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Make archiver process an auxiliary process.

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This commit changes WAL archiver process so that it's treated as
an auxiliary process and can use shared memory. This is an infrastructure
patch required for upcoming shared-memory based stats collector patch
series. These patch series basically need any processes including archiver
that can report the statistics to access to shared memory. Since this patch
itself is useful to simplify the code and when users monitor the status of
archiver, it's committed separately in advance.

This commit simplifies the code for WAL archiving. For example, previously
backends need to signal to archiver via postmaster when they notify
archiver that there are some WAL files to archive. On the other hand,
this commit removes that signal to postmaster and enables backends to
notify archier directly using shared latch.

Also, as the side of this change, the information about archiver process
becomes viewable at pg_stat_activity view.

Author: Kyotaro Horiguchi
Reviewed-by: Andres Freund, Álvaro Herrera, Julien Rouhaud, Tomas Vondra, Arthur Zakirov, Fujii Masao
Discussion: https://postgr.es/m/20180629.173418.190173462.horiguchi.kyotaro@lab.ntt.co.jp
This commit is contained in:
Fujii Masao
2021-03-15 13:13:14 +09:00
parent 0ea71c93a0
commit d75288fb27
11 changed files with 164 additions and 215 deletions
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81
src/backend/postmaster/postmaster.c
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@@ -443,9 +443,10 @@ static void InitPostmasterDeathWatchHandle(void);
* even during recovery.
*/
#define PgArchStartupAllowed() \
((XLogArchivingActive() && pmState == PM_RUN) || \
(XLogArchivingAlways() && \
(pmState == PM_RECOVERY || pmState == PM_HOT_STANDBY)))
(((XLogArchivingActive() && pmState == PM_RUN) || \
(XLogArchivingAlways() && \
(pmState == PM_RECOVERY || pmState == PM_HOT_STANDBY))) && \
PgArchCanRestart())
#ifdef EXEC_BACKEND
@@ -548,6 +549,7 @@ static void ShmemBackendArrayRemove(Backend *bn);
#endif /* EXEC_BACKEND */
#define StartupDataBase() StartChildProcess(StartupProcess)
#define StartArchiver() StartChildProcess(ArchiverProcess)
#define StartBackgroundWriter() StartChildProcess(BgWriterProcess)
#define StartCheckpointer() StartChildProcess(CheckpointerProcess)
#define StartWalWriter() StartChildProcess(WalWriterProcess)
@@ -1792,7 +1794,7 @@ ServerLoop(void)
/* If we have lost the archiver, try to start a new one. */
if (PgArchPID == 0 && PgArchStartupAllowed())
PgArchPID = pgarch_start();
PgArchPID = StartArchiver();
/* If we need to signal the autovacuum launcher, do so now */
if (avlauncher_needs_signal)
@@ -3007,7 +3009,7 @@ reaper(SIGNAL_ARGS)
if (!IsBinaryUpgrade && AutoVacuumingActive() && AutoVacPID == 0)
AutoVacPID = StartAutoVacLauncher();
if (PgArchStartupAllowed() && PgArchPID == 0)
PgArchPID = pgarch_start();
PgArchPID = StartArchiver();
if (PgStatPID == 0)
PgStatPID = pgstat_start();
@@ -3142,20 +3144,22 @@ reaper(SIGNAL_ARGS)
}
/*
* Was it the archiver? If so, just try to start a new one; no need
* to force reset of the rest of the system. (If fail, we'll try
* again in future cycles of the main loop.). Unless we were waiting
* for it to shut down; don't restart it in that case, and
* Was it the archiver? If exit status is zero (normal) or one (FATAL
* exit), we assume everything is all right just like normal backends
* and just try to restart a new one so that we immediately retry
* archiving remaining files. (If fail, we'll try again in future
* cycles of the postmaster's main loop.) Unless we were waiting for
* it to shut down; don't restart it in that case, and
* PostmasterStateMachine() will advance to the next shutdown step.
*/
if (pid == PgArchPID)
{
PgArchPID = 0;
if (!EXIT_STATUS_0(exitstatus))
LogChildExit(LOG, _("archiver process"),
pid, exitstatus);
if (!EXIT_STATUS_0(exitstatus) && !EXIT_STATUS_1(exitstatus))
HandleChildCrash(pid, exitstatus,
_("archiver process"));
if (PgArchStartupAllowed())
PgArchPID = pgarch_start();
PgArchPID = StartArchiver();
continue;
}
@@ -3403,7 +3407,7 @@ CleanupBackend(int pid,
/*
* HandleChildCrash -- cleanup after failed backend, bgwriter, checkpointer,
* walwriter, autovacuum, or background worker.
* walwriter, autovacuum, archiver or background worker.
*
* The objectives here are to clean up our local state about the child
* process, and to signal all other remaining children to quickdie.
@@ -3609,19 +3613,16 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
signal_child(AutoVacPID, (SendStop ? SIGSTOP : SIGQUIT));
}
/*
* Force a power-cycle of the pgarch process too. (This isn't absolutely
* necessary, but it seems like a good idea for robustness, and it
* simplifies the state-machine logic in the case where a shutdown request
* arrives during crash processing.)
*/
if (PgArchPID != 0 && take_action)
/* Take care of the archiver too */
if (pid == PgArchPID)
PgArchPID = 0;
else if (PgArchPID != 0 && take_action)
{
ereport(DEBUG2,
(errmsg_internal("sending %s to process %d",
"SIGQUIT",
(SendStop ? "SIGSTOP" : "SIGQUIT"),
(int) PgArchPID)));
signal_child(PgArchPID, SIGQUIT);
signal_child(PgArchPID, (SendStop ? SIGSTOP : SIGQUIT));
}
/*
@@ -3804,12 +3805,11 @@ PostmasterStateMachine(void)
* (including autovac workers), no bgworkers (including unconnected
* ones), and no walwriter, autovac launcher or bgwriter. If we are
* doing crash recovery or an immediate shutdown then we expect the
* checkpointer to exit as well, otherwise not. The archiver, stats,
* and syslogger processes are disregarded since they are not
* connected to shared memory; we also disregard dead_end children
* here. Walsenders are also disregarded, they will be terminated
* later after writing the checkpoint record, like the archiver
* process.
* checkpointer to exit as well, otherwise not. The stats and
* syslogger processes are disregarded since they are not connected to
* shared memory; we also disregard dead_end children here. Walsenders
* and archiver are also disregarded, they will be terminated later
* after writing the checkpoint record.
*/
if (CountChildren(BACKEND_TYPE_ALL - BACKEND_TYPE_WALSND) == 0 &&
StartupPID == 0 &&
@@ -3912,6 +3912,7 @@ PostmasterStateMachine(void)
Assert(CheckpointerPID == 0);
Assert(WalWriterPID == 0);
Assert(AutoVacPID == 0);
Assert(PgArchPID == 0);
/* syslogger is not considered here */
pmState = PM_NO_CHILDREN;
}
@@ -5037,12 +5038,6 @@ SubPostmasterMain(int argc, char *argv[])
StartBackgroundWorker();
}
if (strcmp(argv[1], "--forkarch") == 0)
{
/* Do not want to attach to shared memory */
PgArchiverMain(argc, argv); /* does not return */
}
if (strcmp(argv[1], "--forkcol") == 0)
{
/* Do not want to attach to shared memory */
@@ -5140,7 +5135,7 @@ sigusr1_handler(SIGNAL_ARGS)
*/
Assert(PgArchPID == 0);
if (XLogArchivingAlways())
PgArchPID = pgarch_start();
PgArchPID = StartArchiver();
/*
* If we aren't planning to enter hot standby mode later, treat
@@ -5194,16 +5189,6 @@ sigusr1_handler(SIGNAL_ARGS)
if (StartWorkerNeeded || HaveCrashedWorker)
maybe_start_bgworkers();
if (CheckPostmasterSignal(PMSIGNAL_WAKEN_ARCHIVER) &&
PgArchPID != 0)
{
/*
* Send SIGUSR1 to archiver process, to wake it up and begin archiving
* next WAL file.
*/
signal_child(PgArchPID, SIGUSR1);
}
/* Tell syslogger to rotate logfile if requested */
if (SysLoggerPID != 0)
{
@@ -5445,6 +5430,10 @@ StartChildProcess(AuxProcType type)
ereport(LOG,
(errmsg("could not fork startup process: %m")));
break;
case ArchiverProcess:
ereport(LOG,
(errmsg("could not fork archiver process: %m")));
break;
case BgWriterProcess:
ereport(LOG,
(errmsg("could not fork background writer process: %m")));