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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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77
src/backend/access/transam/xlogfuncs.c
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@@ -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);
}