diff options
Diffstat (limited to 'src/backend/access/transam/xlogarchive.c')
| -rw-r--r-- | src/backend/access/transam/xlogarchive.c | 731 |
1 files changed, 731 insertions, 0 deletions
diff --git a/src/backend/access/transam/xlogarchive.c b/src/backend/access/transam/xlogarchive.c new file mode 100644 index 0000000..cdd586f --- /dev/null +++ b/src/backend/access/transam/xlogarchive.c @@ -0,0 +1,731 @@ +/*------------------------------------------------------------------------- + * + * xlogarchive.c + * Functions for archiving WAL files and restoring from the archive. + * + * + * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * src/backend/access/transam/xlogarchive.c + * + *------------------------------------------------------------------------- + */ + +#include "postgres.h" + +#include <sys/stat.h> +#include <sys/wait.h> +#include <signal.h> +#include <unistd.h> + +#include "access/xlog.h" +#include "access/xlog_internal.h" +#include "access/xlogarchive.h" +#include "common/archive.h" +#include "miscadmin.h" +#include "postmaster/startup.h" +#include "replication/walsender.h" +#include "storage/fd.h" +#include "storage/ipc.h" +#include "storage/lwlock.h" +#include "storage/pmsignal.h" + +/* + * Attempt to retrieve the specified file from off-line archival storage. + * If successful, fill "path" with its complete path (note that this will be + * a temp file name that doesn't follow the normal naming convention), and + * return true. + * + * If not successful, fill "path" with the name of the normal on-line file + * (which may or may not actually exist, but we'll try to use it), and return + * false. + * + * For fixed-size files, the caller may pass the expected size as an + * additional crosscheck on successful recovery. If the file size is not + * known, set expectedSize = 0. + * + * When 'cleanupEnabled' is false, refrain from deleting any old WAL segments + * in the archive. This is used when fetching the initial checkpoint record, + * when we are not yet sure how far back we need the WAL. + */ +bool +RestoreArchivedFile(char *path, const char *xlogfname, + const char *recovername, off_t expectedSize, + bool cleanupEnabled) +{ + char xlogpath[MAXPGPATH]; + char *xlogRestoreCmd; + char lastRestartPointFname[MAXPGPATH]; + int rc; + struct stat stat_buf; + XLogSegNo restartSegNo; + XLogRecPtr restartRedoPtr; + TimeLineID restartTli; + + /* + * Ignore restore_command when not in archive recovery (meaning we are in + * crash recovery). + */ + if (!ArchiveRecoveryRequested) + goto not_available; + + /* In standby mode, restore_command might not be supplied */ + if (recoveryRestoreCommand == NULL || strcmp(recoveryRestoreCommand, "") == 0) + goto not_available; + + /* + * When doing archive recovery, we always prefer an archived log file even + * if a file of the same name exists in XLOGDIR. The reason is that the + * file in XLOGDIR could be an old, un-filled or partly-filled version + * that was copied and restored as part of backing up $PGDATA. + * + * We could try to optimize this slightly by checking the local copy + * lastchange timestamp against the archived copy, but we have no API to + * do this, nor can we guarantee that the lastchange timestamp was + * preserved correctly when we copied to archive. Our aim is robustness, + * so we elect not to do this. + * + * If we cannot obtain the log file from the archive, however, we will try + * to use the XLOGDIR file if it exists. This is so that we can make use + * of log segments that weren't yet transferred to the archive. + * + * Notice that we don't actually overwrite any files when we copy back + * from archive because the restore_command may inadvertently restore + * inappropriate xlogs, or they may be corrupt, so we may wish to fallback + * to the segments remaining in current XLOGDIR later. The + * copy-from-archive filename is always the same, ensuring that we don't + * run out of disk space on long recoveries. + */ + snprintf(xlogpath, MAXPGPATH, XLOGDIR "/%s", recovername); + + /* + * Make sure there is no existing file named recovername. + */ + if (stat(xlogpath, &stat_buf) != 0) + { + if (errno != ENOENT) + ereport(FATAL, + (errcode_for_file_access(), + errmsg("could not stat file \"%s\": %m", + xlogpath))); + } + else + { + if (unlink(xlogpath) != 0) + ereport(FATAL, + (errcode_for_file_access(), + errmsg("could not remove file \"%s\": %m", + xlogpath))); + } + + /* + * Calculate the archive file cutoff point for use during log shipping + * replication. All files earlier than this point can be deleted from the + * archive, though there is no requirement to do so. + * + * If cleanup is not enabled, initialise this with the filename of + * InvalidXLogRecPtr, which will prevent the deletion of any WAL files + * from the archive because of the alphabetic sorting property of WAL + * filenames. + * + * Once we have successfully located the redo pointer of the checkpoint + * from which we start recovery we never request a file prior to the redo + * pointer of the last restartpoint. When redo begins we know that we have + * successfully located it, so there is no need for additional status + * flags to signify the point when we can begin deleting WAL files from + * the archive. + */ + if (cleanupEnabled) + { + GetOldestRestartPoint(&restartRedoPtr, &restartTli); + XLByteToSeg(restartRedoPtr, restartSegNo, wal_segment_size); + XLogFileName(lastRestartPointFname, restartTli, restartSegNo, + wal_segment_size); + /* we shouldn't need anything earlier than last restart point */ + Assert(strcmp(lastRestartPointFname, xlogfname) <= 0); + } + else + XLogFileName(lastRestartPointFname, 0, 0L, wal_segment_size); + + /* Build the restore command to execute */ + xlogRestoreCmd = BuildRestoreCommand(recoveryRestoreCommand, + xlogpath, xlogfname, + lastRestartPointFname); + if (xlogRestoreCmd == NULL) + elog(ERROR, "could not build restore command \"%s\"", + recoveryRestoreCommand); + + ereport(DEBUG3, + (errmsg_internal("executing restore command \"%s\"", + xlogRestoreCmd))); + + /* + * Check signals before restore command and reset afterwards. + */ + PreRestoreCommand(); + + /* + * Copy xlog from archival storage to XLOGDIR + */ + rc = system(xlogRestoreCmd); + + PostRestoreCommand(); + pfree(xlogRestoreCmd); + + if (rc == 0) + { + /* + * command apparently succeeded, but let's make sure the file is + * really there now and has the correct size. + */ + if (stat(xlogpath, &stat_buf) == 0) + { + if (expectedSize > 0 && stat_buf.st_size != expectedSize) + { + int elevel; + + /* + * If we find a partial file in standby mode, we assume it's + * because it's just being copied to the archive, and keep + * trying. + * + * Otherwise treat a wrong-sized file as FATAL to ensure the + * DBA would notice it, but is that too strong? We could try + * to plow ahead with a local copy of the file ... but the + * problem is that there probably isn't one, and we'd + * incorrectly conclude we've reached the end of WAL and we're + * done recovering ... + */ + if (StandbyMode && stat_buf.st_size < expectedSize) + elevel = DEBUG1; + else + elevel = FATAL; + ereport(elevel, + (errmsg("archive file \"%s\" has wrong size: %lu instead of %lu", + xlogfname, + (unsigned long) stat_buf.st_size, + (unsigned long) expectedSize))); + return false; + } + else + { + ereport(LOG, + (errmsg("restored log file \"%s\" from archive", + xlogfname))); + strcpy(path, xlogpath); + return true; + } + } + else + { + /* stat failed */ + if (errno != ENOENT) + ereport(FATAL, + (errcode_for_file_access(), + errmsg("could not stat file \"%s\": %m", + xlogpath))); + } + } + + /* + * Remember, we rollforward UNTIL the restore fails so failure here is + * just part of the process... that makes it difficult to determine + * whether the restore failed because there isn't an archive to restore, + * or because the administrator has specified the restore program + * incorrectly. We have to assume the former. + * + * However, if the failure was due to any sort of signal, it's best to + * punt and abort recovery. (If we "return false" here, upper levels will + * assume that recovery is complete and start up the database!) It's + * essential to abort on child SIGINT and SIGQUIT, because per spec + * system() ignores SIGINT and SIGQUIT while waiting; if we see one of + * those it's a good bet we should have gotten it too. + * + * On SIGTERM, assume we have received a fast shutdown request, and exit + * cleanly. It's pure chance whether we receive the SIGTERM first, or the + * child process. If we receive it first, the signal handler will call + * proc_exit, otherwise we do it here. If we or the child process received + * SIGTERM for any other reason than a fast shutdown request, postmaster + * will perform an immediate shutdown when it sees us exiting + * unexpectedly. + * + * We treat hard shell errors such as "command not found" as fatal, too. + */ + if (wait_result_is_signal(rc, SIGTERM)) + proc_exit(1); + + ereport(wait_result_is_any_signal(rc, true) ? FATAL : DEBUG2, + (errmsg("could not restore file \"%s\" from archive: %s", + xlogfname, wait_result_to_str(rc)))); + +not_available: + + /* + * if an archived file is not available, there might still be a version of + * this file in XLOGDIR, so return that as the filename to open. + * + * In many recovery scenarios we expect this to fail also, but if so that + * just means we've reached the end of WAL. + */ + snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlogfname); + return false; +} + +/* + * Attempt to execute an external shell command during recovery. + * + * 'command' is the shell command to be executed, 'commandName' is a + * human-readable name describing the command emitted in the logs. If + * 'failOnSignal' is true and the command is killed by a signal, a FATAL + * error is thrown. Otherwise a WARNING is emitted. + * + * This is currently used for recovery_end_command and archive_cleanup_command. + */ +void +ExecuteRecoveryCommand(const char *command, const char *commandName, bool failOnSignal) +{ + char xlogRecoveryCmd[MAXPGPATH]; + char lastRestartPointFname[MAXPGPATH]; + char *dp; + char *endp; + const char *sp; + int rc; + XLogSegNo restartSegNo; + XLogRecPtr restartRedoPtr; + TimeLineID restartTli; + + Assert(command && commandName); + + /* + * Calculate the archive file cutoff point for use during log shipping + * replication. All files earlier than this point can be deleted from the + * archive, though there is no requirement to do so. + */ + GetOldestRestartPoint(&restartRedoPtr, &restartTli); + XLByteToSeg(restartRedoPtr, restartSegNo, wal_segment_size); + XLogFileName(lastRestartPointFname, restartTli, restartSegNo, + wal_segment_size); + + /* + * construct the command to be executed + */ + dp = xlogRecoveryCmd; + endp = xlogRecoveryCmd + MAXPGPATH - 1; + *endp = '\0'; + + for (sp = command; *sp; sp++) + { + if (*sp == '%') + { + switch (sp[1]) + { + case 'r': + /* %r: filename of last restartpoint */ + sp++; + StrNCpy(dp, lastRestartPointFname, endp - dp); + dp += strlen(dp); + break; + case '%': + /* convert %% to a single % */ + sp++; + if (dp < endp) + *dp++ = *sp; + break; + default: + /* otherwise treat the % as not special */ + if (dp < endp) + *dp++ = *sp; + break; + } + } + else + { + if (dp < endp) + *dp++ = *sp; + } + } + *dp = '\0'; + + ereport(DEBUG3, + (errmsg_internal("executing %s \"%s\"", commandName, command))); + + /* + * execute the constructed command + */ + rc = system(xlogRecoveryCmd); + if (rc != 0) + { + /* + * If the failure was due to any sort of signal, it's best to punt and + * abort recovery. See comments in RestoreArchivedFile(). + */ + ereport((failOnSignal && wait_result_is_any_signal(rc, true)) ? FATAL : WARNING, + /*------ + translator: First %s represents a postgresql.conf parameter name like + "recovery_end_command", the 2nd is the value of that parameter, the + third an already translated error message. */ + (errmsg("%s \"%s\": %s", commandName, + command, wait_result_to_str(rc)))); + } +} + + +/* + * A file was restored from the archive under a temporary filename (path), + * and now we want to keep it. Rename it under the permanent filename in + * pg_wal (xlogfname), replacing any existing file with the same name. + */ +void +KeepFileRestoredFromArchive(const char *path, const char *xlogfname) +{ + char xlogfpath[MAXPGPATH]; + bool reload = false; + struct stat statbuf; + + snprintf(xlogfpath, MAXPGPATH, XLOGDIR "/%s", xlogfname); + + if (stat(xlogfpath, &statbuf) == 0) + { + char oldpath[MAXPGPATH]; + +#ifdef WIN32 + static unsigned int deletedcounter = 1; + + /* + * On Windows, if another process (e.g a walsender process) 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, and we cannot rename the new file in its place until + * that. To avoid that problem, rename the old file to a temporary + * name first. Use a counter to create a unique filename, because the + * same file might be restored from the archive multiple times, and a + * walsender could still be holding onto an old deleted version of it. + */ + snprintf(oldpath, MAXPGPATH, "%s.deleted%u", + xlogfpath, deletedcounter++); + if (rename(xlogfpath, oldpath) != 0) + { + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not rename file \"%s\" to \"%s\": %m", + xlogfpath, oldpath))); + } +#else + /* same-size buffers, so this never truncates */ + strlcpy(oldpath, xlogfpath, MAXPGPATH); +#endif + if (unlink(oldpath) != 0) + ereport(FATAL, + (errcode_for_file_access(), + errmsg("could not remove file \"%s\": %m", + xlogfpath))); + reload = true; + } + + durable_rename(path, xlogfpath, ERROR); + + /* + * Create .done file forcibly to prevent the restored segment from being + * archived again later. + */ + if (XLogArchiveMode != ARCHIVE_MODE_ALWAYS) + XLogArchiveForceDone(xlogfname); + else + XLogArchiveNotify(xlogfname); + + /* + * If the existing file was replaced, since walsenders might have it open, + * request them to reload a currently-open segment. This is only required + * for WAL segments, walsenders don't hold other files open, but there's + * no harm in doing this too often, and we don't know what kind of a file + * we're dealing with here. + */ + if (reload) + WalSndRqstFileReload(); + + /* + * Signal walsender that new WAL has arrived. Again, this isn't necessary + * if we restored something other than a WAL segment, but it does no harm + * either. + */ + WalSndWakeup(); +} + +/* + * XLogArchiveNotify + * + * Create an archive notification file + * + * The name of the notification file is the message that will be picked up + * by the archiver, e.g. we write 0000000100000001000000C6.ready + * and the archiver then knows to archive XLOGDIR/0000000100000001000000C6, + * then when complete, rename it to 0000000100000001000000C6.done + */ +void +XLogArchiveNotify(const char *xlog) +{ + char archiveStatusPath[MAXPGPATH]; + FILE *fd; + + /* insert an otherwise empty file called <XLOG>.ready */ + StatusFilePath(archiveStatusPath, xlog, ".ready"); + fd = AllocateFile(archiveStatusPath, "w"); + if (fd == NULL) + { + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not create archive status file \"%s\": %m", + archiveStatusPath))); + return; + } + if (FreeFile(fd)) + { + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not write archive status file \"%s\": %m", + archiveStatusPath))); + return; + } + + /* Notify archiver that it's got something to do */ + if (IsUnderPostmaster) + SendPostmasterSignal(PMSIGNAL_WAKEN_ARCHIVER); +} + +/* + * Convenience routine to notify using segment number representation of filename + */ +void +XLogArchiveNotifySeg(XLogSegNo segno) +{ + char xlog[MAXFNAMELEN]; + + XLogFileName(xlog, ThisTimeLineID, segno, wal_segment_size); + XLogArchiveNotify(xlog); +} + +/* + * XLogArchiveForceDone + * + * Emit notification forcibly that an XLOG segment file has been successfully + * archived, by creating <XLOG>.done regardless of whether <XLOG>.ready + * exists or not. + */ +void +XLogArchiveForceDone(const char *xlog) +{ + char archiveReady[MAXPGPATH]; + char archiveDone[MAXPGPATH]; + struct stat stat_buf; + FILE *fd; + + /* Exit if already known done */ + StatusFilePath(archiveDone, xlog, ".done"); + if (stat(archiveDone, &stat_buf) == 0) + return; + + /* If .ready exists, rename it to .done */ + StatusFilePath(archiveReady, xlog, ".ready"); + if (stat(archiveReady, &stat_buf) == 0) + { + (void) durable_rename(archiveReady, archiveDone, WARNING); + return; + } + + /* insert an otherwise empty file called <XLOG>.done */ + fd = AllocateFile(archiveDone, "w"); + if (fd == NULL) + { + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not create archive status file \"%s\": %m", + archiveDone))); + return; + } + if (FreeFile(fd)) + { + ereport(LOG, + (errcode_for_file_access(), + errmsg("could not write archive status file \"%s\": %m", + archiveDone))); + return; + } +} + +/* + * XLogArchiveCheckDone + * + * This is called when we are ready to delete or recycle an old XLOG segment + * file or backup history file. If it is okay to delete it then return true. + * If it is not time to delete it, make sure a .ready file exists, and return + * false. + * + * If <XLOG>.done exists, then return true; else if <XLOG>.ready exists, + * then return false; else create <XLOG>.ready and return false. + * + * The reason we do things this way is so that if the original attempt to + * create <XLOG>.ready fails, we'll retry during subsequent checkpoints. + */ +bool +XLogArchiveCheckDone(const char *xlog) +{ + char archiveStatusPath[MAXPGPATH]; + struct stat stat_buf; + + /* The file is always deletable if archive_mode is "off". */ + if (!XLogArchivingActive()) + return true; + + /* + * During archive recovery, the file is deletable if archive_mode is not + * "always". + */ + if (!XLogArchivingAlways() && + GetRecoveryState() == RECOVERY_STATE_ARCHIVE) + return true; + + /* + * At this point of the logic, note that we are either a primary with + * archive_mode set to "on" or "always", or a standby with archive_mode + * set to "always". + */ + + /* First check for .done --- this means archiver is done with it */ + StatusFilePath(archiveStatusPath, xlog, ".done"); + if (stat(archiveStatusPath, &stat_buf) == 0) + return true; + + /* check for .ready --- this means archiver is still busy with it */ + StatusFilePath(archiveStatusPath, xlog, ".ready"); + if (stat(archiveStatusPath, &stat_buf) == 0) + return false; + + /* Race condition --- maybe archiver just finished, so recheck */ + StatusFilePath(archiveStatusPath, xlog, ".done"); + if (stat(archiveStatusPath, &stat_buf) == 0) + return true; + + /* Retry creation of the .ready file */ + XLogArchiveNotify(xlog); + return false; +} + +/* + * XLogArchiveIsBusy + * + * Check to see if an XLOG segment file is still unarchived. + * This is almost but not quite the inverse of XLogArchiveCheckDone: in + * the first place we aren't chartered to recreate the .ready file, and + * in the second place we should consider that if the file is already gone + * then it's not busy. (This check is needed to handle the race condition + * that a checkpoint already deleted the no-longer-needed file.) + */ +bool +XLogArchiveIsBusy(const char *xlog) +{ + char archiveStatusPath[MAXPGPATH]; + struct stat stat_buf; + + /* First check for .done --- this means archiver is done with it */ + StatusFilePath(archiveStatusPath, xlog, ".done"); + if (stat(archiveStatusPath, &stat_buf) == 0) + return false; + + /* check for .ready --- this means archiver is still busy with it */ + StatusFilePath(archiveStatusPath, xlog, ".ready"); + if (stat(archiveStatusPath, &stat_buf) == 0) + return true; + + /* Race condition --- maybe archiver just finished, so recheck */ + StatusFilePath(archiveStatusPath, xlog, ".done"); + if (stat(archiveStatusPath, &stat_buf) == 0) + return false; + + /* + * Check to see if the WAL file has been removed by checkpoint, which + * implies it has already been archived, and explains why we can't see a + * status file for it. + */ + snprintf(archiveStatusPath, MAXPGPATH, XLOGDIR "/%s", xlog); + if (stat(archiveStatusPath, &stat_buf) != 0 && + errno == ENOENT) + return false; + + return true; +} + +/* + * XLogArchiveIsReadyOrDone + * + * Check to see if an XLOG segment file has a .ready or .done file. + * This is similar to XLogArchiveIsBusy(), but returns true if the file + * is already archived or is about to be archived. + * + * This is currently only used at recovery. During normal operation this + * would be racy: the file might get removed or marked with .ready as we're + * checking it, or immediately after we return. + */ +bool +XLogArchiveIsReadyOrDone(const char *xlog) +{ + char archiveStatusPath[MAXPGPATH]; + struct stat stat_buf; + + /* First check for .done --- this means archiver is done with it */ + StatusFilePath(archiveStatusPath, xlog, ".done"); + if (stat(archiveStatusPath, &stat_buf) == 0) + return true; + + /* check for .ready --- this means archiver is still busy with it */ + StatusFilePath(archiveStatusPath, xlog, ".ready"); + if (stat(archiveStatusPath, &stat_buf) == 0) + return true; + + /* Race condition --- maybe archiver just finished, so recheck */ + StatusFilePath(archiveStatusPath, xlog, ".done"); + if (stat(archiveStatusPath, &stat_buf) == 0) + return true; + + return false; +} + +/* + * XLogArchiveIsReady + * + * Check to see if an XLOG segment file has an archive notification (.ready) + * file. + */ +bool +XLogArchiveIsReady(const char *xlog) +{ + char archiveStatusPath[MAXPGPATH]; + struct stat stat_buf; + + StatusFilePath(archiveStatusPath, xlog, ".ready"); + if (stat(archiveStatusPath, &stat_buf) == 0) + return true; + + return false; +} + +/* + * XLogArchiveCleanup + * + * Cleanup archive notification file(s) for a particular xlog segment + */ +void +XLogArchiveCleanup(const char *xlog) +{ + char archiveStatusPath[MAXPGPATH]; + + /* Remove the .done file */ + StatusFilePath(archiveStatusPath, xlog, ".done"); + unlink(archiveStatusPath); + /* should we complain about failure? */ + + /* Remove the .ready file if present --- normally it shouldn't be */ + StatusFilePath(archiveStatusPath, xlog, ".ready"); + unlink(archiveStatusPath); + /* should we complain about failure? */ +} |