diff options
Diffstat (limited to 'contrib/pg_prewarm/autoprewarm.c')
| -rw-r--r-- | contrib/pg_prewarm/autoprewarm.c | 905 |
1 files changed, 905 insertions, 0 deletions
diff --git a/contrib/pg_prewarm/autoprewarm.c b/contrib/pg_prewarm/autoprewarm.c new file mode 100644 index 0000000..b3f73ea --- /dev/null +++ b/contrib/pg_prewarm/autoprewarm.c @@ -0,0 +1,905 @@ +/*------------------------------------------------------------------------- + * + * autoprewarm.c + * Periodically dump information about the blocks present in + * shared_buffers, and reload them on server restart. + * + * Due to locking considerations, we can't actually begin prewarming + * until the server reaches a consistent state. We need the catalogs + * to be consistent so that we can figure out which relation to lock, + * and we need to lock the relations so that we don't try to prewarm + * pages from a relation that is in the process of being dropped. + * + * While prewarming, autoprewarm will use two workers. There's a + * leader worker that reads and sorts the list of blocks to be + * prewarmed and then launches a per-database worker for each + * relevant database in turn. The former keeps running after the + * initial prewarm is complete to update the dump file periodically. + * + * Copyright (c) 2016-2021, PostgreSQL Global Development Group + * + * IDENTIFICATION + * contrib/pg_prewarm/autoprewarm.c + * + *------------------------------------------------------------------------- + */ + +#include "postgres.h" + +#include <unistd.h> + +#include "access/relation.h" +#include "access/xact.h" +#include "catalog/pg_class.h" +#include "catalog/pg_type.h" +#include "miscadmin.h" +#include "pgstat.h" +#include "postmaster/bgworker.h" +#include "postmaster/interrupt.h" +#include "storage/buf_internals.h" +#include "storage/dsm.h" +#include "storage/ipc.h" +#include "storage/latch.h" +#include "storage/lwlock.h" +#include "storage/proc.h" +#include "storage/procsignal.h" +#include "storage/shmem.h" +#include "storage/smgr.h" +#include "tcop/tcopprot.h" +#include "utils/acl.h" +#include "utils/datetime.h" +#include "utils/guc.h" +#include "utils/memutils.h" +#include "utils/rel.h" +#include "utils/relfilenodemap.h" +#include "utils/resowner.h" + +#define AUTOPREWARM_FILE "autoprewarm.blocks" + +/* Metadata for each block we dump. */ +typedef struct BlockInfoRecord +{ + Oid database; + Oid tablespace; + Oid filenode; + ForkNumber forknum; + BlockNumber blocknum; +} BlockInfoRecord; + +/* Shared state information for autoprewarm bgworker. */ +typedef struct AutoPrewarmSharedState +{ + LWLock lock; /* mutual exclusion */ + pid_t bgworker_pid; /* for main bgworker */ + pid_t pid_using_dumpfile; /* for autoprewarm or block dump */ + + /* Following items are for communication with per-database worker */ + dsm_handle block_info_handle; + Oid database; + int prewarm_start_idx; + int prewarm_stop_idx; + int prewarmed_blocks; +} AutoPrewarmSharedState; + +void _PG_init(void); +void autoprewarm_main(Datum main_arg); +void autoprewarm_database_main(Datum main_arg); + +PG_FUNCTION_INFO_V1(autoprewarm_start_worker); +PG_FUNCTION_INFO_V1(autoprewarm_dump_now); + +static void apw_load_buffers(void); +static int apw_dump_now(bool is_bgworker, bool dump_unlogged); +static void apw_start_leader_worker(void); +static void apw_start_database_worker(void); +static bool apw_init_shmem(void); +static void apw_detach_shmem(int code, Datum arg); +static int apw_compare_blockinfo(const void *p, const void *q); + +/* Pointer to shared-memory state. */ +static AutoPrewarmSharedState *apw_state = NULL; + +/* GUC variables. */ +static bool autoprewarm = true; /* start worker? */ +static int autoprewarm_interval; /* dump interval */ + +/* + * Module load callback. + */ +void +_PG_init(void) +{ + DefineCustomIntVariable("pg_prewarm.autoprewarm_interval", + "Sets the interval between dumps of shared buffers", + "If set to zero, time-based dumping is disabled.", + &autoprewarm_interval, + 300, + 0, INT_MAX / 1000, + PGC_SIGHUP, + GUC_UNIT_S, + NULL, + NULL, + NULL); + + if (!process_shared_preload_libraries_in_progress) + return; + + /* can't define PGC_POSTMASTER variable after startup */ + DefineCustomBoolVariable("pg_prewarm.autoprewarm", + "Starts the autoprewarm worker.", + NULL, + &autoprewarm, + true, + PGC_POSTMASTER, + 0, + NULL, + NULL, + NULL); + + EmitWarningsOnPlaceholders("pg_prewarm"); + + RequestAddinShmemSpace(MAXALIGN(sizeof(AutoPrewarmSharedState))); + + /* Register autoprewarm worker, if enabled. */ + if (autoprewarm) + apw_start_leader_worker(); +} + +/* + * Main entry point for the leader autoprewarm process. Per-database workers + * have a separate entry point. + */ +void +autoprewarm_main(Datum main_arg) +{ + bool first_time = true; + bool final_dump_allowed = true; + TimestampTz last_dump_time = 0; + + /* Establish signal handlers; once that's done, unblock signals. */ + pqsignal(SIGTERM, SignalHandlerForShutdownRequest); + pqsignal(SIGHUP, SignalHandlerForConfigReload); + pqsignal(SIGUSR1, procsignal_sigusr1_handler); + BackgroundWorkerUnblockSignals(); + + /* Create (if necessary) and attach to our shared memory area. */ + if (apw_init_shmem()) + first_time = false; + + /* Set on-detach hook so that our PID will be cleared on exit. */ + on_shmem_exit(apw_detach_shmem, 0); + + /* + * Store our PID in the shared memory area --- unless there's already + * another worker running, in which case just exit. + */ + LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE); + if (apw_state->bgworker_pid != InvalidPid) + { + LWLockRelease(&apw_state->lock); + ereport(LOG, + (errmsg("autoprewarm worker is already running under PID %lu", + (unsigned long) apw_state->bgworker_pid))); + return; + } + apw_state->bgworker_pid = MyProcPid; + LWLockRelease(&apw_state->lock); + + /* + * Preload buffers from the dump file only if we just created the shared + * memory region. Otherwise, it's either already been done or shouldn't + * be done - e.g. because the old dump file has been overwritten since the + * server was started. + * + * There's not much point in performing a dump immediately after we finish + * preloading; so, if we do end up preloading, consider the last dump time + * to be equal to the current time. + * + * If apw_load_buffers() is terminated early by a shutdown request, + * prevent dumping out our state below the loop, because we'd effectively + * just truncate the saved state to however much we'd managed to preload. + */ + if (first_time) + { + apw_load_buffers(); + final_dump_allowed = !ShutdownRequestPending; + last_dump_time = GetCurrentTimestamp(); + } + + /* Periodically dump buffers until terminated. */ + while (!ShutdownRequestPending) + { + /* In case of a SIGHUP, just reload the configuration. */ + if (ConfigReloadPending) + { + ConfigReloadPending = false; + ProcessConfigFile(PGC_SIGHUP); + } + + if (autoprewarm_interval <= 0) + { + /* We're only dumping at shutdown, so just wait forever. */ + (void) WaitLatch(MyLatch, + WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, + -1L, + PG_WAIT_EXTENSION); + } + else + { + TimestampTz next_dump_time; + long delay_in_ms; + + /* Compute the next dump time. */ + next_dump_time = + TimestampTzPlusMilliseconds(last_dump_time, + autoprewarm_interval * 1000); + delay_in_ms = + TimestampDifferenceMilliseconds(GetCurrentTimestamp(), + next_dump_time); + + /* Perform a dump if it's time. */ + if (delay_in_ms <= 0) + { + last_dump_time = GetCurrentTimestamp(); + apw_dump_now(true, false); + continue; + } + + /* Sleep until the next dump time. */ + (void) WaitLatch(MyLatch, + WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH, + delay_in_ms, + PG_WAIT_EXTENSION); + } + + /* Reset the latch, loop. */ + ResetLatch(MyLatch); + } + + /* + * Dump one last time. We assume this is probably the result of a system + * shutdown, although it's possible that we've merely been terminated. + */ + if (final_dump_allowed) + apw_dump_now(true, true); +} + +/* + * Read the dump file and launch per-database workers one at a time to + * prewarm the buffers found there. + */ +static void +apw_load_buffers(void) +{ + FILE *file = NULL; + int num_elements, + i; + BlockInfoRecord *blkinfo; + dsm_segment *seg; + + /* + * Skip the prewarm if the dump file is in use; otherwise, prevent any + * other process from writing it while we're using it. + */ + LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE); + if (apw_state->pid_using_dumpfile == InvalidPid) + apw_state->pid_using_dumpfile = MyProcPid; + else + { + LWLockRelease(&apw_state->lock); + ereport(LOG, + (errmsg("skipping prewarm because block dump file is being written by PID %lu", + (unsigned long) apw_state->pid_using_dumpfile))); + return; + } + LWLockRelease(&apw_state->lock); + + /* + * Open the block dump file. Exit quietly if it doesn't exist, but report + * any other error. + */ + file = AllocateFile(AUTOPREWARM_FILE, "r"); + if (!file) + { + if (errno == ENOENT) + { + LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE); + apw_state->pid_using_dumpfile = InvalidPid; + LWLockRelease(&apw_state->lock); + return; /* No file to load. */ + } + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not read file \"%s\": %m", + AUTOPREWARM_FILE))); + } + + /* First line of the file is a record count. */ + if (fscanf(file, "<<%d>>\n", &num_elements) != 1) + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not read from file \"%s\": %m", + AUTOPREWARM_FILE))); + + /* Allocate a dynamic shared memory segment to store the record data. */ + seg = dsm_create(sizeof(BlockInfoRecord) * num_elements, 0); + blkinfo = (BlockInfoRecord *) dsm_segment_address(seg); + + /* Read records, one per line. */ + for (i = 0; i < num_elements; i++) + { + unsigned forknum; + + if (fscanf(file, "%u,%u,%u,%u,%u\n", &blkinfo[i].database, + &blkinfo[i].tablespace, &blkinfo[i].filenode, + &forknum, &blkinfo[i].blocknum) != 5) + ereport(ERROR, + (errmsg("autoprewarm block dump file is corrupted at line %d", + i + 1))); + blkinfo[i].forknum = forknum; + } + + FreeFile(file); + + /* Sort the blocks to be loaded. */ + pg_qsort(blkinfo, num_elements, sizeof(BlockInfoRecord), + apw_compare_blockinfo); + + /* Populate shared memory state. */ + apw_state->block_info_handle = dsm_segment_handle(seg); + apw_state->prewarm_start_idx = apw_state->prewarm_stop_idx = 0; + apw_state->prewarmed_blocks = 0; + + /* Get the info position of the first block of the next database. */ + while (apw_state->prewarm_start_idx < num_elements) + { + int j = apw_state->prewarm_start_idx; + Oid current_db = blkinfo[j].database; + + /* + * Advance the prewarm_stop_idx to the first BlockInfoRecord that does + * not belong to this database. + */ + j++; + while (j < num_elements) + { + if (current_db != blkinfo[j].database) + { + /* + * Combine BlockInfoRecords for global objects with those of + * the database. + */ + if (current_db != InvalidOid) + break; + current_db = blkinfo[j].database; + } + + j++; + } + + /* + * If we reach this point with current_db == InvalidOid, then only + * BlockInfoRecords belonging to global objects exist. We can't + * prewarm without a database connection, so just bail out. + */ + if (current_db == InvalidOid) + break; + + /* Configure stop point and database for next per-database worker. */ + apw_state->prewarm_stop_idx = j; + apw_state->database = current_db; + Assert(apw_state->prewarm_start_idx < apw_state->prewarm_stop_idx); + + /* If we've run out of free buffers, don't launch another worker. */ + if (!have_free_buffer()) + break; + + /* + * Likewise, don't launch if we've already been told to shut down. + * (The launch would fail anyway, but we might as well skip it.) + */ + if (ShutdownRequestPending) + break; + + /* + * Start a per-database worker to load blocks for this database; this + * function will return once the per-database worker exits. + */ + apw_start_database_worker(); + + /* Prepare for next database. */ + apw_state->prewarm_start_idx = apw_state->prewarm_stop_idx; + } + + /* Clean up. */ + dsm_detach(seg); + LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE); + apw_state->block_info_handle = DSM_HANDLE_INVALID; + apw_state->pid_using_dumpfile = InvalidPid; + LWLockRelease(&apw_state->lock); + + /* Report our success, if we were able to finish. */ + if (!ShutdownRequestPending) + ereport(LOG, + (errmsg("autoprewarm successfully prewarmed %d of %d previously-loaded blocks", + apw_state->prewarmed_blocks, num_elements))); +} + +/* + * Prewarm all blocks for one database (and possibly also global objects, if + * those got grouped with this database). + */ +void +autoprewarm_database_main(Datum main_arg) +{ + int pos; + BlockInfoRecord *block_info; + Relation rel = NULL; + BlockNumber nblocks = 0; + BlockInfoRecord *old_blk = NULL; + dsm_segment *seg; + + /* Establish signal handlers; once that's done, unblock signals. */ + pqsignal(SIGTERM, die); + BackgroundWorkerUnblockSignals(); + + /* Connect to correct database and get block information. */ + apw_init_shmem(); + seg = dsm_attach(apw_state->block_info_handle); + if (seg == NULL) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("could not map dynamic shared memory segment"))); + BackgroundWorkerInitializeConnectionByOid(apw_state->database, InvalidOid, 0); + block_info = (BlockInfoRecord *) dsm_segment_address(seg); + pos = apw_state->prewarm_start_idx; + + /* + * Loop until we run out of blocks to prewarm or until we run out of free + * buffers. + */ + while (pos < apw_state->prewarm_stop_idx && have_free_buffer()) + { + BlockInfoRecord *blk = &block_info[pos++]; + Buffer buf; + + CHECK_FOR_INTERRUPTS(); + + /* + * Quit if we've reached records for another database. If previous + * blocks are of some global objects, then continue pre-warming. + */ + if (old_blk != NULL && old_blk->database != blk->database && + old_blk->database != 0) + break; + + /* + * As soon as we encounter a block of a new relation, close the old + * relation. Note that rel will be NULL if try_relation_open failed + * previously; in that case, there is nothing to close. + */ + if (old_blk != NULL && old_blk->filenode != blk->filenode && + rel != NULL) + { + relation_close(rel, AccessShareLock); + rel = NULL; + CommitTransactionCommand(); + } + + /* + * Try to open each new relation, but only once, when we first + * encounter it. If it's been dropped, skip the associated blocks. + */ + if (old_blk == NULL || old_blk->filenode != blk->filenode) + { + Oid reloid; + + Assert(rel == NULL); + StartTransactionCommand(); + reloid = RelidByRelfilenode(blk->tablespace, blk->filenode); + if (OidIsValid(reloid)) + rel = try_relation_open(reloid, AccessShareLock); + + if (!rel) + CommitTransactionCommand(); + } + if (!rel) + { + old_blk = blk; + continue; + } + + /* Once per fork, check for fork existence and size. */ + if (old_blk == NULL || + old_blk->filenode != blk->filenode || + old_blk->forknum != blk->forknum) + { + RelationOpenSmgr(rel); + + /* + * smgrexists is not safe for illegal forknum, hence check whether + * the passed forknum is valid before using it in smgrexists. + */ + if (blk->forknum > InvalidForkNumber && + blk->forknum <= MAX_FORKNUM && + smgrexists(rel->rd_smgr, blk->forknum)) + nblocks = RelationGetNumberOfBlocksInFork(rel, blk->forknum); + else + nblocks = 0; + } + + /* Check whether blocknum is valid and within fork file size. */ + if (blk->blocknum >= nblocks) + { + /* Move to next forknum. */ + old_blk = blk; + continue; + } + + /* Prewarm buffer. */ + buf = ReadBufferExtended(rel, blk->forknum, blk->blocknum, RBM_NORMAL, + NULL); + if (BufferIsValid(buf)) + { + apw_state->prewarmed_blocks++; + ReleaseBuffer(buf); + } + + old_blk = blk; + } + + dsm_detach(seg); + + /* Release lock on previous relation. */ + if (rel) + { + relation_close(rel, AccessShareLock); + CommitTransactionCommand(); + } +} + +/* + * Dump information on blocks in shared buffers. We use a text format here + * so that it's easy to understand and even change the file contents if + * necessary. + * Returns the number of blocks dumped. + */ +static int +apw_dump_now(bool is_bgworker, bool dump_unlogged) +{ + int num_blocks; + int i; + int ret; + BlockInfoRecord *block_info_array; + BufferDesc *bufHdr; + FILE *file; + char transient_dump_file_path[MAXPGPATH]; + pid_t pid; + + LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE); + pid = apw_state->pid_using_dumpfile; + if (apw_state->pid_using_dumpfile == InvalidPid) + apw_state->pid_using_dumpfile = MyProcPid; + LWLockRelease(&apw_state->lock); + + if (pid != InvalidPid) + { + if (!is_bgworker) + ereport(ERROR, + (errmsg("could not perform block dump because dump file is being used by PID %lu", + (unsigned long) apw_state->pid_using_dumpfile))); + + ereport(LOG, + (errmsg("skipping block dump because it is already being performed by PID %lu", + (unsigned long) apw_state->pid_using_dumpfile))); + return 0; + } + + block_info_array = + (BlockInfoRecord *) palloc(sizeof(BlockInfoRecord) * NBuffers); + + for (num_blocks = 0, i = 0; i < NBuffers; i++) + { + uint32 buf_state; + + CHECK_FOR_INTERRUPTS(); + + bufHdr = GetBufferDescriptor(i); + + /* Lock each buffer header before inspecting. */ + buf_state = LockBufHdr(bufHdr); + + /* + * Unlogged tables will be automatically truncated after a crash or + * unclean shutdown. In such cases we need not prewarm them. Dump them + * only if requested by caller. + */ + if (buf_state & BM_TAG_VALID && + ((buf_state & BM_PERMANENT) || dump_unlogged)) + { + block_info_array[num_blocks].database = bufHdr->tag.rnode.dbNode; + block_info_array[num_blocks].tablespace = bufHdr->tag.rnode.spcNode; + block_info_array[num_blocks].filenode = bufHdr->tag.rnode.relNode; + block_info_array[num_blocks].forknum = bufHdr->tag.forkNum; + block_info_array[num_blocks].blocknum = bufHdr->tag.blockNum; + ++num_blocks; + } + + UnlockBufHdr(bufHdr, buf_state); + } + + snprintf(transient_dump_file_path, MAXPGPATH, "%s.tmp", AUTOPREWARM_FILE); + file = AllocateFile(transient_dump_file_path, "w"); + if (!file) + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not open file \"%s\": %m", + transient_dump_file_path))); + + ret = fprintf(file, "<<%d>>\n", num_blocks); + if (ret < 0) + { + int save_errno = errno; + + FreeFile(file); + unlink(transient_dump_file_path); + errno = save_errno; + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not write to file \"%s\": %m", + transient_dump_file_path))); + } + + for (i = 0; i < num_blocks; i++) + { + CHECK_FOR_INTERRUPTS(); + + ret = fprintf(file, "%u,%u,%u,%u,%u\n", + block_info_array[i].database, + block_info_array[i].tablespace, + block_info_array[i].filenode, + (uint32) block_info_array[i].forknum, + block_info_array[i].blocknum); + if (ret < 0) + { + int save_errno = errno; + + FreeFile(file); + unlink(transient_dump_file_path); + errno = save_errno; + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not write to file \"%s\": %m", + transient_dump_file_path))); + } + } + + pfree(block_info_array); + + /* + * Rename transient_dump_file_path to AUTOPREWARM_FILE to make things + * permanent. + */ + ret = FreeFile(file); + if (ret != 0) + { + int save_errno = errno; + + unlink(transient_dump_file_path); + errno = save_errno; + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not close file \"%s\": %m", + transient_dump_file_path))); + } + + (void) durable_rename(transient_dump_file_path, AUTOPREWARM_FILE, ERROR); + apw_state->pid_using_dumpfile = InvalidPid; + + ereport(DEBUG1, + (errmsg_internal("wrote block details for %d blocks", num_blocks))); + return num_blocks; +} + +/* + * SQL-callable function to launch autoprewarm. + */ +Datum +autoprewarm_start_worker(PG_FUNCTION_ARGS) +{ + pid_t pid; + + if (!autoprewarm) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("autoprewarm is disabled"))); + + apw_init_shmem(); + LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE); + pid = apw_state->bgworker_pid; + LWLockRelease(&apw_state->lock); + + if (pid != InvalidPid) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("autoprewarm worker is already running under PID %lu", + (unsigned long) pid))); + + apw_start_leader_worker(); + + PG_RETURN_VOID(); +} + +/* + * SQL-callable function to perform an immediate block dump. + * + * Note: this is declared to return int8, as insurance against some + * very distant day when we might make NBuffers wider than int. + */ +Datum +autoprewarm_dump_now(PG_FUNCTION_ARGS) +{ + int num_blocks; + + apw_init_shmem(); + + PG_ENSURE_ERROR_CLEANUP(apw_detach_shmem, 0); + { + num_blocks = apw_dump_now(false, true); + } + PG_END_ENSURE_ERROR_CLEANUP(apw_detach_shmem, 0); + + PG_RETURN_INT64((int64) num_blocks); +} + +/* + * Allocate and initialize autoprewarm related shared memory, if not already + * done, and set up backend-local pointer to that state. Returns true if an + * existing shared memory segment was found. + */ +static bool +apw_init_shmem(void) +{ + bool found; + + LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE); + apw_state = ShmemInitStruct("autoprewarm", + sizeof(AutoPrewarmSharedState), + &found); + if (!found) + { + /* First time through ... */ + LWLockInitialize(&apw_state->lock, LWLockNewTrancheId()); + apw_state->bgworker_pid = InvalidPid; + apw_state->pid_using_dumpfile = InvalidPid; + } + LWLockRelease(AddinShmemInitLock); + + LWLockRegisterTranche(apw_state->lock.tranche, "autoprewarm"); + + return found; +} + +/* + * Clear our PID from autoprewarm shared state. + */ +static void +apw_detach_shmem(int code, Datum arg) +{ + LWLockAcquire(&apw_state->lock, LW_EXCLUSIVE); + if (apw_state->pid_using_dumpfile == MyProcPid) + apw_state->pid_using_dumpfile = InvalidPid; + if (apw_state->bgworker_pid == MyProcPid) + apw_state->bgworker_pid = InvalidPid; + LWLockRelease(&apw_state->lock); +} + +/* + * Start autoprewarm leader worker process. + */ +static void +apw_start_leader_worker(void) +{ + BackgroundWorker worker; + BackgroundWorkerHandle *handle; + BgwHandleStatus status; + pid_t pid; + + MemSet(&worker, 0, sizeof(BackgroundWorker)); + worker.bgw_flags = BGWORKER_SHMEM_ACCESS; + worker.bgw_start_time = BgWorkerStart_ConsistentState; + strcpy(worker.bgw_library_name, "pg_prewarm"); + strcpy(worker.bgw_function_name, "autoprewarm_main"); + strcpy(worker.bgw_name, "autoprewarm leader"); + strcpy(worker.bgw_type, "autoprewarm leader"); + + if (process_shared_preload_libraries_in_progress) + { + RegisterBackgroundWorker(&worker); + return; + } + + /* must set notify PID to wait for startup */ + worker.bgw_notify_pid = MyProcPid; + + if (!RegisterDynamicBackgroundWorker(&worker, &handle)) + ereport(ERROR, + (errcode(ERRCODE_INSUFFICIENT_RESOURCES), + errmsg("could not register background process"), + errhint("You may need to increase max_worker_processes."))); + + status = WaitForBackgroundWorkerStartup(handle, &pid); + if (status != BGWH_STARTED) + ereport(ERROR, + (errcode(ERRCODE_INSUFFICIENT_RESOURCES), + errmsg("could not start background process"), + errhint("More details may be available in the server log."))); +} + +/* + * Start autoprewarm per-database worker process. + */ +static void +apw_start_database_worker(void) +{ + BackgroundWorker worker; + BackgroundWorkerHandle *handle; + + MemSet(&worker, 0, sizeof(BackgroundWorker)); + worker.bgw_flags = + BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION; + worker.bgw_start_time = BgWorkerStart_ConsistentState; + worker.bgw_restart_time = BGW_NEVER_RESTART; + strcpy(worker.bgw_library_name, "pg_prewarm"); + strcpy(worker.bgw_function_name, "autoprewarm_database_main"); + strcpy(worker.bgw_name, "autoprewarm worker"); + strcpy(worker.bgw_type, "autoprewarm worker"); + + /* must set notify PID to wait for shutdown */ + worker.bgw_notify_pid = MyProcPid; + + if (!RegisterDynamicBackgroundWorker(&worker, &handle)) + ereport(ERROR, + (errcode(ERRCODE_INSUFFICIENT_RESOURCES), + errmsg("registering dynamic bgworker autoprewarm failed"), + errhint("Consider increasing configuration parameter \"max_worker_processes\"."))); + + /* + * Ignore return value; if it fails, postmaster has died, but we have + * checks for that elsewhere. + */ + WaitForBackgroundWorkerShutdown(handle); +} + +/* Compare member elements to check whether they are not equal. */ +#define cmp_member_elem(fld) \ +do { \ + if (a->fld < b->fld) \ + return -1; \ + else if (a->fld > b->fld) \ + return 1; \ +} while(0) + +/* + * apw_compare_blockinfo + * + * We depend on all records for a particular database being consecutive + * in the dump file; each per-database worker will preload blocks until + * it sees a block for some other database. Sorting by tablespace, + * filenode, forknum, and blocknum isn't critical for correctness, but + * helps us get a sequential I/O pattern. + */ +static int +apw_compare_blockinfo(const void *p, const void *q) +{ + const BlockInfoRecord *a = (const BlockInfoRecord *) p; + const BlockInfoRecord *b = (const BlockInfoRecord *) q; + + cmp_member_elem(database); + cmp_member_elem(tablespace); + cmp_member_elem(filenode); + cmp_member_elem(forknum); + cmp_member_elem(blocknum); + + return 0; +} |