /* highest allocated xlog buffer index */ /* * InsertTimeLineID is the timeline into which new WAL is being inserted * and flushed. It is zero during recovery, and does not change once set. * * If we create a new timeline when the system was started up, * PrevTimeLineID is the old timeline's ID that we forked off from. * Otherwise it's equal to InsertTimeLineID. */ TimeLineID InsertTimeLineID; TimeLineID PrevTimeLineID; /* * SharedRecoveryState indicates if we're still in crash or archive * recovery. Protected by info_lck. */ RecoveryState SharedRecoveryState; /* * InstallXLogFileSegmentActive indicates whether the checkpointer should * arrange for future segments by recycling and/or PreallocXlogFiles(). * Protected by ControlFileLock. Only the startup process changes it. If * true, anyone can use InstallXLogFileSegment(). If false, the startup * process owns the exclusive right to install segments, by reading from * the archive and possibly replacing existing files. */ bool InstallXLogFileSegmentActive; /* * WalWriterSleeping indicates whether the WAL writer is currently in * low-power mode (and hence should be nudged if an async commit occurs). * Protected by info_lck. */ bool WalWriterSleeping; /* * During recovery, we keep a copy of the latest checkpoint record here. * lastCheckPointRecPtr points to start of checkpoint record and * lastCheckPointEndPtr points to end+1 of checkpoint record. Used by the * checkpointer when it wants to create a restartpoint. * * Protected by info_lck. */ XLogRecPtr lastCheckPointRecPtr; XLogRecPtr lastCheckPointEndPtr; CheckPoint lastCheckPoint; /* * lastFpwDisableRecPtr points to the start of the last replayed * XLOG_FPW_CHANGE record that instructs full_page_writes is disabled. */ XLogRecPtr lastFpwDisableRecPtr; slock_t info_lck; /* locks shared variables shown above */ } XLogCtlData; static XLogCtlData *XLogCtl = NULL; /* a private copy of XLogCtl->Insert.WALInsertLocks, for convenience */ static WALInsertLockPadded *WALInsertLocks = NULL; /* * We maintain an image of pg_control in shared memory. */ static ControlFileData *ControlFile = NULL; /* * Calculate the amount of space left on the page after 'endptr'. Beware * multiple evaluation! */ #define INSERT_FREESPACE(endptr) \ (((endptr) % XLOG_BLCKSZ == 0) ? 0 : (XLOG_BLCKSZ - (endptr) % XLOG_BLCKSZ)) /* Macro to advance to next buffer index. */ #define NextBufIdx(idx) \ (((idx) == XLogCtl->XLogCacheBlck) ? 0 : ((idx) + 1)) /* * XLogRecPtrToBufIdx returns the index of the WAL buffer that holds, or * would hold if it was in cache, the page containing 'recptr'. */ #define XLogRecPtrToBufIdx(recptr) \ (((recptr) / XLOG_BLCKSZ) % (XLogCtl->XLogCacheBlck + 1)) /* * These are the number of bytes in a WAL page usable for WAL data. */ #define UsableBytesInPage (XLOG_BLCKSZ - SizeOfXLogShortPHD) /* * Convert values of GUCs measured in megabytes to equiv. segment count. * Rounds down. */ #define ConvertToXSegs(x, segsize) XLogMBVarToSegs((x), (segsize)) /* The number of bytes in a WAL segment usable for WAL data. */ static int UsableBytesInSegment; /* * Private, possibly out-of-date copy of shared LogwrtResult. * See discussion above. */ static XLogwrtResult LogwrtResult = {0, 0}; /* * openLogFile is -1 or a kernel FD for an open log file segment. * openLogSegNo identifies the segment, and openLogTLI the corresponding TLI. * These variables are only used to write the XLOG, and so will normally refer * to the active segment. * * Note: call Reserve/ReleaseExternalFD to track consumption of this FD. */ static int openLogFile = -1; static XLogSegNo openLogSegNo = 0; static TimeLineID openLogTLI = 0; /* * Local copies of equivalent fields in the control file. When running * crash recovery, LocalMinRecoveryPoint is set to InvalidXLogRecPtr as we * expect to replay all the WAL available, and updateMinRecoveryPoint is * switched to false to prevent any updates while replaying records. * Those values are kept consistent as long as crash recovery runs. */ static XLogRecPtr LocalMinRecoveryPoint; static TimeLineID LocalMinRecoveryPointTLI; static bool updateMinRecoveryPoint = true; /* For WALInsertLockAcquire/Release functions */ static int MyLockNo = 0; static bool holdingAllLocks = false; #ifdef WAL_DEBUG static MemoryContext walDebugCxt = NULL; #endif static void CleanupAfterArchiveRecovery(TimeLineID EndOfLogTLI, XLogRecPtr EndOfLog, TimeLineID newTLI); static void CheckRequiredParameterValues(void); static void XLogReportParameters(void); static int LocalSetXLogInsertAllowed(void); static void CreateEndOfRecoveryRecord(void); static XLogRecPtr CreateOverwriteContrecordRecord(XLogRecPtr aborted_lsn, XLogRecPtr pagePtr, TimeLineID newTLI); static void CheckPointGuts(XLogRecPtr checkPointRedo, int flags); static void KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo); static XLogRecPtr XLogGetReplicationSlotMinimumLSN(void); static void AdvanceXLInsertBuffer(XLogRecPtr upto, TimeLineID tli, bool opportunistic); static void XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible); static bool InstallXLogFileSegment(XLogSegNo *segno, char *tmppath, bool find_free, XLogSegNo max_segno, TimeLineID tli); static void XLogFileClose(void); static void PreallocXlogFiles(XLogRecPtr endptr, TimeLineID tli); static void RemoveTempXlogFiles(void); static void RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr lastredoptr, XLogRecPtr endptr, TimeLineID insertTLI); static void RemoveXlogFile(const struct dirent *segment_de, XLogSegNo recycleSegNo, XLogSegNo *endlogSegNo, TimeLineID insertTLI); static void UpdateLastRemovedPtr(char *filename); static void ValidateXLOGDirectoryStructure(void); static void CleanupBackupHistory(void); static void UpdateMinRecoveryPoint(XLogRecPtr lsn, bool force); static bool PerformRecoveryXLogAction(void); static void InitControlFile(uint64 sysidentifier); static void WriteControlFile(void); static void ReadControlFile(void); static void UpdateControlFile(void); static char *str_time(pg_time_t tnow); static int get_sync_bit(int method); static void CopyXLogRecordToWAL(int write_len, bool isLogSwitch, XLogRecData *rdata, XLogRecPtr StartPos, XLogRecPtr EndPos, TimeLineID tli); static void ReserveXLogInsertLocation(int size, XLogRecPtr *StartPos, XLogRecPtr *EndPos, XLogRecPtr *PrevPtr); static bool ReserveXLogSwitch(XLogRecPtr *StartPos, XLogRecPtr *EndPos, XLogRecPtr *PrevPtr); static XLogRecPtr WaitXLogInsertionsToFinish(XLogRecPtr upto); static char *GetXLogBuffer(XLogRecPtr ptr, TimeLineID tli); static XLogRecPtr XLogBytePosToRecPtr(uint64 bytepos); static XLogRecPtr XLogBytePosToEndRecPtr(uint64 bytepos); static uint64 XLogRecPtrToBytePos(XLogRecPtr ptr); static void WALInsertLockAcquire(void); static void WALInsertLockAcquireExclusive(void); static void WALInsertLockRelease(void); static void WALInsertLockUpdateInsertingAt(XLogRecPtr insertingAt); /* * Insert an XLOG record represented by an already-constructed chain of data * chunks. This is a low-level routine; to construct the WAL record header * and data, use the higher-level routines in xloginsert.c. * * If 'fpw_lsn' is valid, it is the oldest LSN among the pages that this * WAL record applies to, that were not included in the record as full page * images. If fpw_lsn <= RedoRecPtr, the function does not perform the * insertion and returns InvalidXLogRecPtr. The caller can then recalculate * which pages need a full-page image, and retry. If fpw_lsn is invalid, the * record is always inserted. * * 'flags' gives more in-depth control on the record being inserted. See * XLogSetRecordFlags() for details. * * 'topxid_included' tells whether the top-transaction id is logged along with * current subtransaction. See XLogRecordAssemble(). * * The first XLogRecData in the chain must be for the record header, and its * data must be MAXALIGNed. XLogInsertRecord fills in the xl_prev and * xl_crc fields in the header, the rest of the header must already be filled * by the caller. * * Returns XLOG pointer to end of record (beginning of next record). * This can be used as LSN for data pages affected by the logged action. * (LSN is the XLOG point up to which the XLOG must be flushed to disk * before the data page can be written out. This implements the basic * WAL rule "write the log before the data".) */ XLogRecPtr XLogInsertRecord(XLogRecData *rdata, XLogRecPtr fpw_lsn, uint8 flags, int num_fpi, bool topxid_included) { XLogCtlInsert *Insert = &XLogCtl->Insert; pg_crc32c rdata_crc; bool inserted; XLogRecord *rechdr = (XLogRecord *) rdata->data; uint8 info = rechdr->xl_info & ~XLR_INFO_MASK; bool isLogSwitch = (rechdr->xl_rmid == RM_XLOG_ID && info == XLOG_SWITCH); XLogRecPtr StartPos; XLogRecPtr EndPos; bool prevDoPageWrites = doPageWrites; TimeLineID insertTLI; /* we assume that all of the record header is in the first chunk */ Assert(rdata->len >= SizeOfXLogRecord); /* cross-check on whether we should be here or not */ if (!XLogInsertAllowed()) elog(ERROR, "cannot make new WAL entries during recovery"); /* * Given that we're not in recovery, InsertTimeLineID is set and can't * change, so we can read it without a lock. */ insertTLI = XLogCtl->InsertTimeLineID; /*---------- * * We have now done all the preparatory work we can without holding a * lock or modifying shared state. From here on, inserting the new WAL * record to the shared WAL buffer cache is a two-step process: * * 1. Reserve the right amount of space from the WAL. The current head of * reserved space is kept in Insert->CurrBytePos, and is protected by * insertpos_lck. * * 2. Copy the record to the reserved WAL space. This involves finding the * correct WAL buffer containing the reserved space, and copying the * record in place. This can be done concurrently in multiple processes. * * To keep track of which insertions are still in-progress, each concurrent * inserter acquires an insertion lock. In addition to just indicating that * an insertion is in progress, the lock tells others how far the inserter * has progressed. There is a small fixed number of insertion locks, * determined by NUM_XLOGINSERT_LOCKS. When an inserter crosses a page * boundary, it updates the value stored in the lock to the how far it has * inserted, to allow the previous buffer to be flushed. * * Holding onto an insertion lock also protects RedoRecPtr and * fullPageWrites from changing until the insertion is finished. * * Step 2 can usually be done completely in parallel. If the required WAL * page is not initialized yet, you have to grab WALBufMappingLock to * initialize it, but the WAL writer tries to do that ahead of insertions * to avoid that from happening in the critical path. * *---------- */ START_CRIT_SECTION(); if (isLogSwitch) WALInsertLockAcquireExclusive(); else WALInsertLockAcquire(); /* * Check to see if my copy of RedoRecPtr is out of date. If so, may have * to go back and have the caller recompute everything. This can only * happen just after a checkpoint, so it's better to be slow in this case * and fast otherwise. * * Also check to see if fullPageWrites was just turned on or there's a * running backup (which forces full-page writes); if we weren't already * doing full-page writes then go back and recompute. * * If we aren't doing full-page writes then RedoRecPtr doesn't actually * affect the contents of the XLOG record, so we'll update our local copy * but not force a recomputation. (If doPageWrites was just turned off, * we could recompute the record without full pages, but we choose not to * bother.) */ if (RedoRecPtr != Insert->RedoRecPtr) { Assert(RedoRecPtr < Insert->RedoRecPtr); RedoRecPtr = Insert->RedoRecPtr; } doPageWrites = (Insert->fullPageWrites || Insert->runningBackups > 0); if (doPageWrites && (!prevDoPageWrites || (fpw_lsn != InvalidXLogRecPtr && fpw_lsn <= RedoRecPtr))) { /* * Oops, some buffer now needs to be backed up that the caller didn't * back up. Start over. */ WALInsertLockRelease(); END_CRIT_SECTION(); return InvalidXLogRecPtr; } /* * Reserve space for the record in the WAL. This also sets the xl_prev * pointer. */ if (isLogSwitch) inserted = ReserveXLogSwitch(&StartPos, &EndPos, &rechdr->xl_prev); else { ReserveXLogInsertLocation(rechdr->xl_tot_len, &StartPos, &EndPos, &rechdr->xl_prev); inserted = true; } if (inserted) { /* * Now that xl_prev has been filled in, calculate CRC of the record * header. */ rdata_crc = rechdr->xl_crc; COMP_CRC32C(rdata_crc, rechdr, offsetof(XLogRecord, xl_crc)); FIN_CRC32C(rdata_crc); rechdr->xl_crc = rdata_crc; /* * All the record data, including the header, is now ready to be * inserted. Copy the record in the space reserved. */ CopyXLogRecordToWAL(rechdr->xl_tot_len, isLogSwitch, rdata, StartPos, EndPos, insertTLI); /* * Unless record is flagged as not important, update LSN of last * important record in the current slot. When holding all locks, just * update the first one. */ if ((flags & XLOG_MARK_UNIMPORTANT) == 0) { int lockno = holdingAllLocks ? 0 : MyLockNo; WALInsertLocks[lockno].l.lastImportantAt = StartPos; } } else { /* * This was an xlog-switch record, but the current insert location was * already exactly at the beginning of a segment, so there was no need * to do anything. */ } /* * Done! Let others know that we're finished. */ WALInsertLockRelease(); END_CRIT_SECTION(); MarkCurrentTransactionIdLoggedIfAny(); /* * Mark top transaction id is logged (if needed) so that we should not try * to log it again with the next WAL record in the current subtransaction. */ if (topxid_included) MarkSubxactTopXidLogged(); /* * Update shared LogwrtRqst.Write, if we crossed page boundary. */ if (StartPos / XLOG_BLCKSZ != EndPos / XLOG_BLCKSZ) { SpinLockAcquire(&XLogCtl->info_lck); /* advance global request to include new block(s) */ if (XLogCtl->LogwrtRqst.Write < EndPos) XLogCtl->LogwrtRqst.Write = EndPos; /* update local result copy while I have the chance */ LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); } /* * If this was an XLOG_SWITCH record, flush the record and the empty * padding space that fills the rest of the segment, and perform * end-of-segment actions (eg, notifying archiver). */ if (isLogSwitch) { TRACE_POSTGRESQL_WAL_SWITCH(); XLogFlush(EndPos); /* * Even though we reserved the rest of the segment for us, which is * reflected in EndPos, we return a pointer to just the end of the * xlog-switch record. */ if (inserted) { EndPos = StartPos + SizeOfXLogRecord; if (StartPos / XLOG_BLCKSZ != EndPos / XLOG_BLCKSZ) { uint64 offset = XLogSegmentOffset(EndPos, wal_segment_size); if (offset == EndPos % XLOG_BLCKSZ) EndPos += SizeOfXLogLongPHD; else EndPos += SizeOfXLogShortPHD; } } } #ifdef WAL_DEBUG if (XLOG_DEBUG) { static XLogReaderState *debug_reader = NULL; XLogRecord *record; DecodedXLogRecord *decoded; StringInfoData buf; StringInfoData recordBuf; char *errormsg = NULL; MemoryContext oldCxt; oldCxt = MemoryContextSwitchTo(walDebugCxt); initStringInfo(&buf); appendStringInfo(&buf, "INSERT @ %X/%X: ", LSN_FORMAT_ARGS(EndPos)); /* * We have to piece together the WAL record data from the XLogRecData * entries, so that we can pass it to the rm_desc function as one * contiguous chunk. */ initStringInfo(&recordBuf); for (; rdata != NULL; rdata = rdata->next) appendBinaryStringInfo(&recordBuf, rdata->data, rdata->len); /* We also need temporary space to decode the record. */ record = (XLogRecord *) recordBuf.data; decoded = (DecodedXLogRecord *) palloc(DecodeXLogRecordRequiredSpace(record->xl_tot_len)); if (!debug_reader) debug_reader = XLogReaderAllocate(wal_segment_size, NULL, XL_ROUTINE(.page_read = NULL, .segment_open = NULL, .segment_close = NULL), NULL); if (!debug_reader) { appendStringInfoString(&buf, "error decoding record: out of memory while allocating a WAL reading processor"); } else if (!DecodeXLogRecord(debug_reader, decoded, record, EndPos, &errormsg)) { appendStringInfo(&buf, "error decoding record: %s", errormsg ? errormsg : "no error message"); } else { appendStringInfoString(&buf, " - "); debug_reader->record = decoded; xlog_outdesc(&buf, debug_reader); debug_reader->record = NULL; } elog(LOG, "%s", buf.data); pfree(decoded); pfree(buf.data); pfree(recordBuf.data); MemoryContextSwitchTo(oldCxt); } #endif /* * Update our global variables */ ProcLastRecPtr = StartPos; XactLastRecEnd = EndPos; /* Report WAL traffic to the instrumentation. */ if (inserted) { pgWalUsage.wal_bytes += rechdr->xl_tot_len; pgWalUsage.wal_records++; pgWalUsage.wal_fpi += num_fpi; } return EndPos; } /* * Reserves the right amount of space for a record of given size from the WAL. * *StartPos is set to the beginning of the reserved section, *EndPos to * its end+1. *PrevPtr is set to the beginning of the previous record; it is * used to set the xl_prev of this record. * * This is the performance critical part of XLogInsert that must be serialized * across backends. The rest can happen mostly in parallel. Try to keep this * section as short as possible, insertpos_lck can be heavily contended on a * busy system. * * NB: The space calculation here must match the code in CopyXLogRecordToWAL, * where we actually copy the record to the reserved space. */ static void ReserveXLogInsertLocation(int size, XLogRecPtr *StartPos, XLogRecPtr *EndPos, XLogRecPtr *PrevPtr) { XLogCtlInsert *Insert = &XLogCtl->Insert; uint64 startbytepos; uint64 endbytepos; uint64 prevbytepos; size = MAXALIGN(size); /* All (non xlog-switch) records should contain data. */ Assert(size > SizeOfXLogRecord); /* * The duration the spinlock needs to be held is minimized by minimizing * the calculations that have to be done while holding the lock. The * current tip of reserved WAL is kept in CurrBytePos, as a byte position * that only counts "usable" bytes in WAL, that is, it excludes all WAL * page headers. The mapping between "usable" byte positions and physical * positions (XLogRecPtrs) can be done outside the locked region, and * because the usable byte position doesn't include any headers, reserving * X bytes from WAL is almost as simple as "CurrBytePos += X". */ SpinLockAcquire(&Insert->insertpos_lck); startbytepos = Insert->CurrBytePos; endbytepos = startbytepos + size; prevbytepos = Insert->PrevBytePos; Insert->CurrBytePos = endbytepos; Insert->PrevBytePos = startbytepos; SpinLockRelease(&Insert->insertpos_lck); *StartPos = XLogBytePosToRecPtr(startbytepos); *EndPos = XLogBytePosToEndRecPtr(endbytepos); *PrevPtr = XLogBytePosToRecPtr(prevbytepos); /* * Check that the conversions between "usable byte positions" and * XLogRecPtrs work consistently in both directions. */ Assert(XLogRecPtrToBytePos(*StartPos) == startbytepos); Assert(XLogRecPtrToBytePos(*EndPos) == endbytepos); Assert(XLogRecPtrToBytePos(*PrevPtr) == prevbytepos); } /* * Like ReserveXLogInsertLocation(), but for an xlog-switch record. * * A log-switch record is handled slightly differently. The rest of the * segment will be reserved for this insertion, as indicated by the returned * *EndPos value. However, if we are already at the beginning of the current * segment, *StartPos and *EndPos are set to the current location without * reserving any space, and the function returns false. */ static bool ReserveXLogSwitch(XLogRecPtr *StartPos, XLogRecPtr *EndPos, XLogRecPtr *PrevPtr) { XLogCtlInsert *Insert = &XLogCtl->Insert; uint64 startbytepos; uint64 endbytepos; uint64 prevbytepos; uint32 size = MAXALIGN(SizeOfXLogRecord); XLogRecPtr ptr; uint32 segleft; /* * These calculations are a bit heavy-weight to be done while holding a * spinlock, but since we're holding all the WAL insertion locks, there * are no other inserters competing for it. GetXLogInsertRecPtr() does * compete for it, but that's not called very frequently. */ SpinLockAcquire(&Insert->insertpos_lck); startbytepos = Insert->CurrBytePos; ptr = XLogBytePosToEndRecPtr(startbytepos); if (XLogSegmentOffset(ptr, wal_segment_size) == 0) { SpinLockRelease(&Insert->insertpos_lck); *EndPos = *StartPos = ptr; return false; } endbytepos = startbytepos + size; prevbytepos = Insert->PrevBytePos; *StartPos = XLogBytePosToRecPtr(startbytepos); *EndPos = XLogBytePosToEndRecPtr(endbytepos); segleft = wal_segment_size - XLogSegmentOffset(*EndPos, wal_segment_size); if (segleft != wal_segment_size) { /* consume the rest of the segment */ *EndPos += segleft; endbytepos = XLogRecPtrToBytePos(*EndPos); } Insert->CurrBytePos = endbytepos; Insert->PrevBytePos = startbytepos; SpinLockRelease(&Insert->insertpos_lck); *PrevPtr = XLogBytePosToRecPtr(prevbytepos); Assert(XLogSegmentOffset(*EndPos, wal_segment_size) == 0); Assert(XLogRecPtrToBytePos(*EndPos) == endbytepos); Assert(XLogRecPtrToBytePos(*StartPos) == startbytepos); Assert(XLogRecPtrToBytePos(*PrevPtr) == prevbytepos); return true; } /* * Subroutine of XLogInsertRecord. Copies a WAL record to an already-reserved * area in the WAL. */ static void CopyXLogRecordToWAL(int write_len, bool isLogSwitch, XLogRecData *rdata, XLogRecPtr StartPos, XLogRecPtr EndPos, TimeLineID tli) { char *currpos; int freespace; int written; XLogRecPtr CurrPos; XLogPageHeader pagehdr; /* * Get a pointer to the right place in the right WAL buffer to start * inserting to. */ CurrPos = StartPos; currpos = GetXLogBuffer(CurrPos, tli); freespace = INSERT_FREESPACE(CurrPos); /* * there should be enough space for at least the first field (xl_tot_len) * on this page. */ Assert(freespace >= sizeof(uint32)); /* Copy record data */ written = 0; while (rdata != NULL) { char *rdata_data = rdata->data; int rdata_len = rdata->len; while (rdata_len > freespace) { /* * Write what fits on this page, and continue on the next page. */ Assert(CurrPos % XLOG_BLCKSZ >= SizeOfXLogShortPHD || freespace == 0); memcpy(currpos, rdata_data, freespace); rdata_data += freespace; rdata_len -= freespace; written += freespace; CurrPos += freespace; /* * Get pointer to beginning of next page, and set the xlp_rem_len * in the page header. Set XLP_FIRST_IS_CONTRECORD. * * It's safe to set the contrecord flag and xlp_rem_len without a * lock on the page. All the other flags were already set when the * page was initialized, in AdvanceXLInsertBuffer, and we're the * only backend that needs to set the contrecord flag. */ currpos = GetXLogBuffer(CurrPos, tli); pagehdr = (XLogPageHeader) currpos; pagehdr->xlp_rem_len = write_len - written; pagehdr->xlp_info |= XLP_FIRST_IS_CONTRECORD; /* skip over the page header */ if (XLogSegmentOffset(CurrPos, wal_segment_size) == 0) { CurrPos += SizeOfXLogLongPHD; currpos += SizeOfXLogLongPHD; } else { CurrPos += SizeOfXLogShortPHD; currpos += SizeOfXLogShortPHD; } freespace = INSERT_FREESPACE(CurrPos); } Assert(CurrPos % XLOG_BLCKSZ >= SizeOfXLogShortPHD || rdata_len == 0); memcpy(currpos, rdata_data, rdata_len); currpos += rdata_len; CurrPos += rdata_len; freespace -= rdata_len; written += rdata_len; rdata = rdata->next; } Assert(written == write_len); /* * If this was an xlog-switch, it's not enough to write the switch record, * we also have to consume all the remaining space in the WAL segment. We * have already reserved that space, but we need to actually fill it. */ if (isLogSwitch && XLogSegmentOffset(CurrPos, wal_segment_size) != 0) { /* An xlog-switch record doesn't contain any data besides the header */ Assert(write_len == SizeOfXLogRecord); /* Assert that we did reserve the right amount of space */ Assert(XLogSegmentOffset(EndPos, wal_segment_size) == 0); /* Use up all the remaining space on the current page */ CurrPos += freespace; /* * Cause all remaining pages in the segment to be flushed, leaving the * XLog position where it should be, at the start of the next segment. * We do this one page at a time, to make sure we don't deadlock * against ourselves if wal_buffers < wal_segment_size. */ while (CurrPos < EndPos) { /* * The minimal action to flush the page would be to call * WALInsertLockUpdateInsertingAt(CurrPos) followed by * AdvanceXLInsertBuffer(...). The page would be left initialized * mostly to zeros, except for the page header (always the short * variant, as this is never a segment's first page). * * The large vistas of zeros are good for compressibility, but the * headers interrupting them every XLOG_BLCKSZ (with values that * differ from page to page) are not. The effect varies with * compression tool, but bzip2 for instance compresses about an * order of magnitude worse if those headers are left in place. * * Rather than complicating AdvanceXLInsertBuffer itself (which is * called in heavily-loaded circumstances as well as this lightly- * loaded one) with variant behavior, we just use GetXLogBuffer * (which itself calls the two methods we need) to get the pointer * and zero most of the page. Then we just zero the page header. */ currpos = GetXLogBuffer(CurrPos, tli); MemSet(currpos, 0, SizeOfXLogShortPHD); CurrPos += XLOG_BLCKSZ; } } else { /* Align the end position, so that the next record starts aligned */ CurrPos = MAXALIGN64(CurrPos); } if (CurrPos != EndPos) elog(PANIC, "space reserved for WAL record does not match what was written"); } /* * Acquire a WAL insertion lock, for inserting to WAL. */ static void WALInsertLockAcquire(void) { bool immed; /* * It doesn't matter which of the WAL insertion locks we acquire, so try * the one we used last time. If the system isn't particularly busy, it's * a good bet that it's still available, and it's good to have some * affinity to a particular lock so that you don't unnecessarily bounce * cache lines between processes when there's no contention. * * If this is the first time through in this backend, pick a lock * (semi-)randomly. This allows the locks to be used evenly if you have a * lot of very short connections. */ static int lockToTry = -1; if (lockToTry == -1) lockToTry = MyProc->pgprocno % NUM_XLOGINSERT_LOCKS; MyLockNo = lockToTry; /* * The insertingAt value is initially set to 0, as we don't know our * insert location yet. */ immed = LWLockAcquire(&WALInsertLocks[MyLockNo].l.lock, LW_EXCLUSIVE); if (!immed) { /* * If we couldn't get the lock immediately, try another lock next * time. On a system with more insertion locks than concurrent * inserters, this causes all the inserters to eventually migrate to a * lock that no-one else is using. On a system with more inserters * than locks, it still helps to distribute the inserters evenly * across the locks. */ lockToTry = (lockToTry + 1) % NUM_XLOGINSERT_LOCKS; } } /* * Acquire all WAL insertion locks, to prevent other backends from inserting * to WAL. */ static void WALInsertLockAcquireExclusive(void) { int i; /* * When holding all the locks, all but the last lock's insertingAt * indicator is set to 0xFFFFFFFFFFFFFFFF, which is higher than any real * XLogRecPtr value, to make sure that no-one blocks waiting on those. */ for (i = 0; i < NUM_XLOGINSERT_LOCKS - 1; i++) { LWLockAcquire(&WALInsertLocks[i].l.lock, LW_EXCLUSIVE); LWLockUpdateVar(&WALInsertLocks[i].l.lock, &WALInsertLocks[i].l.insertingAt, PG_UINT64_MAX); } /* Variable value reset to 0 at release */ LWLockAcquire(&WALInsertLocks[i].l.lock, LW_EXCLUSIVE); holdingAllLocks = true; } /* * Release our insertion lock (or locks, if we're holding them all). * * NB: Reset all variables to 0, so they cause LWLockWaitForVar to block the * next time the lock is acquired. */ static void WALInsertLockRelease(void) { if (holdingAllLocks) { int i; for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) LWLockReleaseClearVar(&WALInsertLocks[i].l.lock, &WALInsertLocks[i].l.insertingAt, 0); holdingAllLocks = false; } else { LWLockReleaseClearVar(&WALInsertLocks[MyLockNo].l.lock, &WALInsertLocks[MyLockNo].l.insertingAt, 0); } } /* * Update our insertingAt value, to let others know that we've finished * inserting up to that point. */ static void WALInsertLockUpdateInsertingAt(XLogRecPtr insertingAt) { if (holdingAllLocks) { /* * We use the last lock to mark our actual position, see comments in * WALInsertLockAcquireExclusive. */ LWLockUpdateVar(&WALInsertLocks[NUM_XLOGINSERT_LOCKS - 1].l.lock, &WALInsertLocks[NUM_XLOGINSERT_LOCKS - 1].l.insertingAt, insertingAt); } else LWLockUpdateVar(&WALInsertLocks[MyLockNo].l.lock, &WALInsertLocks[MyLockNo].l.insertingAt, insertingAt); } /* * Wait for any WAL insertions < upto to finish. * * Returns the location of the oldest insertion that is still in-progress. * Any WAL prior to that point has been fully copied into WAL buffers, and * can be flushed out to disk. Because this waits for any insertions older * than 'upto' to finish, the return value is always >= 'upto'. * * Note: When you are about to write out WAL, you must call this function * *before* acquiring WALWriteLock, to avoid deadlocks. This function might * need to wait for an insertion to finish (or at least advance to next * uninitialized page), and the inserter might need to evict an old WAL buffer * to make room for a new one, which in turn requires WALWriteLock. */ static XLogRecPtr WaitXLogInsertionsToFinish(XLogRecPtr upto) { uint64 bytepos; XLogRecPtr reservedUpto; XLogRecPtr finishedUpto; XLogCtlInsert *Insert = &XLogCtl->Insert; int i; if (MyProc == NULL) elog(PANIC, "cannot wait without a PGPROC structure"); /* Read the current insert position */ SpinLockAcquire(&Insert->insertpos_lck); bytepos = Insert->CurrBytePos; SpinLockRelease(&Insert->insertpos_lck); reservedUpto = XLogBytePosToEndRecPtr(bytepos); /* * No-one should request to flush a piece of WAL that hasn't even been * reserved yet. However, it can happen if there is a block with a bogus * LSN on disk, for example. XLogFlush checks for that situation and * complains, but only after the flush. Here we just assume that to mean * that all WAL that has been reserved needs to be finished. In this * corner-case, the return value can be smaller than 'upto' argument. */ if (upto > reservedUpto) { ereport(LOG, (errmsg("request to flush past end of generated WAL; request %X/%X, current position %X/%X", LSN_FORMAT_ARGS(upto), LSN_FORMAT_ARGS(reservedUpto)))); upto = reservedUpto; } /* * Loop through all the locks, sleeping on any in-progress insert older * than 'upto'. * * finishedUpto is our return value, indicating the point upto which all * the WAL insertions have been finished. Initialize it to the head of * reserved WAL, and as we iterate through the insertion locks, back it * out for any insertion that's still in progress. */ finishedUpto = reservedUpto; for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) { XLogRecPtr insertingat = InvalidXLogRecPtr; do { /* * See if this insertion is in progress. LWLockWaitForVar will * wait for the lock to be released, or for the 'value' to be set * by a LWLockUpdateVar call. When a lock is initially acquired, * its value is 0 (InvalidXLogRecPtr), which means that we don't * know where it's inserting yet. We will have to wait for it. If * it's a small insertion, the record will most likely fit on the * same page and the inserter will release the lock without ever * calling LWLockUpdateVar. But if it has to sleep, it will * advertise the insertion point with LWLockUpdateVar before * sleeping. */ if (LWLockWaitForVar(&WALInsertLocks[i].l.lock, &WALInsertLocks[i].l.insertingAt, insertingat, &insertingat)) { /* the lock was free, so no insertion in progress */ insertingat = InvalidXLogRecPtr; break; } /* * This insertion is still in progress. Have to wait, unless the * inserter has proceeded past 'upto'. */ } while (insertingat < upto); if (insertingat != InvalidXLogRecPtr && insertingat < finishedUpto) finishedUpto = insertingat; } return finishedUpto; } /* * Get a pointer to the right location in the WAL buffer containing the * given XLogRecPtr. * * If the page is not initialized yet, it is initialized. That might require * evicting an old dirty buffer from the buffer cache, which means I/O. * * The caller must ensure that the page containing the requested location * isn't evicted yet, and won't be evicted. The way to ensure that is to * hold onto a WAL insertion lock with the insertingAt position set to * something <= ptr. GetXLogBuffer() will update insertingAt if it needs * to evict an old page from the buffer. (This means that once you call * GetXLogBuffer() with a given 'ptr', you must not access anything before * that point anymore, and must not call GetXLogBuffer() with an older 'ptr' * later, because older buffers might be recycled already) */ static char * GetXLogBuffer(XLogRecPtr ptr, TimeLineID tli) { int idx; XLogRecPtr endptr; static uint64 cachedPage = 0; static char *cachedPos = NULL; XLogRecPtr expectedEndPtr; /* * Fast path for the common case that we need to access again the same * page as last time. */ if (ptr / XLOG_BLCKSZ == cachedPage) { Assert(((XLogPageHeader) cachedPos)->xlp_magic == XLOG_PAGE_MAGIC); Assert(((XLogPageHeader) cachedPos)->xlp_pageaddr == ptr - (ptr % XLOG_BLCKSZ)); return cachedPos + ptr % XLOG_BLCKSZ; } /* * The XLog buffer cache is organized so that a page is always loaded to a * particular buffer. That way we can easily calculate the buffer a given * page must be loaded into, from the XLogRecPtr alone. */ idx = XLogRecPtrToBufIdx(ptr); /* * See what page is loaded in the buffer at the moment. It could be the * page we're looking for, or something older. It can't be anything newer * - that would imply the page we're looking for has already been written * out to disk and evicted, and the caller is responsible for making sure * that doesn't happen. * * However, we don't hold a lock while we read the value. If someone has * just initialized the page, it's possible that we get a "torn read" of * the XLogRecPtr if 64-bit fetches are not atomic on this platform. In * that case we will see a bogus value. That's ok, we'll grab the mapping * lock (in AdvanceXLInsertBuffer) and retry if we see anything else than * the page we're looking for. But it means that when we do this unlocked * read, we might see a value that appears to be ahead of the page we're * looking for. Don't PANIC on that, until we've verified the value while * holding the lock. */ expectedEndPtr = ptr; expectedEndPtr += XLOG_BLCKSZ - ptr % XLOG_BLCKSZ; endptr = XLogCtl->xlblocks[idx]; if (expectedEndPtr != endptr) { XLogRecPtr initializedUpto; /* * Before calling AdvanceXLInsertBuffer(), which can block, let others * know how far we're finished with inserting the record. * * NB: If 'ptr' points to just after the page header, advertise a * position at the beginning of the page rather than 'ptr' itself. If * there are no other insertions running, someone might try to flush * up to our advertised location. If we advertised a position after * the page header, someone might try to flush the page header, even * though page might actually not be initialized yet. As the first * inserter on the page, we are effectively responsible for making * sure that it's initialized, before we let insertingAt to move past * the page header. */ if (ptr % XLOG_BLCKSZ == SizeOfXLogShortPHD && XLogSegmentOffset(ptr, wal_segment_size) > XLOG_BLCKSZ) initializedUpto = ptr - SizeOfXLogShortPHD; else if (ptr % XLOG_BLCKSZ == SizeOfXLogLongPHD && XLogSegmentOffset(ptr, wal_segment_size) < XLOG_BLCKSZ) initializedUpto = ptr - SizeOfXLogLongPHD; else initializedUpto = ptr; WALInsertLockUpdateInsertingAt(initializedUpto); AdvanceXLInsertBuffer(ptr, tli, false); endptr = XLogCtl->xlblocks[idx]; if (expectedEndPtr != endptr) elog(PANIC, "could not find WAL buffer for %X/%X", LSN_FORMAT_ARGS(ptr)); } else { /* * Make sure the initialization of the page is visible to us, and * won't arrive later to overwrite the WAL data we write on the page. */ pg_memory_barrier(); } /* * Found the buffer holding this page. Return a pointer to the right * offset within the page. */ cachedPage = ptr / XLOG_BLCKSZ; cachedPos = XLogCtl->pages + idx * (Size) XLOG_BLCKSZ; Assert(((XLogPageHeader) cachedPos)->xlp_magic == XLOG_PAGE_MAGIC); Assert(((XLogPageHeader) cachedPos)->xlp_pageaddr == ptr - (ptr % XLOG_BLCKSZ)); return cachedPos + ptr % XLOG_BLCKSZ; } /* * Converts a "usable byte position" to XLogRecPtr. A usable byte position * is the position starting from the beginning of WAL, excluding all WAL * page headers. */ static XLogRecPtr XLogBytePosToRecPtr(uint64 bytepos) { uint64 fullsegs; uint64 fullpages; uint64 bytesleft; uint32 seg_offset; XLogRecPtr result; fullsegs = bytepos / UsableBytesInSegment; bytesleft = bytepos % UsableBytesInSegment; if (bytesleft < XLOG_BLCKSZ - SizeOfXLogLongPHD) { /* fits on first page of segment */ seg_offset = bytesleft + SizeOfXLogLongPHD; } else { /* account for the first page on segment with long header */ seg_offset = XLOG_BLCKSZ; bytesleft -= XLOG_BLCKSZ - SizeOfXLogLongPHD; fullpages = bytesleft / UsableBytesInPage; bytesleft = bytesleft % UsableBytesInPage; seg_offset += fullpages * XLOG_BLCKSZ + bytesleft + SizeOfXLogShortPHD; } XLogSegNoOffsetToRecPtr(fullsegs, seg_offset, wal_segment_size, result); return result; } /* * Like XLogBytePosToRecPtr, but if the position is at a page boundary, * returns a pointer to the beginning of the page (ie. before page header), * not to where the first xlog record on that page would go to. This is used * when converting a pointer to the end of a record. */ static XLogRecPtr XLogBytePosToEndRecPtr(uint64 bytepos) { uint64 fullsegs; uint64 fullpages; uint64 bytesleft; uint32 seg_offset; XLogRecPtr result; fullsegs = bytepos / UsableBytesInSegment; bytesleft = bytepos % UsableBytesInSegment; if (bytesleft < XLOG_BLCKSZ - SizeOfXLogLongPHD) { /* fits on first page of segment */ if (bytesleft == 0) seg_offset = 0; else seg_offset = bytesleft + SizeOfXLogLongPHD; } else { /* account for the first page on segment with long header */ seg_offset = XLOG_BLCKSZ; bytesleft -= XLOG_BLCKSZ - SizeOfXLogLongPHD; fullpages = bytesleft / UsableBytesInPage; bytesleft = bytesleft % UsableBytesInPage; if (bytesleft == 0) seg_offset += fullpages * XLOG_BLCKSZ + bytesleft; else seg_offset += fullpages * XLOG_BLCKSZ + bytesleft + SizeOfXLogShortPHD; } XLogSegNoOffsetToRecPtr(fullsegs, seg_offset, wal_segment_size, result); return result; } /* * Convert an XLogRecPtr to a "usable byte position". */ static uint64 XLogRecPtrToBytePos(XLogRecPtr ptr) { uint64 fullsegs; uint32 fullpages; uint32 offset; uint64 result; XLByteToSeg(ptr, fullsegs, wal_segment_size); fullpages = (XLogSegmentOffset(ptr, wal_segment_size)) / XLOG_BLCKSZ; offset = ptr % XLOG_BLCKSZ; if (fullpages == 0) { result = fullsegs * UsableBytesInSegment; if (offset > 0) { Assert(offset >= SizeOfXLogLongPHD); result += offset - SizeOfXLogLongPHD; } } else { result = fullsegs * UsableBytesInSegment + (XLOG_BLCKSZ - SizeOfXLogLongPHD) + /* account for first page */ (fullpages - 1) * UsableBytesInPage; /* full pages */ if (offset > 0) { Assert(offset >= SizeOfXLogShortPHD); result += offset - SizeOfXLogShortPHD; } } return result; } /* * Initialize XLOG buffers, writing out old buffers if they still contain * unwritten data, upto the page containing 'upto'. Or if 'opportunistic' is * true, initialize as many pages as we can without having to write out * unwritten data. Any new pages are initialized to zeros, with pages headers * initialized properly. */ static void AdvanceXLInsertBuffer(XLogRecPtr upto, TimeLineID tli, bool opportunistic) { XLogCtlInsert *Insert = &XLogCtl->Insert; int nextidx; XLogRecPtr OldPageRqstPtr; XLogwrtRqst WriteRqst; XLogRecPtr NewPageEndPtr = InvalidXLogRecPtr; XLogRecPtr NewPageBeginPtr; XLogPageHeader NewPage; int npages pg_attribute_unused() = 0; LWLockAcquire(WALBufMappingLock, LW_EXCLUSIVE); /* * Now that we have the lock, check if someone initialized the page * already. */ while (upto >= XLogCtl->InitializedUpTo || opportunistic) { nextidx = XLogRecPtrToBufIdx(XLogCtl->InitializedUpTo); /* * Get ending-offset of the buffer page we need to replace (this may * be zero if the buffer hasn't been used yet). Fall through if it's * already written out. */ OldPageRqstPtr = XLogCtl->xlblocks[nextidx]; if (LogwrtResult.Write < OldPageRqstPtr) { /* * Nope, got work to do. If we just want to pre-initialize as much * as we can without flushing, give up now. */ if (opportunistic) break; /* Before waiting, get info_lck and update LogwrtResult */ SpinLockAcquire(&XLogCtl->info_lck); if (XLogCtl->LogwrtRqst.Write < OldPageRqstPtr) XLogCtl->LogwrtRqst.Write = OldPageRqstPtr; LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); /* * Now that we have an up-to-date LogwrtResult value, see if we * still need to write it or if someone else already did. */ if (LogwrtResult.Write < OldPageRqstPtr) { /* * Must acquire write lock. Release WALBufMappingLock first, * to make sure that all insertions that we need to wait for * can finish (up to this same position). Otherwise we risk * deadlock. */ LWLockRelease(WALBufMappingLock); WaitXLogInsertionsToFinish(OldPageRqstPtr); LWLockAcquire(WALWriteLock, LW_EXCLUSIVE); LogwrtResult = XLogCtl->LogwrtResult; if (LogwrtResult.Write >= OldPageRqstPtr) { /* OK, someone wrote it already */ LWLockRelease(WALWriteLock); } else { /* Have to write it ourselves */ TRACE_POSTGRESQL_WAL_BUFFER_WRITE_DIRTY_START(); WriteRqst.Write = OldPageRqstPtr; WriteRqst.Flush = 0; XLogWrite(WriteRqst, tli, false); LWLockRelease(WALWriteLock); PendingWalStats.wal_buffers_full++; TRACE_POSTGRESQL_WAL_BUFFER_WRITE_DIRTY_DONE(); } /* Re-acquire WALBufMappingLock and retry */ LWLockAcquire(WALBufMappingLock, LW_EXCLUSIVE); continue; } } /* * Now the next buffer slot is free and we can set it up to be the * next output page. */ NewPageBeginPtr = XLogCtl->InitializedUpTo; NewPageEndPtr = NewPageBeginPtr + XLOG_BLCKSZ; Assert(XLogRecPtrToBufIdx(NewPageBeginPtr) == nextidx); NewPage = (XLogPageHeader) (XLogCtl->pages + nextidx * (Size) XLOG_BLCKSZ); /* * Be sure to re-zero the buffer so that bytes beyond what we've * written will look like zeroes and not valid XLOG records... */ MemSet((char *) NewPage, 0, XLOG_BLCKSZ); /* * Fill the new page's header */ NewPage->xlp_magic = XLOG_PAGE_MAGIC; /* NewPage->xlp_info = 0; */ /* done by memset */ NewPage->xlp_tli = tli; NewPage->xlp_pageaddr = NewPageBeginPtr; /* NewPage->xlp_rem_len = 0; */ /* done by memset */ /* * If online backup is not in progress, mark the header to indicate * that WAL records beginning in this page have removable backup * blocks. This allows the WAL archiver to know whether it is safe to * compress archived WAL data by transforming full-block records into * the non-full-block format. It is sufficient to record this at the * page level because we force a page switch (in fact a segment * switch) when starting a backup, so the flag will be off before any * records can be written during the backup. At the end of a backup, * the last page will be marked as all unsafe when perhaps only part * is unsafe, but at worst the archiver would miss the opportunity to * compress a few records. */ if (Insert->runningBackups == 0) NewPage->xlp_info |= XLP_BKP_REMOVABLE; /* * If first page of an XLOG segment file, make it a long header. */ if ((XLogSegmentOffset(NewPage->xlp_pageaddr, wal_segment_size)) == 0) { XLogLongPageHeader NewLongPage = (XLogLongPageHeader) NewPage; NewLongPage->xlp_sysid = ControlFile->system_identifier; NewLongPage->xlp_seg_size = wal_segment_size; NewLongPage->xlp_xlog_blcksz = XLOG_BLCKSZ; NewPage->xlp_info |= XLP_LONG_HEADER; } /* * Make sure the initialization of the page becomes visible to others * before the xlblocks update. GetXLogBuffer() reads xlblocks without * holding a lock. */ pg_write_barrier(); *((volatile XLogRecPtr *) &XLogCtl->xlblocks[nextidx]) = NewPageEndPtr; XLogCtl->InitializedUpTo = NewPageEndPtr; npages++; } LWLockRelease(WALBufMappingLock); #ifdef WAL_DEBUG if (XLOG_DEBUG && npages > 0) { elog(DEBUG1, "initialized %d pages, up to %X/%X", npages, LSN_FORMAT_ARGS(NewPageEndPtr)); } #endif } /* * Calculate CheckPointSegments based on max_wal_size_mb and * checkpoint_completion_target. */ static void CalculateCheckpointSegments(void) { double target; /*------- * Calculate the distance at which to trigger a checkpoint, to avoid * exceeding max_wal_size_mb. This is based on two assumptions: * * a) we keep WAL for only one checkpoint cycle (prior to PG11 we kept * WAL for two checkpoint cycles to allow us to recover from the * secondary checkpoint if the first checkpoint failed, though we * only did this on the primary anyway, not on standby. Keeping just * one checkpoint simplifies processing and reduces disk space in * many smaller databases.) * b) during checkpoint, we consume checkpoint_completion_target * * number of segments consumed between checkpoints. *------- */ target = (double) ConvertToXSegs(max_wal_size_mb, wal_segment_size) / (1.0 + CheckPointCompletionTarget); /* round down */ CheckPointSegments = (int) target; if (CheckPointSegments < 1) CheckPointSegments = 1; } void assign_max_wal_size(int newval, void *extra) { max_wal_size_mb = newval; CalculateCheckpointSegments(); } void assign_checkpoint_completion_target(double newval, void *extra) { CheckPointCompletionTarget = newval; CalculateCheckpointSegments(); } /* * At a checkpoint, how many WAL segments to recycle as preallocated future * XLOG segments? Returns the highest segment that should be preallocated. */ static XLogSegNo XLOGfileslop(XLogRecPtr lastredoptr) { XLogSegNo minSegNo; XLogSegNo maxSegNo; double distance; XLogSegNo recycleSegNo; /* * Calculate the segment numbers that min_wal_size_mb and max_wal_size_mb * correspond to. Always recycle enough segments to meet the minimum, and * remove enough segments to stay below the maximum. */ minSegNo = lastredoptr / wal_segment_size + ConvertToXSegs(min_wal_size_mb, wal_segment_size) - 1; maxSegNo = lastredoptr / wal_segment_size + ConvertToXSegs(max_wal_size_mb, wal_segment_size) - 1; /* * Between those limits, recycle enough segments to get us through to the * estimated end of next checkpoint. * * To estimate where the next checkpoint will finish, assume that the * system runs steadily consuming CheckPointDistanceEstimate bytes between * every checkpoint. */ distance = (1.0 + CheckPointCompletionTarget) * CheckPointDistanceEstimate; /* add 10% for good measure. */ distance *= 1.10; recycleSegNo = (XLogSegNo) ceil(((double) lastredoptr + distance) / wal_segment_size); if (recycleSegNo < minSegNo) recycleSegNo = minSegNo; if (recycleSegNo > maxSegNo) recycleSegNo = maxSegNo; return recycleSegNo; } /* * Check whether we've consumed enough xlog space that a checkpoint is needed. * * new_segno indicates a log file that has just been filled up (or read * during recovery). We measure the distance from RedoRecPtr to new_segno * and see if that exceeds CheckPointSegments. * * Note: it is caller's responsibility that RedoRecPtr is up-to-date. */ bool XLogCheckpointNeeded(XLogSegNo new_segno) { XLogSegNo old_segno; XLByteToSeg(RedoRecPtr, old_segno, wal_segment_size); if (new_segno >= old_segno + (uint64) (CheckPointSegments - 1)) return true; return false; } /* * Write and/or fsync the log at least as far as WriteRqst indicates. * * If flexible == true, we don't have to write as far as WriteRqst, but * may stop at any convenient boundary (such as a cache or logfile boundary). * This option allows us to avoid uselessly issuing multiple writes when a * single one would do. * * Must be called with WALWriteLock held. WaitXLogInsertionsToFinish(WriteRqst) * must be called before grabbing the lock, to make sure the data is ready to * write. */ static void XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible) { bool ispartialpage; bool last_iteration; bool finishing_seg; int curridx; int npages; int startidx; uint32 startoffset; /* We should always be inside a critical section here */ Assert(CritSectionCount > 0); /* * Update local LogwrtResult (caller probably did this already, but...) */ LogwrtResult = XLogCtl->LogwrtResult; /* * Since successive pages in the xlog cache are consecutively allocated, * we can usually gather multiple pages together and issue just one * write() call. npages is the number of pages we have determined can be * written together; startidx is the cache block index of the first one, * and startoffset is the file offset at which it should go. The latter * two variables are only valid when npages > 0, but we must initialize * all of them to keep the compiler quiet. */ npages = 0; startidx = 0; startoffset = 0; /* * Within the loop, curridx is the cache block index of the page to * consider writing. Begin at the buffer containing the next unwritten * page, or last partially written page. */ curridx = XLogRecPtrToBufIdx(LogwrtResult.Write); while (LogwrtResult.Write < WriteRqst.Write) { /* * Make sure we're not ahead of the insert process. This could happen * if we're passed a bogus WriteRqst.Write that is past the end of the * last page that's been initialized by AdvanceXLInsertBuffer. */ XLogRecPtr EndPtr = XLogCtl->xlblocks[curridx]; if (LogwrtResult.Write >= EndPtr) elog(PANIC, "xlog write request %X/%X is past end of log %X/%X", LSN_FORMAT_ARGS(LogwrtResult.Write), LSN_FORMAT_ARGS(EndPtr)); /* Advance LogwrtResult.Write to end of current buffer page */ LogwrtResult.Write = EndPtr; ispartialpage = WriteRqst.Write < LogwrtResult.Write; if (!XLByteInPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size)) { /* * Switch to new logfile segment. We cannot have any pending * pages here (since we dump what we have at segment end). */ Assert(npages == 0); if (openLogFile >= 0) XLogFileClose(); XLByteToPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size); openLogTLI = tli; /* create/use new log file */ openLogFile = XLogFileInit(openLogSegNo, tli); ReserveExternalFD(); } /* Make sure we have the current logfile open */ if (openLogFile < 0) { XLByteToPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size); openLogTLI = tli; openLogFile = XLogFileOpen(openLogSegNo, tli); ReserveExternalFD(); } /* Add current page to the set of pending pages-to-dump */ if (npages == 0) { /* first of group */ startidx = curridx; startoffset = XLogSegmentOffset(LogwrtResult.Write - XLOG_BLCKSZ, wal_segment_size); } npages++; /* * Dump the set if this will be the last loop iteration, or if we are * at the last page of the cache area (since the next page won't be * contiguous in memory), or if we are at the end of the logfile * segment. */ last_iteration = WriteRqst.Write <= LogwrtResult.Write; finishing_seg = !ispartialpage && (startoffset + npages * XLOG_BLCKSZ) >= wal_segment_size; if (last_iteration || curridx == XLogCtl->XLogCacheBlck || finishing_seg) { char *from; Size nbytes; Size nleft; int written; instr_time start; /* OK to write the page(s) */ from = XLogCtl->pages + startidx * (Size) XLOG_BLCKSZ; nbytes = npages * (Size) XLOG_BLCKSZ; nleft = nbytes; do { errno = 0; /* Measure I/O timing to write WAL data */ if (track_wal_io_timing) INSTR_TIME_SET_CURRENT(start); else INSTR_TIME_SET_ZERO(start); pgstat_report_wait_start(WAIT_EVENT_WAL_WRITE); written = pg_pwrite(openLogFile, from, nleft, startoffset); pgstat_report_wait_end(); /* * Increment the I/O timing and the number of times WAL data * were written out to disk. */ if (track_wal_io_timing) { instr_time duration; INSTR_TIME_SET_CURRENT(duration); INSTR_TIME_ACCUM_DIFF(PendingWalStats.wal_write_time, duration, start); } PendingWalStats.wal_write++; if (written <= 0) { char xlogfname[MAXFNAMELEN]; int save_errno; if (errno == EINTR) continue; save_errno = errno; XLogFileName(xlogfname, tli, openLogSegNo, wal_segment_size); errno = save_errno; ereport(PANIC, (errcode_for_file_access(), errmsg("could not write to log file %s " "at offset %u, length %zu: %m", xlogfname, startoffset, nleft))); } nleft -= written; from += written; startoffset += written; } while (nleft > 0); npages = 0; /* * If we just wrote the whole last page of a logfile segment, * fsync the segment immediately. This avoids having to go back * and re-open prior segments when an fsync request comes along * later. Doing it here ensures that one and only one backend will * perform this fsync. * * This is also the right place to notify the Archiver that the * segment is ready to copy to archival storage, and to update the * timer for archive_timeout, and to signal for a checkpoint if * too many logfile segments have been used since the last * checkpoint. */ if (finishing_seg) { issue_xlog_fsync(openLogFile, openLogSegNo, tli); /* signal that we need to wakeup walsenders later */ WalSndWakeupRequest(); LogwrtResult.Flush = LogwrtResult.Write; /* end of page */ if (XLogArchivingActive()) XLogArchiveNotifySeg(openLogSegNo, tli); XLogCtl->lastSegSwitchTime = (pg_time_t) time(NULL); XLogCtl->lastSegSwitchLSN = LogwrtResult.Flush; /* * Request a checkpoint if we've consumed too much xlog since * the last one. For speed, we first check using the local * copy of RedoRecPtr, which might be out of date; if it looks * like a checkpoint is needed, forcibly update RedoRecPtr and * recheck. */ if (IsUnderPostmaster && XLogCheckpointNeeded(openLogSegNo)) { (void) GetRedoRecPtr(); if (XLogCheckpointNeeded(openLogSegNo)) RequestCheckpoint(CHECKPOINT_CAUSE_XLOG); } } } if (ispartialpage) { /* Only asked to write a partial page */ LogwrtResult.Write = WriteRqst.Write; break; } curridx = NextBufIdx(curridx); /* If flexible, break out of loop as soon as we wrote something */ if (flexible && npages == 0) break; } Assert(npages == 0); /* * If asked to flush, do so */ if (LogwrtResult.Flush < WriteRqst.Flush && LogwrtResult.Flush < LogwrtResult.Write) { /* * Could get here without iterating above loop, in which case we might * have no open file or the wrong one. However, we do not need to * fsync more than one file. */ if (sync_method != SYNC_METHOD_OPEN && sync_method != SYNC_METHOD_OPEN_DSYNC) { if (openLogFile >= 0 && !XLByteInPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size)) XLogFileClose(); if (openLogFile < 0) { XLByteToPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size); openLogTLI = tli; openLogFile = XLogFileOpen(openLogSegNo, tli); ReserveExternalFD(); } issue_xlog_fsync(openLogFile, openLogSegNo, tli); } /* signal that we need to wakeup walsenders later */ WalSndWakeupRequest(); LogwrtResult.Flush = LogwrtResult.Write; } /* * Update shared-memory status * * We make sure that the shared 'request' values do not fall behind the * 'result' values. This is not absolutely essential, but it saves some * code in a couple of places. */ { SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->LogwrtResult = LogwrtResult; if (XLogCtl->LogwrtRqst.Write < LogwrtResult.Write) XLogCtl->LogwrtRqst.Write = LogwrtResult.Write; if (XLogCtl->LogwrtRqst.Flush < LogwrtResult.Flush) XLogCtl->LogwrtRqst.Flush = LogwrtResult.Flush; SpinLockRelease(&XLogCtl->info_lck); } } /* * Record the LSN for an asynchronous transaction commit/abort * and nudge the WALWriter if there is work for it to do. * (This should not be called for synchronous commits.) */ void XLogSetAsyncXactLSN(XLogRecPtr asyncXactLSN) { XLogRecPtr WriteRqstPtr = asyncXactLSN; bool sleeping; SpinLockAcquire(&XLogCtl->info_lck); LogwrtResult = XLogCtl->LogwrtResult; sleeping = XLogCtl->WalWriterSleeping; if (XLogCtl->asyncXactLSN < asyncXactLSN) XLogCtl->asyncXactLSN = asyncXactLSN; SpinLockRelease(&XLogCtl->info_lck); /* * If the WALWriter is sleeping, we should kick it to make it come out of * low-power mode. Otherwise, determine whether there's a full page of * WAL available to write. */ if (!sleeping) { /* back off to last completed page boundary */ WriteRqstPtr -= WriteRqstPtr % XLOG_BLCKSZ; /* if we have already flushed that far, we're done */ if (WriteRqstPtr <= LogwrtResult.Flush) return; } /* * Nudge the WALWriter: it has a full page of WAL to write, or we want it * to come out of low-power mode so that this async commit will reach disk * within the expected amount of time. */ if (ProcGlobal->walwriterLatch) SetLatch(ProcGlobal->walwriterLatch); } /* * Record the LSN up to which we can remove WAL because it's not required by * any replication slot. */ void XLogSetReplicationSlotMinimumLSN(XLogRecPtr lsn) { SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->replicationSlotMinLSN = lsn; SpinLockRelease(&XLogCtl->info_lck); } /* * Return the oldest LSN we must retain to satisfy the needs of some * replication slot. */ static XLogRecPtr XLogGetReplicationSlotMinimumLSN(void) { XLogRecPtr retval; SpinLockAcquire(&XLogCtl->info_lck); retval = XLogCtl->replicationSlotMinLSN; SpinLockRelease(&XLogCtl->info_lck); return retval; } /* * Advance minRecoveryPoint in control file. * * If we crash during recovery, we must reach this point again before the * database is consistent. * * If 'force' is true, 'lsn' argument is ignored. Otherwise, minRecoveryPoint * is only updated if it's not already greater than or equal to 'lsn'. */ static void UpdateMinRecoveryPoint(XLogRecPtr lsn, bool force) { /* Quick check using our local copy of the variable */ if (!updateMinRecoveryPoint || (!force && lsn <= LocalMinRecoveryPoint)) return; /* * An invalid minRecoveryPoint means that we need to recover all the WAL, * i.e., we're doing crash recovery. We never modify the control file's * value in that case, so we can short-circuit future checks here too. The * local values of minRecoveryPoint and minRecoveryPointTLI should not be * updated until crash recovery finishes. We only do this for the startup * process as it should not update its own reference of minRecoveryPoint * until it has finished crash recovery to make sure that all WAL * available is replayed in this case. This also saves from extra locks * taken on the control file from the startup process. */ if (XLogRecPtrIsInvalid(LocalMinRecoveryPoint) && InRecovery) { updateMinRecoveryPoint = false; return; } LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); /* update local copy */ LocalMinRecoveryPoint = ControlFile->minRecoveryPoint; LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI; if (XLogRecPtrIsInvalid(LocalMinRecoveryPoint)) updateMinRecoveryPoint = false; else if (force || LocalMinRecoveryPoint < lsn) { XLogRecPtr newMinRecoveryPoint; TimeLineID newMinRecoveryPointTLI; /* * To avoid having to update the control file too often, we update it * all the way to the last record being replayed, even though 'lsn' * would suffice for correctness. This also allows the 'force' case * to not need a valid 'lsn' value. * * Another important reason for doing it this way is that the passed * 'lsn' value could be bogus, i.e., past the end of available WAL, if * the caller got it from a corrupted heap page. Accepting such a * value as the min recovery point would prevent us from coming up at * all. Instead, we just log a warning and continue with recovery. * (See also the comments about corrupt LSNs in XLogFlush.) */ newMinRecoveryPoint = GetCurrentReplayRecPtr(&newMinRecoveryPointTLI); if (!force && newMinRecoveryPoint < lsn) elog(WARNING, "xlog min recovery request %X/%X is past current point %X/%X", LSN_FORMAT_ARGS(lsn), LSN_FORMAT_ARGS(newMinRecoveryPoint)); /* update control file */ if (ControlFile->minRecoveryPoint < newMinRecoveryPoint) { ControlFile->minRecoveryPoint = newMinRecoveryPoint; ControlFile->minRecoveryPointTLI = newMinRecoveryPointTLI; UpdateControlFile(); LocalMinRecoveryPoint = newMinRecoveryPoint; LocalMinRecoveryPointTLI = newMinRecoveryPointTLI; ereport(DEBUG2, (errmsg_internal("updated min recovery point to %X/%X on timeline %u", LSN_FORMAT_ARGS(newMinRecoveryPoint), newMinRecoveryPointTLI))); } } LWLockRelease(ControlFileLock); } /* * Ensure that all XLOG data through the given position is flushed to disk. * * NOTE: this differs from XLogWrite mainly in that the WALWriteLock is not * already held, and we try to avoid acquiring it if possible. */ void XLogFlush(XLogRecPtr record) { XLogRecPtr WriteRqstPtr; XLogwrtRqst WriteRqst; TimeLineID insertTLI = XLogCtl->InsertTimeLineID; /* * During REDO, we are reading not writing WAL. Therefore, instead of * trying to flush the WAL, we should update minRecoveryPoint instead. We * test XLogInsertAllowed(), not InRecovery, because we need checkpointer * to act this way too, and because when it tries to write the * end-of-recovery checkpoint, it should indeed flush. */ if (!XLogInsertAllowed()) { UpdateMinRecoveryPoint(record, false); return; } /* Quick exit if already known flushed */ if (record <= LogwrtResult.Flush) return; #ifdef WAL_DEBUG if (XLOG_DEBUG) elog(LOG, "xlog flush request %X/%X; write %X/%X; flush %X/%X", LSN_FORMAT_ARGS(record), LSN_FORMAT_ARGS(LogwrtResult.Write), LSN_FORMAT_ARGS(LogwrtResult.Flush)); #endif START_CRIT_SECTION(); /* * Since fsync is usually a horribly expensive operation, we try to * piggyback as much data as we can on each fsync: if we see any more data * entered into the xlog buffer, we'll write and fsync that too, so that * the final value of LogwrtResult.Flush is as large as possible. This * gives us some chance of avoiding another fsync immediately after. */ /* initialize to given target; may increase below */ WriteRqstPtr = record; /* * Now wait until we get the write lock, or someone else does the flush * for us. */ for (;;) { XLogRecPtr insertpos; /* read LogwrtResult and update local state */ SpinLockAcquire(&XLogCtl->info_lck); if (WriteRqstPtr < XLogCtl->LogwrtRqst.Write) WriteRqstPtr = XLogCtl->LogwrtRqst.Write; LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); /* done already? */ if (record <= LogwrtResult.Flush) break; /* * Before actually performing the write, wait for all in-flight * insertions to the pages we're about to write to finish. */ insertpos = WaitXLogInsertionsToFinish(WriteRqstPtr); /* * Try to get the write lock. If we can't get it immediately, wait * until it's released, and recheck if we still need to do the flush * or if the backend that held the lock did it for us already. This * helps to maintain a good rate of group committing when the system * is bottlenecked by the speed of fsyncing. */ if (!LWLockAcquireOrWait(WALWriteLock, LW_EXCLUSIVE)) { /* * The lock is now free, but we didn't acquire it yet. Before we * do, loop back to check if someone else flushed the record for * us already. */ continue; } /* Got the lock; recheck whether request is satisfied */ LogwrtResult = XLogCtl->LogwrtResult; if (record <= LogwrtResult.Flush) { LWLockRelease(WALWriteLock); break; } /* * Sleep before flush! By adding a delay here, we may give further * backends the opportunity to join the backlog of group commit * followers; this can significantly improve transaction throughput, * at the risk of increasing transaction latency. * * We do not sleep if enableFsync is not turned on, nor if there are * fewer than CommitSiblings other backends with active transactions. */ if (CommitDelay > 0 && enableFsync && MinimumActiveBackends(CommitSiblings)) { pg_usleep(CommitDelay); /* * Re-check how far we can now flush the WAL. It's generally not * safe to call WaitXLogInsertionsToFinish while holding * WALWriteLock, because an in-progress insertion might need to * also grab WALWriteLock to make progress. But we know that all * the insertions up to insertpos have already finished, because * that's what the earlier WaitXLogInsertionsToFinish() returned. * We're only calling it again to allow insertpos to be moved * further forward, not to actually wait for anyone. */ insertpos = WaitXLogInsertionsToFinish(insertpos); } /* try to write/flush later additions to XLOG as well */ WriteRqst.Write = insertpos; WriteRqst.Flush = insertpos; XLogWrite(WriteRqst, insertTLI, false); LWLockRelease(WALWriteLock); /* done */ break; } END_CRIT_SECTION(); /* wake up walsenders now that we've released heavily contended locks */ WalSndWakeupProcessRequests(true, !RecoveryInProgress()); /* * If we still haven't flushed to the request point then we have a * problem; most likely, the requested flush point is past end of XLOG. * This has been seen to occur when a disk page has a corrupted LSN. * * Formerly we treated this as a PANIC condition, but that hurts the * system's robustness rather than helping it: we do not want to take down * the whole system due to corruption on one data page. In particular, if * the bad page is encountered again during recovery then we would be * unable to restart the database at all! (This scenario actually * happened in the field several times with 7.1 releases.) As of 8.4, bad * LSNs encountered during recovery are UpdateMinRecoveryPoint's problem; * the only time we can reach here during recovery is while flushing the * end-of-recovery checkpoint record, and we don't expect that to have a * bad LSN. * * Note that for calls from xact.c, the ERROR will be promoted to PANIC * since xact.c calls this routine inside a critical section. However, * calls from bufmgr.c are not within critical sections and so we will not * force a restart for a bad LSN on a data page. */ if (LogwrtResult.Flush < record) elog(ERROR, "xlog flush request %X/%X is not satisfied --- flushed only to %X/%X", LSN_FORMAT_ARGS(record), LSN_FORMAT_ARGS(LogwrtResult.Flush)); } /* * Write & flush xlog, but without specifying exactly where to. * * We normally write only completed blocks; but if there is nothing to do on * that basis, we check for unwritten async commits in the current incomplete * block, and write through the latest one of those. Thus, if async commits * are not being used, we will write complete blocks only. * * If, based on the above, there's anything to write we do so immediately. But * to avoid calling fsync, fdatasync et. al. at a rate that'd impact * concurrent IO, we only flush WAL every wal_writer_delay ms, or if there's * more than wal_writer_flush_after unflushed blocks. * * We can guarantee that async commits reach disk after at most three * wal_writer_delay cycles. (When flushing complete blocks, we allow XLogWrite * to write "flexibly", meaning it can stop at the end of the buffer ring; * this makes a difference only with very high load or long wal_writer_delay, * but imposes one extra cycle for the worst case for async commits.) * * This routine is invoked periodically by the background walwriter process. * * Returns true if there was any work to do, even if we skipped flushing due * to wal_writer_delay/wal_writer_flush_after. */ bool XLogBackgroundFlush(void) { XLogwrtRqst WriteRqst; bool flexible = true; static TimestampTz lastflush; TimestampTz now; int flushbytes; TimeLineID insertTLI; /* XLOG doesn't need flushing during recovery */ if (RecoveryInProgress()) return false; /* * Since we're not in recovery, InsertTimeLineID is set and can't change, * so we can read it without a lock. */ insertTLI = XLogCtl->InsertTimeLineID; /* read LogwrtResult and update local state */ SpinLockAcquire(&XLogCtl->info_lck); LogwrtResult = XLogCtl->LogwrtResult; WriteRqst = XLogCtl->LogwrtRqst; SpinLockRelease(&XLogCtl->info_lck); /* back off to last completed page boundary */ WriteRqst.Write -= WriteRqst.Write % XLOG_BLCKSZ; /* if we have already flushed that far, consider async commit records */ if (WriteRqst.Write <= LogwrtResult.Flush) { SpinLockAcquire(&XLogCtl->info_lck); WriteRqst.Write = XLogCtl->asyncXactLSN; SpinLockRelease(&XLogCtl->info_lck); flexible = false; /* ensure it all gets written */ } /* * If already known flushed, we're done. Just need to check if we are * holding an open file handle to a logfile that's no longer in use, * preventing the file from being deleted. */ if (WriteRqst.Write <= LogwrtResult.Flush) { if (openLogFile >= 0) { if (!XLByteInPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size)) { XLogFileClose(); } } return false; } /* * Determine how far to flush WAL, based on the wal_writer_delay and * wal_writer_flush_after GUCs. */ now = GetCurrentTimestamp(); flushbytes = WriteRqst.Write / XLOG_BLCKSZ - LogwrtResult.Flush / XLOG_BLCKSZ; if (WalWriterFlushAfter == 0 || lastflush == 0) { /* first call, or block based limits disabled */ WriteRqst.Flush = WriteRqst.Write; lastflush = now; } else if (TimestampDifferenceExceeds(lastflush, now, WalWriterDelay)) { /* * Flush the writes at least every WalWriterDelay ms. This is * important to bound the amount of time it takes for an asynchronous * commit to hit disk. */ WriteRqst.Flush = WriteRqst.Write; lastflush = now; } else if (flushbytes >= WalWriterFlushAfter) { /* exceeded wal_writer_flush_after blocks, flush */ WriteRqst.Flush = WriteRqst.Write; lastflush = now; } else { /* no flushing, this time round */ WriteRqst.Flush = 0; } #ifdef WAL_DEBUG if (XLOG_DEBUG) elog(LOG, "xlog bg flush request write %X/%X; flush: %X/%X, current is write %X/%X; flush %X/%X", LSN_FORMAT_ARGS(WriteRqst.Write), LSN_FORMAT_ARGS(WriteRqst.Flush), LSN_FORMAT_ARGS(LogwrtResult.Write), LSN_FORMAT_ARGS(LogwrtResult.Flush)); #endif START_CRIT_SECTION(); /* now wait for any in-progress insertions to finish and get write lock */ WaitXLogInsertionsToFinish(WriteRqst.Write); LWLockAcquire(WALWriteLock, LW_EXCLUSIVE); LogwrtResult = XLogCtl->LogwrtResult; if (WriteRqst.Write > LogwrtResult.Write || WriteRqst.Flush > LogwrtResult.Flush) { XLogWrite(WriteRqst, insertTLI, flexible); } LWLockRelease(WALWriteLock); END_CRIT_SECTION(); /* wake up walsenders now that we've released heavily contended locks */ WalSndWakeupProcessRequests(true, !RecoveryInProgress()); /* * Great, done. To take some work off the critical path, try to initialize * as many of the no-longer-needed WAL buffers for future use as we can. */ AdvanceXLInsertBuffer(InvalidXLogRecPtr, insertTLI, true); /* * If we determined that we need to write data, but somebody else * wrote/flushed already, it should be considered as being active, to * avoid hibernating too early. */ return true; } /* * Test whether XLOG data has been flushed up to (at least) the given position. * * Returns true if a flush is still needed. (It may be that someone else * is already in process of flushing that far, however.) */ bool XLogNeedsFlush(XLogRecPtr record) { /* * During recovery, we don't flush WAL but update minRecoveryPoint * instead. So "needs flush" is taken to mean whether minRecoveryPoint * would need to be updated. */ if (RecoveryInProgress()) { /* * An invalid minRecoveryPoint means that we need to recover all the * WAL, i.e., we're doing crash recovery. We never modify the control * file's value in that case, so we can short-circuit future checks * here too. This triggers a quick exit path for the startup process, * which cannot update its local copy of minRecoveryPoint as long as * it has not replayed all WAL available when doing crash recovery. */ if (XLogRecPtrIsInvalid(LocalMinRecoveryPoint) && InRecovery) updateMinRecoveryPoint = false; /* Quick exit if already known to be updated or cannot be updated */ if (record <= LocalMinRecoveryPoint || !updateMinRecoveryPoint) return false; /* * Update local copy of minRecoveryPoint. But if the lock is busy, * just return a conservative guess. */ if (!LWLockConditionalAcquire(ControlFileLock, LW_SHARED)) return true; LocalMinRecoveryPoint = ControlFile->minRecoveryPoint; LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI; LWLockRelease(ControlFileLock); /* * Check minRecoveryPoint for any other process than the startup * process doing crash recovery, which should not update the control * file value if crash recovery is still running. */ if (XLogRecPtrIsInvalid(LocalMinRecoveryPoint)) updateMinRecoveryPoint = false; /* check again */ if (record <= LocalMinRecoveryPoint || !updateMinRecoveryPoint) return false; else return true; } /* Quick exit if already known flushed */ if (record <= LogwrtResult.Flush) return false; /* read LogwrtResult and update local state */ SpinLockAcquire(&XLogCtl->info_lck); LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); /* check again */ if (record <= LogwrtResult.Flush) return false; return true; } /* * Try to make a given XLOG file segment exist. * * logsegno: identify segment. * * *added: on return, true if this call raised the number of extant segments. * * path: on return, this char[MAXPGPATH] has the path to the logsegno file. * * Returns -1 or FD of opened file. A -1 here is not an error; a caller * wanting an open segment should attempt to open "path", which usually will * succeed. (This is weird, but it's efficient for the callers.) */ static int XLogFileInitInternal(XLogSegNo logsegno, TimeLineID logtli, bool *added, char *path) { char tmppath[MAXPGPATH]; XLogSegNo installed_segno; XLogSegNo max_segno; int fd; int save_errno; int open_flags = O_RDWR | O_CREAT | O_EXCL | PG_BINARY; Assert(logtli != 0); XLogFilePath(path, logtli, logsegno, wal_segment_size); /* * Try to use existent file (checkpoint maker may have created it already) */ *added = false; fd = BasicOpenFile(path, O_RDWR | PG_BINARY | O_CLOEXEC | get_sync_bit(sync_method)); if (fd < 0) { if (errno != ENOENT) ereport(ERROR, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", path))); } else return fd; /* * Initialize an empty (all zeroes) segment. NOTE: it is possible that * another process is doing the same thing. If so, we will end up * pre-creating an extra log segment. That seems OK, and better than * holding the lock throughout this lengthy process. */ elog(DEBUG2, "creating and filling new WAL file"); snprintf(tmppath, MAXPGPATH, XLOGDIR "/xlogtemp.%d", (int) getpid()); unlink(tmppath); if (io_direct_flags & IO_DIRECT_WAL_INIT) open_flags |= PG_O_DIRECT; /* do not use get_sync_bit() here --- want to fsync only at end of fill */ fd = BasicOpenFile(tmppath, open_flags); if (fd < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", tmppath))); pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_WRITE); save_errno = 0; if (wal_init_zero) { ssize_t rc; /* * Zero-fill the file. With this setting, we do this the hard way to * ensure that all the file space has really been allocated. On * platforms that allow "holes" in files, just seeking to the end * doesn't allocate intermediate space. This way, we know that we * have all the space and (after the fsync below) that all the * indirect blocks are down on disk. Therefore, fdatasync(2) or * O_DSYNC will be sufficient to sync future writes to the log file. */ rc = pg_pwrite_zeros(fd, wal_segment_size, 0); if (rc < 0) save_errno = errno; } else { /* * Otherwise, seeking to the end and writing a solitary byte is * enough. */ errno = 0; if (pg_pwrite(fd, "\0", 1, wal_segment_size - 1) != 1) { /* if write didn't set errno, assume no disk space */ save_errno = errno ? errno : ENOSPC; } } pgstat_report_wait_end(); if (save_errno) { /* * If we fail to make the file, delete it to release disk space */ unlink(tmppath); close(fd); errno = save_errno; ereport(ERROR, (errcode_for_file_access(), errmsg("could not write to file \"%s\": %m", tmppath))); } pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_SYNC); if (pg_fsync(fd) != 0) { save_errno = errno; close(fd); errno = save_errno; ereport(ERROR, (errcode_for_file_access(), errmsg("could not fsync file \"%s\": %m", tmppath))); } pgstat_report_wait_end(); if (close(fd) != 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", tmppath))); /* * Now move the segment into place with its final name. Cope with * possibility that someone else has created the file while we were * filling ours: if so, use ours to pre-create a future log segment. */ installed_segno = logsegno; /* * XXX: What should we use as max_segno? We used to use XLOGfileslop when * that was a constant, but that was always a bit dubious: normally, at a * checkpoint, XLOGfileslop was the offset from the checkpoint record, but * here, it was the offset from the insert location. We can't do the * normal XLOGfileslop calculation here because we don't have access to * the prior checkpoint's redo location. So somewhat arbitrarily, just use * CheckPointSegments. */ max_segno = logsegno + CheckPointSegments; if (InstallXLogFileSegment(&installed_segno, tmppath, true, max_segno, logtli)) { *added = true; elog(DEBUG2, "done creating and filling new WAL file"); } else { /* * No need for any more future segments, or InstallXLogFileSegment() * failed to rename the file into place. If the rename failed, a * caller opening the file may fail. */ unlink(tmppath); elog(DEBUG2, "abandoned new WAL file"); } return -1; } /* * Create a new XLOG file segment, or open a pre-existing one. * * logsegno: identify segment to be created/opened. * * Returns FD of opened file. * * Note: errors here are ERROR not PANIC because we might or might not be * inside a critical section (eg, during checkpoint there is no reason to * take down the system on failure). They will promote to PANIC if we are * in a critical section. */ int XLogFileInit(XLogSegNo logsegno, TimeLineID logtli) { bool ignore_added; char path[MAXPGPATH]; int fd; Assert(logtli != 0); fd = XLogFileInitInternal(logsegno, logtli, &ignore_added, path); if (fd >= 0) return fd; /* Now open original target segment (might not be file I just made) */ fd = BasicOpenFile(path, O_RDWR | PG_BINARY | O_CLOEXEC | get_sync_bit(sync_method)); if (fd < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", path))); return fd; } /* * Create a new XLOG file segment by copying a pre-existing one. * * destsegno: identify segment to be created. * * srcTLI, srcsegno: identify segment to be copied (could be from * a different timeline) * * upto: how much of the source file to copy (the rest is filled with * zeros) * * Currently this is only used during recovery, and so there are no locking * considerations. But we should be just as tense as XLogFileInit to avoid * emplacing a bogus file. */ static void XLogFileCopy(TimeLineID destTLI, XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno, int upto) { char path[MAXPGPATH]; char tmppath[MAXPGPATH]; PGAlignedXLogBlock buffer; int srcfd; int fd; int nbytes; /* * Open the source file */ XLogFilePath(path, srcTLI, srcsegno, wal_segment_size); srcfd = OpenTransientFile(path, O_RDONLY | PG_BINARY); if (srcfd < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", path))); /* * Copy into a temp file name. */ snprintf(tmppath, MAXPGPATH, XLOGDIR "/xlogtemp.%d", (int) getpid()); unlink(tmppath); /* do not use get_sync_bit() here --- want to fsync only at end of fill */ fd = OpenTransientFile(tmppath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY); if (fd < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", tmppath))); /* * Do the data copying. */ for (nbytes = 0; nbytes < wal_segment_size; nbytes += sizeof(buffer)) { int nread; nread = upto - nbytes; /* * The part that is not read from the source file is filled with * zeros. */ if (nread < sizeof(buffer)) memset(buffer.data, 0, sizeof(buffer)); if (nread > 0) { int r; if (nread > sizeof(buffer)) nread = sizeof(buffer); pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_READ); r = read(srcfd, buffer.data, nread); if (r != nread) { if (r < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", path))); else ereport(ERROR, (errcode(ERRCODE_DATA_CORRUPTED), errmsg("could not read file \"%s\": read %d of %zu", path, r, (Size) nread))); } pgstat_report_wait_end(); } errno = 0; pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_WRITE); if ((int) write(fd, buffer.data, sizeof(buffer)) != (int) sizeof(buffer)) { int save_errno = errno; /* * If we fail to make the file, delete it to release disk space */ unlink(tmppath); /* if write didn't set errno, assume problem is no disk space */ errno = save_errno ? save_errno : ENOSPC; ereport(ERROR, (errcode_for_file_access(), errmsg("could not write to file \"%s\": %m", tmppath))); } pgstat_report_wait_end(); } pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_SYNC); if (pg_fsync(fd) != 0) ereport(data_sync_elevel(ERROR), (errcode_for_file_access(), errmsg("could not fsync file \"%s\": %m", tmppath))); pgstat_report_wait_end(); if (CloseTransientFile(fd) != 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", tmppath))); if (CloseTransientFile(srcfd) != 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", path))); /* * Now move the segment into place with its final name. */ if (!InstallXLogFileSegment(&destsegno, tmppath, false, 0, destTLI)) elog(ERROR, "InstallXLogFileSegment should not have failed"); } /* * Install a new XLOG segment file as a current or future log segment. * * This is used both to install a newly-created segment (which has a temp * filename while it's being created) and to recycle an old segment. * * *segno: identify segment to install as (or first possible target). * When find_free is true, this is modified on return to indicate the * actual installation location or last segment searched. * * tmppath: initial name of file to install. It will be renamed into place. * * find_free: if true, install the new segment at the first empty segno * number at or after the passed numbers. If false, install the new segment * exactly where specified, deleting any existing segment file there. * * max_segno: maximum segment number to install the new file as. Fail if no * free slot is found between *segno and max_segno. (Ignored when find_free * is false.) * * tli: The timeline on which the new segment should be installed. * * Returns true if the file was installed successfully. false indicates that * max_segno limit was exceeded, the startup process has disabled this * function for now, or an error occurred while renaming the file into place. */ static bool InstallXLogFileSegment(XLogSegNo *segno, char *tmppath, bool find_free, XLogSegNo max_segno, TimeLineID tli) { char path[MAXPGPATH]; struct stat stat_buf; Assert(tli != 0); XLogFilePath(path, tli, *segno, wal_segment_size); LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); if (!XLogCtl->InstallXLogFileSegmentActive) { LWLockRelease(ControlFileLock); return false; } if (!find_free) { /* Force installation: get rid of any pre-existing segment file */ durable_unlink(path, DEBUG1); } else { /* Find a free slot to put it in */ while (stat(path, &stat_buf) == 0) { if ((*segno) >= max_segno) { /* Failed to find a free slot within specified range */ LWLockRelease(ControlFileLock); return false; } (*segno)++; XLogFilePath(path, tli, *segno, wal_segment_size); } } Assert(access(path, F_OK) != 0 && errno == ENOENT); if (durable_rename(tmppath, path, LOG) != 0) { LWLockRelease(ControlFileLock); /* durable_rename already emitted log message */ return false; } LWLockRelease(ControlFileLock); return true; } /* * Open a pre-existing logfile segment for writing. */ int XLogFileOpen(XLogSegNo segno, TimeLineID tli) { char path[MAXPGPATH]; int fd; XLogFilePath(path, tli, segno, wal_segment_size); fd = BasicOpenFile(path, O_RDWR | PG_BINARY | O_CLOEXEC | get_sync_bit(sync_method)); if (fd < 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", path))); return fd; } /* * Close the current logfile segment for writing. */ static void XLogFileClose(void) { Assert(openLogFile >= 0); /* * WAL segment files will not be re-read in normal operation, so we advise * the OS to release any cached pages. But do not do so if WAL archiving * or streaming is active, because archiver and walsender process could * use the cache to read the WAL segment. */ #if defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED) if (!XLogIsNeeded() && (io_direct_flags & IO_DIRECT_WAL) == 0) (void) posix_fadvise(openLogFile, 0, 0, POSIX_FADV_DONTNEED); #endif if (close(openLogFile) != 0) { char xlogfname[MAXFNAMELEN]; int save_errno = errno; XLogFileName(xlogfname, openLogTLI, openLogSegNo, wal_segment_size); errno = save_errno; ereport(PANIC, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", xlogfname))); } openLogFile = -1; ReleaseExternalFD(); } /* * Preallocate log files beyond the specified log endpoint. * * XXX this is currently extremely conservative, since it forces only one * future log segment to exist, and even that only if we are 75% done with * the current one. This is only appropriate for very low-WAL-volume systems. * High-volume systems will be OK once they've built up a sufficient set of * recycled log segments, but the startup transient is likely to include * a lot of segment creations by foreground processes, which is not so good. * * XLogFileInitInternal() can ereport(ERROR). All known causes indicate big * trouble; for example, a full filesystem is one cause. The checkpoint WAL * and/or ControlFile updates already completed. If a RequestCheckpoint() * initiated the present checkpoint and an ERROR ends this function, the * command that called RequestCheckpoint() fails. That's not ideal, but it's * not worth contorting more functions to use caller-specified elevel values. * (With or without RequestCheckpoint(), an ERROR forestalls some inessential * reporting and resource reclamation.) */ static void PreallocXlogFiles(XLogRecPtr endptr, TimeLineID tli) { XLogSegNo _logSegNo; int lf; bool added; char path[MAXPGPATH]; uint64 offset; if (!XLogCtl->InstallXLogFileSegmentActive) return; /* unlocked check says no */ XLByteToPrevSeg(endptr, _logSegNo, wal_segment_size); offset = XLogSegmentOffset(endptr - 1, wal_segment_size); if (offset >= (uint32) (0.75 * wal_segment_size)) { _logSegNo++; lf = XLogFileInitInternal(_logSegNo, tli, &added, path); if (lf >= 0) close(lf); if (added) CheckpointStats.ckpt_segs_added++; } } /* * Throws an error if the given log segment has already been removed or * recycled. The caller should only pass a segment that it knows to have * existed while the server has been running, as this function always * succeeds if no WAL segments have been removed since startup. * 'tli' is only used in the error message. * * Note: this function guarantees to keep errno unchanged on return. * This supports callers that use this to possibly deliver a better * error message about a missing file, while still being able to throw * a normal file-access error afterwards, if this does return. */ void CheckXLogRemoved(XLogSegNo segno, TimeLineID tli) { int save_errno = errno; XLogSegNo lastRemovedSegNo; SpinLockAcquire(&XLogCtl->info_lck); lastRemovedSegNo = XLogCtl->lastRemovedSegNo; SpinLockRelease(&XLogCtl->info_lck); if (segno <= lastRemovedSegNo) { char filename[MAXFNAMELEN]; XLogFileName(filename, tli, segno, wal_segment_size); errno = save_errno; ereport(ERROR, (errcode_for_file_access(), errmsg("requested WAL segment %s has already been removed", filename))); } errno = save_errno; } /* * Return the last WAL segment removed, or 0 if no segment has been removed * since startup. * * NB: the result can be out of date arbitrarily fast, the caller has to deal * with that. */ XLogSegNo XLogGetLastRemovedSegno(void) { XLogSegNo lastRemovedSegNo; SpinLockAcquire(&XLogCtl->info_lck); lastRemovedSegNo = XLogCtl->lastRemovedSegNo; SpinLockRelease(&XLogCtl->info_lck); return lastRemovedSegNo; } /* * Update the last removed segno pointer in shared memory, to reflect that the * given XLOG file has been removed. */ static void UpdateLastRemovedPtr(char *filename) { uint32 tli; XLogSegNo segno; XLogFromFileName(filename, &tli, &segno, wal_segment_size); SpinLockAcquire(&XLogCtl->info_lck); if (segno > XLogCtl->lastRemovedSegNo) XLogCtl->lastRemovedSegNo = segno; SpinLockRelease(&XLogCtl->info_lck); } /* * Remove all temporary log files in pg_wal * * This is called at the beginning of recovery after a previous crash, * at a point where no other processes write fresh WAL data. */ static void RemoveTempXlogFiles(void) { DIR *xldir; struct dirent *xlde; elog(DEBUG2, "removing all temporary WAL segments"); xldir = AllocateDir(XLOGDIR); while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { char path[MAXPGPATH]; if (strncmp(xlde->d_name, "xlogtemp.", 9) != 0) continue; snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlde->d_name); unlink(path); elog(DEBUG2, "removed temporary WAL segment \"%s\"", path); } FreeDir(xldir); } /* * Recycle or remove all log files older or equal to passed segno. * * endptr is current (or recent) end of xlog, and lastredoptr is the * redo pointer of the last checkpoint. These are used to determine * whether we want to recycle rather than delete no-longer-wanted log files. * * insertTLI is the current timeline for XLOG insertion. Any recycled * segments should be reused for this timeline. */ static void RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr lastredoptr, XLogRecPtr endptr, TimeLineID insertTLI) { DIR *xldir; struct dirent *xlde; char lastoff[MAXFNAMELEN]; XLogSegNo endlogSegNo; XLogSegNo recycleSegNo; /* Initialize info about where to try to recycle to */ XLByteToSeg(endptr, endlogSegNo, wal_segment_size); recycleSegNo = XLOGfileslop(lastredoptr); /* * Construct a filename of the last segment to be kept. The timeline ID * doesn't matter, we ignore that in the comparison. (During recovery, * InsertTimeLineID isn't set, so we can't use that.) */ XLogFileName(lastoff, 0, segno, wal_segment_size); elog(DEBUG2, "attempting to remove WAL segments older than log file %s", lastoff); xldir = AllocateDir(XLOGDIR); while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { /* Ignore files that are not XLOG segments */ if (!IsXLogFileName(xlde->d_name) && !IsPartialXLogFileName(xlde->d_name)) continue; /* * We ignore the timeline part of the XLOG segment identifiers in * deciding whether a segment is still needed. This ensures that we * won't prematurely remove a segment from a parent timeline. We could * probably be a little more proactive about removing segments of * non-parent timelines, but that would be a whole lot more * complicated. * * We use the alphanumeric sorting property of the filenames to decide * which ones are earlier than the lastoff segment. */ if (strcmp(xlde->d_name + 8, lastoff + 8) <= 0) { if (XLogArchiveCheckDone(xlde->d_name)) { /* Update the last removed location in shared memory first */ UpdateLastRemovedPtr(xlde->d_name); RemoveXlogFile(xlde, recycleSegNo, &endlogSegNo, insertTLI); } } } FreeDir(xldir); } /* * Remove WAL files that are not part of the given timeline's history. * * This is called during recovery, whenever we switch to follow a new * timeline, and at the end of recovery when we create a new timeline. We * wouldn't otherwise care about extra WAL files lying in pg_wal, but they * might be leftover pre-allocated or recycled WAL segments on the old timeline * that we haven't used yet, and contain garbage. If we just leave them in * pg_wal, they will eventually be archived, and we can't let that happen. * Files that belong to our timeline history are valid, because we have * successfully replayed them, but from others we can't be sure. * * 'switchpoint' is the current point in WAL where we switch to new timeline, * and 'newTLI' is the new timeline we switch to. */ void RemoveNonParentXlogFiles(XLogRecPtr switchpoint, TimeLineID newTLI) { DIR *xldir; struct dirent *xlde; char switchseg[MAXFNAMELEN]; XLogSegNo endLogSegNo; XLogSegNo switchLogSegNo; XLogSegNo recycleSegNo; /* * Initialize info about where to begin the work. This will recycle, * somewhat arbitrarily, 10 future segments. */ XLByteToPrevSeg(switchpoint, switchLogSegNo, wal_segment_size); XLByteToSeg(switchpoint, endLogSegNo, wal_segment_size); recycleSegNo = endLogSegNo + 10; /* * Construct a filename of the last segment to be kept. */ XLogFileName(switchseg, newTLI, switchLogSegNo, wal_segment_size); elog(DEBUG2, "attempting to remove WAL segments newer than log file %s", switchseg); xldir = AllocateDir(XLOGDIR); while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { /* Ignore files that are not XLOG segments */ if (!IsXLogFileName(xlde->d_name)) continue; /* * Remove files that are on a timeline older than the new one we're * switching to, but with a segment number >= the first segment on the * new timeline. */ if (strncmp(xlde->d_name, switchseg, 8) < 0 && strcmp(xlde->d_name + 8, switchseg + 8) > 0) { /* * If the file has already been marked as .ready, however, don't * remove it yet. It should be OK to remove it - files that are * not part of our timeline history are not required for recovery * - but seems safer to let them be archived and removed later. */ if (!XLogArchiveIsReady(xlde->d_name)) RemoveXlogFile(xlde, recycleSegNo, &endLogSegNo, newTLI); } } FreeDir(xldir); } /* * Recycle or remove a log file that's no longer needed. * * segment_de is the dirent structure of the segment to recycle or remove. * recycleSegNo is the segment number to recycle up to. endlogSegNo is * the segment number of the current (or recent) end of WAL. * * endlogSegNo gets incremented if the segment is recycled so as it is not * checked again with future callers of this function. * * insertTLI is the current timeline for XLOG insertion. Any recycled segments * should be used for this timeline. */ static void RemoveXlogFile(const struct dirent *segment_de, XLogSegNo recycleSegNo, XLogSegNo *endlogSegNo, TimeLineID insertTLI) { char path[MAXPGPATH]; #ifdef WIN32 char newpath[MAXPGPATH]; #endif const char *segname = segment_de->d_name; snprintf(path, MAXPGPATH, XLOGDIR "/%s", segname); /* * Before deleting the file, see if it can be recycled as a future log * segment. Only recycle normal files, because we don't want to recycle * symbolic links pointing to a separate archive directory. */ if (wal_recycle && *endlogSegNo <= recycleSegNo && XLogCtl->InstallXLogFileSegmentActive && /* callee rechecks this */ get_dirent_type(path, segment_de, false, DEBUG2) == PGFILETYPE_REG && InstallXLogFileSegment(endlogSegNo, path, true, recycleSegNo, insertTLI)) { ereport(DEBUG2, (errmsg_internal("recycled write-ahead log file \"%s\"", segname))); CheckpointStats.ckpt_segs_recycled++; /* Needn't recheck that slot on future iterations */ (*endlogSegNo)++; } else { /* No need for any more future segments, or recycling failed ... */ int rc; ereport(DEBUG2, (errmsg_internal("removing write-ahead log file \"%s\"", segname))); #ifdef WIN32 /* * On Windows, if another process (e.g another backend) holds the file * open in FILE_SHARE_DELETE mode, unlink will succeed, but the file * will still show up in directory listing until the last handle is * closed. To avoid confusing the lingering deleted file for a live * WAL file that needs to be archived, rename it before deleting it. * * If another process holds the file open without FILE_SHARE_DELETE * flag, rename will fail. We'll try again at the next checkpoint. */ snprintf(newpath, MAXPGPATH, "%s.deleted", path); if (rename(path, newpath) != 0) { ereport(LOG, (errcode_for_file_access(), errmsg("could not rename file \"%s\": %m", path))); return; } rc = durable_unlink(newpath, LOG); #else rc = durable_unlink(path, LOG); #endif if (rc != 0) { /* Message already logged by durable_unlink() */ return; } CheckpointStats.ckpt_segs_removed++; } XLogArchiveCleanup(segname); } /* * Verify whether pg_wal and pg_wal/archive_status exist. * If the latter does not exist, recreate it. * * It is not the goal of this function to verify the contents of these * directories, but to help in cases where someone has performed a cluster * copy for PITR purposes but omitted pg_wal from the copy. * * We could also recreate pg_wal if it doesn't exist, but a deliberate * policy decision was made not to. It is fairly common for pg_wal to be * a symlink, and if that was the DBA's intent then automatically making a * plain directory would result in degraded performance with no notice. */ static void ValidateXLOGDirectoryStructure(void) { char path[MAXPGPATH]; struct stat stat_buf; /* Check for pg_wal; if it doesn't exist, error out */ if (stat(XLOGDIR, &stat_buf) != 0 || !S_ISDIR(stat_buf.st_mode)) ereport(FATAL, (errmsg("required WAL directory \"%s\" does not exist", XLOGDIR))); /* Check for archive_status */ snprintf(path, MAXPGPATH, XLOGDIR "/archive_status"); if (stat(path, &stat_buf) == 0) { /* Check for weird cases where it exists but isn't a directory */ if (!S_ISDIR(stat_buf.st_mode)) ereport(FATAL, (errmsg("required WAL directory \"%s\" does not exist", path))); } else { ereport(LOG, (errmsg("creating missing WAL directory \"%s\"", path))); if (MakePGDirectory(path) < 0) ereport(FATAL, (errmsg("could not create missing directory \"%s\": %m", path))); } } /* * Remove previous backup history files. This also retries creation of * .ready files for any backup history files for which XLogArchiveNotify * failed earlier. */ static void CleanupBackupHistory(void) { DIR *xldir; struct dirent *xlde; char path[MAXPGPATH + sizeof(XLOGDIR)]; xldir = AllocateDir(XLOGDIR); while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { if (IsBackupHistoryFileName(xlde->d_name)) { if (XLogArchiveCheckDone(xlde->d_name)) { elog(DEBUG2, "removing WAL backup history file \"%s\"", xlde->d_name); snprintf(path, sizeof(path), XLOGDIR "/%s", xlde->d_name); unlink(path); XLogArchiveCleanup(xlde->d_name); } } } FreeDir(xldir); } /* * I/O routines for pg_control * * *ControlFile is a buffer in shared memory that holds an image of the * contents of pg_control. WriteControlFile() initializes pg_control * given a preloaded buffer, ReadControlFile() loads the buffer from * the pg_control file (during postmaster or standalone-backend startup), * and UpdateControlFile() rewrites pg_control after we modify xlog state. * InitControlFile() fills the buffer with initial values. * * For simplicity, WriteControlFile() initializes the fields of pg_control * that are related to checking backend/database compatibility, and * ReadControlFile() verifies they are correct. We could split out the * I/O and compatibility-check functions, but there seems no need currently. */ static void InitControlFile(uint64 sysidentifier) { char mock_auth_nonce[MOCK_AUTH_NONCE_LEN]; /* * Generate a random nonce. This is used for authentication requests that * will fail because the user does not exist. The nonce is used to create * a genuine-looking password challenge for the non-existent user, in lieu * of an actual stored password. */ if (!pg_strong_random(mock_auth_nonce, MOCK_AUTH_NONCE_LEN)) ereport(PANIC, (errcode(ERRCODE_INTERNAL_ERROR), errmsg("could not generate secret authorization token"))); memset(ControlFile, 0, sizeof(ControlFileData)); /* Initialize pg_control status fields */ ControlFile->system_identifier = sysidentifier; memcpy(ControlFile->mock_authentication_nonce, mock_auth_nonce, MOCK_AUTH_NONCE_LEN); ControlFile->state = DB_SHUTDOWNED; ControlFile->unloggedLSN = FirstNormalUnloggedLSN; /* Set important parameter values for use when replaying WAL */ ControlFile->MaxConnections = MaxConnections; ControlFile->max_worker_processes = max_worker_processes; ControlFile->max_wal_senders = max_wal_senders; ControlFile->max_prepared_xacts = max_prepared_xacts; ControlFile->max_locks_per_xact = max_locks_per_xact; ControlFile->wal_level = wal_level; ControlFile->wal_log_hints = wal_log_hints; ControlFile->track_commit_timestamp = track_commit_timestamp; ControlFile->data_checksum_version = bootstrap_data_checksum_version; } static void WriteControlFile(void) { int fd; char buffer[PG_CONTROL_FILE_SIZE]; /* need not be aligned */ /* * Initialize version and compatibility-check fields */ ControlFile->pg_control_version = PG_CONTROL_VERSION; ControlFile->catalog_version_no = CATALOG_VERSION_NO; ControlFile->maxAlign = MAXIMUM_ALIGNOF; ControlFile->floatFormat = FLOATFORMAT_VALUE; ControlFile->blcksz = BLCKSZ; ControlFile->relseg_size = RELSEG_SIZE; ControlFile->xlog_blcksz = XLOG_BLCKSZ; ControlFile->xlog_seg_size = wal_segment_size; ControlFile->nameDataLen = NAMEDATALEN; ControlFile->indexMaxKeys = INDEX_MAX_KEYS; ControlFile->toast_max_chunk_size = TOAST_MAX_CHUNK_SIZE; ControlFile->loblksize = LOBLKSIZE; ControlFile->float8ByVal = FLOAT8PASSBYVAL; /* Contents are protected with a CRC */ INIT_CRC32C(ControlFile->crc); COMP_CRC32C(ControlFile->crc, (char *) ControlFile, offsetof(ControlFileData, crc)); FIN_CRC32C(ControlFile->crc); /* * We write out PG_CONTROL_FILE_SIZE bytes into pg_control, zero-padding * the excess over sizeof(ControlFileData). This reduces the odds of * premature-EOF errors when reading pg_control. We'll still fail when we * check the contents of the file, but hopefully with a more specific * error than "couldn't read pg_control". */ memset(buffer, 0, PG_CONTROL_FILE_SIZE); memcpy(buffer, ControlFile, sizeof(ControlFileData)); fd = BasicOpenFile(XLOG_CONTROL_FILE, O_RDWR | O_CREAT | O_EXCL | PG_BINARY); if (fd < 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", XLOG_CONTROL_FILE))); errno = 0; pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_WRITE); if (write(fd, buffer, PG_CONTROL_FILE_SIZE) != PG_CONTROL_FILE_SIZE) { /* if write didn't set errno, assume problem is no disk space */ if (errno == 0) errno = ENOSPC; ereport(PANIC, (errcode_for_file_access(), errmsg("could not write to file \"%s\": %m", XLOG_CONTROL_FILE))); } pgstat_report_wait_end(); pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_SYNC); if (pg_fsync(fd) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not fsync file \"%s\": %m", XLOG_CONTROL_FILE))); pgstat_report_wait_end(); if (close(fd) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", XLOG_CONTROL_FILE))); } static void ReadControlFile(void) { pg_crc32c crc; int fd; static char wal_segsz_str[20]; int r; /* * Read data... */ fd = BasicOpenFile(XLOG_CONTROL_FILE, O_RDWR | PG_BINARY); if (fd < 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", XLOG_CONTROL_FILE))); pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_READ); r = read(fd, ControlFile, sizeof(ControlFileData)); if (r != sizeof(ControlFileData)) { if (r < 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", XLOG_CONTROL_FILE))); else ereport(PANIC, (errcode(ERRCODE_DATA_CORRUPTED), errmsg("could not read file \"%s\": read %d of %zu", XLOG_CONTROL_FILE, r, sizeof(ControlFileData)))); } pgstat_report_wait_end(); close(fd); /* * Check for expected pg_control format version. If this is wrong, the * CRC check will likely fail because we'll be checking the wrong number * of bytes. Complaining about wrong version will probably be more * enlightening than complaining about wrong CRC. */ if (ControlFile->pg_control_version != PG_CONTROL_VERSION && ControlFile->pg_control_version % 65536 == 0 && ControlFile->pg_control_version / 65536 != 0) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with PG_CONTROL_VERSION %d (0x%08x)," " but the server was compiled with PG_CONTROL_VERSION %d (0x%08x).", ControlFile->pg_control_version, ControlFile->pg_control_version, PG_CONTROL_VERSION, PG_CONTROL_VERSION), errhint("This could be a problem of mismatched byte ordering. It looks like you need to initdb."))); if (ControlFile->pg_control_version != PG_CONTROL_VERSION) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with PG_CONTROL_VERSION %d," " but the server was compiled with PG_CONTROL_VERSION %d.", ControlFile->pg_control_version, PG_CONTROL_VERSION), errhint("It looks like you need to initdb."))); /* Now check the CRC. */ INIT_CRC32C(crc); COMP_CRC32C(crc, (char *) ControlFile, offsetof(ControlFileData, crc)); FIN_CRC32C(crc); if (!EQ_CRC32C(crc, ControlFile->crc)) ereport(FATAL, (errmsg("incorrect checksum in control file"))); /* * Do compatibility checking immediately. If the database isn't * compatible with the backend executable, we want to abort before we can * possibly do any damage. */ if (ControlFile->catalog_version_no != CATALOG_VERSION_NO) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with CATALOG_VERSION_NO %d," " but the server was compiled with CATALOG_VERSION_NO %d.", ControlFile->catalog_version_no, CATALOG_VERSION_NO), errhint("It looks like you need to initdb."))); if (ControlFile->maxAlign != MAXIMUM_ALIGNOF) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with MAXALIGN %d," " but the server was compiled with MAXALIGN %d.", ControlFile->maxAlign, MAXIMUM_ALIGNOF), errhint("It looks like you need to initdb."))); if (ControlFile->floatFormat != FLOATFORMAT_VALUE) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster appears to use a different floating-point number format than the server executable."), errhint("It looks like you need to initdb."))); if (ControlFile->blcksz != BLCKSZ) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with BLCKSZ %d," " but the server was compiled with BLCKSZ %d.", ControlFile->blcksz, BLCKSZ), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->relseg_size != RELSEG_SIZE) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with RELSEG_SIZE %d," " but the server was compiled with RELSEG_SIZE %d.", ControlFile->relseg_size, RELSEG_SIZE), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->xlog_blcksz != XLOG_BLCKSZ) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with XLOG_BLCKSZ %d," " but the server was compiled with XLOG_BLCKSZ %d.", ControlFile->xlog_blcksz, XLOG_BLCKSZ), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->nameDataLen != NAMEDATALEN) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with NAMEDATALEN %d," " but the server was compiled with NAMEDATALEN %d.", ControlFile->nameDataLen, NAMEDATALEN), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->indexMaxKeys != INDEX_MAX_KEYS) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with INDEX_MAX_KEYS %d," " but the server was compiled with INDEX_MAX_KEYS %d.", ControlFile->indexMaxKeys, INDEX_MAX_KEYS), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->toast_max_chunk_size != TOAST_MAX_CHUNK_SIZE) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with TOAST_MAX_CHUNK_SIZE %d," " but the server was compiled with TOAST_MAX_CHUNK_SIZE %d.", ControlFile->toast_max_chunk_size, (int) TOAST_MAX_CHUNK_SIZE), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->loblksize != LOBLKSIZE) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with LOBLKSIZE %d," " but the server was compiled with LOBLKSIZE %d.", ControlFile->loblksize, (int) LOBLKSIZE), errhint("It looks like you need to recompile or initdb."))); #ifdef USE_FLOAT8_BYVAL if (ControlFile->float8ByVal != true) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized without USE_FLOAT8_BYVAL" " but the server was compiled with USE_FLOAT8_BYVAL."), errhint("It looks like you need to recompile or initdb."))); #else if (ControlFile->float8ByVal != false) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with USE_FLOAT8_BYVAL" " but the server was compiled without USE_FLOAT8_BYVAL."), errhint("It looks like you need to recompile or initdb."))); #endif wal_segment_size = ControlFile->xlog_seg_size; if (!IsValidWalSegSize(wal_segment_size)) ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg_plural("WAL segment size must be a power of two between 1 MB and 1 GB, but the control file specifies %d byte", "WAL segment size must be a power of two between 1 MB and 1 GB, but the control file specifies %d bytes", wal_segment_size, wal_segment_size))); snprintf(wal_segsz_str, sizeof(wal_segsz_str), "%d", wal_segment_size); SetConfigOption("wal_segment_size", wal_segsz_str, PGC_INTERNAL, PGC_S_DYNAMIC_DEFAULT); /* check and update variables dependent on wal_segment_size */ if (ConvertToXSegs(min_wal_size_mb, wal_segment_size) < 2) ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("\"min_wal_size\" must be at least twice \"wal_segment_size\""))); if (ConvertToXSegs(max_wal_size_mb, wal_segment_size) < 2) ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("\"max_wal_size\" must be at least twice \"wal_segment_size\""))); UsableBytesInSegment = (wal_segment_size / XLOG_BLCKSZ * UsableBytesInPage) - (SizeOfXLogLongPHD - SizeOfXLogShortPHD); CalculateCheckpointSegments(); /* Make the initdb settings visible as GUC variables, too */ SetConfigOption("data_checksums", DataChecksumsEnabled() ? "yes" : "no", PGC_INTERNAL, PGC_S_DYNAMIC_DEFAULT); } /* * Utility wrapper to update the control file. Note that the control * file gets flushed. */ static void UpdateControlFile(void) { update_controlfile(DataDir, ControlFile, true); } /* * Returns the unique system identifier from control file. */ uint64 GetSystemIdentifier(void) { Assert(ControlFile != NULL); return ControlFile->system_identifier; } /* * Returns the random nonce from control file. */ char * GetMockAuthenticationNonce(void) { Assert(ControlFile != NULL); return ControlFile->mock_authentication_nonce; } /* * Are checksums enabled for data pages? */ bool DataChecksumsEnabled(void) { Assert(ControlFile != NULL); return (ControlFile->data_checksum_version > 0); } /* * Returns a fake LSN for unlogged relations. * * Each call generates an LSN that is greater than any previous value * returned. The current counter value is saved and restored across clean * shutdowns, but like unlogged relations, does not survive a crash. This can * be used in lieu of real LSN values returned by XLogInsert, if you need an * LSN-like increasing sequence of numbers without writing any WAL. */ XLogRecPtr GetFakeLSNForUnloggedRel(void) { XLogRecPtr nextUnloggedLSN; /* increment the unloggedLSN counter, need SpinLock */ SpinLockAcquire(&XLogCtl->ulsn_lck); nextUnloggedLSN = XLogCtl->unloggedLSN++; SpinLockRelease(&XLogCtl->ulsn_lck); return nextUnloggedLSN; } /* * Auto-tune the number of XLOG buffers. * * The preferred setting for wal_buffers is about 3% of shared_buffers, with * a maximum of one XLOG segment (there is little reason to think that more * is helpful, at least so long as we force an fsync when switching log files) * and a minimum of 8 blocks (which was the default value prior to PostgreSQL * 9.1, when auto-tuning was added). * * This should not be called until NBuffers has received its final value. */ static int XLOGChooseNumBuffers(void) { int xbuffers; xbuffers = NBuffers / 32; if (xbuffers > (wal_segment_size / XLOG_BLCKSZ)) xbuffers = (wal_segment_size / XLOG_BLCKSZ); if (xbuffers < 8) xbuffers = 8; return xbuffers; } /* * GUC check_hook for wal_buffers */ bool check_wal_buffers(int *newval, void **extra, GucSource source) { /* * -1 indicates a request for auto-tune. */ if (*newval == -1) { /* * If we haven't yet changed the boot_val default of -1, just let it * be. We'll fix it when XLOGShmemSize is called. */ if (XLOGbuffers == -1) return true; /* Otherwise, substitute the auto-tune value */ *newval = XLOGChooseNumBuffers(); } /* * We clamp manually-set values to at least 4 blocks. Prior to PostgreSQL * 9.1, a minimum of 4 was enforced by guc.c, but since that is no longer * the case, we just silently treat such values as a request for the * minimum. (We could throw an error instead, but that doesn't seem very * helpful.) */ if (*newval < 4) *newval = 4; return true; } /* * GUC check_hook for wal_consistency_checking */ bool check_wal_consistency_checking(char **newval, void **extra, GucSource source) { char *rawstring; List *elemlist; ListCell *l; bool newwalconsistency[RM_MAX_ID + 1]; /* Initialize the array */ MemSet(newwalconsistency, 0, (RM_MAX_ID + 1) * sizeof(bool)); /* Need a modifiable copy of string */ rawstring = pstrdup(*newval); /* Parse string into list of identifiers */ if (!SplitIdentifierString(rawstring, ',', &elemlist)) { /* syntax error in list */ GUC_check_errdetail("List syntax is invalid."); pfree(rawstring); list_free(elemlist); return false; } foreach(l, elemlist) { char *tok = (char *) lfirst(l); int rmid; /* Check for 'all'. */ if (pg_strcasecmp(tok, "all") == 0) { for (rmid = 0; rmid <= RM_MAX_ID; rmid++) if (RmgrIdExists(rmid) && GetRmgr(rmid).rm_mask != NULL) newwalconsistency[rmid] = true; } else { /* Check if the token matches any known resource manager. */ bool found = false; for (rmid = 0; rmid <= RM_MAX_ID; rmid++) { if (RmgrIdExists(rmid) && GetRmgr(rmid).rm_mask != NULL && pg_strcasecmp(tok, GetRmgr(rmid).rm_name) == 0) { newwalconsistency[rmid] = true; found = true; break; } } if (!found) { /* * During startup, it might be a not-yet-loaded custom * resource manager. Defer checking until * InitializeWalConsistencyChecking(). */ if (!process_shared_preload_libraries_done) { check_wal_consistency_checking_deferred = true; } else { GUC_check_errdetail("Unrecognized key word: \"%s\".", tok); pfree(rawstring); list_free(elemlist); return false; } } } } pfree(rawstring); list_free(elemlist); /* assign new value */ *extra = guc_malloc(ERROR, (RM_MAX_ID + 1) * sizeof(bool)); memcpy(*extra, newwalconsistency, (RM_MAX_ID + 1) * sizeof(bool)); return true; } /* * GUC assign_hook for wal_consistency_checking */ void assign_wal_consistency_checking(const char *newval, void *extra) { /* * If some checks were deferred, it's possible that the checks will fail * later during InitializeWalConsistencyChecking(). But in that case, the * postmaster will exit anyway, so it's safe to proceed with the * assignment. * * Any built-in resource managers specified are assigned immediately, * which affects WAL created before shared_preload_libraries are * processed. Any custom resource managers specified won't be assigned * until after shared_preload_libraries are processed, but that's OK * because WAL for a custom resource manager can't be written before the * module is loaded anyway. */ wal_consistency_checking = extra; } /* * InitializeWalConsistencyChecking: run after loading custom resource managers * * If any unknown resource managers were specified in the * wal_consistency_checking GUC, processing was deferred. Now that * shared_preload_libraries have been loaded, process wal_consistency_checking * again. */ void InitializeWalConsistencyChecking(void) { Assert(process_shared_preload_libraries_done); if (check_wal_consistency_checking_deferred) { struct config_generic *guc; guc = find_option("wal_consistency_checking", false, false, ERROR); check_wal_consistency_checking_deferred = false; set_config_option_ext("wal_consistency_checking", wal_consistency_checking_string, guc->scontext, guc->source, guc->srole, GUC_ACTION_SET, true, ERROR, false); /* checking should not be deferred again */ Assert(!check_wal_consistency_checking_deferred); } } /* * GUC show_hook for archive_command */ const char * show_archive_command(void) { if (XLogArchivingActive()) return XLogArchiveCommand; else return "(disabled)"; } /* * GUC show_hook for in_hot_standby */ const char * show_in_hot_standby(void) { /* * We display the actual state based on shared memory, so that this GUC * reports up-to-date state if examined intra-query. The underlying * variable (in_hot_standby_guc) changes only when we transmit a new value * to the client. */ return RecoveryInProgress() ? "on" : "off"; } /* * Read the control file, set respective GUCs. * * This is to be called during startup, including a crash recovery cycle, * unless in bootstrap mode, where no control file yet exists. As there's no * usable shared memory yet (its sizing can depend on the contents of the * control file!), first store the contents in local memory. XLOGShmemInit() * will then copy it to shared memory later. * * reset just controls whether previous contents are to be expected (in the * reset case, there's a dangling pointer into old shared memory), or not. */ void LocalProcessControlFile(bool reset) { Assert(reset || ControlFile == NULL); ControlFile = palloc(sizeof(ControlFileData)); ReadControlFile(); } /* * Get the wal_level from the control file. For a standby, this value should be * considered as its active wal_level, because it may be different from what * was originally configured on standby. */ WalLevel GetActiveWalLevelOnStandby(void) { return ControlFile->wal_level; } /* * Initialization of shared memory for XLOG */ Size XLOGShmemSize(void) { Size size; /* * If the value of wal_buffers is -1, use the preferred auto-tune value. * This isn't an amazingly clean place to do this, but we must wait till * NBuffers has received its final value, and must do it before using the * value of XLOGbuffers to do anything important. * * We prefer to report this value's source as PGC_S_DYNAMIC_DEFAULT. * However, if the DBA explicitly set wal_buffers = -1 in the config file, * then PGC_S_DYNAMIC_DEFAULT will fail to override that and we must force * the matter with PGC_S_OVERRIDE. */ if (XLOGbuffers == -1) { char buf[32]; snprintf(buf, sizeof(buf), "%d", XLOGChooseNumBuffers()); SetConfigOption("wal_buffers", buf, PGC_POSTMASTER, PGC_S_DYNAMIC_DEFAULT); if (XLOGbuffers == -1) /* failed to apply it? */ SetConfigOption("wal_buffers", buf, PGC_POSTMASTER, PGC_S_OVERRIDE); } Assert(XLOGbuffers > 0); /* XLogCtl */ size = sizeof(XLogCtlData); /* WAL insertion locks, plus alignment */ size = add_size(size, mul_size(sizeof(WALInsertLockPadded), NUM_XLOGINSERT_LOCKS + 1)); /* xlblocks array */ size = add_size(size, mul_size(sizeof(XLogRecPtr), XLOGbuffers)); /* extra alignment padding for XLOG I/O buffers */ size = add_size(size, Max(XLOG_BLCKSZ, PG_IO_ALIGN_SIZE)); /* and the buffers themselves */ size = add_size(size, mul_size(XLOG_BLCKSZ, XLOGbuffers)); /* * Note: we don't count ControlFileData, it comes out of the "slop factor" * added by CreateSharedMemoryAndSemaphores. This lets us use this * routine again below to compute the actual allocation size. */ return size; } void XLOGShmemInit(void) { bool foundCFile, foundXLog; char *allocptr; int i; ControlFileData *localControlFile; #ifdef WAL_DEBUG /* * Create a memory context for WAL debugging that's exempt from the normal * "no pallocs in critical section" rule. Yes, that can lead to a PANIC if * an allocation fails, but wal_debug is not for production use anyway. */ if (walDebugCxt == NULL) { walDebugCxt = AllocSetContextCreate(TopMemoryContext, "WAL Debug", ALLOCSET_DEFAULT_SIZES); MemoryContextAllowInCriticalSection(walDebugCxt, true); } #endif XLogCtl = (XLogCtlData *) ShmemInitStruct("XLOG Ctl", XLOGShmemSize(), &foundXLog); localControlFile = ControlFile; ControlFile = (ControlFileData *) ShmemInitStruct("Control File", sizeof(ControlFileData), &foundCFile); if (foundCFile || foundXLog) { /* both should be present or neither */ Assert(foundCFile && foundXLog); /* Initialize local copy of WALInsertLocks */ WALInsertLocks = XLogCtl->Insert.WALInsertLocks; if (localControlFile) pfree(localControlFile); return; } memset(XLogCtl, 0, sizeof(XLogCtlData)); /* * Already have read control file locally, unless in bootstrap mode. Move * contents into shared memory. */ if (localControlFile) { memcpy(ControlFile, localControlFile, sizeof(ControlFileData)); pfree(localControlFile); } /* * Since XLogCtlData contains XLogRecPtr fields, its sizeof should be a * multiple of the alignment for same, so no extra alignment padding is * needed here. */ allocptr = ((char *) XLogCtl) + sizeof(XLogCtlData); XLogCtl->xlblocks = (XLogRecPtr *) allocptr; memset(XLogCtl->xlblocks, 0, sizeof(XLogRecPtr) * XLOGbuffers); allocptr += sizeof(XLogRecPtr) * XLOGbuffers; /* WAL insertion locks. Ensure they're aligned to the full padded size */ allocptr += sizeof(WALInsertLockPadded) - ((uintptr_t) allocptr) % sizeof(WALInsertLockPadded); WALInsertLocks = XLogCtl->Insert.WALInsertLocks = (WALInsertLockPadded *) allocptr; allocptr += sizeof(WALInsertLockPadded) * NUM_XLOGINSERT_LOCKS; for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) { LWLockInitialize(&WALInsertLocks[i].l.lock, LWTRANCHE_WAL_INSERT); WALInsertLocks[i].l.insertingAt = InvalidXLogRecPtr; WALInsertLocks[i].l.lastImportantAt = InvalidXLogRecPtr; } /* * Align the start of the page buffers to a full xlog block size boundary. * This simplifies some calculations in XLOG insertion. It is also * required for O_DIRECT. */ allocptr = (char *) TYPEALIGN(XLOG_BLCKSZ, allocptr); XLogCtl->pages = allocptr; memset(XLogCtl->pages, 0, (Size) XLOG_BLCKSZ * XLOGbuffers); /* * Do basic initialization of XLogCtl shared data. (StartupXLOG will fill * in additional info.) */ XLogCtl->XLogCacheBlck = XLOGbuffers - 1; XLogCtl->SharedRecoveryState = RECOVERY_STATE_CRASH; XLogCtl->InstallXLogFileSegmentActive = false; XLogCtl->WalWriterSleeping = false; SpinLockInit(&XLogCtl->Insert.insertpos_lck); SpinLockInit(&XLogCtl->info_lck); SpinLockInit(&XLogCtl->ulsn_lck); } /* * This func must be called ONCE on system install. It creates pg_control * and the initial XLOG segment. */ void BootStrapXLOG(void) { CheckPoint checkPoint; char *buffer; XLogPageHeader page; XLogLongPageHeader longpage; XLogRecord *record; char *recptr; uint64 sysidentifier; struct timeval tv; pg_crc32c crc; /* allow ordinary WAL segment creation, like StartupXLOG() would */ SetInstallXLogFileSegmentActive(); /* * Select a hopefully-unique system identifier code for this installation. * We use the result of gettimeofday(), including the fractional seconds * field, as being about as unique as we can easily get. (Think not to * use random(), since it hasn't been seeded and there's no portable way * to seed it other than the system clock value...) The upper half of the * uint64 value is just the tv_sec part, while the lower half contains the * tv_usec part (which must fit in 20 bits), plus 12 bits from our current * PID for a little extra uniqueness. A person knowing this encoding can * determine the initialization time of the installation, which could * perhaps be useful sometimes. */ gettimeofday(&tv, NULL); sysidentifier = ((uint64) tv.tv_sec) << 32; sysidentifier |= ((uint64) tv.tv_usec) << 12; sysidentifier |= getpid() & 0xFFF; /* page buffer must be aligned suitably for O_DIRECT */ buffer = (char *) palloc(XLOG_BLCKSZ + XLOG_BLCKSZ); page = (XLogPageHeader) TYPEALIGN(XLOG_BLCKSZ, buffer); memset(page, 0, XLOG_BLCKSZ); /* * Set up information for the initial checkpoint record * * The initial checkpoint record is written to the beginning of the WAL * segment with logid=0 logseg=1. The very first WAL segment, 0/0, is not * used, so that we can use 0/0 to mean "before any valid WAL segment". */ checkPoint.redo = wal_segment_size + SizeOfXLogLongPHD; checkPoint.ThisTimeLineID = BootstrapTimeLineID; checkPoint.PrevTimeLineID = BootstrapTimeLineID; checkPoint.fullPageWrites = fullPageWrites; checkPoint.nextXid = FullTransactionIdFromEpochAndXid(0, FirstNormalTransactionId); checkPoint.nextOid = FirstGenbkiObjectId; checkPoint.nextMulti = FirstMultiXactId; checkPoint.nextMultiOffset = 0; checkPoint.oldestXid = FirstNormalTransactionId; checkPoint.oldestXidDB = Template1DbOid; checkPoint.oldestMulti = FirstMultiXactId; checkPoint.oldestMultiDB = Template1DbOid; checkPoint.oldestCommitTsXid = InvalidTransactionId; checkPoint.newestCommitTsXid = InvalidTransactionId; checkPoint.time = (pg_time_t) time(NULL); checkPoint.oldestActiveXid = InvalidTransactionId; ShmemVariableCache->nextXid = checkPoint.nextXid; ShmemVariableCache->nextOid = checkPoint.nextOid; ShmemVariableCache->oidCount = 0; MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset); AdvanceOldestClogXid(checkPoint.oldestXid); SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); SetMultiXactIdLimit(checkPoint.oldestMulti, checkPoint.oldestMultiDB, true); SetCommitTsLimit(InvalidTransactionId, InvalidTransactionId); /* Set up the XLOG page header */ page->xlp_magic = XLOG_PAGE_MAGIC; page->xlp_info = XLP_LONG_HEADER; page->xlp_tli = BootstrapTimeLineID; page->xlp_pageaddr = wal_segment_size; longpage = (XLogLongPageHeader) page; longpage->xlp_sysid = sysidentifier; longpage->xlp_seg_size = wal_segment_size; longpage->xlp_xlog_blcksz = XLOG_BLCKSZ; /* Insert the initial checkpoint record */ recptr = ((char *) page + SizeOfXLogLongPHD); record = (XLogRecord *) recptr; record->xl_prev = 0; record->xl_xid = InvalidTransactionId; record->xl_tot_len = SizeOfXLogRecord + SizeOfXLogRecordDataHeaderShort + sizeof(checkPoint); record->xl_info = XLOG_CHECKPOINT_SHUTDOWN; record->xl_rmid = RM_XLOG_ID; recptr += SizeOfXLogRecord; /* fill the XLogRecordDataHeaderShort struct */ *(recptr++) = (char) XLR_BLOCK_ID_DATA_SHORT; *(recptr++) = sizeof(checkPoint); memcpy(recptr, &checkPoint, sizeof(checkPoint)); recptr += sizeof(checkPoint); Assert(recptr - (char *) record == record->xl_tot_len); INIT_CRC32C(crc); COMP_CRC32C(crc, ((char *) record) + SizeOfXLogRecord, record->xl_tot_len - SizeOfXLogRecord); COMP_CRC32C(crc, (char *) record, offsetof(XLogRecord, xl_crc)); FIN_CRC32C(crc); record->xl_crc = crc; /* Create first XLOG segment file */ openLogTLI = BootstrapTimeLineID; openLogFile = XLogFileInit(1, BootstrapTimeLineID); /* * We needn't bother with Reserve/ReleaseExternalFD here, since we'll * close the file again in a moment. */ /* Write the first page with the initial record */ errno = 0; pgstat_report_wait_start(WAIT_EVENT_WAL_BOOTSTRAP_WRITE); if (write(openLogFile, page, XLOG_BLCKSZ) != XLOG_BLCKSZ) { /* if write didn't set errno, assume problem is no disk space */ if (errno == 0) errno = ENOSPC; ereport(PANIC, (errcode_for_file_access(), errmsg("could not write bootstrap write-ahead log file: %m"))); } pgstat_report_wait_end(); pgstat_report_wait_start(WAIT_EVENT_WAL_BOOTSTRAP_SYNC); if (pg_fsync(openLogFile) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not fsync bootstrap write-ahead log file: %m"))); pgstat_report_wait_end(); if (close(openLogFile) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not close bootstrap write-ahead log file: %m"))); openLogFile = -1; /* Now create pg_control */ InitControlFile(sysidentifier); ControlFile->time = checkPoint.time; ControlFile->checkPoint = checkPoint.redo; ControlFile->checkPointCopy = checkPoint; /* some additional ControlFile fields are set in WriteControlFile() */ WriteControlFile(); /* Bootstrap the commit log, too */ BootStrapCLOG(); BootStrapCommitTs(); BootStrapSUBTRANS(); BootStrapMultiXact(); pfree(buffer); /* * Force control file to be read - in contrast to normal processing we'd * otherwise never run the checks and GUC related initializations therein. */ ReadControlFile(); } static char * str_time(pg_time_t tnow) { static char buf[128]; pg_strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S %Z", pg_localtime(&tnow, log_timezone)); return buf; } /* * Initialize the first WAL segment on new timeline. */ static void XLogInitNewTimeline(TimeLineID endTLI, XLogRecPtr endOfLog, TimeLineID newTLI) { char xlogfname[MAXFNAMELEN]; XLogSegNo endLogSegNo; XLogSegNo startLogSegNo; /* we always switch to a new timeline after archive recovery */ Assert(endTLI != newTLI); /* * Update min recovery point one last time. */ UpdateMinRecoveryPoint(InvalidXLogRecPtr, true); /* * Calculate the last segment on the old timeline, and the first segment * on the new timeline. If the switch happens in the middle of a segment, * they are the same, but if the switch happens exactly at a segment * boundary, startLogSegNo will be endLogSegNo + 1. */ XLByteToPrevSeg(endOfLog, endLogSegNo, wal_segment_size); XLByteToSeg(endOfLog, startLogSegNo, wal_segment_size); /* * Initialize the starting WAL segment for the new timeline. If the switch * happens in the middle of a segment, copy data from the last WAL segment * of the old timeline up to the switch point, to the starting WAL segment * on the new timeline. */ if (endLogSegNo == startLogSegNo) { /* * Make a copy of the file on the new timeline. * * Writing WAL isn't allowed yet, so there are no locking * considerations. But we should be just as tense as XLogFileInit to * avoid emplacing a bogus file. */ XLogFileCopy(newTLI, endLogSegNo, endTLI, endLogSegNo, XLogSegmentOffset(endOfLog, wal_segment_size)); } else { /* * The switch happened at a segment boundary, so just create the next * segment on the new timeline. */ int fd; fd = XLogFileInit(startLogSegNo, newTLI); if (close(fd) != 0) { int save_errno = errno; XLogFileName(xlogfname, newTLI, startLogSegNo, wal_segment_size); errno = save_errno; ereport(ERROR, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", xlogfname))); } } /* * Let's just make real sure there are not .ready or .done flags posted * for the new segment. */ XLogFileName(xlogfname, newTLI, startLogSegNo, wal_segment_size); XLogArchiveCleanup(xlogfname); } /* * Perform cleanup actions at the conclusion of archive recovery. */ static void CleanupAfterArchiveRecovery(TimeLineID EndOfLogTLI, XLogRecPtr EndOfLog, TimeLineID newTLI) { /* * Execute the recovery_end_command, if any. */ if (recoveryEndCommand && strcmp(recoveryEndCommand, "") != 0) ExecuteRecoveryCommand(recoveryEndCommand, "recovery_end_command", true, WAIT_EVENT_RECOVERY_END_COMMAND); /* * We switched to a new timeline. Clean up segments on the old timeline. * * If there are any higher-numbered segments on the old timeline, remove * them. They might contain valid WAL, but they might also be * pre-allocated files containing garbage. In any case, they are not part * of the new timeline's history so we don't need them. */ RemoveNonParentXlogFiles(EndOfLog, newTLI); /* * If the switch happened in the middle of a segment, what to do with the * last, partial segment on the old timeline? If we don't archive it, and * the server that created the WAL never archives it either (e.g. because * it was hit by a meteor), it will never make it to the archive. That's * OK from our point of view, because the new segment that we created with * the new TLI contains all the WAL from the old timeline up to the switch * point. But if you later try to do PITR to the "missing" WAL on the old * timeline, recovery won't find it in the archive. It's physically * present in the new file with new TLI, but recovery won't look there * when it's recovering to the older timeline. On the other hand, if we * archive the partial segment, and the original server on that timeline * is still running and archives the completed version of the same segment * later, it will fail. (We used to do that in 9.4 and below, and it * caused such problems). * * As a compromise, we rename the last segment with the .partial suffix, * and archive it. Archive recovery will never try to read .partial * segments, so they will normally go unused. But in the odd PITR case, * the administrator can copy them manually to the pg_wal directory * (removing the suffix). They can be useful in debugging, too. * * If a .done or .ready file already exists for the old timeline, however, * we had already determined that the segment is complete, so we can let * it be archived normally. (In particular, if it was restored from the * archive to begin with, it's expected to have a .done file). */ if (XLogSegmentOffset(EndOfLog, wal_segment_size) != 0 && XLogArchivingActive()) { char origfname[MAXFNAMELEN]; XLogSegNo endLogSegNo; XLByteToPrevSeg(EndOfLog, endLogSegNo, wal_segment_size); XLogFileName(origfname, EndOfLogTLI, endLogSegNo, wal_segment_size); if (!XLogArchiveIsReadyOrDone(origfname)) { char origpath[MAXPGPATH]; char partialfname[MAXFNAMELEN]; char partialpath[MAXPGPATH]; XLogFilePath(origpath, EndOfLogTLI, endLogSegNo, wal_segment_size); snprintf(partialfname, MAXFNAMELEN, "%s.partial", origfname); snprintf(partialpath, MAXPGPATH, "%s.partial", origpath); /* * Make sure there's no .done or .ready file for the .partial * file. */ XLogArchiveCleanup(partialfname); durable_rename(origpath, partialpath, ERROR); XLogArchiveNotify(partialfname); } } } /* * Check to see if required parameters are set high enough on this server * for various aspects of recovery operation. * * Note that all the parameters which this function tests need to be * listed in Administrator's Overview section in high-availability.sgml. * If you change them, don't forget to update the list. */ static void CheckRequiredParameterValues(void) { /* * For archive recovery, the WAL must be generated with at least 'replica' * wal_level. */ if (ArchiveRecoveryRequested && ControlFile->wal_level == WAL_LEVEL_MINIMAL) { ereport(FATAL, (errmsg("WAL was generated with wal_level=minimal, cannot continue recovering"), errdetail("This happens if you temporarily set wal_level=minimal on the server."), errhint("Use a backup taken after setting wal_level to higher than minimal."))); } /* * For Hot Standby, the WAL must be generated with 'replica' mode, and we * must have at least as many backend slots as the primary. */ if (ArchiveRecoveryRequested && EnableHotStandby) { /* We ignore autovacuum_max_workers when we make this test. */ RecoveryRequiresIntParameter("max_connections", MaxConnections, ControlFile->MaxConnections); RecoveryRequiresIntParameter("max_worker_processes", max_worker_processes, ControlFile->max_worker_processes); RecoveryRequiresIntParameter("max_wal_senders", max_wal_senders, ControlFile->max_wal_senders); RecoveryRequiresIntParameter("max_prepared_transactions", max_prepared_xacts, ControlFile->max_prepared_xacts); RecoveryRequiresIntParameter("max_locks_per_transaction", max_locks_per_xact, ControlFile->max_locks_per_xact); } } /* * This must be called ONCE during postmaster or standalone-backend startup */ void StartupXLOG(void) { XLogCtlInsert *Insert; CheckPoint checkPoint; bool wasShutdown; bool didCrash; bool haveTblspcMap; bool haveBackupLabel; XLogRecPtr EndOfLog; TimeLineID EndOfLogTLI; TimeLineID newTLI; bool performedWalRecovery; EndOfWalRecoveryInfo *endOfRecoveryInfo; XLogRecPtr abortedRecPtr; XLogRecPtr missingContrecPtr; TransactionId oldestActiveXID; bool promoted = false; /* * We should have an aux process resource owner to use, and we should not * be in a transaction that's installed some other resowner. */ Assert(AuxProcessResourceOwner != NULL); Assert(CurrentResourceOwner == NULL || CurrentResourceOwner == AuxProcessResourceOwner); CurrentResourceOwner = AuxProcessResourceOwner; /* * Check that contents look valid. */ if (!XRecOffIsValid(ControlFile->checkPoint)) ereport(FATAL, (errmsg("control file contains invalid checkpoint location"))); switch (ControlFile->state) { case DB_SHUTDOWNED: /* * This is the expected case, so don't be chatty in standalone * mode */ ereport(IsPostmasterEnvironment ? LOG : NOTICE, (errmsg("database system was shut down at %s", str_time(ControlFile->time)))); break; case DB_SHUTDOWNED_IN_RECOVERY: ereport(LOG, (errmsg("database system was shut down in recovery at %s", str_time(ControlFile->time)))); break; case DB_SHUTDOWNING: ereport(LOG, (errmsg("database system shutdown was interrupted; last known up at %s", str_time(ControlFile->time)))); break; case DB_IN_CRASH_RECOVERY: ereport(LOG, (errmsg("database system was interrupted while in recovery at %s", str_time(ControlFile->time)), errhint("This probably means that some data is corrupted and" " you will have to use the last backup for recovery."))); break; case DB_IN_ARCHIVE_RECOVERY: ereport(LOG, (errmsg("database system was interrupted while in recovery at log time %s", str_time(ControlFile->checkPointCopy.time)), errhint("If this has occurred more than once some data might be corrupted" " and you might need to choose an earlier recovery target."))); break; case DB_IN_PRODUCTION: ereport(LOG, (errmsg("database system was interrupted; last known up at %s", str_time(ControlFile->time)))); break; default: ereport(FATAL, (errmsg("control file contains invalid database cluster state"))); } /* This is just to allow attaching to startup process with a debugger */ #ifdef XLOG_REPLAY_DELAY if (ControlFile->state != DB_SHUTDOWNED) pg_usleep(60000000L); #endif /* * Verify that pg_wal and pg_wal/archive_status exist. In cases where * someone has performed a copy for PITR, these directories may have been * excluded and need to be re-created. */ ValidateXLOGDirectoryStructure(); /* Set up timeout handler needed to report startup progress. */ if (!IsBootstrapProcessingMode()) RegisterTimeout(STARTUP_PROGRESS_TIMEOUT, startup_progress_timeout_handler); /*---------- * If we previously crashed, perform a couple of actions: * * - The pg_wal directory may still include some temporary WAL segments * used when creating a new segment, so perform some clean up to not * bloat this path. This is done first as there is no point to sync * this temporary data. * * - There might be data which we had written, intending to fsync it, but * which we had not actually fsync'd yet. Therefore, a power failure in * the near future might cause earlier unflushed writes to be lost, even * though more recent data written to disk from here on would be * persisted. To avoid that, fsync the entire data directory. */ if (ControlFile->state != DB_SHUTDOWNED && ControlFile->state != DB_SHUTDOWNED_IN_RECOVERY) { RemoveTempXlogFiles(); SyncDataDirectory(); didCrash = true; } else didCrash = false; /* * Prepare for WAL recovery if needed. * * InitWalRecovery analyzes the control file and the backup label file, if * any. It updates the in-memory ControlFile buffer according to the * starting checkpoint, and sets InRecovery and ArchiveRecoveryRequested. * It also applies the tablespace map file, if any. */ InitWalRecovery(ControlFile, &wasShutdown, &haveBackupLabel, &haveTblspcMap); checkPoint = ControlFile->checkPointCopy; /* initialize shared memory variables from the checkpoint record */ ShmemVariableCache->nextXid = checkPoint.nextXid; ShmemVariableCache->nextOid = checkPoint.nextOid; ShmemVariableCache->oidCount = 0; MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset); AdvanceOldestClogXid(checkPoint.oldestXid); SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); SetMultiXactIdLimit(checkPoint.oldestMulti, checkPoint.oldestMultiDB, true); SetCommitTsLimit(checkPoint.oldestCommitTsXid, checkPoint.newestCommitTsXid); XLogCtl->ckptFullXid = checkPoint.nextXid; /* * Clear out any old relcache cache files. This is *necessary* if we do * any WAL replay, since that would probably result in the cache files * being out of sync with database reality. In theory we could leave them * in place if the database had been cleanly shut down, but it seems * safest to just remove them always and let them be rebuilt during the * first backend startup. These files needs to be removed from all * directories including pg_tblspc, however the symlinks are created only * after reading tablespace_map file in case of archive recovery from * backup, so needs to clear old relcache files here after creating * symlinks. */ RelationCacheInitFileRemove(); /* * Initialize replication slots, before there's a chance to remove * required resources. */ StartupReplicationSlots(); /* * Startup logical state, needs to be setup now so we have proper data * during crash recovery. */ StartupReorderBuffer(); /* * Startup CLOG. This must be done after ShmemVariableCache->nextXid has * been initialized and before we accept connections or begin WAL replay. */ StartupCLOG(); /* * Startup MultiXact. We need to do this early to be able to replay * truncations. */ StartupMultiXact(); /* * Ditto for commit timestamps. Activate the facility if the setting is * enabled in the control file, as there should be no tracking of commit * timestamps done when the setting was disabled. This facility can be * started or stopped when replaying a XLOG_PARAMETER_CHANGE record. */ if (ControlFile->track_commit_timestamp) StartupCommitTs(); /* * Recover knowledge about replay progress of known replication partners. */ StartupReplicationOrigin(); /* * Initialize unlogged LSN. On a clean shutdown, it's restored from the * control file. On recovery, all unlogged relations are blown away, so * the unlogged LSN counter can be reset too. */ if (ControlFile->state == DB_SHUTDOWNED) XLogCtl->unloggedLSN = ControlFile->unloggedLSN; else XLogCtl->unloggedLSN = FirstNormalUnloggedLSN; /* * Copy any missing timeline history files between 'now' and the recovery * target timeline from archive to pg_wal. While we don't need those files * ourselves - the history file of the recovery target timeline covers all * the previous timelines in the history too - a cascading standby server * might be interested in them. Or, if you archive the WAL from this * server to a different archive than the primary, it'd be good for all * the history files to get archived there after failover, so that you can * use one of the old timelines as a PITR target. Timeline history files * are small, so it's better to copy them unnecessarily than not copy them * and regret later. */ restoreTimeLineHistoryFiles(checkPoint.ThisTimeLineID, recoveryTargetTLI); /* * Before running in recovery, scan pg_twophase and fill in its status to * be able to work on entries generated by redo. Doing a scan before * taking any recovery action has the merit to discard any 2PC files that * are newer than the first record to replay, saving from any conflicts at * replay. This avoids as well any subsequent scans when doing recovery * of the on-disk two-phase data. */ restoreTwoPhaseData(); /* * When starting with crash recovery, reset pgstat data - it might not be * valid. Otherwise restore pgstat data. It's safe to do this here, * because postmaster will not yet have started any other processes. * * NB: Restoring replication slot stats relies on slot state to have * already been restored from disk. * * TODO: With a bit of extra work we could just start with a pgstat file * associated with the checkpoint redo location we're starting from. */ if (didCrash) pgstat_discard_stats(); else pgstat_restore_stats(); lastFullPageWrites = checkPoint.fullPageWrites; RedoRecPtr = XLogCtl->RedoRecPtr = XLogCtl->Insert.RedoRecPtr = checkPoint.redo; doPageWrites = lastFullPageWrites; /* REDO */ if (InRecovery) { /* Initialize state for RecoveryInProgress() */ SpinLockAcquire(&XLogCtl->info_lck); if (InArchiveRecovery) XLogCtl->SharedRecoveryState = RECOVERY_STATE_ARCHIVE; else XLogCtl->SharedRecoveryState = RECOVERY_STATE_CRASH; SpinLockRelease(&XLogCtl->info_lck); /* * Update pg_control to show that we are recovering and to show the * selected checkpoint as the place we are starting from. We also mark * pg_control with any minimum recovery stop point obtained from a * backup history file. * * No need to hold ControlFileLock yet, we aren't up far enough. */ UpdateControlFile(); /* * If there was a backup label file, it's done its job and the info * has now been propagated into pg_control. We must get rid of the * label file so that if we crash during recovery, we'll pick up at * the latest recovery restartpoint instead of going all the way back * to the backup start point. It seems prudent though to just rename * the file out of the way rather than delete it completely. */ if (haveBackupLabel) { unlink(BACKUP_LABEL_OLD); durable_rename(BACKUP_LABEL_FILE, BACKUP_LABEL_OLD, FATAL); } /* * If there was a tablespace_map file, it's done its job and the * symlinks have been created. We must get rid of the map file so * that if we crash during recovery, we don't create symlinks again. * It seems prudent though to just rename the file out of the way * rather than delete it completely. */ if (haveTblspcMap) { unlink(TABLESPACE_MAP_OLD); durable_rename(TABLESPACE_MAP, TABLESPACE_MAP_OLD, FATAL); } /* * Initialize our local copy of minRecoveryPoint. When doing crash * recovery we want to replay up to the end of WAL. Particularly, in * the case of a promoted standby minRecoveryPoint value in the * control file is only updated after the first checkpoint. However, * if the instance crashes before the first post-recovery checkpoint * is completed then recovery will use a stale location causing the * startup process to think that there are still invalid page * references when checking for data consistency. */ if (InArchiveRecovery) { LocalMinRecoveryPoint = ControlFile->minRecoveryPoint; LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI; } else { LocalMinRecoveryPoint = InvalidXLogRecPtr; LocalMinRecoveryPointTLI = 0; } /* Check that the GUCs used to generate the WAL allow recovery */ CheckRequiredParameterValues(); /* * We're in recovery, so unlogged relations may be trashed and must be * reset. This should be done BEFORE allowing Hot Standby * connections, so that read-only backends don't try to read whatever * garbage is left over from before. */ ResetUnloggedRelations(UNLOGGED_RELATION_CLEANUP); /* * Likewise, delete any saved transaction snapshot files that got left * behind by crashed backends. */ DeleteAllExportedSnapshotFiles(); /* * Initialize for Hot Standby, if enabled. We won't let backends in * yet, not until we've reached the min recovery point specified in * control file and we've established a recovery snapshot from a * running-xacts WAL record. */ if (ArchiveRecoveryRequested && EnableHotStandby) { TransactionId *xids; int nxids; ereport(DEBUG1, (errmsg_internal("initializing for hot standby"))); InitRecoveryTransactionEnvironment(); if (wasShutdown) oldestActiveXID = PrescanPreparedTransactions(&xids, &nxids); else oldestActiveXID = checkPoint.oldestActiveXid; Assert(TransactionIdIsValid(oldestActiveXID)); /* Tell procarray about the range of xids it has to deal with */ ProcArrayInitRecovery(XidFromFullTransactionId(ShmemVariableCache->nextXid)); /* * Startup subtrans only. CLOG, MultiXact and commit timestamp * have already been started up and other SLRUs are not maintained * during recovery and need not be started yet. */ StartupSUBTRANS(oldestActiveXID); /* * If we're beginning at a shutdown checkpoint, we know that * nothing was running on the primary at this point. So fake-up an * empty running-xacts record and use that here and now. Recover * additional standby state for prepared transactions. */ if (wasShutdown) { RunningTransactionsData running; TransactionId latestCompletedXid; /* * Construct a RunningTransactions snapshot representing a * shut down server, with only prepared transactions still * alive. We're never overflowed at this point because all * subxids are listed with their parent prepared transactions. */ running.xcnt = nxids; running.subxcnt = 0; running.subxid_overflow = false; running.nextXid = XidFromFullTransactionId(checkPoint.nextXid); running.oldestRunningXid = oldestActiveXID; latestCompletedXid = XidFromFullTransactionId(checkPoint.nextXid); TransactionIdRetreat(latestCompletedXid); Assert(TransactionIdIsNormal(latestCompletedXid)); running.latestCompletedXid = latestCompletedXid; running.xids = xids; ProcArrayApplyRecoveryInfo(&running); StandbyRecoverPreparedTransactions(); } } /* * We're all set for replaying the WAL now. Do it. */ PerformWalRecovery(); performedWalRecovery = true; } else performedWalRecovery = false; /* * Finish WAL recovery. */ endOfRecoveryInfo = FinishWalRecovery(); EndOfLog = endOfRecoveryInfo->endOfLog; EndOfLogTLI = endOfRecoveryInfo->endOfLogTLI; abortedRecPtr = endOfRecoveryInfo->abortedRecPtr; missingContrecPtr = endOfRecoveryInfo->missingContrecPtr; /* * Reset ps status display, so as no information related to recovery shows * up. */ set_ps_display(""); /* * When recovering from a backup (we are in recovery, and archive recovery * was requested), complain if we did not roll forward far enough to reach * the point where the database is consistent. For regular online * backup-from-primary, that means reaching the end-of-backup WAL record * (at which point we reset backupStartPoint to be Invalid), for * backup-from-replica (which can't inject records into the WAL stream), * that point is when we reach the minRecoveryPoint in pg_control (which * we purposefully copy last when backing up from a replica). For * pg_rewind (which creates a backup_label with a method of "pg_rewind") * or snapshot-style backups (which don't), backupEndRequired will be set * to false. * * Note: it is indeed okay to look at the local variable * LocalMinRecoveryPoint here, even though ControlFile->minRecoveryPoint * might be further ahead --- ControlFile->minRecoveryPoint cannot have * been advanced beyond the WAL we processed. */ if (InRecovery && (EndOfLog < LocalMinRecoveryPoint || !XLogRecPtrIsInvalid(ControlFile->backupStartPoint))) { /* * Ran off end of WAL before reaching end-of-backup WAL record, or * minRecoveryPoint. That's a bad sign, indicating that you tried to * recover from an online backup but never called pg_backup_stop(), or * you didn't archive all the WAL needed. */ if (ArchiveRecoveryRequested || ControlFile->backupEndRequired) { if (!XLogRecPtrIsInvalid(ControlFile->backupStartPoint) || ControlFile->backupEndRequired) ereport(FATAL, (errmsg("WAL ends before end of online backup"), errhint("All WAL generated while online backup was taken must be available at recovery."))); else ereport(FATAL, (errmsg("WAL ends before consistent recovery point"))); } } /* * Reset unlogged relations to the contents of their INIT fork. This is * done AFTER recovery is complete so as to include any unlogged relations * created during recovery, but BEFORE recovery is marked as having * completed successfully. Otherwise we'd not retry if any of the post * end-of-recovery steps fail. */ if (InRecovery) ResetUnloggedRelations(UNLOGGED_RELATION_INIT); /* * Pre-scan prepared transactions to find out the range of XIDs present. * This information is not quite needed yet, but it is positioned here so * as potential problems are detected before any on-disk change is done. */ oldestActiveXID = PrescanPreparedTransactions(NULL, NULL); /* * Allow ordinary WAL segment creation before possibly switching to a new * timeline, which creates a new segment, and after the last ReadRecord(). */ SetInstallXLogFileSegmentActive(); /* * Consider whether we need to assign a new timeline ID. * * If we did archive recovery, we always assign a new ID. This handles a * couple of issues. If we stopped short of the end of WAL during * recovery, then we are clearly generating a new timeline and must assign * it a unique new ID. Even if we ran to the end, modifying the current * last segment is problematic because it may result in trying to * overwrite an already-archived copy of that segment, and we encourage * DBAs to make their archive_commands reject that. We can dodge the * problem by making the new active segment have a new timeline ID. * * In a normal crash recovery, we can just extend the timeline we were in. */ newTLI = endOfRecoveryInfo->lastRecTLI; if (ArchiveRecoveryRequested) { newTLI = findNewestTimeLine(recoveryTargetTLI) + 1; ereport(LOG, (errmsg("selected new timeline ID: %u", newTLI))); /* * Make a writable copy of the last WAL segment. (Note that we also * have a copy of the last block of the old WAL in * endOfRecovery->lastPage; we will use that below.) */ XLogInitNewTimeline(EndOfLogTLI, EndOfLog, newTLI); /* * Remove the signal files out of the way, so that we don't * accidentally re-enter archive recovery mode in a subsequent crash. */ if (endOfRecoveryInfo->standby_signal_file_found) durable_unlink(STANDBY_SIGNAL_FILE, FATAL); if (endOfRecoveryInfo->recovery_signal_file_found) durable_unlink(RECOVERY_SIGNAL_FILE, FATAL); /* * Write the timeline history file, and have it archived. After this * point (or rather, as soon as the file is archived), the timeline * will appear as "taken" in the WAL archive and to any standby * servers. If we crash before actually switching to the new * timeline, standby servers will nevertheless think that we switched * to the new timeline, and will try to connect to the new timeline. * To minimize the window for that, try to do as little as possible * between here and writing the end-of-recovery record. */ writeTimeLineHistory(newTLI, recoveryTargetTLI, EndOfLog, endOfRecoveryInfo->recoveryStopReason); ereport(LOG, (errmsg("archive recovery complete"))); } /* Save the selected TimeLineID in shared memory, too */ XLogCtl->InsertTimeLineID = newTLI; XLogCtl->PrevTimeLineID = endOfRecoveryInfo->lastRecTLI; /* * Actually, if WAL ended in an incomplete record, skip the parts that * made it through and start writing after the portion that persisted. * (It's critical to first write an OVERWRITE_CONTRECORD message, which * we'll do as soon as we're open for writing new WAL.) */ if (!XLogRecPtrIsInvalid(missingContrecPtr)) { /* * We should only have a missingContrecPtr if we're not switching to a * new timeline. When a timeline switch occurs, WAL is copied from the * old timeline to the new only up to the end of the last complete * record, so there can't be an incomplete WAL record that we need to * disregard. */ Assert(newTLI == endOfRecoveryInfo->lastRecTLI); Assert(!XLogRecPtrIsInvalid(abortedRecPtr)); EndOfLog = missingContrecPtr; } /* * Prepare to write WAL starting at EndOfLog location, and init xlog * buffer cache using the block containing the last record from the * previous incarnation. */ Insert = &XLogCtl->Insert; Insert->PrevBytePos = XLogRecPtrToBytePos(endOfRecoveryInfo->lastRec); Insert->CurrBytePos = XLogRecPtrToBytePos(EndOfLog); /* * Tricky point here: lastPage contains the *last* block that the LastRec * record spans, not the one it starts in. The last block is indeed the * one we want to use. */ if (EndOfLog % XLOG_BLCKSZ != 0) { char *page; int len; int firstIdx; firstIdx = XLogRecPtrToBufIdx(EndOfLog); len = EndOfLog - endOfRecoveryInfo->lastPageBeginPtr; Assert(len < XLOG_BLCKSZ); /* Copy the valid part of the last block, and zero the rest */ page = &XLogCtl->pages[firstIdx * XLOG_BLCKSZ]; memcpy(page, endOfRecoveryInfo->lastPage, len); memset(page + len, 0, XLOG_BLCKSZ - len); XLogCtl->xlblocks[firstIdx] = endOfRecoveryInfo->lastPageBeginPtr + XLOG_BLCKSZ; XLogCtl->InitializedUpTo = endOfRecoveryInfo->lastPageBeginPtr + XLOG_BLCKSZ; } else { /* * There is no partial block to copy. Just set InitializedUpTo, and * let the first attempt to insert a log record to initialize the next * buffer. */ XLogCtl->InitializedUpTo = EndOfLog; } LogwrtResult.Write = LogwrtResult.Flush = EndOfLog; XLogCtl->LogwrtResult = LogwrtResult; XLogCtl->LogwrtRqst.Write = EndOfLog; XLogCtl->LogwrtRqst.Flush = EndOfLog; /* * Preallocate additional log files, if wanted. */ PreallocXlogFiles(EndOfLog, newTLI); /* * Okay, we're officially UP. */ InRecovery = false; /* start the archive_timeout timer and LSN running */ XLogCtl->lastSegSwitchTime = (pg_time_t) time(NULL); XLogCtl->lastSegSwitchLSN = EndOfLog; /* also initialize latestCompletedXid, to nextXid - 1 */ LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); ShmemVariableCache->latestCompletedXid = ShmemVariableCache->nextXid; FullTransactionIdRetreat(&ShmemVariableCache->latestCompletedXid); LWLockRelease(ProcArrayLock); /* * Start up subtrans, if not already done for hot standby. (commit * timestamps are started below, if necessary.) */ if (standbyState == STANDBY_DISABLED) StartupSUBTRANS(oldestActiveXID); /* * Perform end of recovery actions for any SLRUs that need it. */ TrimCLOG(); TrimMultiXact(); /* * Reload shared-memory state for prepared transactions. This needs to * happen before renaming the last partial segment of the old timeline as * it may be possible that we have to recovery some transactions from it. */ RecoverPreparedTransactions(); /* Shut down xlogreader */ ShutdownWalRecovery(); /* Enable WAL writes for this backend only. */ LocalSetXLogInsertAllowed(); /* If necessary, write overwrite-contrecord before doing anything else */ if (!XLogRecPtrIsInvalid(abortedRecPtr)) { Assert(!XLogRecPtrIsInvalid(missingContrecPtr)); CreateOverwriteContrecordRecord(abortedRecPtr, missingContrecPtr, newTLI); } /* * Update full_page_writes in shared memory and write an XLOG_FPW_CHANGE * record before resource manager writes cleanup WAL records or checkpoint * record is written. */ Insert->fullPageWrites = lastFullPageWrites; UpdateFullPageWrites(); /* * Emit checkpoint or end-of-recovery record in XLOG, if required. */ if (performedWalRecovery) promoted = PerformRecoveryXLogAction(); /* * If any of the critical GUCs have changed, log them before we allow * backends to write WAL. */ XLogReportParameters(); /* If this is archive recovery, perform post-recovery cleanup actions. */ if (ArchiveRecoveryRequested) CleanupAfterArchiveRecovery(EndOfLogTLI, EndOfLog, newTLI); /* * Local WAL inserts enabled, so it's time to finish initialization of * commit timestamp. */ CompleteCommitTsInitialization(); /* * All done with end-of-recovery actions. * * Now allow backends to write WAL and update the control file status in * consequence. SharedRecoveryState, that controls if backends can write * WAL, is updated while holding ControlFileLock to prevent other backends * to look at an inconsistent state of the control file in shared memory. * There is still a small window during which backends can write WAL and * the control file is still referring to a system not in DB_IN_PRODUCTION * state while looking at the on-disk control file. * * Also, we use info_lck to update SharedRecoveryState to ensure that * there are no race conditions concerning visibility of other recent * updates to shared memory. */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->state = DB_IN_PRODUCTION; SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->SharedRecoveryState = RECOVERY_STATE_DONE; SpinLockRelease(&XLogCtl->info_lck); UpdateControlFile(); LWLockRelease(ControlFileLock); /* * Shutdown the recovery environment. This must occur after * RecoverPreparedTransactions() (see notes in lock_twophase_recover()) * and after switching SharedRecoveryState to RECOVERY_STATE_DONE so as * any session building a snapshot will not rely on KnownAssignedXids as * RecoveryInProgress() would return false at this stage. This is * particularly critical for prepared 2PC transactions, that would still * need to be included in snapshots once recovery has ended. */ if (standbyState != STANDBY_DISABLED) ShutdownRecoveryTransactionEnvironment(); /* * If there were cascading standby servers connected to us, nudge any wal * sender processes to notice that we've been promoted. */ WalSndWakeup(true, true); /* * If this was a promotion, request an (online) checkpoint now. This isn't * required for consistency, but the last restartpoint might be far back, * and in case of a crash, recovering from it might take a longer than is * appropriate now that we're not in standby mode anymore. */ if (promoted) RequestCheckpoint(CHECKPOINT_FORCE); } /* * Callback from PerformWalRecovery(), called when we switch from crash * recovery to archive recovery mode. Updates the control file accordingly. */ void SwitchIntoArchiveRecovery(XLogRecPtr EndRecPtr, TimeLineID replayTLI) { /* initialize minRecoveryPoint to this record */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->state = DB_IN_ARCHIVE_RECOVERY; if (ControlFile->minRecoveryPoint < EndRecPtr) { ControlFile->minRecoveryPoint = EndRecPtr; ControlFile->minRecoveryPointTLI = replayTLI; } /* update local copy */ LocalMinRecoveryPoint = ControlFile->minRecoveryPoint; LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI; /* * The startup process can update its local copy of minRecoveryPoint from * this point. */ updateMinRecoveryPoint = true; UpdateControlFile(); /* * We update SharedRecoveryState while holding the lock on ControlFileLock * so both states are consistent in shared memory. */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->SharedRecoveryState = RECOVERY_STATE_ARCHIVE; SpinLockRelease(&XLogCtl->info_lck); LWLockRelease(ControlFileLock); } /* * Callback from PerformWalRecovery(), called when we reach the end of backup. * Updates the control file accordingly. */ void ReachedEndOfBackup(XLogRecPtr EndRecPtr, TimeLineID tli) { /* * We have reached the end of base backup, as indicated by pg_control. The * data on disk is now consistent (unless minRecoveryPoint is further * ahead, which can happen if we crashed during previous recovery). Reset * backupStartPoint and backupEndPoint, and update minRecoveryPoint to * make sure we don't allow starting up at an earlier point even if * recovery is stopped and restarted soon after this. */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); if (ControlFile->minRecoveryPoint < EndRecPtr) { ControlFile->minRecoveryPoint = EndRecPtr; ControlFile->minRecoveryPointTLI = tli; } ControlFile->backupStartPoint = InvalidXLogRecPtr; ControlFile->backupEndPoint = InvalidXLogRecPtr; ControlFile->backupEndRequired = false; UpdateControlFile(); LWLockRelease(ControlFileLock); } /* * Perform whatever XLOG actions are necessary at end of REDO. * * The goal here is to make sure that we'll be able to recover properly if * we crash again. If we choose to write a checkpoint, we'll write a shutdown * checkpoint rather than an on-line one. This is not particularly critical, * but since we may be assigning a new TLI, using a shutdown checkpoint allows * us to have the rule that TLI only changes in shutdown checkpoints, which * allows some extra error checking in xlog_redo. */ static bool PerformRecoveryXLogAction(void) { bool promoted = false; /* * Perform a checkpoint to update all our recovery activity to disk. * * Note that we write a shutdown checkpoint rather than an on-line one. * This is not particularly critical, but since we may be assigning a new * TLI, using a shutdown checkpoint allows us to have the rule that TLI * only changes in shutdown checkpoints, which allows some extra error * checking in xlog_redo. * * In promotion, only create a lightweight end-of-recovery record instead * of a full checkpoint. A checkpoint is requested later, after we're * fully out of recovery mode and already accepting queries. */ if (ArchiveRecoveryRequested && IsUnderPostmaster && PromoteIsTriggered()) { promoted = true; /* * Insert a special WAL record to mark the end of recovery, since we * aren't doing a checkpoint. That means that the checkpointer process * may likely be in the middle of a time-smoothed restartpoint and * could continue to be for minutes after this. That sounds strange, * but the effect is roughly the same and it would be stranger to try * to come out of the restartpoint and then checkpoint. We request a * checkpoint later anyway, just for safety. */ CreateEndOfRecoveryRecord(); } else { RequestCheckpoint(CHECKPOINT_END_OF_RECOVERY | CHECKPOINT_IMMEDIATE | CHECKPOINT_WAIT); } return promoted; } /* * Is the system still in recovery? * * Unlike testing InRecovery, this works in any process that's connected to * shared memory. */ bool RecoveryInProgress(void) { /* * We check shared state each time only until we leave recovery mode. We * can't re-enter recovery, so there's no need to keep checking after the * shared variable has once been seen false. */ if (!LocalRecoveryInProgress) return false; else { /* * use volatile pointer to make sure we make a fresh read of the * shared variable. */ volatile XLogCtlData *xlogctl = XLogCtl; LocalRecoveryInProgress = (xlogctl->SharedRecoveryState != RECOVERY_STATE_DONE); /* * Note: We don't need a memory barrier when we're still in recovery. * We might exit recovery immediately after return, so the caller * can't rely on 'true' meaning that we're still in recovery anyway. */ return LocalRecoveryInProgress; } } /* * Returns current recovery state from shared memory. * * This returned state is kept consistent with the contents of the control * file. See details about the possible values of RecoveryState in xlog.h. */ RecoveryState GetRecoveryState(void) { RecoveryState retval; SpinLockAcquire(&XLogCtl->info_lck); retval = XLogCtl->SharedRecoveryState; SpinLockRelease(&XLogCtl->info_lck); return retval; } /* * Is this process allowed to insert new WAL records? * * Ordinarily this is essentially equivalent to !RecoveryInProgress(). * But we also have provisions for forcing the result "true" or "false" * within specific processes regardless of the global state. */ bool XLogInsertAllowed(void) { /* * If value is "unconditionally true" or "unconditionally false", just * return it. This provides the normal fast path once recovery is known * done. */ if (LocalXLogInsertAllowed >= 0) return (bool) LocalXLogInsertAllowed; /* * Else, must check to see if we're still in recovery. */ if (RecoveryInProgress()) return false; /* * On exit from recovery, reset to "unconditionally true", since there is * no need to keep checking. */ LocalXLogInsertAllowed = 1; return true; } /* * Make XLogInsertAllowed() return true in the current process only. * * Note: it is allowed to switch LocalXLogInsertAllowed back to -1 later, * and even call LocalSetXLogInsertAllowed() again after that. * * Returns the previous value of LocalXLogInsertAllowed. */ static int LocalSetXLogInsertAllowed(void) { int oldXLogAllowed = LocalXLogInsertAllowed; LocalXLogInsertAllowed = 1; return oldXLogAllowed; } /* * Return the current Redo pointer from shared memory. * * As a side-effect, the local RedoRecPtr copy is updated. */ XLogRecPtr GetRedoRecPtr(void) { XLogRecPtr ptr; /* * The possibly not up-to-date copy in XlogCtl is enough. Even if we * grabbed a WAL insertion lock to read the authoritative value in * Insert->RedoRecPtr, someone might update it just after we've released * the lock. */ SpinLockAcquire(&XLogCtl->info_lck); ptr = XLogCtl->RedoRecPtr; SpinLockRelease(&XLogCtl->info_lck); if (RedoRecPtr < ptr) RedoRecPtr = ptr; return RedoRecPtr; } /* * Return information needed to decide whether a modified block needs a * full-page image to be included in the WAL record. * * The returned values are cached copies from backend-private memory, and * possibly out-of-date or, indeed, uninitialized, in which case they will * be InvalidXLogRecPtr and false, respectively. XLogInsertRecord will * re-check them against up-to-date values, while holding the WAL insert lock. */ void GetFullPageWriteInfo(XLogRecPtr *RedoRecPtr_p, bool *doPageWrites_p) { *RedoRecPtr_p = RedoRecPtr; *doPageWrites_p = doPageWrites; } /* * GetInsertRecPtr -- Returns the current insert position. * * NOTE: The value *actually* returned is the position of the last full * xlog page. It lags behind the real insert position by at most 1 page. * For that, we don't need to scan through WAL insertion locks, and an * approximation is enough for the current usage of this function. */ XLogRecPtr GetInsertRecPtr(void) { XLogRecPtr recptr; SpinLockAcquire(&XLogCtl->info_lck); recptr = XLogCtl->LogwrtRqst.Write; SpinLockRelease(&XLogCtl->info_lck); return recptr; } /* * GetFlushRecPtr -- Returns the current flush position, ie, the last WAL * position known to be fsync'd to disk. This should only be used on a * system that is known not to be in recovery. */ XLogRecPtr GetFlushRecPtr(TimeLineID *insertTLI) { Assert(XLogCtl->SharedRecoveryState == RECOVERY_STATE_DONE); SpinLockAcquire(&XLogCtl->info_lck); LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); /* * If we're writing and flushing WAL, the time line can't be changing, so * no lock is required. */ if (insertTLI) *insertTLI = XLogCtl->InsertTimeLineID; return LogwrtResult.Flush; } /* * GetWALInsertionTimeLine -- Returns the current timeline of a system that * is not in recovery. */ TimeLineID GetWALInsertionTimeLine(void) { Assert(XLogCtl->SharedRecoveryState == RECOVERY_STATE_DONE); /* Since the value can't be changing, no lock is required. */ return XLogCtl->InsertTimeLineID; } /* * GetLastImportantRecPtr -- Returns the LSN of the last important record * inserted. All records not explicitly marked as unimportant are considered * important. * * The LSN is determined by computing the maximum of * WALInsertLocks[i].lastImportantAt. */ XLogRecPtr GetLastImportantRecPtr(void) { XLogRecPtr res = InvalidXLogRecPtr; int i; for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) { XLogRecPtr last_important; /* * Need to take a lock to prevent torn reads of the LSN, which are * possible on some of the supported platforms. WAL insert locks only * support exclusive mode, so we have to use that. */ LWLockAcquire(&WALInsertLocks[i].l.lock, LW_EXCLUSIVE); last_important = WALInsertLocks[i].l.lastImportantAt; LWLockRelease(&WALInsertLocks[i].l.lock); if (res < last_important) res = last_important; } return res; } /* * Get the time and LSN of the last xlog segment switch */ pg_time_t GetLastSegSwitchData(XLogRecPtr *lastSwitchLSN) { pg_time_t result; /* Need WALWriteLock, but shared lock is sufficient */ LWLockAcquire(WALWriteLock, LW_SHARED); result = XLogCtl->lastSegSwitchTime; *lastSwitchLSN = XLogCtl->lastSegSwitchLSN; LWLockRelease(WALWriteLock); return result; } /* * This must be called ONCE during postmaster or standalone-backend shutdown */ void ShutdownXLOG(int code, Datum arg) { /* * We should have an aux process resource owner to use, and we should not * be in a transaction that's installed some other resowner. */ Assert(AuxProcessResourceOwner != NULL); Assert(CurrentResourceOwner == NULL || CurrentResourceOwner == AuxProcessResourceOwner); CurrentResourceOwner = AuxProcessResourceOwner; /* Don't be chatty in standalone mode */ ereport(IsPostmasterEnvironment ? LOG : NOTICE, (errmsg("shutting down"))); /* * Signal walsenders to move to stopping state. */ WalSndInitStopping(); /* * Wait for WAL senders to be in stopping state. This prevents commands * from writing new WAL. */ WalSndWaitStopping(); if (RecoveryInProgress()) CreateRestartPoint(CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_IMMEDIATE); else { /* * If archiving is enabled, rotate the last XLOG file so that all the * remaining records are archived (postmaster wakes up the archiver * process one more time at the end of shutdown). The checkpoint * record will go to the next XLOG file and won't be archived (yet). */ if (XLogArchivingActive()) RequestXLogSwitch(false); CreateCheckPoint(CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_IMMEDIATE); } } /* * Log start of a checkpoint. */ static void LogCheckpointStart(int flags, bool restartpoint) { if (restartpoint) ereport(LOG, /* translator: the placeholders show checkpoint options */ (errmsg("restartpoint starting:%s%s%s%s%s%s%s%s", (flags & CHECKPOINT_IS_SHUTDOWN) ? " shutdown" : "", (flags & CHECKPOINT_END_OF_RECOVERY) ? " end-of-recovery" : "", (flags & CHECKPOINT_IMMEDIATE) ? " immediate" : "", (flags & CHECKPOINT_FORCE) ? " force" : "", (flags & CHECKPOINT_WAIT) ? " wait" : "", (flags & CHECKPOINT_CAUSE_XLOG) ? " wal" : "", (flags & CHECKPOINT_CAUSE_TIME) ? " time" : "", (flags & CHECKPOINT_FLUSH_ALL) ? " flush-all" : ""))); else ereport(LOG, /* translator: the placeholders show checkpoint options */ (errmsg("checkpoint starting:%s%s%s%s%s%s%s%s", (flags & CHECKPOINT_IS_SHUTDOWN) ? " shutdown" : "", (flags & CHECKPOINT_END_OF_RECOVERY) ? " end-of-recovery" : "", (flags & CHECKPOINT_IMMEDIATE) ? " immediate" : "", (flags & CHECKPOINT_FORCE) ? " force" : "", (flags & CHECKPOINT_WAIT) ? " wait" : "", (flags & CHECKPOINT_CAUSE_XLOG) ? " wal" : "", (flags & CHECKPOINT_CAUSE_TIME) ? " time" : "", (flags & CHECKPOINT_FLUSH_ALL) ? " flush-all" : ""))); } /* * Log end of a checkpoint. */ static void LogCheckpointEnd(bool restartpoint) { long write_msecs, sync_msecs, total_msecs, longest_msecs, average_msecs; uint64 average_sync_time; CheckpointStats.ckpt_end_t = GetCurrentTimestamp(); write_msecs = TimestampDifferenceMilliseconds(CheckpointStats.ckpt_write_t, CheckpointStats.ckpt_sync_t); sync_msecs = TimestampDifferenceMilliseconds(CheckpointStats.ckpt_sync_t, CheckpointStats.ckpt_sync_end_t); /* Accumulate checkpoint timing summary data, in milliseconds. */ PendingCheckpointerStats.checkpoint_write_time += write_msecs; PendingCheckpointerStats.checkpoint_sync_time += sync_msecs; /* * All of the published timing statistics are accounted for. Only * continue if a log message is to be written. */ if (!log_checkpoints) return; total_msecs = TimestampDifferenceMilliseconds(CheckpointStats.ckpt_start_t, CheckpointStats.ckpt_end_t); /* * Timing values returned from CheckpointStats are in microseconds. * Convert to milliseconds for consistent printing. */ longest_msecs = (long) ((CheckpointStats.ckpt_longest_sync + 999) / 1000); average_sync_time = 0; if (CheckpointStats.ckpt_sync_rels > 0) average_sync_time = CheckpointStats.ckpt_agg_sync_time / CheckpointStats.ckpt_sync_rels; average_msecs = (long) ((average_sync_time + 999) / 1000); /* * ControlFileLock is not required to see ControlFile->checkPoint and * ->checkPointCopy here as we are the only updator of those variables at * this moment. */ if (restartpoint) ereport(LOG, (errmsg("restartpoint complete: wrote %d buffers (%.1f%%); " "%d WAL file(s) added, %d removed, %d recycled; " "write=%ld.%03d s, sync=%ld.%03d s, total=%ld.%03d s; " "sync files=%d, longest=%ld.%03d s, average=%ld.%03d s; " "distance=%d kB, estimate=%d kB; " "lsn=%X/%X, redo lsn=%X/%X", CheckpointStats.ckpt_bufs_written, (double) CheckpointStats.ckpt_bufs_written * 100 / NBuffers, CheckpointStats.ckpt_segs_added, CheckpointStats.ckpt_segs_removed, CheckpointStats.ckpt_segs_recycled, write_msecs / 1000, (int) (write_msecs % 1000), sync_msecs / 1000, (int) (sync_msecs % 1000), total_msecs / 1000, (int) (total_msecs % 1000), CheckpointStats.ckpt_sync_rels, longest_msecs / 1000, (int) (longest_msecs % 1000), average_msecs / 1000, (int) (average_msecs % 1000), (int) (PrevCheckPointDistance / 1024.0), (int) (CheckPointDistanceEstimate / 1024.0), LSN_FORMAT_ARGS(ControlFile->checkPoint), LSN_FORMAT_ARGS(ControlFile->checkPointCopy.redo)))); else ereport(LOG, (errmsg("checkpoint complete: wrote %d buffers (%.1f%%); " "%d WAL file(s) added, %d removed, %d recycled; " "write=%ld.%03d s, sync=%ld.%03d s, total=%ld.%03d s; " "sync files=%d, longest=%ld.%03d s, average=%ld.%03d s; " "distance=%d kB, estimate=%d kB; " "lsn=%X/%X, redo lsn=%X/%X", CheckpointStats.ckpt_bufs_written, (double) CheckpointStats.ckpt_bufs_written * 100 / NBuffers, CheckpointStats.ckpt_segs_added, CheckpointStats.ckpt_segs_removed, CheckpointStats.ckpt_segs_recycled, write_msecs / 1000, (int) (write_msecs % 1000), sync_msecs / 1000, (int) (sync_msecs % 1000), total_msecs / 1000, (int) (total_msecs % 1000), CheckpointStats.ckpt_sync_rels, longest_msecs / 1000, (int) (longest_msecs % 1000), average_msecs / 1000, (int) (average_msecs % 1000), (int) (PrevCheckPointDistance / 1024.0), (int) (CheckPointDistanceEstimate / 1024.0), LSN_FORMAT_ARGS(ControlFile->checkPoint), LSN_FORMAT_ARGS(ControlFile->checkPointCopy.redo)))); } /* * Update the estimate of distance between checkpoints. * * The estimate is used to calculate the number of WAL segments to keep * preallocated, see XLOGfileslop(). */ static void UpdateCheckPointDistanceEstimate(uint64 nbytes) { /* * To estimate the number of segments consumed between checkpoints, keep a * moving average of the amount of WAL generated in previous checkpoint * cycles. However, if the load is bursty, with quiet periods and busy * periods, we want to cater for the peak load. So instead of a plain * moving average, let the average decline slowly if the previous cycle * used less WAL than estimated, but bump it up immediately if it used * more. * * When checkpoints are triggered by max_wal_size, this should converge to * CheckpointSegments * wal_segment_size, * * Note: This doesn't pay any attention to what caused the checkpoint. * Checkpoints triggered manually with CHECKPOINT command, or by e.g. * starting a base backup, are counted the same as those created * automatically. The slow-decline will largely mask them out, if they are * not frequent. If they are frequent, it seems reasonable to count them * in as any others; if you issue a manual checkpoint every 5 minutes and * never let a timed checkpoint happen, it makes sense to base the * preallocation on that 5 minute interval rather than whatever * checkpoint_timeout is set to. */ PrevCheckPointDistance = nbytes; if (CheckPointDistanceEstimate < nbytes) CheckPointDistanceEstimate = nbytes; else CheckPointDistanceEstimate = (0.90 * CheckPointDistanceEstimate + 0.10 * (double) nbytes); } /* * Update the ps display for a process running a checkpoint. Note that * this routine should not do any allocations so as it can be called * from a critical section. */ static void update_checkpoint_display(int flags, bool restartpoint, bool reset) { /* * The status is reported only for end-of-recovery and shutdown * checkpoints or shutdown restartpoints. Updating the ps display is * useful in those situations as it may not be possible to rely on * pg_stat_activity to see the status of the checkpointer or the startup * process. */ if ((flags & (CHECKPOINT_END_OF_RECOVERY | CHECKPOINT_IS_SHUTDOWN)) == 0) return; if (reset) set_ps_display(""); else { char activitymsg[128]; snprintf(activitymsg, sizeof(activitymsg), "performing %s%s%s", (flags & CHECKPOINT_END_OF_RECOVERY) ? "end-of-recovery " : "", (flags & CHECKPOINT_IS_SHUTDOWN) ? "shutdown " : "", restartpoint ? "restartpoint" : "checkpoint"); set_ps_display(activitymsg); } } /* * Perform a checkpoint --- either during shutdown, or on-the-fly * * flags is a bitwise OR of the following: * CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown. * CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery. * CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP, * ignoring checkpoint_completion_target parameter. * CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occurred * since the last one (implied by CHECKPOINT_IS_SHUTDOWN or * CHECKPOINT_END_OF_RECOVERY). * CHECKPOINT_FLUSH_ALL: also flush buffers of unlogged tables. * * Note: flags contains other bits, of interest here only for logging purposes. * In particular note that this routine is synchronous and does not pay * attention to CHECKPOINT_WAIT. * * If !shutdown then we are writing an online checkpoint. This is a very special * kind of operation and WAL record because the checkpoint action occurs over * a period of time yet logically occurs at just a single LSN. The logical * position of the WAL record (redo ptr) is the same or earlier than the * physical position. When we replay WAL we locate the checkpoint via its * physical position then read the redo ptr and actually start replay at the * earlier logical position. Note that we don't write *anything* to WAL at * the logical position, so that location could be any other kind of WAL record. * All of this mechanism allows us to continue working while we checkpoint. * As a result, timing of actions is critical here and be careful to note that * this function will likely take minutes to execute on a busy system. */ void CreateCheckPoint(int flags) { bool shutdown; CheckPoint checkPoint; XLogRecPtr recptr; XLogSegNo _logSegNo; XLogCtlInsert *Insert = &XLogCtl->Insert; uint32 freespace; XLogRecPtr PriorRedoPtr; XLogRecPtr curInsert; XLogRecPtr last_important_lsn; VirtualTransactionId *vxids; int nvxids; int oldXLogAllowed = 0; /* * An end-of-recovery checkpoint is really a shutdown checkpoint, just * issued at a different time. */ if (flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY)) shutdown = true; else shutdown = false; /* sanity check */ if (RecoveryInProgress() && (flags & CHECKPOINT_END_OF_RECOVERY) == 0) elog(ERROR, "can't create a checkpoint during recovery"); /* * Prepare to accumulate statistics. * * Note: because it is possible for log_checkpoints to change while a * checkpoint proceeds, we always accumulate stats, even if * log_checkpoints is currently off. */ MemSet(&CheckpointStats, 0, sizeof(CheckpointStats)); CheckpointStats.ckpt_start_t = GetCurrentTimestamp(); /* * Let smgr prepare for checkpoint; this has to happen outside the * critical section and before we determine the REDO pointer. Note that * smgr must not do anything that'd have to be undone if we decide no * checkpoint is needed. */ SyncPreCheckpoint(); /* * Use a critical section to force system panic if we have trouble. */ START_CRIT_SECTION(); if (shutdown) { LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->state = DB_SHUTDOWNING; UpdateControlFile(); LWLockRelease(ControlFileLock); } /* Begin filling in the checkpoint WAL record */ MemSet(&checkPoint, 0, sizeof(checkPoint)); checkPoint.time = (pg_time_t) time(NULL); /* * For Hot Standby, derive the oldestActiveXid before we fix the redo * pointer. This allows us to begin accumulating changes to assemble our * starting snapshot of locks and transactions. */ if (!shutdown && XLogStandbyInfoActive()) checkPoint.oldestActiveXid = GetOldestActiveTransactionId(); else checkPoint.oldestActiveXid = InvalidTransactionId; /* * Get location of last important record before acquiring insert locks (as * GetLastImportantRecPtr() also locks WAL locks). */ last_important_lsn = GetLastImportantRecPtr(); /* * We must block concurrent insertions while examining insert state to * determine the checkpoint REDO pointer. */ WALInsertLockAcquireExclusive(); curInsert = XLogBytePosToRecPtr(Insert->CurrBytePos); /* * If this isn't a shutdown or forced checkpoint, and if there has been no * WAL activity requiring a checkpoint, skip it. The idea here is to * avoid inserting duplicate checkpoints when the system is idle. */ if ((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY | CHECKPOINT_FORCE)) == 0) { if (last_important_lsn == ControlFile->checkPoint) { WALInsertLockRelease(); END_CRIT_SECTION(); ereport(DEBUG1, (errmsg_internal("checkpoint skipped because system is idle"))); return; } } /* * An end-of-recovery checkpoint is created before anyone is allowed to * write WAL. To allow us to write the checkpoint record, temporarily * enable XLogInsertAllowed. */ if (flags & CHECKPOINT_END_OF_RECOVERY) oldXLogAllowed = LocalSetXLogInsertAllowed(); checkPoint.ThisTimeLineID = XLogCtl->InsertTimeLineID; if (flags & CHECKPOINT_END_OF_RECOVERY) checkPoint.PrevTimeLineID = XLogCtl->PrevTimeLineID; else checkPoint.PrevTimeLineID = checkPoint.ThisTimeLineID; checkPoint.fullPageWrites = Insert->fullPageWrites; /* * Compute new REDO record ptr = location of next XLOG record. * * NB: this is NOT necessarily where the checkpoint record itself will be, * since other backends may insert more XLOG records while we're off doing * the buffer flush work. Those XLOG records are logically after the * checkpoint, even though physically before it. Got that? */ freespace = INSERT_FREESPACE(curInsert); if (freespace == 0) { if (XLogSegmentOffset(curInsert, wal_segment_size) == 0) curInsert += SizeOfXLogLongPHD; else curInsert += SizeOfXLogShortPHD; } checkPoint.redo = curInsert; /* * Here we update the shared RedoRecPtr for future XLogInsert calls; this * must be done while holding all the insertion locks. * * Note: if we fail to complete the checkpoint, RedoRecPtr will be left * pointing past where it really needs to point. This is okay; the only * consequence is that XLogInsert might back up whole buffers that it * didn't really need to. We can't postpone advancing RedoRecPtr because * XLogInserts that happen while we are dumping buffers must assume that * their buffer changes are not included in the checkpoint. */ RedoRecPtr = XLogCtl->Insert.RedoRecPtr = checkPoint.redo; /* * Now we can release the WAL insertion locks, allowing other xacts to * proceed while we are flushing disk buffers. */ WALInsertLockRelease(); /* Update the info_lck-protected copy of RedoRecPtr as well */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->RedoRecPtr = checkPoint.redo; SpinLockRelease(&XLogCtl->info_lck); /* * If enabled, log checkpoint start. We postpone this until now so as not * to log anything if we decided to skip the checkpoint. */ if (log_checkpoints) LogCheckpointStart(flags, false); /* Update the process title */ update_checkpoint_display(flags, false, false); TRACE_POSTGRESQL_CHECKPOINT_START(flags); /* * Get the other info we need for the checkpoint record. * * We don't need to save oldestClogXid in the checkpoint, it only matters * for the short period in which clog is being truncated, and if we crash * during that we'll redo the clog truncation and fix up oldestClogXid * there. */ LWLockAcquire(XidGenLock, LW_SHARED); checkPoint.nextXid = ShmemVariableCache->nextXid; checkPoint.oldestXid = ShmemVariableCache->oldestXid; checkPoint.oldestXidDB = ShmemVariableCache->oldestXidDB; LWLockRelease(XidGenLock); LWLockAcquire(CommitTsLock, LW_SHARED); checkPoint.oldestCommitTsXid = ShmemVariableCache->oldestCommitTsXid; checkPoint.newestCommitTsXid = ShmemVariableCache->newestCommitTsXid; LWLockRelease(CommitTsLock); LWLockAcquire(OidGenLock, LW_SHARED); checkPoint.nextOid = ShmemVariableCache->nextOid; if (!shutdown) checkPoint.nextOid += ShmemVariableCache->oidCount; LWLockRelease(OidGenLock); MultiXactGetCheckptMulti(shutdown, &checkPoint.nextMulti, &checkPoint.nextMultiOffset, &checkPoint.oldestMulti, &checkPoint.oldestMultiDB); /* * Having constructed the checkpoint record, ensure all shmem disk buffers * and commit-log buffers are flushed to disk. * * This I/O could fail for various reasons. If so, we will fail to * complete the checkpoint, but there is no reason to force a system * panic. Accordingly, exit critical section while doing it. */ END_CRIT_SECTION(); /* * In some cases there are groups of actions that must all occur on one * side or the other of a checkpoint record. Before flushing the * checkpoint record we must explicitly wait for any backend currently * performing those groups of actions. * * One example is end of transaction, so we must wait for any transactions * that are currently in commit critical sections. If an xact inserted * its commit record into XLOG just before the REDO point, then a crash * restart from the REDO point would not replay that record, which means * that our flushing had better include the xact's update of pg_xact. So * we wait till he's out of his commit critical section before proceeding. * See notes in RecordTransactionCommit(). * * Because we've already released the insertion locks, this test is a bit * fuzzy: it is possible that we will wait for xacts we didn't really need * to wait for. But the delay should be short and it seems better to make * checkpoint take a bit longer than to hold off insertions longer than * necessary. (In fact, the whole reason we have this issue is that xact.c * does commit record XLOG insertion and clog update as two separate steps * protected by different locks, but again that seems best on grounds of * minimizing lock contention.) * * A transaction that has not yet set delayChkptFlags when we look cannot * be at risk, since it has not inserted its commit record yet; and one * that's already cleared it is not at risk either, since it's done fixing * clog and we will correctly flush the update below. So we cannot miss * any xacts we need to wait for. */ vxids = GetVirtualXIDsDelayingChkpt(&nvxids, DELAY_CHKPT_START); if (nvxids > 0) { do { pg_usleep(10000L); /* wait for 10 msec */ } while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids, DELAY_CHKPT_START)); } pfree(vxids); CheckPointGuts(checkPoint.redo, flags); vxids = GetVirtualXIDsDelayingChkpt(&nvxids, DELAY_CHKPT_COMPLETE); if (nvxids > 0) { do { pg_usleep(10000L); /* wait for 10 msec */ } while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids, DELAY_CHKPT_COMPLETE)); } pfree(vxids); /* * Take a snapshot of running transactions and write this to WAL. This * allows us to reconstruct the state of running transactions during * archive recovery, if required. Skip, if this info disabled. * * If we are shutting down, or Startup process is completing crash * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) LogStandbySnapshot(); START_CRIT_SECTION(); /* * Now insert the checkpoint record into XLOG. */ XLogBeginInsert(); XLogRegisterData((char *) (&checkPoint), sizeof(checkPoint)); recptr = XLogInsert(RM_XLOG_ID, shutdown ? XLOG_CHECKPOINT_SHUTDOWN : XLOG_CHECKPOINT_ONLINE); XLogFlush(recptr); /* * We mustn't write any new WAL after a shutdown checkpoint, or it will be * overwritten at next startup. No-one should even try, this just allows * sanity-checking. In the case of an end-of-recovery checkpoint, we want * to just temporarily disable writing until the system has exited * recovery. */ if (shutdown) { if (flags & CHECKPOINT_END_OF_RECOVERY) LocalXLogInsertAllowed = oldXLogAllowed; else LocalXLogInsertAllowed = 0; /* never again write WAL */ } /* * We now have ProcLastRecPtr = start of actual checkpoint record, recptr * = end of actual checkpoint record. */ if (shutdown && checkPoint.redo != ProcLastRecPtr) ereport(PANIC, (errmsg("concurrent write-ahead log activity while database system is shutting down"))); /* * Remember the prior checkpoint's redo ptr for * UpdateCheckPointDistanceEstimate() */ PriorRedoPtr = ControlFile->checkPointCopy.redo; /* * Update the control file. */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); if (shutdown) ControlFile->state = DB_SHUTDOWNED; ControlFile->checkPoint = ProcLastRecPtr; ControlFile->checkPointCopy = checkPoint; /* crash recovery should always recover to the end of WAL */ ControlFile->minRecoveryPoint = InvalidXLogRecPtr; ControlFile->minRecoveryPointTLI = 0; /* * Persist unloggedLSN value. It's reset on crash recovery, so this goes * unused on non-shutdown checkpoints, but seems useful to store it always * for debugging purposes. */ SpinLockAcquire(&XLogCtl->ulsn_lck); ControlFile->unloggedLSN = XLogCtl->unloggedLSN; SpinLockRelease(&XLogCtl->ulsn_lck); UpdateControlFile(); LWLockRelease(ControlFileLock); /* Update shared-memory copy of checkpoint XID/epoch */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->ckptFullXid = checkPoint.nextXid; SpinLockRelease(&XLogCtl->info_lck); /* * We are now done with critical updates; no need for system panic if we * have trouble while fooling with old log segments. */ END_CRIT_SECTION(); /* * Let smgr do post-checkpoint cleanup (eg, deleting old files). */ SyncPostCheckpoint(); /* * Update the average distance between checkpoints if the prior checkpoint * exists. */ if (PriorRedoPtr != InvalidXLogRecPtr) UpdateCheckPointDistanceEstimate(RedoRecPtr - PriorRedoPtr); /* * Delete old log files, those no longer needed for last checkpoint to * prevent the disk holding the xlog from growing full. */ XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size); KeepLogSeg(recptr, &_logSegNo); if (InvalidateObsoleteReplicationSlots(RS_INVAL_WAL_REMOVED, _logSegNo, InvalidOid, InvalidTransactionId)) { /* * Some slots have been invalidated; recalculate the old-segment * horizon, starting again from RedoRecPtr. */ XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size); KeepLogSeg(recptr, &_logSegNo); } _logSegNo--; RemoveOldXlogFiles(_logSegNo, RedoRecPtr, recptr, checkPoint.ThisTimeLineID); /* * Make more log segments if needed. (Do this after recycling old log * segments, since that may supply some of the needed files.) */ if (!shutdown) PreallocXlogFiles(recptr, checkPoint.ThisTimeLineID); /* * Truncate pg_subtrans if possible. We can throw away all data before * the oldest XMIN of any running transaction. No future transaction will * attempt to reference any pg_subtrans entry older than that (see Asserts * in subtrans.c). During recovery, though, we mustn't do this because * StartupSUBTRANS hasn't been called yet. */ if (!RecoveryInProgress()) TruncateSUBTRANS(GetOldestTransactionIdConsideredRunning()); /* Real work is done; log and update stats. */ LogCheckpointEnd(false); /* Reset the process title */ update_checkpoint_display(flags, false, true); TRACE_POSTGRESQL_CHECKPOINT_DONE(CheckpointStats.ckpt_bufs_written, NBuffers, CheckpointStats.ckpt_segs_added, CheckpointStats.ckpt_segs_removed, CheckpointStats.ckpt_segs_recycled); } /* * Mark the end of recovery in WAL though without running a full checkpoint. * We can expect that a restartpoint is likely to be in progress as we * do this, though we are unwilling to wait for it to complete. * * CreateRestartPoint() allows for the case where recovery may end before * the restartpoint completes so there is no concern of concurrent behaviour. */ static void CreateEndOfRecoveryRecord(void) { xl_end_of_recovery xlrec; XLogRecPtr recptr; /* sanity check */ if (!RecoveryInProgress()) elog(ERROR, "can only be used to end recovery"); xlrec.end_time = GetCurrentTimestamp(); WALInsertLockAcquireExclusive(); xlrec.ThisTimeLineID = XLogCtl->InsertTimeLineID; xlrec.PrevTimeLineID = XLogCtl->PrevTimeLineID; WALInsertLockRelease(); START_CRIT_SECTION(); XLogBeginInsert(); XLogRegisterData((char *) &xlrec, sizeof(xl_end_of_recovery)); recptr = XLogInsert(RM_XLOG_ID, XLOG_END_OF_RECOVERY); XLogFlush(recptr); /* * Update the control file so that crash recovery can follow the timeline * changes to this point. */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->minRecoveryPoint = recptr; ControlFile->minRecoveryPointTLI = xlrec.ThisTimeLineID; UpdateControlFile(); LWLockRelease(ControlFileLock); END_CRIT_SECTION(); } /* * Write an OVERWRITE_CONTRECORD message. * * When on WAL replay we expect a continuation record at the start of a page * that is not there, recovery ends and WAL writing resumes at that point. * But it's wrong to resume writing new WAL back at the start of the record * that was broken, because downstream consumers of that WAL (physical * replicas) are not prepared to "rewind". So the first action after * finishing replay of all valid WAL must be to write a record of this type * at the point where the contrecord was missing; to support xlogreader * detecting the special case, XLP_FIRST_IS_OVERWRITE_CONTRECORD is also added * to the page header where the record occurs. xlogreader has an ad-hoc * mechanism to report metadata about the broken record, which is what we * use here. * * At replay time, XLP_FIRST_IS_OVERWRITE_CONTRECORD instructs xlogreader to * skip the record it was reading, and pass back the LSN of the skipped * record, so that its caller can verify (on "replay" of that record) that the * XLOG_OVERWRITE_CONTRECORD matches what was effectively overwritten. * * 'aborted_lsn' is the beginning position of the record that was incomplete. * It is included in the WAL record. 'pagePtr' and 'newTLI' point to the * beginning of the XLOG page where the record is to be inserted. They must * match the current WAL insert position, they're passed here just so that we * can verify that. */ static XLogRecPtr CreateOverwriteContrecordRecord(XLogRecPtr aborted_lsn, XLogRecPtr pagePtr, TimeLineID newTLI) { xl_overwrite_contrecord xlrec; XLogRecPtr recptr; XLogPageHeader pagehdr; XLogRecPtr startPos; /* sanity checks */ if (!RecoveryInProgress()) elog(ERROR, "can only be used at end of recovery"); if (pagePtr % XLOG_BLCKSZ != 0) elog(ERROR, "invalid position for missing continuation record %X/%X", LSN_FORMAT_ARGS(pagePtr)); /* The current WAL insert position should be right after the page header */ startPos = pagePtr; if (XLogSegmentOffset(startPos, wal_segment_size) == 0) startPos += SizeOfXLogLongPHD; else startPos += SizeOfXLogShortPHD; recptr = GetXLogInsertRecPtr(); if (recptr != startPos) elog(ERROR, "invalid WAL insert position %X/%X for OVERWRITE_CONTRECORD", LSN_FORMAT_ARGS(recptr)); START_CRIT_SECTION(); /* * Initialize the XLOG page header (by GetXLogBuffer), and set the * XLP_FIRST_IS_OVERWRITE_CONTRECORD flag. * * No other backend is allowed to write WAL yet, so acquiring the WAL * insertion lock is just pro forma. */ WALInsertLockAcquire(); pagehdr = (XLogPageHeader) GetXLogBuffer(pagePtr, newTLI); pagehdr->xlp_info |= XLP_FIRST_IS_OVERWRITE_CONTRECORD; WALInsertLockRelease(); /* * Insert the XLOG_OVERWRITE_CONTRECORD record as the first record on the * page. We know it becomes the first record, because no other backend is * allowed to write WAL yet. */ XLogBeginInsert(); xlrec.overwritten_lsn = aborted_lsn; xlrec.overwrite_time = GetCurrentTimestamp(); XLogRegisterData((char *) &xlrec, sizeof(xl_overwrite_contrecord)); recptr = XLogInsert(RM_XLOG_ID, XLOG_OVERWRITE_CONTRECORD); /* check that the record was inserted to the right place */ if (ProcLastRecPtr != startPos) elog(ERROR, "OVERWRITE_CONTRECORD was inserted to unexpected position %X/%X", LSN_FORMAT_ARGS(ProcLastRecPtr)); XLogFlush(recptr); END_CRIT_SECTION(); return recptr; } /* * Flush all data in shared memory to disk, and fsync * * This is the common code shared between regular checkpoints and * recovery restartpoints. */ static void CheckPointGuts(XLogRecPtr checkPointRedo, int flags) { CheckPointRelationMap(); CheckPointReplicationSlots(); CheckPointSnapBuild(); CheckPointLogicalRewriteHeap(); CheckPointReplicationOrigin(); /* Write out all dirty data in SLRUs and the main buffer pool */ TRACE_POSTGRESQL_BUFFER_CHECKPOINT_START(flags); CheckpointStats.ckpt_write_t = GetCurrentTimestamp(); CheckPointCLOG(); CheckPointCommitTs(); CheckPointSUBTRANS(); CheckPointMultiXact(); CheckPointPredicate(); CheckPointBuffers(flags); /* Perform all queued up fsyncs */ TRACE_POSTGRESQL_BUFFER_CHECKPOINT_SYNC_START(); CheckpointStats.ckpt_sync_t = GetCurrentTimestamp(); ProcessSyncRequests(); CheckpointStats.ckpt_sync_end_t = GetCurrentTimestamp(); TRACE_POSTGRESQL_BUFFER_CHECKPOINT_DONE(); /* We deliberately delay 2PC checkpointing as long as possible */ CheckPointTwoPhase(checkPointRedo); } /* * Save a checkpoint for recovery restart if appropriate * * This function is called each time a checkpoint record is read from XLOG. * It must determine whether the checkpoint represents a safe restartpoint or * not. If so, the checkpoint record is stashed in shared memory so that * CreateRestartPoint can consult it. (Note that the latter function is * executed by the checkpointer, while this one will be executed by the * startup process.) */ static void RecoveryRestartPoint(const CheckPoint *checkPoint, XLogReaderState *record) { /* * Also refrain from creating a restartpoint if we have seen any * references to non-existent pages. Restarting recovery from the * restartpoint would not see the references, so we would lose the * cross-check that the pages belonged to a relation that was dropped * later. */ if (XLogHaveInvalidPages()) { elog(trace_recovery(DEBUG2), "could not record restart point at %X/%X because there " "are unresolved references to invalid pages", LSN_FORMAT_ARGS(checkPoint->redo)); return; } /* * Copy the checkpoint record to shared memory, so that checkpointer can * work out the next time it wants to perform a restartpoint. */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->lastCheckPointRecPtr = record->ReadRecPtr; XLogCtl->lastCheckPointEndPtr = record->EndRecPtr; XLogCtl->lastCheckPoint = *checkPoint; SpinLockRelease(&XLogCtl->info_lck); } /* * Establish a restartpoint if possible. * * This is similar to CreateCheckPoint, but is used during WAL recovery * to establish a point from which recovery can roll forward without * replaying the entire recovery log. * * Returns true if a new restartpoint was established. We can only establish * a restartpoint if we have replayed a safe checkpoint record since last * restartpoint. */ bool CreateRestartPoint(int flags) { XLogRecPtr lastCheckPointRecPtr; XLogRecPtr lastCheckPointEndPtr; CheckPoint lastCheckPoint; XLogRecPtr PriorRedoPtr; XLogRecPtr receivePtr; XLogRecPtr replayPtr; TimeLineID replayTLI; XLogRecPtr endptr; XLogSegNo _logSegNo; TimestampTz xtime; /* Concurrent checkpoint/restartpoint cannot happen */ Assert(!IsUnderPostmaster || MyBackendType == B_CHECKPOINTER); /* Get a local copy of the last safe checkpoint record. */ SpinLockAcquire(&XLogCtl->info_lck); lastCheckPointRecPtr = XLogCtl->lastCheckPointRecPtr; lastCheckPointEndPtr = XLogCtl->lastCheckPointEndPtr; lastCheckPoint = XLogCtl->lastCheckPoint; SpinLockRelease(&XLogCtl->info_lck); /* * Check that we're still in recovery mode. It's ok if we exit recovery * mode after this check, the restart point is valid anyway. */ if (!RecoveryInProgress()) { ereport(DEBUG2, (errmsg_internal("skipping restartpoint, recovery has already ended"))); return false; } /* * If the last checkpoint record we've replayed is already our last * restartpoint, we can't perform a new restart point. We still update * minRecoveryPoint in that case, so that if this is a shutdown restart * point, we won't start up earlier than before. That's not strictly * necessary, but when hot standby is enabled, it would be rather weird if * the database opened up for read-only connections at a point-in-time * before the last shutdown. Such time travel is still possible in case of * immediate shutdown, though. * * We don't explicitly advance minRecoveryPoint when we do create a * restartpoint. It's assumed that flushing the buffers will do that as a * side-effect. */ if (XLogRecPtrIsInvalid(lastCheckPointRecPtr) || lastCheckPoint.redo <= ControlFile->checkPointCopy.redo) { ereport(DEBUG2, (errmsg_internal("skipping restartpoint, already performed at %X/%X", LSN_FORMAT_ARGS(lastCheckPoint.redo)))); UpdateMinRecoveryPoint(InvalidXLogRecPtr, true); if (flags & CHECKPOINT_IS_SHUTDOWN) { LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY; UpdateControlFile(); LWLockRelease(ControlFileLock); } return false; } /* * Update the shared RedoRecPtr so that the startup process can calculate * the number of segments replayed since last restartpoint, and request a * restartpoint if it exceeds CheckPointSegments. * * Like in CreateCheckPoint(), hold off insertions to update it, although * during recovery this is just pro forma, because no WAL insertions are * happening. */ WALInsertLockAcquireExclusive(); RedoRecPtr = XLogCtl->Insert.RedoRecPtr = lastCheckPoint.redo; WALInsertLockRelease(); /* Also update the info_lck-protected copy */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->RedoRecPtr = lastCheckPoint.redo; SpinLockRelease(&XLogCtl->info_lck); /* * Prepare to accumulate statistics. * * Note: because it is possible for log_checkpoints to change while a * checkpoint proceeds, we always accumulate stats, even if * log_checkpoints is currently off. */ MemSet(&CheckpointStats, 0, sizeof(CheckpointStats)); CheckpointStats.ckpt_start_t = GetCurrentTimestamp(); if (log_checkpoints) LogCheckpointStart(flags, true); /* Update the process title */ update_checkpoint_display(flags, true, false); CheckPointGuts(lastCheckPoint.redo, flags); /* * Remember the prior checkpoint's redo ptr for * UpdateCheckPointDistanceEstimate() */ PriorRedoPtr = ControlFile->checkPointCopy.redo; /* * Update pg_control, using current time. Check that it still shows an * older checkpoint, else do nothing; this is a quick hack to make sure * nothing really bad happens if somehow we get here after the * end-of-recovery checkpoint. */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); if (ControlFile->checkPointCopy.redo < lastCheckPoint.redo) { /* * Update the checkpoint information. We do this even if the cluster * does not show DB_IN_ARCHIVE_RECOVERY to match with the set of WAL * segments recycled below. */ ControlFile->checkPoint = lastCheckPointRecPtr; ControlFile->checkPointCopy = lastCheckPoint; /* * Ensure minRecoveryPoint is past the checkpoint record and update it * if the control file still shows DB_IN_ARCHIVE_RECOVERY. Normally, * this will have happened already while writing out dirty buffers, * but not necessarily - e.g. because no buffers were dirtied. We do * this because a backup performed in recovery uses minRecoveryPoint * to determine which WAL files must be included in the backup, and * the file (or files) containing the checkpoint record must be * included, at a minimum. Note that for an ordinary restart of * recovery there's no value in having the minimum recovery point any * earlier than this anyway, because redo will begin just after the * checkpoint record. */ if (ControlFile->state == DB_IN_ARCHIVE_RECOVERY) { if (ControlFile->minRecoveryPoint < lastCheckPointEndPtr) { ControlFile->minRecoveryPoint = lastCheckPointEndPtr; ControlFile->minRecoveryPointTLI = lastCheckPoint.ThisTimeLineID; /* update local copy */ LocalMinRecoveryPoint = ControlFile->minRecoveryPoint; LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI; } if (flags & CHECKPOINT_IS_SHUTDOWN) ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY; } UpdateControlFile(); } LWLockRelease(ControlFileLock); /* * Update the average distance between checkpoints/restartpoints if the * prior checkpoint exists. */ if (PriorRedoPtr != InvalidXLogRecPtr) UpdateCheckPointDistanceEstimate(RedoRecPtr - PriorRedoPtr); /* * Delete old log files, those no longer needed for last restartpoint to * prevent the disk holding the xlog from growing full. */ XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size); /* * Retreat _logSegNo using the current end of xlog replayed or received, * whichever is later. */ receivePtr = GetWalRcvFlushRecPtr(NULL, NULL); replayPtr = GetXLogReplayRecPtr(&replayTLI); endptr = (receivePtr < replayPtr) ? replayPtr : receivePtr; KeepLogSeg(endptr, &_logSegNo); if (InvalidateObsoleteReplicationSlots(RS_INVAL_WAL_REMOVED, _logSegNo, InvalidOid, InvalidTransactionId)) { /* * Some slots have been invalidated; recalculate the old-segment * horizon, starting again from RedoRecPtr. */ XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size); KeepLogSeg(endptr, &_logSegNo); } _logSegNo--; /* * Try to recycle segments on a useful timeline. If we've been promoted * since the beginning of this restartpoint, use the new timeline chosen * at end of recovery. If we're still in recovery, use the timeline we're * currently replaying. * * There is no guarantee that the WAL segments will be useful on the * current timeline; if recovery proceeds to a new timeline right after * this, the pre-allocated WAL segments on this timeline will not be used, * and will go wasted until recycled on the next restartpoint. We'll live * with that. */ if (!RecoveryInProgress()) replayTLI = XLogCtl->InsertTimeLineID; RemoveOldXlogFiles(_logSegNo, RedoRecPtr, endptr, replayTLI); /* * Make more log segments if needed. (Do this after recycling old log * segments, since that may supply some of the needed files.) */ PreallocXlogFiles(endptr, replayTLI); /* * Truncate pg_subtrans if possible. We can throw away all data before * the oldest XMIN of any running transaction. No future transaction will * attempt to reference any pg_subtrans entry older than that (see Asserts * in subtrans.c). When hot standby is disabled, though, we mustn't do * this because StartupSUBTRANS hasn't been called yet. */ if (EnableHotStandby) TruncateSUBTRANS(GetOldestTransactionIdConsideredRunning()); /* Real work is done; log and update stats. */ LogCheckpointEnd(true); /* Reset the process title */ update_checkpoint_display(flags, true, true); xtime = GetLatestXTime(); ereport((log_checkpoints ? LOG : DEBUG2), (errmsg("recovery restart point at %X/%X", LSN_FORMAT_ARGS(lastCheckPoint.redo)), xtime ? errdetail("Last completed transaction was at log time %s.", timestamptz_to_str(xtime)) : 0)); /* * Finally, execute archive_cleanup_command, if any. */ if (archiveCleanupCommand && strcmp(archiveCleanupCommand, "") != 0) ExecuteRecoveryCommand(archiveCleanupCommand, "archive_cleanup_command", false, WAIT_EVENT_ARCHIVE_CLEANUP_COMMAND); return true; } /* * Report availability of WAL for the given target LSN * (typically a slot's restart_lsn) * * Returns one of the following enum values: * * * WALAVAIL_RESERVED means targetLSN is available and it is in the range of * max_wal_size. * * * WALAVAIL_EXTENDED means it is still available by preserving extra * segments beyond max_wal_size. If max_slot_wal_keep_size is smaller * than max_wal_size, this state is not returned. * * * WALAVAIL_UNRESERVED means it is being lost and the next checkpoint will * remove reserved segments. The walsender using this slot may return to the * above. * * * WALAVAIL_REMOVED means it has been removed. A replication stream on * a slot with this LSN cannot continue. (Any associated walsender * processes should have been terminated already.) * * * WALAVAIL_INVALID_LSN means the slot hasn't been set to reserve WAL. */ WALAvailability GetWALAvailability(XLogRecPtr targetLSN) { XLogRecPtr currpos; /* current write LSN */ XLogSegNo currSeg; /* segid of currpos */ XLogSegNo targetSeg; /* segid of targetLSN */ XLogSegNo oldestSeg; /* actual oldest segid */ XLogSegNo oldestSegMaxWalSize; /* oldest segid kept by max_wal_size */ XLogSegNo oldestSlotSeg; /* oldest segid kept by slot */ uint64 keepSegs; /* * slot does not reserve WAL. Either deactivated, or has never been active */ if (XLogRecPtrIsInvalid(targetLSN)) return WALAVAIL_INVALID_LSN; /* * Calculate the oldest segment currently reserved by all slots, * considering wal_keep_size and max_slot_wal_keep_size. Initialize * oldestSlotSeg to the current segment. */ currpos = GetXLogWriteRecPtr(); XLByteToSeg(currpos, oldestSlotSeg, wal_segment_size); KeepLogSeg(currpos, &oldestSlotSeg); /* * Find the oldest extant segment file. We get 1 until checkpoint removes * the first WAL segment file since startup, which causes the status being * wrong under certain abnormal conditions but that doesn't actually harm. */ oldestSeg = XLogGetLastRemovedSegno() + 1; /* calculate oldest segment by max_wal_size */ XLByteToSeg(currpos, currSeg, wal_segment_size); keepSegs = ConvertToXSegs(max_wal_size_mb, wal_segment_size) + 1; if (currSeg > keepSegs) oldestSegMaxWalSize = currSeg - keepSegs; else oldestSegMaxWalSize = 1; /* the segment we care about */ XLByteToSeg(targetLSN, targetSeg, wal_segment_size); /* * No point in returning reserved or extended status values if the * targetSeg is known to be lost. */ if (targetSeg >= oldestSlotSeg) { /* show "reserved" when targetSeg is within max_wal_size */ if (targetSeg >= oldestSegMaxWalSize) return WALAVAIL_RESERVED; /* being retained by slots exceeding max_wal_size */ return WALAVAIL_EXTENDED; } /* WAL segments are no longer retained but haven't been removed yet */ if (targetSeg >= oldestSeg) return WALAVAIL_UNRESERVED; /* Definitely lost */ return WALAVAIL_REMOVED; } /* * Retreat *logSegNo to the last segment that we need to retain because of * either wal_keep_size or replication slots. * * This is calculated by subtracting wal_keep_size from the given xlog * location, recptr and by making sure that that result is below the * requirement of replication slots. For the latter criterion we do consider * the effects of max_slot_wal_keep_size: reserve at most that much space back * from recptr. * * Note about replication slots: if this function calculates a value * that's further ahead than what slots need reserved, then affected * slots need to be invalidated and this function invoked again. * XXX it might be a good idea to rewrite this function so that * invalidation is optionally done here, instead. */ static void KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo) { XLogSegNo currSegNo; XLogSegNo segno; XLogRecPtr keep; XLByteToSeg(recptr, currSegNo, wal_segment_size); segno = currSegNo; /* * Calculate how many segments are kept by slots first, adjusting for * max_slot_wal_keep_size. */ keep = XLogGetReplicationSlotMinimumLSN(); if (keep != InvalidXLogRecPtr && keep < recptr) { XLByteToSeg(keep, segno, wal_segment_size); /* Cap by max_slot_wal_keep_size ... */ if (max_slot_wal_keep_size_mb >= 0) { uint64 slot_keep_segs; slot_keep_segs = ConvertToXSegs(max_slot_wal_keep_size_mb, wal_segment_size); if (currSegNo - segno > slot_keep_segs) segno = currSegNo - slot_keep_segs; } } /* but, keep at least wal_keep_size if that's set */ if (wal_keep_size_mb > 0) { uint64 keep_segs; keep_segs = ConvertToXSegs(wal_keep_size_mb, wal_segment_size); if (currSegNo - segno < keep_segs) { /* avoid underflow, don't go below 1 */ if (currSegNo <= keep_segs) segno = 1; else segno = currSegNo - keep_segs; } } /* don't delete WAL segments newer than the calculated segment */ if (segno < *logSegNo) *logSegNo = segno; } /* * Write a NEXTOID log record */ void XLogPutNextOid(Oid nextOid) { XLogBeginInsert(); XLogRegisterData((char *) (&nextOid), sizeof(Oid)); (void) XLogInsert(RM_XLOG_ID, XLOG_NEXTOID); /* * We need not flush the NEXTOID record immediately, because any of the * just-allocated OIDs could only reach disk as part of a tuple insert or * update that would have its own XLOG record that must follow the NEXTOID * record. Therefore, the standard buffer LSN interlock applied to those * records will ensure no such OID reaches disk before the NEXTOID record * does. * * Note, however, that the above statement only covers state "within" the * database. When we use a generated OID as a file or directory name, we * are in a sense violating the basic WAL rule, because that filesystem * change may reach disk before the NEXTOID WAL record does. The impact * of this is that if a database crash occurs immediately afterward, we * might after restart re-generate the same OID and find that it conflicts * with the leftover file or directory. But since for safety's sake we * always loop until finding a nonconflicting filename, this poses no real * problem in practice. See pgsql-hackers discussion 27-Sep-2006. */ } /* * Write an XLOG SWITCH record. * * Here we just blindly issue an XLogInsert request for the record. * All the magic happens inside XLogInsert. * * The return value is either the end+1 address of the switch record, * or the end+1 address of the prior segment if we did not need to * write a switch record because we are already at segment start. */ XLogRecPtr RequestXLogSwitch(bool mark_unimportant) { XLogRecPtr RecPtr; /* XLOG SWITCH has no data */ XLogBeginInsert(); if (mark_unimportant) XLogSetRecordFlags(XLOG_MARK_UNIMPORTANT); RecPtr = XLogInsert(RM_XLOG_ID, XLOG_SWITCH); return RecPtr; } /* * Write a RESTORE POINT record */ XLogRecPtr XLogRestorePoint(const char *rpName) { XLogRecPtr RecPtr; xl_restore_point xlrec; xlrec.rp_time = GetCurrentTimestamp(); strlcpy(xlrec.rp_name, rpName, MAXFNAMELEN); XLogBeginInsert(); XLogRegisterData((char *) &xlrec, sizeof(xl_restore_point)); RecPtr = XLogInsert(RM_XLOG_ID, XLOG_RESTORE_POINT); ereport(LOG, (errmsg("restore point \"%s\" created at %X/%X", rpName, LSN_FORMAT_ARGS(RecPtr)))); return RecPtr; } /* * Check if any of the GUC parameters that are critical for hot standby * have changed, and update the value in pg_control file if necessary. */ static void XLogReportParameters(void) { if (wal_level != ControlFile->wal_level || wal_log_hints != ControlFile->wal_log_hints || MaxConnections != ControlFile->MaxConnections || max_worker_processes != ControlFile->max_worker_processes || max_wal_senders != ControlFile->max_wal_senders || max_prepared_xacts != ControlFile->max_prepared_xacts || max_locks_per_xact != ControlFile->max_locks_per_xact || track_commit_timestamp != ControlFile->track_commit_timestamp) { /* * The change in number of backend slots doesn't need to be WAL-logged * if archiving is not enabled, as you can't start archive recovery * with wal_level=minimal anyway. We don't really care about the * values in pg_control either if wal_level=minimal, but seems better * to keep them up-to-date to avoid confusion. */ if (wal_level != ControlFile->wal_level || XLogIsNeeded()) { xl_parameter_change xlrec; XLogRecPtr recptr; xlrec.MaxConnections = MaxConnections; xlrec.max_worker_processes = max_worker_processes; xlrec.max_wal_senders = max_wal_senders; xlrec.max_prepared_xacts = max_prepared_xacts; xlrec.max_locks_per_xact = max_locks_per_xact; xlrec.wal_level = wal_level; xlrec.wal_log_hints = wal_log_hints; xlrec.track_commit_timestamp = track_commit_timestamp; XLogBeginInsert(); XLogRegisterData((char *) &xlrec, sizeof(xlrec)); recptr = XLogInsert(RM_XLOG_ID, XLOG_PARAMETER_CHANGE); XLogFlush(recptr); } LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->MaxConnections = MaxConnections; ControlFile->max_worker_processes = max_worker_processes; ControlFile->max_wal_senders = max_wal_senders; ControlFile->max_prepared_xacts = max_prepared_xacts; ControlFile->max_locks_per_xact = max_locks_per_xact; ControlFile->wal_level = wal_level; ControlFile->wal_log_hints = wal_log_hints; ControlFile->track_commit_timestamp = track_commit_timestamp; UpdateControlFile(); LWLockRelease(ControlFileLock); } } /* * Update full_page_writes in shared memory, and write an * XLOG_FPW_CHANGE record if necessary. * * Note: this function assumes there is no other process running * concurrently that could update it. */ void UpdateFullPageWrites(void) { XLogCtlInsert *Insert = &XLogCtl->Insert; bool recoveryInProgress; /* * Do nothing if full_page_writes has not been changed. * * It's safe to check the shared full_page_writes without the lock, * because we assume that there is no concurrently running process which * can update it. */ if (fullPageWrites == Insert->fullPageWrites) return; /* * Perform this outside critical section so that the WAL insert * initialization done by RecoveryInProgress() doesn't trigger an * assertion failure. */ recoveryInProgress = RecoveryInProgress(); START_CRIT_SECTION(); /* * It's always safe to take full page images, even when not strictly * required, but not the other round. So if we're setting full_page_writes * to true, first set it true and then write the WAL record. If we're * setting it to false, first write the WAL record and then set the global * flag. */ if (fullPageWrites) { WALInsertLockAcquireExclusive(); Insert->fullPageWrites = true; WALInsertLockRelease(); } /* * Write an XLOG_FPW_CHANGE record. This allows us to keep track of * full_page_writes during archive recovery, if required. */ if (XLogStandbyInfoActive() && !recoveryInProgress) { XLogBeginInsert(); XLogRegisterData((char *) (&fullPageWrites), sizeof(bool)); XLogInsert(RM_XLOG_ID, XLOG_FPW_CHANGE); } if (!fullPageWrites) { WALInsertLockAcquireExclusive(); Insert->fullPageWrites = false; WALInsertLockRelease(); } END_CRIT_SECTION(); } /* * XLOG resource manager's routines * * Definitions of info values are in include/catalog/pg_control.h, though * not all record types are related to control file updates. * * NOTE: Some XLOG record types that are directly related to WAL recovery * are handled in xlogrecovery_redo(). */ void xlog_redo(XLogReaderState *record) { uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK; XLogRecPtr lsn = record->EndRecPtr; /* * In XLOG rmgr, backup blocks are only used by XLOG_FPI and * XLOG_FPI_FOR_HINT records. */ Assert(info == XLOG_FPI || info == XLOG_FPI_FOR_HINT || !XLogRecHasAnyBlockRefs(record)); if (info == XLOG_NEXTOID) { Oid nextOid; /* * We used to try to take the maximum of ShmemVariableCache->nextOid * and the recorded nextOid, but that fails if the OID counter wraps * around. Since no OID allocation should be happening during replay * anyway, better to just believe the record exactly. We still take * OidGenLock while setting the variable, just in case. */ memcpy(&nextOid, XLogRecGetData(record), sizeof(Oid)); LWLockAcquire(OidGenLock, LW_EXCLUSIVE); ShmemVariableCache->nextOid = nextOid; ShmemVariableCache->oidCount = 0; LWLockRelease(OidGenLock); } else if (info == XLOG_CHECKPOINT_SHUTDOWN) { CheckPoint checkPoint; TimeLineID replayTLI; memcpy(&checkPoint, XLogRecGetData(record), sizeof(CheckPoint)); /* In a SHUTDOWN checkpoint, believe the counters exactly */ LWLockAcquire(XidGenLock, LW_EXCLUSIVE); ShmemVariableCache->nextXid = checkPoint.nextXid; LWLockRelease(XidGenLock); LWLockAcquire(OidGenLock, LW_EXCLUSIVE); ShmemVariableCache->nextOid = checkPoint.nextOid; ShmemVariableCache->oidCount = 0; LWLockRelease(OidGenLock); MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset); MultiXactAdvanceOldest(checkPoint.oldestMulti, checkPoint.oldestMultiDB); /* * No need to set oldestClogXid here as well; it'll be set when we * redo an xl_clog_truncate if it changed since initialization. */ SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); /* * If we see a shutdown checkpoint while waiting for an end-of-backup * record, the backup was canceled and the end-of-backup record will * never arrive. */ if (ArchiveRecoveryRequested && !XLogRecPtrIsInvalid(ControlFile->backupStartPoint) && XLogRecPtrIsInvalid(ControlFile->backupEndPoint)) ereport(PANIC, (errmsg("online backup was canceled, recovery cannot continue"))); /* * If we see a shutdown checkpoint, we know that nothing was running * on the primary at this point. So fake-up an empty running-xacts * record and use that here and now. Recover additional standby state * for prepared transactions. */ if (standbyState >= STANDBY_INITIALIZED) { TransactionId *xids; int nxids; TransactionId oldestActiveXID; TransactionId latestCompletedXid; RunningTransactionsData running; oldestActiveXID = PrescanPreparedTransactions(&xids, &nxids); /* * Construct a RunningTransactions snapshot representing a shut * down server, with only prepared transactions still alive. We're * never overflowed at this point because all subxids are listed * with their parent prepared transactions. */ running.xcnt = nxids; running.subxcnt = 0; running.subxid_overflow = false; running.nextXid = XidFromFullTransactionId(checkPoint.nextXid); running.oldestRunningXid = oldestActiveXID; latestCompletedXid = XidFromFullTransactionId(checkPoint.nextXid); TransactionIdRetreat(latestCompletedXid); Assert(TransactionIdIsNormal(latestCompletedXid)); running.latestCompletedXid = latestCompletedXid; running.xids = xids; ProcArrayApplyRecoveryInfo(&running); StandbyRecoverPreparedTransactions(); } /* ControlFile->checkPointCopy always tracks the latest ckpt XID */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->checkPointCopy.nextXid = checkPoint.nextXid; LWLockRelease(ControlFileLock); /* Update shared-memory copy of checkpoint XID/epoch */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->ckptFullXid = checkPoint.nextXid; SpinLockRelease(&XLogCtl->info_lck); /* * We should've already switched to the new TLI before replaying this * record. */ (void) GetCurrentReplayRecPtr(&replayTLI); if (checkPoint.ThisTimeLineID != replayTLI) ereport(PANIC, (errmsg("unexpected timeline ID %u (should be %u) in shutdown checkpoint record", checkPoint.ThisTimeLineID, replayTLI))); RecoveryRestartPoint(&checkPoint, record); } else if (info == XLOG_CHECKPOINT_ONLINE) { CheckPoint checkPoint; TimeLineID replayTLI; memcpy(&checkPoint, XLogRecGetData(record), sizeof(CheckPoint)); /* In an ONLINE checkpoint, treat the XID counter as a minimum */ LWLockAcquire(XidGenLock, LW_EXCLUSIVE); if (FullTransactionIdPrecedes(ShmemVariableCache->nextXid, checkPoint.nextXid)) ShmemVariableCache->nextXid = checkPoint.nextXid; LWLockRelease(XidGenLock); /* * We ignore the nextOid counter in an ONLINE checkpoint, preferring * to track OID assignment through XLOG_NEXTOID records. The nextOid * counter is from the start of the checkpoint and might well be stale * compared to later XLOG_NEXTOID records. We could try to take the * maximum of the nextOid counter and our latest value, but since * there's no particular guarantee about the speed with which the OID * counter wraps around, that's a risky thing to do. In any case, * users of the nextOid counter are required to avoid assignment of * duplicates, so that a somewhat out-of-date value should be safe. */ /* Handle multixact */ MultiXactAdvanceNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset); /* * NB: This may perform multixact truncation when replaying WAL * generated by an older primary. */ MultiXactAdvanceOldest(checkPoint.oldestMulti, checkPoint.oldestMultiDB); if (TransactionIdPrecedes(ShmemVariableCache->oldestXid, checkPoint.oldestXid)) SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); /* ControlFile->checkPointCopy always tracks the latest ckpt XID */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->checkPointCopy.nextXid = checkPoint.nextXid; LWLockRelease(ControlFileLock); /* Update shared-memory copy of checkpoint XID/epoch */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->ckptFullXid = checkPoint.nextXid; SpinLockRelease(&XLogCtl->info_lck); /* TLI should not change in an on-line checkpoint */ (void) GetCurrentReplayRecPtr(&replayTLI); if (checkPoint.ThisTimeLineID != replayTLI) ereport(PANIC, (errmsg("unexpected timeline ID %u (should be %u) in online checkpoint record", checkPoint.ThisTimeLineID, replayTLI))); RecoveryRestartPoint(&checkPoint, record); } else if (info == XLOG_OVERWRITE_CONTRECORD) { /* nothing to do here, handled in xlogrecovery_redo() */ } else if (info == XLOG_END_OF_RECOVERY) { xl_end_of_recovery xlrec; TimeLineID replayTLI; memcpy(&xlrec, XLogRecGetData(record), sizeof(xl_end_of_recovery)); /* * For Hot Standby, we could treat this like a Shutdown Checkpoint, * but this case is rarer and harder to test, so the benefit doesn't * outweigh the potential extra cost of maintenance. */ /* * We should've already switched to the new TLI before replaying this * record. */ (void) GetCurrentReplayRecPtr(&replayTLI); if (xlrec.ThisTimeLineID != replayTLI) ereport(PANIC, (errmsg("unexpected timeline ID %u (should be %u) in end-of-recovery record", xlrec.ThisTimeLineID, replayTLI))); } else if (info == XLOG_NOOP) { /* nothing to do here */ } else if (info == XLOG_SWITCH) { /* nothing to do here */ } else if (info == XLOG_RESTORE_POINT) { /* nothing to do here, handled in xlogrecovery.c */ } else if (info == XLOG_FPI || info == XLOG_FPI_FOR_HINT) { /* * XLOG_FPI records contain nothing else but one or more block * references. Every block reference must include a full-page image * even if full_page_writes was disabled when the record was generated * - otherwise there would be no point in this record. * * XLOG_FPI_FOR_HINT records are generated when a page needs to be * WAL-logged because of a hint bit update. They are only generated * when checksums and/or wal_log_hints are enabled. They may include * no full-page images if full_page_writes was disabled when they were * generated. In this case there is nothing to do here. * * No recovery conflicts are generated by these generic records - if a * resource manager needs to generate conflicts, it has to define a * separate WAL record type and redo routine. */ for (uint8 block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++) { Buffer buffer; if (!XLogRecHasBlockImage(record, block_id)) { if (info == XLOG_FPI) elog(ERROR, "XLOG_FPI record did not contain a full-page image"); continue; } if (XLogReadBufferForRedo(record, block_id, &buffer) != BLK_RESTORED) elog(ERROR, "unexpected XLogReadBufferForRedo result when restoring backup block"); UnlockReleaseBuffer(buffer); } } else if (info == XLOG_BACKUP_END) { /* nothing to do here, handled in xlogrecovery_redo() */ } else if (info == XLOG_PARAMETER_CHANGE) { xl_parameter_change xlrec; /* Update our copy of the parameters in pg_control */ memcpy(&xlrec, XLogRecGetData(record), sizeof(xl_parameter_change)); /* * Invalidate logical slots if we are in hot standby and the primary * does not have a WAL level sufficient for logical decoding. No need * to search for potentially conflicting logically slots if standby is * running with wal_level lower than logical, because in that case, we * would have either disallowed creation of logical slots or * invalidated existing ones. */ if (InRecovery && InHotStandby && xlrec.wal_level < WAL_LEVEL_LOGICAL && wal_level >= WAL_LEVEL_LOGICAL) InvalidateObsoleteReplicationSlots(RS_INVAL_WAL_LEVEL, 0, InvalidOid, InvalidTransactionId); LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->MaxConnections = xlrec.MaxConnections; ControlFile->max_worker_processes = xlrec.max_worker_processes; ControlFile->max_wal_senders = xlrec.max_wal_senders; ControlFile->max_prepared_xacts = xlrec.max_prepared_xacts; ControlFile->max_locks_per_xact = xlrec.max_locks_per_xact; ControlFile->wal_level = xlrec.wal_level; ControlFile->wal_log_hints = xlrec.wal_log_hints; /* * Update minRecoveryPoint to ensure that if recovery is aborted, we * recover back up to this point before allowing hot standby again. * This is important if the max_* settings are decreased, to ensure * you don't run queries against the WAL preceding the change. The * local copies cannot be updated as long as crash recovery is * happening and we expect all the WAL to be replayed. */ if (InArchiveRecovery) { LocalMinRecoveryPoint = ControlFile->minRecoveryPoint; LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI; } if (LocalMinRecoveryPoint != InvalidXLogRecPtr && LocalMinRecoveryPoint < lsn) { TimeLineID replayTLI; (void) GetCurrentReplayRecPtr(&replayTLI); ControlFile->minRecoveryPoint = lsn; ControlFile->minRecoveryPointTLI = replayTLI; } CommitTsParameterChange(xlrec.track_commit_timestamp, ControlFile->track_commit_timestamp); ControlFile->track_commit_timestamp = xlrec.track_commit_timestamp; UpdateControlFile(); LWLockRelease(ControlFileLock); /* Check to see if any parameter change gives a problem on recovery */ CheckRequiredParameterValues(); } else if (info == XLOG_FPW_CHANGE) { bool fpw; memcpy(&fpw, XLogRecGetData(record), sizeof(bool)); /* * Update the LSN of the last replayed XLOG_FPW_CHANGE record so that * do_pg_backup_start() and do_pg_backup_stop() can check whether * full_page_writes has been disabled during online backup. */ if (!fpw) { SpinLockAcquire(&XLogCtl->info_lck); if (XLogCtl->lastFpwDisableRecPtr < record->ReadRecPtr) XLogCtl->lastFpwDisableRecPtr = record->ReadRecPtr; SpinLockRelease(&XLogCtl->info_lck); } /* Keep track of full_page_writes */ lastFullPageWrites = fpw; } } /* * Return the extra open flags used for opening a file, depending on the * value of the GUCs wal_sync_method, fsync and io_direct. */ static int get_sync_bit(int method) { int o_direct_flag = 0; /* * Use O_DIRECT if requested, except in walreceiver process. The WAL * written by walreceiver is normally read by the startup process soon * after it's written. Also, walreceiver performs unaligned writes, which * don't work with O_DIRECT, so it is required for correctness too. */ if ((io_direct_flags & IO_DIRECT_WAL) && !AmWalReceiverProcess()) o_direct_flag = PG_O_DIRECT; /* If fsync is disabled, never open in sync mode */ if (!enableFsync) return o_direct_flag; switch (method) { /* * enum values for all sync options are defined even if they are * not supported on the current platform. But if not, they are * not included in the enum option array, and therefore will never * be seen here. */ case SYNC_METHOD_FSYNC: case SYNC_METHOD_FSYNC_WRITETHROUGH: case SYNC_METHOD_FDATASYNC: return o_direct_flag; #ifdef O_SYNC case SYNC_METHOD_OPEN: return O_SYNC | o_direct_flag; #endif #ifdef O_DSYNC case SYNC_METHOD_OPEN_DSYNC: return O_DSYNC | o_direct_flag; #endif default: /* can't happen (unless we are out of sync with option array) */ elog(ERROR, "unrecognized wal_sync_method: %d", method); return 0; /* silence warning */ } } /* * GUC support */ void assign_xlog_sync_method(int new_sync_method, void *extra) { if (sync_method != new_sync_method) { /* * To ensure that no blocks escape unsynced, force an fsync on the * currently open log segment (if any). Also, if the open flag is * changing, close the log file so it will be reopened (with new flag * bit) at next use. */ if (openLogFile >= 0) { pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC_METHOD_ASSIGN); if (pg_fsync(openLogFile) != 0) { char xlogfname[MAXFNAMELEN]; int save_errno; save_errno = errno; XLogFileName(xlogfname, openLogTLI, openLogSegNo, wal_segment_size); errno = save_errno; ereport(PANIC, (errcode_for_file_access(), errmsg("could not fsync file \"%s\": %m", xlogfname))); } pgstat_report_wait_end(); if (get_sync_bit(sync_method) != get_sync_bit(new_sync_method)) XLogFileClose(); } } } /* * Issue appropriate kind of fsync (if any) for an XLOG output file. * * 'fd' is a file descriptor for the XLOG file to be fsync'd. * 'segno' is for error reporting purposes. */ void issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli) { char *msg = NULL; instr_time start; Assert(tli != 0); /* * Quick exit if fsync is disabled or write() has already synced the WAL * file. */ if (!enableFsync || sync_method == SYNC_METHOD_OPEN || sync_method == SYNC_METHOD_OPEN_DSYNC) return; /* Measure I/O timing to sync the WAL file */ if (track_wal_io_timing) INSTR_TIME_SET_CURRENT(start); else INSTR_TIME_SET_ZERO(start); pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC); switch (sync_method) { case SYNC_METHOD_FSYNC: if (pg_fsync_no_writethrough(fd) != 0) msg = _("could not fsync file \"%s\": %m"); break; #ifdef HAVE_FSYNC_WRITETHROUGH case SYNC_METHOD_FSYNC_WRITETHROUGH: if (pg_fsync_writethrough(fd) != 0) msg = _("could not fsync write-through file \"%s\": %m"); break; #endif case SYNC_METHOD_FDATASYNC: if (pg_fdatasync(fd) != 0) msg = _("could not fdatasync file \"%s\": %m"); break; case SYNC_METHOD_OPEN: case SYNC_METHOD_OPEN_DSYNC: /* not reachable */ Assert(false); break; default: elog(PANIC, "unrecognized wal_sync_method: %d", sync_method); break; } /* PANIC if failed to fsync */ if (msg) { char xlogfname[MAXFNAMELEN]; int save_errno = errno; XLogFileName(xlogfname, tli, segno, wal_segment_size); errno = save_errno; ereport(PANIC, (errcode_for_file_access(), errmsg(msg, xlogfname))); } pgstat_report_wait_end(); /* * Increment the I/O timing and the number of times WAL files were synced. */ if (track_wal_io_timing) { instr_time duration; INSTR_TIME_SET_CURRENT(duration); INSTR_TIME_ACCUM_DIFF(PendingWalStats.wal_sync_time, duration, start); } PendingWalStats.wal_sync++; } /* * do_pg_backup_start is the workhorse of the user-visible pg_backup_start() * function. It creates the necessary starting checkpoint and constructs the * backup state and tablespace map. * * Input parameters are "state" (the backup state), "fast" (if true, we do * the checkpoint in immediate mode to make it faster), and "tablespaces" * (if non-NULL, indicates a list of tablespaceinfo structs describing the * cluster's tablespaces.). * * The tablespace map contents are appended to passed-in parameter * tablespace_map and the caller is responsible for including it in the backup * archive as 'tablespace_map'. The tablespace_map file is required mainly for * tar format in windows as native windows utilities are not able to create * symlinks while extracting files from tar. However for consistency and * platform-independence, we do it the same way everywhere. * * It fills in "state" with the information required for the backup, such * as the minimum WAL location that must be present to restore from this * backup (starttli) and the corresponding timeline ID (starttli). * * Every successfully started backup must be stopped by calling * do_pg_backup_stop() or do_pg_abort_backup(). There can be many * backups active at the same time. * * It is the responsibility of the caller of this function to verify the * permissions of the calling user! */ void do_pg_backup_start(const char *backupidstr, bool fast, List **tablespaces, BackupState *state, StringInfo tblspcmapfile) { bool backup_started_in_recovery; Assert(state != NULL); backup_started_in_recovery = RecoveryInProgress(); /* * During recovery, we don't need to check WAL level. Because, if WAL * level is not sufficient, it's impossible to get here during recovery. */ if (!backup_started_in_recovery && !XLogIsNeeded()) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("WAL level not sufficient for making an online backup"), errhint("wal_level must be set to \"replica\" or \"logical\" at server start."))); if (strlen(backupidstr) > MAXPGPATH) ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("backup label too long (max %d bytes)", MAXPGPATH))); memcpy(state->name, backupidstr, strlen(backupidstr)); /* * Mark backup active in shared memory. We must do full-page WAL writes * during an on-line backup even if not doing so at other times, because * it's quite possible for the backup dump to obtain a "torn" (partially * written) copy of a database page if it reads the page concurrently with * our write to the same page. This can be fixed as long as the first * write to the page in the WAL sequence is a full-page write. Hence, we * increment runningBackups then force a CHECKPOINT, to ensure there are * no dirty pages in shared memory that might get dumped while the backup * is in progress without having a corresponding WAL record. (Once the * backup is complete, we need not force full-page writes anymore, since * we expect that any pages not modified during the backup interval must * have been correctly captured by the backup.) * * Note that forcing full-page writes has no effect during an online * backup from the standby. * * We must hold all the insertion locks to change the value of * runningBackups, to ensure adequate interlocking against * XLogInsertRecord(). */ WALInsertLockAcquireExclusive(); XLogCtl->Insert.runningBackups++; WALInsertLockRelease(); /* * Ensure we decrement runningBackups if we fail below. NB -- for this to * work correctly, it is critical that sessionBackupState is only updated * after this block is over. */ PG_ENSURE_ERROR_CLEANUP(do_pg_abort_backup, DatumGetBool(true)); { bool gotUniqueStartpoint = false; DIR *tblspcdir; struct dirent *de; tablespaceinfo *ti; int datadirpathlen; /* * Force an XLOG file switch before the checkpoint, to ensure that the * WAL segment the checkpoint is written to doesn't contain pages with * old timeline IDs. That would otherwise happen if you called * pg_backup_start() right after restoring from a PITR archive: the * first WAL segment containing the startup checkpoint has pages in * the beginning with the old timeline ID. That can cause trouble at * recovery: we won't have a history file covering the old timeline if * pg_wal directory was not included in the base backup and the WAL * archive was cleared too before starting the backup. * * This also ensures that we have emitted a WAL page header that has * XLP_BKP_REMOVABLE off before we emit the checkpoint record. * Therefore, if a WAL archiver (such as pglesslog) is trying to * compress out removable backup blocks, it won't remove any that * occur after this point. * * During recovery, we skip forcing XLOG file switch, which means that * the backup taken during recovery is not available for the special * recovery case described above. */ if (!backup_started_in_recovery) RequestXLogSwitch(false); do { bool checkpointfpw; /* * Force a CHECKPOINT. Aside from being necessary to prevent torn * page problems, this guarantees that two successive backup runs * will have different checkpoint positions and hence different * history file names, even if nothing happened in between. * * During recovery, establish a restartpoint if possible. We use * the last restartpoint as the backup starting checkpoint. This * means that two successive backup runs can have same checkpoint * positions. * * Since the fact that we are executing do_pg_backup_start() * during recovery means that checkpointer is running, we can use * RequestCheckpoint() to establish a restartpoint. * * We use CHECKPOINT_IMMEDIATE only if requested by user (via * passing fast = true). Otherwise this can take awhile. */ RequestCheckpoint(CHECKPOINT_FORCE | CHECKPOINT_WAIT | (fast ? CHECKPOINT_IMMEDIATE : 0)); /* * Now we need to fetch the checkpoint record location, and also * its REDO pointer. The oldest point in WAL that would be needed * to restore starting from the checkpoint is precisely the REDO * pointer. */ LWLockAcquire(ControlFileLock, LW_SHARED); state->checkpointloc = ControlFile->checkPoint; state->startpoint = ControlFile->checkPointCopy.redo; state->starttli = ControlFile->checkPointCopy.ThisTimeLineID; checkpointfpw = ControlFile->checkPointCopy.fullPageWrites; LWLockRelease(ControlFileLock); if (backup_started_in_recovery) { XLogRecPtr recptr; /* * Check to see if all WAL replayed during online backup * (i.e., since last restartpoint used as backup starting * checkpoint) contain full-page writes. */ SpinLockAcquire(&XLogCtl->info_lck); recptr = XLogCtl->lastFpwDisableRecPtr; SpinLockRelease(&XLogCtl->info_lck); if (!checkpointfpw || state->startpoint <= recptr) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("WAL generated with full_page_writes=off was replayed " "since last restartpoint"), errhint("This means that the backup being taken on the standby " "is corrupt and should not be used. " "Enable full_page_writes and run CHECKPOINT on the primary, " "and then try an online backup again."))); /* * During recovery, since we don't use the end-of-backup WAL * record and don't write the backup history file, the * starting WAL location doesn't need to be unique. This means * that two base backups started at the same time might use * the same checkpoint as starting locations. */ gotUniqueStartpoint = true; } /* * If two base backups are started at the same time (in WAL sender * processes), we need to make sure that they use different * checkpoints as starting locations, because we use the starting * WAL location as a unique identifier for the base backup in the * end-of-backup WAL record and when we write the backup history * file. Perhaps it would be better generate a separate unique ID * for each backup instead of forcing another checkpoint, but * taking a checkpoint right after another is not that expensive * either because only few buffers have been dirtied yet. */ WALInsertLockAcquireExclusive(); if (XLogCtl->Insert.lastBackupStart < state->startpoint) { XLogCtl->Insert.lastBackupStart = state->startpoint; gotUniqueStartpoint = true; } WALInsertLockRelease(); } while (!gotUniqueStartpoint); /* * Construct tablespace_map file. */ datadirpathlen = strlen(DataDir); /* Collect information about all tablespaces */ tblspcdir = AllocateDir("pg_tblspc"); while ((de = ReadDir(tblspcdir, "pg_tblspc")) != NULL) { char fullpath[MAXPGPATH + 10]; char linkpath[MAXPGPATH]; char *relpath = NULL; char *s; PGFileType de_type; /* Skip anything that doesn't look like a tablespace */ if (strspn(de->d_name, "0123456789") != strlen(de->d_name)) continue; snprintf(fullpath, sizeof(fullpath), "pg_tblspc/%s", de->d_name); de_type = get_dirent_type(fullpath, de, false, ERROR); if (de_type == PGFILETYPE_LNK) { StringInfoData escapedpath; int rllen; rllen = readlink(fullpath, linkpath, sizeof(linkpath)); if (rllen < 0) { ereport(WARNING, (errmsg("could not read symbolic link \"%s\": %m", fullpath))); continue; } else if (rllen >= sizeof(linkpath)) { ereport(WARNING, (errmsg("symbolic link \"%s\" target is too long", fullpath))); continue; } linkpath[rllen] = '\0'; /* * Relpath holds the relative path of the tablespace directory * when it's located within PGDATA, or NULL if it's located * elsewhere. */ if (rllen > datadirpathlen && strncmp(linkpath, DataDir, datadirpathlen) == 0 && IS_DIR_SEP(linkpath[datadirpathlen])) relpath = pstrdup(linkpath + datadirpathlen + 1); /* * Add a backslash-escaped version of the link path to the * tablespace map file. */ initStringInfo(&escapedpath); for (s = linkpath; *s; s++) { if (*s == '\n' || *s == '\r' || *s == '\\') appendStringInfoChar(&escapedpath, '\\'); appendStringInfoChar(&escapedpath, *s); } appendStringInfo(tblspcmapfile, "%s %s\n", de->d_name, escapedpath.data); pfree(escapedpath.data); } else if (de_type == PGFILETYPE_DIR) { /* * It's possible to use allow_in_place_tablespaces to create * directories directly under pg_tblspc, for testing purposes * only. * * In this case, we store a relative path rather than an * absolute path into the tablespaceinfo. */ snprintf(linkpath, sizeof(linkpath), "pg_tblspc/%s", de->d_name); relpath = pstrdup(linkpath); } else { /* Skip any other file type that appears here. */ continue; } ti = palloc(sizeof(tablespaceinfo)); ti->oid = pstrdup(de->d_name); ti->path = pstrdup(linkpath); ti->rpath = relpath; ti->size = -1; if (tablespaces) *tablespaces = lappend(*tablespaces, ti); } FreeDir(tblspcdir); state->starttime = (pg_time_t) time(NULL); } PG_END_ENSURE_ERROR_CLEANUP(do_pg_abort_backup, DatumGetBool(true)); state->started_in_recovery = backup_started_in_recovery; /* * Mark that the start phase has correctly finished for the backup. */ sessionBackupState = SESSION_BACKUP_RUNNING; } /* * Utility routine to fetch the session-level status of a backup running. */ SessionBackupState get_backup_status(void) { return sessionBackupState; } /* * do_pg_backup_stop * * Utility function called at the end of an online backup. It creates history * file (if required), resets sessionBackupState and so on. It can optionally * wait for WAL segments to be archived. * * "state" is filled with the information necessary to restore from this * backup with its stop LSN (stoppoint), its timeline ID (stoptli), etc. * * It is the responsibility of the caller of this function to verify the * permissions of the calling user! */ void do_pg_backup_stop(BackupState *state, bool waitforarchive) { bool backup_stopped_in_recovery = false; char histfilepath[MAXPGPATH]; char lastxlogfilename[MAXFNAMELEN]; char histfilename[MAXFNAMELEN]; XLogSegNo _logSegNo; FILE *fp; int seconds_before_warning; int waits = 0; bool reported_waiting = false; Assert(state != NULL); backup_stopped_in_recovery = RecoveryInProgress(); /* * During recovery, we don't need to check WAL level. Because, if WAL * level is not sufficient, it's impossible to get here during recovery. */ if (!backup_stopped_in_recovery && !XLogIsNeeded()) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("WAL level not sufficient for making an online backup"), errhint("wal_level must be set to \"replica\" or \"logical\" at server start."))); /* * OK to update backup counter and session-level lock. * * Note that CHECK_FOR_INTERRUPTS() must not occur while updating them, * otherwise they can be updated inconsistently, which might cause * do_pg_abort_backup() to fail. */ WALInsertLockAcquireExclusive(); /* * It is expected that each do_pg_backup_start() call is matched by * exactly one do_pg_backup_stop() call. */ Assert(XLogCtl->Insert.runningBackups > 0); XLogCtl->Insert.runningBackups--; /* * Clean up session-level lock. * * You might think that WALInsertLockRelease() can be called before * cleaning up session-level lock because session-level lock doesn't need * to be protected with WAL insertion lock. But since * CHECK_FOR_INTERRUPTS() can occur in it, session-level lock must be * cleaned up before it. */ sessionBackupState = SESSION_BACKUP_NONE; WALInsertLockRelease(); /* * If we are taking an online backup from the standby, we confirm that the * standby has not been promoted during the backup. */ if (state->started_in_recovery && !backup_stopped_in_recovery) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("the standby was promoted during online backup"), errhint("This means that the backup being taken is corrupt " "and should not be used. " "Try taking another online backup."))); /* * During recovery, we don't write an end-of-backup record. We assume that * pg_control was backed up last and its minimum recovery point can be * available as the backup end location. Since we don't have an * end-of-backup record, we use the pg_control value to check whether * we've reached the end of backup when starting recovery from this * backup. We have no way of checking if pg_control wasn't backed up last * however. * * We don't force a switch to new WAL file but it is still possible to * wait for all the required files to be archived if waitforarchive is * true. This is okay if we use the backup to start a standby and fetch * the missing WAL using streaming replication. But in the case of an * archive recovery, a user should set waitforarchive to true and wait for * them to be archived to ensure that all the required files are * available. * * We return the current minimum recovery point as the backup end * location. Note that it can be greater than the exact backup end * location if the minimum recovery point is updated after the backup of * pg_control. This is harmless for current uses. * * XXX currently a backup history file is for informational and debug * purposes only. It's not essential for an online backup. Furthermore, * even if it's created, it will not be archived during recovery because * an archiver is not invoked. So it doesn't seem worthwhile to write a * backup history file during recovery. */ if (backup_stopped_in_recovery) { XLogRecPtr recptr; /* * Check to see if all WAL replayed during online backup contain * full-page writes. */ SpinLockAcquire(&XLogCtl->info_lck); recptr = XLogCtl->lastFpwDisableRecPtr; SpinLockRelease(&XLogCtl->info_lck); if (state->startpoint <= recptr) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("WAL generated with full_page_writes=off was replayed " "during online backup"), errhint("This means that the backup being taken on the standby " "is corrupt and should not be used. " "Enable full_page_writes and run CHECKPOINT on the primary, " "and then try an online backup again."))); LWLockAcquire(ControlFileLock, LW_SHARED); state->stoppoint = ControlFile->minRecoveryPoint; state->stoptli = ControlFile->minRecoveryPointTLI; LWLockRelease(ControlFileLock); } else { char *history_file; /* * Write the backup-end xlog record */ XLogBeginInsert(); XLogRegisterData((char *) (&state->startpoint), sizeof(state->startpoint)); state->stoppoint = XLogInsert(RM_XLOG_ID, XLOG_BACKUP_END); /* * Given that we're not in recovery, InsertTimeLineID is set and can't * change, so we can read it without a lock. */ state->stoptli = XLogCtl->InsertTimeLineID; /* * Force a switch to a new xlog segment file, so that the backup is * valid as soon as archiver moves out the current segment file. */ RequestXLogSwitch(false); state->stoptime = (pg_time_t) time(NULL); /* * Write the backup history file */ XLByteToSeg(state->startpoint, _logSegNo, wal_segment_size); BackupHistoryFilePath(histfilepath, state->stoptli, _logSegNo, state->startpoint, wal_segment_size); fp = AllocateFile(histfilepath, "w"); if (!fp) ereport(ERROR, (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", histfilepath))); /* Build and save the contents of the backup history file */ history_file = build_backup_content(state, true); fprintf(fp, "%s", history_file); pfree(history_file); if (fflush(fp) || ferror(fp) || FreeFile(fp)) ereport(ERROR, (errcode_for_file_access(), errmsg("could not write file \"%s\": %m", histfilepath))); /* * Clean out any no-longer-needed history files. As a side effect, * this will post a .ready file for the newly created history file, * notifying the archiver that history file may be archived * immediately. */ CleanupBackupHistory(); } /* * If archiving is enabled, wait for all the required WAL files to be * archived before returning. If archiving isn't enabled, the required WAL * needs to be transported via streaming replication (hopefully with * wal_keep_size set high enough), or some more exotic mechanism like * polling and copying files from pg_wal with script. We have no knowledge * of those mechanisms, so it's up to the user to ensure that he gets all * the required WAL. * * We wait until both the last WAL file filled during backup and the * history file have been archived, and assume that the alphabetic sorting * property of the WAL files ensures any earlier WAL files are safely * archived as well. * * We wait forever, since archive_command is supposed to work and we * assume the admin wanted his backup to work completely. If you don't * wish to wait, then either waitforarchive should be passed in as false, * or you can set statement_timeout. Also, some notices are issued to * clue in anyone who might be doing this interactively. */ if (waitforarchive && ((!backup_stopped_in_recovery && XLogArchivingActive()) || (backup_stopped_in_recovery && XLogArchivingAlways()))) { XLByteToPrevSeg(state->stoppoint, _logSegNo, wal_segment_size); XLogFileName(lastxlogfilename, state->stoptli, _logSegNo, wal_segment_size); XLByteToSeg(state->startpoint, _logSegNo, wal_segment_size); BackupHistoryFileName(histfilename, state->stoptli, _logSegNo, state->startpoint, wal_segment_size); seconds_before_warning = 60; waits = 0; while (XLogArchiveIsBusy(lastxlogfilename) || XLogArchiveIsBusy(histfilename)) { CHECK_FOR_INTERRUPTS(); if (!reported_waiting && waits > 5) { ereport(NOTICE, (errmsg("base backup done, waiting for required WAL segments to be archived"))); reported_waiting = true; } (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH, 1000L, WAIT_EVENT_BACKUP_WAIT_WAL_ARCHIVE); ResetLatch(MyLatch); if (++waits >= seconds_before_warning) { seconds_before_warning *= 2; /* This wraps in >10 years... */ ereport(WARNING, (errmsg("still waiting for all required WAL segments to be archived (%d seconds elapsed)", waits), errhint("Check that your archive_command is executing properly. " "You can safely cancel this backup, " "but the database backup will not be usable without all the WAL segments."))); } } ereport(NOTICE, (errmsg("all required WAL segments have been archived"))); } else if (waitforarchive) ereport(NOTICE, (errmsg("WAL archiving is not enabled; you must ensure that all required WAL segments are copied through other means to complete the backup"))); } /* * do_pg_abort_backup: abort a running backup * * This does just the most basic steps of do_pg_backup_stop(), by taking the * system out of backup mode, thus making it a lot more safe to call from * an error handler. * * 'arg' indicates that it's being called during backup setup; so * sessionBackupState has not been modified yet, but runningBackups has * already been incremented. When it's false, then it's invoked as a * before_shmem_exit handler, and therefore we must not change state * unless sessionBackupState indicates that a backup is actually running. * * NB: This gets used as a PG_ENSURE_ERROR_CLEANUP callback and * before_shmem_exit handler, hence the odd-looking signature. */ void do_pg_abort_backup(int code, Datum arg) { bool during_backup_start = DatumGetBool(arg); /* If called during backup start, there shouldn't be one already running */ Assert(!during_backup_start || sessionBackupState == SESSION_BACKUP_NONE); if (during_backup_start || sessionBackupState != SESSION_BACKUP_NONE) { WALInsertLockAcquireExclusive(); Assert(XLogCtl->Insert.runningBackups > 0); XLogCtl->Insert.runningBackups--; sessionBackupState = SESSION_BACKUP_NONE; WALInsertLockRelease(); if (!during_backup_start) ereport(WARNING, errmsg("aborting backup due to backend exiting before pg_backup_stop was called")); } } /* * Register a handler that will warn about unterminated backups at end of * session, unless this has already been done. */ void register_persistent_abort_backup_handler(void) { static bool already_done = false; if (already_done) return; before_shmem_exit(do_pg_abort_backup, DatumGetBool(false)); already_done = true; } /* * Get latest WAL insert pointer */ XLogRecPtr GetXLogInsertRecPtr(void) { XLogCtlInsert *Insert = &XLogCtl->Insert; uint64 current_bytepos; SpinLockAcquire(&Insert->insertpos_lck); current_bytepos = Insert->CurrBytePos; SpinLockRelease(&Insert->insertpos_lck); return XLogBytePosToRecPtr(current_bytepos); } /* * Get latest WAL write pointer */ XLogRecPtr GetXLogWriteRecPtr(void) { SpinLockAcquire(&XLogCtl->info_lck); LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); return LogwrtResult.Write; } /* * Returns the redo pointer of the last checkpoint or restartpoint. This is * the oldest point in WAL that we still need, if we have to restart recovery. */ void GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli) { LWLockAcquire(ControlFileLock, LW_SHARED); *oldrecptr = ControlFile->checkPointCopy.redo; *oldtli = ControlFile->checkPointCopy.ThisTimeLineID; LWLockRelease(ControlFileLock); } /* Thin wrapper around ShutdownWalRcv(). */ void XLogShutdownWalRcv(void) { ShutdownWalRcv(); LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); XLogCtl->InstallXLogFileSegmentActive = false; LWLockRelease(ControlFileLock); } /* Enable WAL file recycling and preallocation. */ void SetInstallXLogFileSegmentActive(void) { LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); XLogCtl->InstallXLogFileSegmentActive = true; LWLockRelease(ControlFileLock); } bool IsInstallXLogFileSegmentActive(void) { bool result; LWLockAcquire(ControlFileLock, LW_SHARED); result = XLogCtl->InstallXLogFileSegmentActive; LWLockRelease(ControlFileLock); return result; } /* * Update the WalWriterSleeping flag. */ void SetWalWriterSleeping(bool sleeping) { SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->WalWriterSleeping = sleeping; SpinLockRelease(&XLogCtl->info_lck); }