Basic Recovery Control functions for use in Hot Standby. Pause, Resume,
Status check functions only. Also, new recovery.conf parameter to pause_at_recovery_target, default on. Simon Riggs, reviewed by Fujii Masao
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Simon Riggs
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@ -14173,6 +14173,64 @@ postgres=# SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup());
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</tgroup>
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</table>
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<para>
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The functions shown in <xref
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linkend="functions-recovery-control-table"> control the progress of recovery.
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These functions may be executed only during recovery.
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</para>
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<table id="functions-recovery-control-table">
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<title>Recovery Control Functions</title>
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<tgroup cols="3">
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<thead>
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<row><entry>Name</entry> <entry>Return Type</entry> <entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>
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<literal><function>pg_is_xlog_replay_paused()</function></literal>
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</entry>
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<entry><type>bool</type></entry>
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<entry>True if recovery is paused.
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</entry>
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</row>
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<row>
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<entry>
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<literal><function>pg_xlog_replay_pause()</function></literal>
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</entry>
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<entry><type>void</type></entry>
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<entry>Pauses recovery immediately.
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</entry>
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</row>
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<row>
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<entry>
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<literal><function>pg_xlog_replay_resume()</function></literal>
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</entry>
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<entry><type>void</type></entry>
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<entry>Restarts recovery if it was paused.
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</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>
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While recovery is paused no further database changes are applied.
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If in hot standby, all new queries will see the same consistent snapshot
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of the database, and no further query conflicts will be generated until
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recovery is resumed.
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</para>
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<para>
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If streaming replication is disabled, the paused state may continue
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indefinitely without problem. While streaming replication is in
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progress WAL records will continue to be received, which will
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eventually fill available disk space, depending upon the duration of
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the pause, the rate of WAL generation and available disk space.
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</para>
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<para>
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The functions shown in <xref linkend="functions-admin-dbsize"> calculate
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the disk space usage of database objects.
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@ -227,6 +227,31 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
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</listitem>
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</varlistentry>
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<varlistentry id="pause-at-recovery-target"
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xreflabel="pause_at_recovery_target">
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<term><varname>pause_at_recovery_target</varname>
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(<type>boolean</type>)
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</term>
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<indexterm>
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<primary><varname>pause_at_recovery_target</> recovery parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Specifies whether recovery should pause when the recovery target
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is reached. The default is true, if a recovery target is set.
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This is intended to allow queries to be executed against the
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database to check if this recovery target is the most desirable
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point for recovery. The paused state can be resumed by using
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<function>pg_xlog_replay_resume()</> (See
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<xref linkend="functions-recovery-control-table">), which then
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causes recovery to end. If this recovery target is not the
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desired stopping point, then shutdown the server, change the
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recovery target settings to a later target and restart to
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continue recovery.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect1>
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@ -182,6 +182,7 @@ static char *recoveryEndCommand = NULL;
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static char *archiveCleanupCommand = NULL;
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static RecoveryTargetType recoveryTarget = RECOVERY_TARGET_UNSET;
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static bool recoveryTargetInclusive = true;
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static bool recoveryPauseAtTarget = true;
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static TransactionId recoveryTargetXid;
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static TimestampTz recoveryTargetTime;
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@ -423,6 +424,8 @@ typedef struct XLogCtlData
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XLogRecPtr recoveryLastRecPtr;
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/* timestamp of last COMMIT/ABORT record replayed (or being replayed) */
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TimestampTz recoveryLastXTime;
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/* Are we requested to pause recovery? */
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bool recoveryPause;
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slock_t info_lck; /* locks shared variables shown above */
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} XLogCtlData;
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@ -570,6 +573,9 @@ static void readRecoveryCommandFile(void);
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static void exitArchiveRecovery(TimeLineID endTLI,
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uint32 endLogId, uint32 endLogSeg);
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static bool recoveryStopsHere(XLogRecord *record, bool *includeThis);
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static void recoveryPausesHere(void);
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static bool RecoveryIsPaused(void);
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static void SetRecoveryPause(bool recoveryPause);
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static void SetLatestXTime(TimestampTz xtime);
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static TimestampTz GetLatestXTime(void);
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static void CheckRequiredParameterValues(void);
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@ -5126,6 +5132,15 @@ readRecoveryCommandFile(void)
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(errmsg("archive_cleanup_command = '%s'",
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archiveCleanupCommand)));
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}
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else if (strcmp(item->name, "pause_at_recovery_target") == 0)
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{
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if (!parse_bool(item->value, &recoveryPauseAtTarget))
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ereport(ERROR,
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(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("parameter \"%s\" requires a Boolean value", "pause_at_recovery_target")));
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ereport(DEBUG2,
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(errmsg("pause_at_recovery_target = '%s'", item->value)));
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}
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else if (strcmp(item->name, "recovery_target_timeline") == 0)
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{
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rtliGiven = true;
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@ -5508,6 +5523,110 @@ recoveryStopsHere(XLogRecord *record, bool *includeThis)
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return stopsHere;
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}
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/*
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* Recheck shared recoveryPause by polling.
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*
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* XXX Can also be done with shared latch.
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*/
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static void
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recoveryPausesHere(void)
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{
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while (RecoveryIsPaused());
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{
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pg_usleep(1000000L); /* 1000 ms */
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HandleStartupProcInterrupts();
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};
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}
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static bool
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RecoveryIsPaused(void)
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{
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/* use volatile pointer to prevent code rearrangement */
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volatile XLogCtlData *xlogctl = XLogCtl;
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bool recoveryPause;
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SpinLockAcquire(&xlogctl->info_lck);
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recoveryPause = xlogctl->recoveryPause;
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SpinLockRelease(&xlogctl->info_lck);
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return recoveryPause;
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}
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static void
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SetRecoveryPause(bool recoveryPause)
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{
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/* use volatile pointer to prevent code rearrangement */
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volatile XLogCtlData *xlogctl = XLogCtl;
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SpinLockAcquire(&xlogctl->info_lck);
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xlogctl->recoveryPause = recoveryPause;
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SpinLockRelease(&xlogctl->info_lck);
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}
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/*
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* pg_xlog_replay_pause - pause recovery now
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*/
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Datum
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pg_xlog_replay_pause(PG_FUNCTION_ARGS)
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{
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if (!superuser())
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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(errmsg("must be superuser to control recovery"))));
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if (!RecoveryInProgress())
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ereport(ERROR,
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(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
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errmsg("recovery is not in progress"),
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errhint("Recovery control functions can only be executed during recovery.")));
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SetRecoveryPause(true);
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PG_RETURN_VOID();
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}
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/*
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* pg_xlog_replay_resume - resume recovery now
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*/
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Datum
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pg_xlog_replay_resume(PG_FUNCTION_ARGS)
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{
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if (!superuser())
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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(errmsg("must be superuser to control recovery"))));
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if (!RecoveryInProgress())
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ereport(ERROR,
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(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
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errmsg("recovery is not in progress"),
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errhint("Recovery control functions can only be executed during recovery.")));
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SetRecoveryPause(false);
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PG_RETURN_VOID();
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}
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/*
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* pg_is_xlog_replay_paused
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*/
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Datum
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pg_is_xlog_replay_paused(PG_FUNCTION_ARGS)
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{
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if (!superuser())
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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(errmsg("must be superuser to control recovery"))));
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if (!RecoveryInProgress())
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ereport(ERROR,
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(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
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errmsg("recovery is not in progress"),
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errhint("Recovery control functions can only be executed during recovery.")));
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PG_RETURN_BOOL(RecoveryIsPaused());
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}
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/*
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* Save timestamp of latest processed commit/abort record.
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*
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@ -6074,6 +6193,13 @@ StartupXLOG(void)
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StandbyRecoverPreparedTransactions(false);
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}
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}
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else
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{
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/*
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* Must not pause unless we are going to enter Hot Standby.
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*/
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recoveryPauseAtTarget = false;
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}
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/* Initialize resource managers */
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for (rmid = 0; rmid <= RM_MAX_ID; rmid++)
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@ -6098,6 +6224,7 @@ StartupXLOG(void)
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xlogctl->replayEndRecPtr = ReadRecPtr;
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xlogctl->recoveryLastRecPtr = ReadRecPtr;
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xlogctl->recoveryLastXTime = 0;
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xlogctl->recoveryPause = false;
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SpinLockRelease(&xlogctl->info_lck);
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/* Also ensure XLogReceiptTime has a sane value */
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@ -6146,6 +6273,7 @@ StartupXLOG(void)
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{
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bool recoveryContinue = true;
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bool recoveryApply = true;
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bool recoveryPause = false;
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ErrorContextCallback errcontext;
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TimestampTz xtime;
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@ -6192,6 +6320,11 @@ StartupXLOG(void)
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*/
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if (recoveryStopsHere(record, &recoveryApply))
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{
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if (recoveryPauseAtTarget)
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{
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SetRecoveryPause(true);
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recoveryPausesHere();
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}
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reachedStopPoint = true; /* see below */
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recoveryContinue = false;
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if (!recoveryApply)
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@ -6218,8 +6351,12 @@ StartupXLOG(void)
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*/
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SpinLockAcquire(&xlogctl->info_lck);
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xlogctl->replayEndRecPtr = EndRecPtr;
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recoveryPause = xlogctl->recoveryPause;
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SpinLockRelease(&xlogctl->info_lck);
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if (recoveryPause)
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recoveryPausesHere();
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/*
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* If we are attempting to enter Hot Standby mode, process
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* XIDs we see
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@ -275,5 +275,8 @@ extern Datum pg_last_xact_replay_timestamp(PG_FUNCTION_ARGS);
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extern Datum pg_xlogfile_name_offset(PG_FUNCTION_ARGS);
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extern Datum pg_xlogfile_name(PG_FUNCTION_ARGS);
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extern Datum pg_is_in_recovery(PG_FUNCTION_ARGS);
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extern Datum pg_xlog_replay_pause(PG_FUNCTION_ARGS);
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extern Datum pg_xlog_replay_resume(PG_FUNCTION_ARGS);
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extern Datum pg_is_xlog_replay_paused(PG_FUNCTION_ARGS);
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#endif /* XLOG_INTERNAL_H */
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@ -3416,6 +3416,13 @@ DESCR("last xlog replay location");
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DATA(insert OID = 3830 ( pg_last_xact_replay_timestamp PGNSP PGUID 12 1 0 0 f f f t f v 0 0 1184 "" _null_ _null_ _null_ _null_ pg_last_xact_replay_timestamp _null_ _null_ _null_ ));
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DESCR("timestamp of last replay xact");
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DATA(insert OID = 3071 ( pg_xlog_replay_pause PGNSP PGUID 12 1 0 0 f f f t f v 0 0 2278 "" _null_ _null_ _null_ _null_ pg_xlog_replay_pause _null_ _null_ _null_ ));
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DESCR("pauses xlog replay");
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DATA(insert OID = 3072 ( pg_xlog_replay_resume PGNSP PGUID 12 1 0 0 f f f t f v 0 0 2278 "" _null_ _null_ _null_ _null_ pg_xlog_replay_resume _null_ _null_ _null_ ));
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DESCR("resumes xlog replay, if it was paused");
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DATA(insert OID = 3073 ( pg_is_xlog_replay_paused PGNSP PGUID 12 1 0 0 f f f t f v 0 0 16 "" _null_ _null_ _null_ _null_ pg_is_xlog_replay_paused _null_ _null_ _null_ ));
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DESCR("true if xlog replay is paused");
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DATA(insert OID = 2621 ( pg_reload_conf PGNSP PGUID 12 1 0 0 f f f t f v 0 0 16 "" _null_ _null_ _null_ _null_ pg_reload_conf _null_ _null_ _null_ ));
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DESCR("reload configuration files");
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DATA(insert OID = 2622 ( pg_rotate_logfile PGNSP PGUID 12 1 0 0 f f f t f v 0 0 16 "" _null_ _null_ _null_ _null_ pg_rotate_logfile _null_ _null_ _null_ ));
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