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Commit1007465

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Add pg_promote function
This function is able to promote a standby with this new SQL-callablefunction. Execution access can be granted to non-superusers so thatfailover tools can observe the principle of least privilege.Catalog version is bumped.Author: Laurenz AlbeReviewed-by: Michael Paquier, Masahiko SawadaDiscussion:https://postgr.es/m/6e7c79b3ec916cf49742fb8849ed17cd87aed620.camel@cybertec.at
1 parent0a8590b commit1007465

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13 files changed

+143
-20
lines changed

13 files changed

+143
-20
lines changed

‎doc/src/sgml/func.sgml‎

Lines changed: 19 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -19202,6 +19202,9 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
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<indexterm>
1920319203
<primary>pg_is_wal_replay_paused</primary>
1920419204
</indexterm>
19205+
<indexterm>
19206+
<primary>pg_promote</primary>
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</indexterm>
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<indexterm>
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<primary>pg_wal_replay_pause</primary>
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</indexterm>
@@ -19232,6 +19235,22 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
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<entry>True if recovery is paused.
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</entry>
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</row>
19238+
<row>
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<entry>
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<literal><function>pg_promote(<parameter>wait</parameter> <type>boolean</type> DEFAULT true, <parameter>wait_seconds</parameter> <type>integer</type> DEFAULT 60)</function></literal>
19241+
</entry>
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<entry><type>boolean</type></entry>
19243+
<entry>
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Promotes a physical standby server. Returns <literal>true</literal>
19245+
if promotion is successful and <literal>false</literal> otherwise.
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With <parameter>wait</parameter> set to <literal>true</literal>, the
19247+
default, the function waits until promotion is completed or
19248+
<parameter>wait_seconds</parameter> seconds have passed, otherwise the
19249+
function returns immediately after sending the promotion signal to the
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postmaster. This function is restricted to superusers by default, but
19251+
other users can be granted EXECUTE to run the function.
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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_wal_replay_pause()</function></literal>

‎doc/src/sgml/high-availability.sgml‎

Lines changed: 11 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -1471,14 +1471,17 @@ synchronous_standby_names = 'ANY 2 (s1, s2, s3)'
14711471
</para>
14721472

14731473
<para>
1474-
To trigger failover of a log-shipping standby server,
1475-
run <command>pg_ctl promote</command> or create a trigger
1476-
file with the file name and path specified by the <varname>trigger_file</varname>
1477-
setting in <filename>recovery.conf</filename>. If you're planning to use
1478-
<command>pg_ctl promote</command> to fail over, <varname>trigger_file</varname> is
1479-
not required. If you're setting up the reporting servers that are
1480-
only used to offload read-only queries from the primary, not for high
1481-
availability purposes, you don't need to promote it.
1474+
To trigger failover of a log-shipping standby server, run
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<command>pg_ctl promote</command>, call <function>pg_promote</function>,
1476+
or create a trigger file with the file name and path specified by the
1477+
<varname>trigger_file</varname> setting in
1478+
<filename>recovery.conf</filename>. If you're planning to use
1479+
<command>pg_ctl promote</command> or to call
1480+
<function>pg_promote</function> to fail over,
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<varname>trigger_file</varname> is not required. If you're
1482+
setting up the reporting servers that are only used to offload read-only
1483+
queries from the primary, not for high availability purposes, you don't
1484+
need to promote it.
14821485
</para>
14831486
</sect1>
14841487

‎doc/src/sgml/monitoring.sgml‎

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1268,7 +1268,7 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
12681268
<entry>Waiting in an extension.</entry>
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</row>
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<row>
1271-
<entry morerows="33"><literal>IPC</literal></entry>
1271+
<entry morerows="34"><literal>IPC</literal></entry>
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<entry><literal>BgWorkerShutdown</literal></entry>
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<entry>Waiting for background worker to shut down.</entry>
12741274
</row>
@@ -1388,6 +1388,10 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
13881388
<entry><literal>ProcArrayGroupUpdate</literal></entry>
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<entry>Waiting for group leader to clear transaction id at transaction end.</entry>
13901390
</row>
1391+
<row>
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<entry><literal>Promote</literal></entry>
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<entry>Waiting for standby promotion.</entry>
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</row>
13911395
<row>
13921396
<entry><literal>ReplicationOriginDrop</literal></entry>
13931397
<entry>Waiting for a replication origin to become inactive to be dropped.</entry>

‎doc/src/sgml/recovery-config.sgml‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -439,7 +439,8 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
439439
<para>
440440
Specifies a trigger file whose presence ends recovery in the
441441
standby. Even if this value is not set, you can still promote
442-
the standby using <command>pg_ctl promote</command>.
442+
the standby using <command>pg_ctl promote</command> or calling
443+
<function>pg_promote</function>.
443444
This setting has no effect if <varname>standby_mode</varname> is <literal>off</literal>.
444445
</para>
445446
</listitem>

‎src/backend/access/transam/xlog.c‎

Lines changed: 0 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -78,12 +78,6 @@
7878

7979
externuint32bootstrap_data_checksum_version;
8080

81-
/* File path names (all relative to $PGDATA) */
82-
#defineRECOVERY_COMMAND_FILE"recovery.conf"
83-
#defineRECOVERY_COMMAND_DONE"recovery.done"
84-
#definePROMOTE_SIGNAL_FILE"promote"
85-
#defineFALLBACK_PROMOTE_SIGNAL_FILE "fallback_promote"
86-
8781

8882
/* User-settable parameters */
8983
intmax_wal_size_mb=1024;/* 1 GB */

‎src/backend/access/transam/xlogfuncs.c‎

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Original file line numberDiff line numberDiff line change
@@ -16,13 +16,16 @@
1616
*/
1717
#include"postgres.h"
1818

19+
#include<unistd.h>
20+
1921
#include"access/htup_details.h"
2022
#include"access/xlog.h"
2123
#include"access/xlog_internal.h"
2224
#include"access/xlogutils.h"
2325
#include"catalog/pg_type.h"
2426
#include"funcapi.h"
2527
#include"miscadmin.h"
28+
#include"pgstat.h"
2629
#include"replication/walreceiver.h"
2730
#include"storage/smgr.h"
2831
#include"utils/builtins.h"
@@ -697,3 +700,77 @@ pg_backup_start_time(PG_FUNCTION_ARGS)
697700

698701
PG_RETURN_DATUM(xtime);
699702
}
703+
704+
/*
705+
* Promotes a standby server.
706+
*
707+
* A result of "true" means that promotion has been completed if "wait" is
708+
* "true", or initiated if "wait" is false.
709+
*/
710+
Datum
711+
pg_promote(PG_FUNCTION_ARGS)
712+
{
713+
boolwait=PG_GETARG_BOOL(0);
714+
intwait_seconds=PG_GETARG_INT32(1);
715+
FILE*promote_file;
716+
inti;
717+
718+
if (!RecoveryInProgress())
719+
ereport(ERROR,
720+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
721+
errmsg("recovery is not in progress"),
722+
errhint("Recovery control functions can only be executed during recovery.")));
723+
724+
if (wait_seconds <=0)
725+
ereport(ERROR,
726+
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
727+
errmsg("\"wait_seconds\" cannot be negative or equal zero")));
728+
729+
/* create the promote signal file */
730+
promote_file=AllocateFile(PROMOTE_SIGNAL_FILE,"w");
731+
if (!promote_file)
732+
ereport(ERROR,
733+
(errcode_for_file_access(),
734+
errmsg("could not create file \"%s\": %m",
735+
PROMOTE_SIGNAL_FILE)));
736+
737+
if (FreeFile(promote_file))
738+
ereport(ERROR,
739+
(errcode_for_file_access(),
740+
errmsg("could not write file \"%s\": %m",
741+
PROMOTE_SIGNAL_FILE)));
742+
743+
/* signal the postmaster */
744+
if (kill(PostmasterPid,SIGUSR1)!=0)
745+
{
746+
ereport(WARNING,
747+
(errmsg("failed to send signal to postmaster: %m")));
748+
(void)unlink(PROMOTE_SIGNAL_FILE);
749+
PG_RETURN_BOOL(false);
750+
}
751+
752+
/* return immediately if waiting was not requested */
753+
if (!wait)
754+
PG_RETURN_BOOL(true);
755+
756+
/* wait for the amount of time wanted until promotion */
757+
#defineWAITS_PER_SECOND 10
758+
for (i=0;i<WAITS_PER_SECOND*wait_seconds;i++)
759+
{
760+
ResetLatch(MyLatch);
761+
762+
if (!RecoveryInProgress())
763+
PG_RETURN_BOOL(true);
764+
765+
CHECK_FOR_INTERRUPTS();
766+
767+
WaitLatch(MyLatch,
768+
WL_LATCH_SET |WL_TIMEOUT |WL_POSTMASTER_DEATH,
769+
1000L /WAITS_PER_SECOND,
770+
WAIT_EVENT_PROMOTE);
771+
}
772+
773+
ereport(WARNING,
774+
(errmsg("server did not promote within %d seconds",wait_seconds)));
775+
PG_RETURN_BOOL(false);
776+
}

‎src/backend/catalog/system_views.sql‎

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1027,6 +1027,11 @@ CREATE OR REPLACE FUNCTION pg_stop_backup (
10271027
RETURNS SETOF record STRICT VOLATILE LANGUAGE internalas'pg_stop_backup_v2'
10281028
PARALLEL RESTRICTED;
10291029

1030+
CREATEOR REPLACE FUNCTION
1031+
pg_promote(waitboolean DEFAULT true, wait_secondsinteger DEFAULT60)
1032+
RETURNSboolean STRICT VOLATILE LANGUAGE INTERNALAS'pg_promote'
1033+
PARALLEL RESTRICTED;
1034+
10301035
-- legacy definition for compatibility with 9.3
10311036
CREATEOR REPLACE FUNCTION
10321037
json_populate_record(base anyelement, from_json json, use_json_as_textboolean DEFAULT false)
@@ -1138,6 +1143,7 @@ REVOKE EXECUTE ON FUNCTION pg_rotate_logfile() FROM public;
11381143
REVOKE EXECUTEON FUNCTION pg_reload_conf()FROM public;
11391144
REVOKE EXECUTEON FUNCTION pg_current_logfile()FROM public;
11401145
REVOKE EXECUTEON FUNCTION pg_current_logfile(text)FROM public;
1146+
REVOKE EXECUTEON FUNCTION pg_promote(boolean,integer)FROM public;
11411147

11421148
REVOKE EXECUTEON FUNCTION pg_stat_reset()FROM public;
11431149
REVOKE EXECUTEON FUNCTION pg_stat_reset_shared(text)FROM public;

‎src/backend/postmaster/pgstat.c‎

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -3663,6 +3663,9 @@ pgstat_get_wait_ipc(WaitEventIPC w)
36633663
caseWAIT_EVENT_PROCARRAY_GROUP_UPDATE:
36643664
event_name="ProcArrayGroupUpdate";
36653665
break;
3666+
caseWAIT_EVENT_PROMOTE:
3667+
event_name="Promote";
3668+
break;
36663669
caseWAIT_EVENT_REPLICATION_ORIGIN_DROP:
36673670
event_name="ReplicationOriginDrop";
36683671
break;

‎src/include/access/xlog.h‎

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -319,10 +319,16 @@ extern void do_pg_abort_backup(void);
319319
externSessionBackupStateget_backup_status(void);
320320

321321
/* File path names (all relative to $PGDATA) */
322+
#defineRECOVERY_COMMAND_FILE"recovery.conf"
323+
#defineRECOVERY_COMMAND_DONE"recovery.done"
322324
#defineBACKUP_LABEL_FILE"backup_label"
323325
#defineBACKUP_LABEL_OLD"backup_label.old"
324326

325327
#defineTABLESPACE_MAP"tablespace_map"
326328
#defineTABLESPACE_MAP_OLD"tablespace_map.old"
327329

330+
/* files to signal promotion to primary */
331+
#definePROMOTE_SIGNAL_FILE"promote"
332+
#defineFALLBACK_PROMOTE_SIGNAL_FILE "fallback_promote"
333+
328334
#endif/* XLOG_H */

‎src/include/catalog/catversion.h‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -53,6 +53,6 @@
5353
*/
5454

5555
/*yyyymmddN */
56-
#defineCATALOG_VERSION_NO201810111
56+
#defineCATALOG_VERSION_NO201810251
5757

5858
#endif

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