/*------------------------------------------------------------------------- * * pgarch.c * * PostgreSQL WAL archiver * * All functions relating to archiver are included here * * - All functions executed by archiver process * * - archiver is forked from postmaster, and the two * processes then communicate using signals. All functions * executed by postmaster are included in this file. * * Initial author: Simon Riggs simon@2ndquadrant.com * * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/backend/postmaster/pgarch.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include #include #include #include #include #include #include #include "access/xlog.h" #include "access/xlog_internal.h" #include "libpq/pqsignal.h" #include "miscadmin.h" #include "pgstat.h" #include "postmaster/interrupt.h" #include "postmaster/pgarch.h" #include "storage/fd.h" #include "storage/ipc.h" #include "storage/latch.h" #include "storage/pmsignal.h" #include "storage/proc.h" #include "storage/procsignal.h" #include "storage/shmem.h" #include "utils/guc.h" #include "utils/ps_status.h" /* ---------- * Timer definitions. * ---------- */ #define PGARCH_AUTOWAKE_INTERVAL 60 /* How often to force a poll of the * archive status directory; in seconds. */ #define PGARCH_RESTART_INTERVAL 10 /* How often to attempt to restart a * failed archiver; in seconds. */ /* * Maximum number of retries allowed when attempting to archive a WAL * file. */ #define NUM_ARCHIVE_RETRIES 3 /* * Maximum number of retries allowed when attempting to remove an * orphan archive status file. */ #define NUM_ORPHAN_CLEANUP_RETRIES 3 /* Shared memory area for archiver process */ typedef struct PgArchData { int pgprocno; /* pgprocno of archiver process */ } PgArchData; /* ---------- * Local data * ---------- */ static time_t last_sigterm_time = 0; static PgArchData *PgArch = NULL; /* * Flags set by interrupt handlers for later service in the main loop. */ static volatile sig_atomic_t ready_to_stop = false; /* ---------- * Local function forward declarations * ---------- */ static void pgarch_waken_stop(SIGNAL_ARGS); static void pgarch_MainLoop(void); static void pgarch_ArchiverCopyLoop(void); static bool pgarch_archiveXlog(char *xlog); static bool pgarch_readyXlog(char *xlog); static void pgarch_archiveDone(char *xlog); static void pgarch_die(int code, Datum arg); static void HandlePgArchInterrupts(void); /* Report shared memory space needed by PgArchShmemInit */ Size PgArchShmemSize(void) { Size size = 0; size = add_size(size, sizeof(PgArchData)); return size; } /* Allocate and initialize archiver-related shared memory */ void PgArchShmemInit(void) { bool found; PgArch = (PgArchData *) ShmemInitStruct("Archiver Data", PgArchShmemSize(), &found); if (!found) { /* First time through, so initialize */ MemSet(PgArch, 0, PgArchShmemSize()); PgArch->pgprocno = INVALID_PGPROCNO; } } /* * PgArchCanRestart * * Return true and archiver is allowed to restart if enough time has * passed since it was launched last to reach PGARCH_RESTART_INTERVAL. * Otherwise return false. * * This is a safety valve to protect against continuous respawn attempts if the * archiver is dying immediately at launch. Note that since we will retry to * launch the archiver from the postmaster main loop, we will get another * chance later. */ bool PgArchCanRestart(void) { static time_t last_pgarch_start_time = 0; time_t curtime = time(NULL); /* * Return false and don't restart archiver if too soon since last archiver * start. */ if ((unsigned int) (curtime - last_pgarch_start_time) < (unsigned int) PGARCH_RESTART_INTERVAL) return false; last_pgarch_start_time = curtime; return true; } /* Main entry point for archiver process */ void PgArchiverMain(void) { /* * Ignore all signals usually bound to some action in the postmaster, * except for SIGHUP, SIGTERM, SIGUSR1, SIGUSR2, and SIGQUIT. */ pqsignal(SIGHUP, SignalHandlerForConfigReload); pqsignal(SIGINT, SIG_IGN); pqsignal(SIGTERM, SignalHandlerForShutdownRequest); /* SIGQUIT handler was already set up by InitPostmasterChild */ pqsignal(SIGALRM, SIG_IGN); pqsignal(SIGPIPE, SIG_IGN); pqsignal(SIGUSR1, procsignal_sigusr1_handler); pqsignal(SIGUSR2, pgarch_waken_stop); /* Reset some signals that are accepted by postmaster but not here */ pqsignal(SIGCHLD, SIG_DFL); /* Unblock signals (they were blocked when the postmaster forked us) */ PG_SETMASK(&UnBlockSig); /* We shouldn't be launched unnecessarily. */ Assert(XLogArchivingActive()); /* Arrange to clean up at archiver exit */ on_shmem_exit(pgarch_die, 0); /* * Advertise our pgprocno so that backends can use our latch to wake us up * while we're sleeping. */ PgArch->pgprocno = MyProc->pgprocno; pgarch_MainLoop(); proc_exit(0); } /* * Wake up the archiver */ void PgArchWakeup(void) { int arch_pgprocno = PgArch->pgprocno; /* * We don't acquire ProcArrayLock here. It's actually fine because * procLatch isn't ever freed, so we just can potentially set the wrong * process' (or no process') latch. Even in that case the archiver will * be relaunched shortly and will start archiving. */ if (arch_pgprocno != INVALID_PGPROCNO) SetLatch(&ProcGlobal->allProcs[arch_pgprocno].procLatch); } /* SIGUSR2 signal handler for archiver process */ static void pgarch_waken_stop(SIGNAL_ARGS) { int save_errno = errno; /* set flag to do a final cycle and shut down afterwards */ ready_to_stop = true; SetLatch(MyLatch); errno = save_errno; } /* * pgarch_MainLoop * * Main loop for archiver */ static void pgarch_MainLoop(void) { pg_time_t last_copy_time = 0; bool time_to_stop; /* * There shouldn't be anything for the archiver to do except to wait for a * signal ... however, the archiver exists to protect our data, so she * wakes up occasionally to allow herself to be proactive. */ do { ResetLatch(MyLatch); /* When we get SIGUSR2, we do one more archive cycle, then exit */ time_to_stop = ready_to_stop; /* Check for barrier events and config update */ HandlePgArchInterrupts(); /* * If we've gotten SIGTERM, we normally just sit and do nothing until * SIGUSR2 arrives. However, that means a random SIGTERM would * disable archiving indefinitely, which doesn't seem like a good * idea. If more than 60 seconds pass since SIGTERM, exit anyway, so * that the postmaster can start a new archiver if needed. */ if (ShutdownRequestPending) { time_t curtime = time(NULL); if (last_sigterm_time == 0) last_sigterm_time = curtime; else if ((unsigned int) (curtime - last_sigterm_time) >= (unsigned int) 60) break; } /* Do what we're here for */ pgarch_ArchiverCopyLoop(); last_copy_time = time(NULL); /* * Sleep until a signal is received, or until a poll is forced by * PGARCH_AUTOWAKE_INTERVAL having passed since last_copy_time, or * until postmaster dies. */ if (!time_to_stop) /* Don't wait during last iteration */ { pg_time_t curtime = (pg_time_t) time(NULL); int timeout; timeout = PGARCH_AUTOWAKE_INTERVAL - (curtime - last_copy_time); if (timeout > 0) { int rc; rc = WaitLatch(MyLatch, WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH, timeout * 1000L, WAIT_EVENT_ARCHIVER_MAIN); if (rc & WL_POSTMASTER_DEATH) time_to_stop = true; } } /* * The archiver quits either when the postmaster dies (not expected) * or after completing one more archiving cycle after receiving * SIGUSR2. */ } while (!time_to_stop); } /* * pgarch_ArchiverCopyLoop * * Archives all outstanding xlogs then returns */ static void pgarch_ArchiverCopyLoop(void) { char xlog[MAX_XFN_CHARS + 1]; /* * loop through all xlogs with archive_status of .ready and archive * them...mostly we expect this to be a single file, though it is possible * some backend will add files onto the list of those that need archiving * while we are still copying earlier archives */ while (pgarch_readyXlog(xlog)) { int failures = 0; int failures_orphan = 0; for (;;) { struct stat stat_buf; char pathname[MAXPGPATH]; /* * Do not initiate any more archive commands after receiving * SIGTERM, nor after the postmaster has died unexpectedly. The * first condition is to try to keep from having init SIGKILL the * command, and the second is to avoid conflicts with another * archiver spawned by a newer postmaster. */ if (ShutdownRequestPending || !PostmasterIsAlive()) return; /* * Check for barrier events and config update. This is so that * we'll adopt a new setting for archive_command as soon as * possible, even if there is a backlog of files to be archived. */ HandlePgArchInterrupts(); /* can't do anything if no command ... */ if (!XLogArchiveCommandSet()) { ereport(WARNING, (errmsg("archive_mode enabled, yet archive_command is not set"))); return; } /* * Since archive status files are not removed in a durable manner, * a system crash could leave behind .ready files for WAL segments * that have already been recycled or removed. In this case, * simply remove the orphan status file and move on. unlink() is * used here as even on subsequent crashes the same orphan files * would get removed, so there is no need to worry about * durability. */ snprintf(pathname, MAXPGPATH, XLOGDIR "/%s", xlog); if (stat(pathname, &stat_buf) != 0 && errno == ENOENT) { char xlogready[MAXPGPATH]; StatusFilePath(xlogready, xlog, ".ready"); if (unlink(xlogready) == 0) { ereport(WARNING, (errmsg("removed orphan archive status file \"%s\"", xlogready))); /* leave loop and move to the next status file */ break; } if (++failures_orphan >= NUM_ORPHAN_CLEANUP_RETRIES) { ereport(WARNING, (errmsg("removal of orphan archive status file \"%s\" failed too many times, will try again later", xlogready))); /* give up cleanup of orphan status files */ return; } /* wait a bit before retrying */ pg_usleep(1000000L); continue; } if (pgarch_archiveXlog(xlog)) { /* successful */ pgarch_archiveDone(xlog); /* * Tell the collector about the WAL file that we successfully * archived */ pgstat_send_archiver(xlog, false); break; /* out of inner retry loop */ } else { /* * Tell the collector about the WAL file that we failed to * archive */ pgstat_send_archiver(xlog, true); if (++failures >= NUM_ARCHIVE_RETRIES) { ereport(WARNING, (errmsg("archiving write-ahead log file \"%s\" failed too many times, will try again later", xlog))); return; /* give up archiving for now */ } pg_usleep(1000000L); /* wait a bit before retrying */ } } } } /* * pgarch_archiveXlog * * Invokes system(3) to copy one archive file to wherever it should go * * Returns true if successful */ static bool pgarch_archiveXlog(char *xlog) { char xlogarchcmd[MAXPGPATH]; char pathname[MAXPGPATH]; char activitymsg[MAXFNAMELEN + 16]; char *dp; char *endp; const char *sp; int rc; snprintf(pathname, MAXPGPATH, XLOGDIR "/%s", xlog); /* * construct the command to be executed */ dp = xlogarchcmd; endp = xlogarchcmd + MAXPGPATH - 1; *endp = '\0'; for (sp = XLogArchiveCommand; *sp; sp++) { if (*sp == '%') { switch (sp[1]) { case 'p': /* %p: relative path of source file */ sp++; strlcpy(dp, pathname, endp - dp); make_native_path(dp); dp += strlen(dp); break; case 'f': /* %f: filename of source file */ sp++; strlcpy(dp, xlog, 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 archive command \"%s\"", xlogarchcmd))); /* Report archive activity in PS display */ snprintf(activitymsg, sizeof(activitymsg), "archiving %s", xlog); set_ps_display(activitymsg); rc = system(xlogarchcmd); if (rc != 0) { /* * If either the shell itself, or a called command, died on a signal, * abort the archiver. We do this because system() ignores SIGINT and * SIGQUIT while waiting; so a signal is very likely something that * should have interrupted us too. Also die if the shell got a hard * "command not found" type of error. If we overreact it's no big * deal, the postmaster will just start the archiver again. */ int lev = wait_result_is_any_signal(rc, true) ? FATAL : LOG; if (WIFEXITED(rc)) { ereport(lev, (errmsg("archive command failed with exit code %d", WEXITSTATUS(rc)), errdetail("The failed archive command was: %s", xlogarchcmd))); } else if (WIFSIGNALED(rc)) { #if defined(WIN32) ereport(lev, (errmsg("archive command was terminated by exception 0x%X", WTERMSIG(rc)), errhint("See C include file \"ntstatus.h\" for a description of the hexadecimal value."), errdetail("The failed archive command was: %s", xlogarchcmd))); #else ereport(lev, (errmsg("archive command was terminated by signal %d: %s", WTERMSIG(rc), pg_strsignal(WTERMSIG(rc))), errdetail("The failed archive command was: %s", xlogarchcmd))); #endif } else { ereport(lev, (errmsg("archive command exited with unrecognized status %d", rc), errdetail("The failed archive command was: %s", xlogarchcmd))); } snprintf(activitymsg, sizeof(activitymsg), "failed on %s", xlog); set_ps_display(activitymsg); return false; } elog(DEBUG1, "archived write-ahead log file \"%s\"", xlog); snprintf(activitymsg, sizeof(activitymsg), "last was %s", xlog); set_ps_display(activitymsg); return true; } /* * pgarch_readyXlog * * Return name of the oldest xlog file that has not yet been archived. * No notification is set that file archiving is now in progress, so * this would need to be extended if multiple concurrent archival * tasks were created. If a failure occurs, we will completely * re-copy the file at the next available opportunity. * * It is important that we return the oldest, so that we archive xlogs * in order that they were written, for two reasons: * 1) to maintain the sequential chain of xlogs required for recovery * 2) because the oldest ones will sooner become candidates for * recycling at time of checkpoint * * NOTE: the "oldest" comparison will consider any .history file to be older * than any other file except another .history file. Segments on a timeline * with a smaller ID will be older than all segments on a timeline with a * larger ID; the net result being that past timelines are given higher * priority for archiving. This seems okay, or at least not obviously worth * changing. */ static bool pgarch_readyXlog(char *xlog) { /* * open xlog status directory and read through list of xlogs that have the * .ready suffix, looking for earliest file. It is possible to optimise * this code, though only a single file is expected on the vast majority * of calls, so.... */ char XLogArchiveStatusDir[MAXPGPATH]; DIR *rldir; struct dirent *rlde; bool found = false; bool historyFound = false; snprintf(XLogArchiveStatusDir, MAXPGPATH, XLOGDIR "/archive_status"); rldir = AllocateDir(XLogArchiveStatusDir); while ((rlde = ReadDir(rldir, XLogArchiveStatusDir)) != NULL) { int basenamelen = (int) strlen(rlde->d_name) - 6; char basename[MAX_XFN_CHARS + 1]; bool ishistory; /* Ignore entries with unexpected number of characters */ if (basenamelen < MIN_XFN_CHARS || basenamelen > MAX_XFN_CHARS) continue; /* Ignore entries with unexpected characters */ if (strspn(rlde->d_name, VALID_XFN_CHARS) < basenamelen) continue; /* Ignore anything not suffixed with .ready */ if (strcmp(rlde->d_name + basenamelen, ".ready") != 0) continue; /* Truncate off the .ready */ memcpy(basename, rlde->d_name, basenamelen); basename[basenamelen] = '\0'; /* Is this a history file? */ ishistory = IsTLHistoryFileName(basename); /* * Consume the file to archive. History files have the highest * priority. If this is the first file or the first history file * ever, copy it. In the presence of a history file already chosen as * target, ignore all other files except history files which have been * generated for an older timeline than what is already chosen as * target to archive. */ if (!found || (ishistory && !historyFound)) { strcpy(xlog, basename); found = true; historyFound = ishistory; } else if (ishistory || !historyFound) { if (strcmp(basename, xlog) < 0) strcpy(xlog, basename); } } FreeDir(rldir); return found; } /* * pgarch_archiveDone * * Emit notification that an xlog file has been successfully archived. * We do this by renaming the status file from NNN.ready to NNN.done. * Eventually, a checkpoint process will notice this and delete both the * NNN.done file and the xlog file itself. */ static void pgarch_archiveDone(char *xlog) { char rlogready[MAXPGPATH]; char rlogdone[MAXPGPATH]; StatusFilePath(rlogready, xlog, ".ready"); StatusFilePath(rlogdone, xlog, ".done"); (void) durable_rename(rlogready, rlogdone, WARNING); } /* * pgarch_die * * Exit-time cleanup handler */ static void pgarch_die(int code, Datum arg) { PgArch->pgprocno = INVALID_PGPROCNO; } /* * Interrupt handler for WAL archiver process. * * This is called in the loops pgarch_MainLoop and pgarch_ArchiverCopyLoop. * It checks for barrier events and config update, but not shutdown request * because how to handle shutdown request is different between those loops. */ static void HandlePgArchInterrupts(void) { if (ProcSignalBarrierPending) ProcessProcSignalBarrier(); if (ConfigReloadPending) { ConfigReloadPending = false; ProcessConfigFile(PGC_SIGHUP); } }