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Add pg_promote function

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This function is able to promote a standby with this new SQL-callable
function.  Execution access can be granted to non-superusers so that
failover tools can observe the principle of least privilege.

Catalog version is bumped.

Author: Laurenz Albe
Reviewed-by: Michael Paquier, Masahiko Sawada
Discussion: https://postgr.es/m/6e7c79b3ec916cf49742fb8849ed17cd87aed620.camel@cybertec.at
This commit is contained in:
Michael Paquier 2018-10-25 09:46:00 +09:00
parent 0a8590b2a0
commit 10074651e3
13 changed files with 143 additions and 20 deletions
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19
doc/src/sgml/func.sgml
View File

@ -19202,6 +19202,9 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
<indexterm>
<primary>pg_is_wal_replay_paused</primary>
</indexterm>
<indexterm>
<primary>pg_promote</primary>
</indexterm>
<indexterm>
<primary>pg_wal_replay_pause</primary>
</indexterm>
@ -19232,6 +19235,22 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
<entry>True if recovery is paused.
</entry>
</row>
<row>
<entry>
<literal><function>pg_promote(<parameter>wait</parameter> <type>boolean</type> DEFAULT true, <parameter>wait_seconds</parameter> <type>integer</type> DEFAULT 60)</function></literal>
</entry>
<entry><type>boolean</type></entry>
<entry>
Promotes a physical standby server. Returns <literal>true</literal>
if promotion is successful and <literal>false</literal> otherwise.
With <parameter>wait</parameter> set to <literal>true</literal>, the
default, the function waits until promotion is completed or
<parameter>wait_seconds</parameter> seconds have passed, otherwise the
function returns immediately after sending the promotion signal to the
postmaster. This function is restricted to superusers by default, but
other users can be granted EXECUTE to run the function.
</entry>
</row>
<row>
<entry>
<literal><function>pg_wal_replay_pause()</function></literal>

19
doc/src/sgml/high-availability.sgml
View File

@ -1471,14 +1471,17 @@ synchronous_standby_names = 'ANY 2 (s1, s2, s3)'
</para>
<para>
To trigger failover of a log-shipping standby server,
run <command>pg_ctl promote</command> or create a trigger
file with the file name and path specified by the <varname>trigger_file</varname>
setting in <filename>recovery.conf</filename>. If you're planning to use
<command>pg_ctl promote</command> to fail over, <varname>trigger_file</varname> is
not required. If you're setting up the reporting servers that are
only used to offload read-only queries from the primary, not for high
availability purposes, you don't need to promote it.
To trigger failover of a log-shipping standby server, run
<command>pg_ctl promote</command>, call <function>pg_promote</function>,
or create a trigger file with the file name and path specified by the
<varname>trigger_file</varname> setting in
<filename>recovery.conf</filename>. If you're planning to use
<command>pg_ctl promote</command> or to call
<function>pg_promote</function> to fail over,
<varname>trigger_file</varname> is not required. If you're
setting up the reporting servers that are only used to offload read-only
queries from the primary, not for high availability purposes, you don't
need to promote it.
</para>
</sect1>

6
doc/src/sgml/monitoring.sgml
View File

@ -1268,7 +1268,7 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
<entry>Waiting in an extension.</entry>
</row>
<row>
<entry morerows="33"><literal>IPC</literal></entry>
<entry morerows="34"><literal>IPC</literal></entry>
<entry><literal>BgWorkerShutdown</literal></entry>
<entry>Waiting for background worker to shut down.</entry>
</row>
@ -1388,6 +1388,10 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
<entry><literal>ProcArrayGroupUpdate</literal></entry>
<entry>Waiting for group leader to clear transaction id at transaction end.</entry>
</row>
<row>
<entry><literal>Promote</literal></entry>
<entry>Waiting for standby promotion.</entry>
</row>
<row>
<entry><literal>ReplicationOriginDrop</literal></entry>
<entry>Waiting for a replication origin to become inactive to be dropped.</entry>

3
doc/src/sgml/recovery-config.sgml
View File

@ -439,7 +439,8 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
<para>
Specifies a trigger file whose presence ends recovery in the
standby. Even if this value is not set, you can still promote
the standby using <command>pg_ctl promote</command>.
the standby using <command>pg_ctl promote</command> or calling
<function>pg_promote</function>.
This setting has no effect if <varname>standby_mode</varname> is <literal>off</literal>.
</para>
</listitem>

6
src/backend/access/transam/xlog.c
View File

@ -78,12 +78,6 @@
extern uint32 bootstrap_data_checksum_version;
/* File path names (all relative to $PGDATA) */
#define RECOVERY_COMMAND_FILE "recovery.conf"
#define RECOVERY_COMMAND_DONE "recovery.done"
#define PROMOTE_SIGNAL_FILE "promote"
#define FALLBACK_PROMOTE_SIGNAL_FILE "fallback_promote"
/* User-settable parameters */
int max_wal_size_mb = 1024; /* 1 GB */

77
src/backend/access/transam/xlogfuncs.c
View File

@ -16,6 +16,8 @@
*/
#include "postgres.h"
#include <unistd.h>
#include "access/htup_details.h"
#include "access/xlog.h"
#include "access/xlog_internal.h"
@ -23,6 +25,7 @@
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "replication/walreceiver.h"
#include "storage/smgr.h"
#include "utils/builtins.h"
@ -697,3 +700,77 @@ pg_backup_start_time(PG_FUNCTION_ARGS)
PG_RETURN_DATUM(xtime);
}
/*
* Promotes a standby server.
*
* A result of "true" means that promotion has been completed if "wait" is
* "true", or initiated if "wait" is false.
*/
Datum
pg_promote(PG_FUNCTION_ARGS)
{
bool wait = PG_GETARG_BOOL(0);
int wait_seconds = PG_GETARG_INT32(1);
FILE *promote_file;
int i;
if (!RecoveryInProgress())
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("recovery is not in progress"),
errhint("Recovery control functions can only be executed during recovery.")));
if (wait_seconds <= 0)
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("\"wait_seconds\" cannot be negative or equal zero")));
/* create the promote signal file */
promote_file = AllocateFile(PROMOTE_SIGNAL_FILE, "w");
if (!promote_file)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not create file \"%s\": %m",
PROMOTE_SIGNAL_FILE)));
if (FreeFile(promote_file))
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PROMOTE_SIGNAL_FILE)));
/* signal the postmaster */
if (kill(PostmasterPid, SIGUSR1) != 0)
{
ereport(WARNING,
(errmsg("failed to send signal to postmaster: %m")));
(void) unlink(PROMOTE_SIGNAL_FILE);
PG_RETURN_BOOL(false);
}
/* return immediately if waiting was not requested */
if (!wait)
PG_RETURN_BOOL(true);
/* wait for the amount of time wanted until promotion */
#define WAITS_PER_SECOND 10
for (i = 0; i < WAITS_PER_SECOND * wait_seconds; i++)
{
ResetLatch(MyLatch);
if (!RecoveryInProgress())
PG_RETURN_BOOL(true);
CHECK_FOR_INTERRUPTS();
WaitLatch(MyLatch,
WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
1000L / WAITS_PER_SECOND,
WAIT_EVENT_PROMOTE);
}
ereport(WARNING,
(errmsg("server did not promote within %d seconds", wait_seconds)));
PG_RETURN_BOOL(false);
}

6
src/backend/catalog/system_views.sql
View File

@ -1027,6 +1027,11 @@ CREATE OR REPLACE FUNCTION pg_stop_backup (
RETURNS SETOF record STRICT VOLATILE LANGUAGE internal as 'pg_stop_backup_v2'
PARALLEL RESTRICTED;
CREATE OR REPLACE FUNCTION
pg_promote(wait boolean DEFAULT true, wait_seconds integer DEFAULT 60)
RETURNS boolean STRICT VOLATILE LANGUAGE INTERNAL AS 'pg_promote'
PARALLEL RESTRICTED;
-- legacy definition for compatibility with 9.3
CREATE OR REPLACE FUNCTION
json_populate_record(base anyelement, from_json json, use_json_as_text boolean DEFAULT false)
@ -1138,6 +1143,7 @@ REVOKE EXECUTE ON FUNCTION pg_rotate_logfile() FROM public;
REVOKE EXECUTE ON FUNCTION pg_reload_conf() FROM public;
REVOKE EXECUTE ON FUNCTION pg_current_logfile() FROM public;
REVOKE EXECUTE ON FUNCTION pg_current_logfile(text) FROM public;
REVOKE EXECUTE ON FUNCTION pg_promote(boolean, integer) FROM public;
REVOKE EXECUTE ON FUNCTION pg_stat_reset() FROM public;
REVOKE EXECUTE ON FUNCTION pg_stat_reset_shared(text) FROM public;

3
src/backend/postmaster/pgstat.c
View File

@ -3663,6 +3663,9 @@ pgstat_get_wait_ipc(WaitEventIPC w)
case WAIT_EVENT_PROCARRAY_GROUP_UPDATE:
event_name = "ProcArrayGroupUpdate";
break;
case WAIT_EVENT_PROMOTE:
event_name = "Promote";
break;
case WAIT_EVENT_REPLICATION_ORIGIN_DROP:
event_name = "ReplicationOriginDrop";
break;

6
src/include/access/xlog.h
View File

@ -319,10 +319,16 @@ extern void do_pg_abort_backup(void);
extern SessionBackupState get_backup_status(void);
/* File path names (all relative to $PGDATA) */
#define RECOVERY_COMMAND_FILE "recovery.conf"
#define RECOVERY_COMMAND_DONE "recovery.done"
#define BACKUP_LABEL_FILE "backup_label"
#define BACKUP_LABEL_OLD "backup_label.old"
#define TABLESPACE_MAP "tablespace_map"
#define TABLESPACE_MAP_OLD "tablespace_map.old"
/* files to signal promotion to primary */
#define PROMOTE_SIGNAL_FILE "promote"
#define FALLBACK_PROMOTE_SIGNAL_FILE "fallback_promote"
#endif /* XLOG_H */

2
src/include/catalog/catversion.h
View File

@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 201810111
#define CATALOG_VERSION_NO 201810251
#endif

4
src/include/catalog/pg_proc.dat
View File

@ -5824,6 +5824,10 @@
proname => 'pg_backup_start_time', provolatile => 's',
prorettype => 'timestamptz', proargtypes => '',
prosrc => 'pg_backup_start_time' },
{ oid => '3436', descr => 'promote standby server',
proname => 'pg_promote', provolatile => 'v',
prorettype => 'bool', proargtypes => 'bool int4', proargnames => '{wait,wait_seconds}',
prosrc => 'pg_promote' },
{ oid => '2848', descr => 'switch to new wal file',
proname => 'pg_switch_wal', provolatile => 'v', prorettype => 'pg_lsn',
proargtypes => '', prosrc => 'pg_switch_wal' },

1
src/include/pgstat.h
View File

@ -829,6 +829,7 @@ typedef enum
WAIT_EVENT_PARALLEL_CREATE_INDEX_SCAN,
WAIT_EVENT_PARALLEL_FINISH,
WAIT_EVENT_PROCARRAY_GROUP_UPDATE,
WAIT_EVENT_PROMOTE,
WAIT_EVENT_REPLICATION_ORIGIN_DROP,
WAIT_EVENT_REPLICATION_SLOT_DROP,
WAIT_EVENT_SAFE_SNAPSHOT,

11
src/test/recovery/t/004_timeline_switch.pl
View File

@ -6,7 +6,7 @@ use warnings;
use File::Path qw(rmtree);
use PostgresNode;
use TestLib;
use Test::More tests => 1;
use Test::More tests => 2;
$ENV{PGDATABASE} = 'postgres';
@ -37,9 +37,14 @@ $node_master->safe_psql('postgres',
$node_master->wait_for_catchup($node_standby_1, 'replay',
$node_master->lsn('write'));
# Stop and remove master, and promote standby 1, switching it to a new timeline
# Stop and remove master
$node_master->teardown_node;
$node_standby_1->promote;
# promote standby 1 using "pg_promote", switching it to a new timeline
my $psql_out = '';
$node_standby_1->psql('postgres', "SELECT pg_promote(wait_seconds => 300)",
stdout => \$psql_out);
is($psql_out, 't', "promotion of standby with pg_promote");
# Switch standby 2 to replay from standby 1
rmtree($node_standby_2->data_dir . '/recovery.conf');