Hi,
As Amul sent a patch about "ALTER SYSTEM READ ONLY"[1], with similar futur
objectives than mine, I decided to share the humble patch I am playing with to
step down an instance from primary to standby status.
I'm still wondering about the coding style, but as the discussion about this
kind of feature is rising, I share it in an early stage so it has a chance to
be discussed.
I'm opening a new discussion to avoid disturbing Amul's one.
The design of my patch is similar to the crash recovery code, without resetting
the shared memory. It supports smart and fast demote. The only existing user
interface currently is "pg_ctl [-m smart|fast] demote". An SQL admin function,
eg. pg_demote(), would be easy to add.
Main difference with Amul's patch is that all backends must be disconnected to
process with the demote. Either we wait for them to disconnect (smart) or we
kill them (fast). This makes life much easier from the code point of view, but
much more naive as well. Eg. calling "SELECT pg_demote('fast')" as an admin
would kill the session, with no options to wait for the action to finish, as we
do with pg_promote(). Keeping read only session around could probably be
achieved using global barrier as Amul did, but without all the complexity
related to WAL writes prohibition.
There's still some questions in the current patch. As I wrote, it's an humble
patch, a proof of concept, a bit naive.
Does it worth discussing it and improving it further or do I miss something
obvious in this design that leads to a dead end?
Thanks.
Regards,
[1]
https://www.postgresql.org/message-id/flat/CAAJ_b97KZzdJsffwRK7w0XU5HnXkcgKgTR69t8cOZztsyXjkQw%40mail.gmail.com
>From 2075441bebc47d3dd5b6e0a76e16f5ebb12858af Mon Sep 17 00:00:00 2001
From: Jehan-Guillaume de Rorthais <j...@dalibo.com>
Date: Fri, 10 Apr 2020 18:01:45 +0200
Subject: [PATCH] Demote PoC
---
src/backend/access/transam/xlog.c | 3 +-
src/backend/postmaster/postmaster.c | 206 ++++++++++++++++++------
src/bin/pg_controldata/pg_controldata.c | 2 +
src/bin/pg_ctl/pg_ctl.c | 105 ++++++++++++
src/include/catalog/pg_control.h | 1 +
src/include/libpq/libpq-be.h | 7 +-
src/include/utils/pidfile.h | 1 +
7 files changed, 271 insertions(+), 54 deletions(-)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 55cac186dc..8a7f1a0855 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8493,6 +8493,7 @@ ShutdownXLOG(int code, Datum arg)
CurrentResourceOwner = AuxProcessResourceOwner;
/* Don't be chatty in standalone mode */
+ // FIXME: what message when demoting?
ereport(IsPostmasterEnvironment ? LOG : NOTICE,
(errmsg("shutting down")));
@@ -8760,7 +8761,7 @@ CreateCheckPoint(int flags)
if (shutdown)
{
LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
- ControlFile->state = DB_SHUTDOWNING;
+ ControlFile->state = DB_SHUTDOWNING; // DEMOTING?
ControlFile->time = (pg_time_t) time(NULL);
UpdateControlFile();
LWLockRelease(ControlFileLock);
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index b4d475bb0b..465d020f9d 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -150,6 +150,9 @@
#define BACKEND_TYPE_WORKER (BACKEND_TYPE_AUTOVAC | BACKEND_TYPE_BGWORKER)
+/* file to signal demotion from primary to standby */
+#define DEMOTE_SIGNAL_FILE "demote"
+
/*
* List of active backends (or child processes anyway; we don't actually
* know whether a given child has become a backend or is still in the
@@ -269,18 +272,23 @@ typedef enum
static StartupStatusEnum StartupStatus = STARTUP_NOT_RUNNING;
/* Startup/shutdown state */
-#define NoShutdown 0
-#define SmartShutdown 1
-#define FastShutdown 2
-#define ImmediateShutdown 3
-
-static int Shutdown = NoShutdown;
+typedef enum StepDownState {
+ NoShutdown = 0, /* find better label? */
+ SmartShutdown,
+ SmartDemote,
+ FastShutdown,
+ FastDemote,
+ ImmediateShutdown
+} StepDownState;
+
+static StepDownState StepDown = NoShutdown;
+static bool DemoteSignal = false; /* true on demote request */
static bool FatalError = false; /* T if recovering from backend crash */
/*
- * We use a simple state machine to control startup, shutdown, and
- * crash recovery (which is rather like shutdown followed by startup).
+ * We use a simple state machine to control startup, shutdown, demote and
+ * crash recovery (both are rather like shutdown followed by startup).
*
* After doing all the postmaster initialization work, we enter PM_STARTUP
* state and the startup process is launched. The startup process begins by
@@ -314,7 +322,7 @@ static bool FatalError = false; /* T if recovering from backend crash */
* will not be very long).
*
* Notice that this state variable does not distinguish *why* we entered
- * states later than PM_RUN --- Shutdown and FatalError must be consulted
+ * states later than PM_RUN --- StepDown and FatalError must be consulted
* to find that out. FatalError is never true in PM_RECOVERY_* or PM_RUN
* states, nor in PM_SHUTDOWN states (because we don't enter those states
* when trying to recover from a crash). It can be true in PM_STARTUP state,
@@ -414,6 +422,8 @@ static bool RandomCancelKey(int32 *cancel_key);
static void signal_child(pid_t pid, int signal);
static bool SignalSomeChildren(int signal, int targets);
static void TerminateChildren(int signal);
+static bool CheckDemoteSignal(void);
+
#define SignalChildren(sig) SignalSomeChildren(sig, BACKEND_TYPE_ALL)
@@ -1550,7 +1560,7 @@ DetermineSleepTime(struct timeval *timeout)
* Normal case: either there are no background workers at all, or we're in
* a shutdown sequence (during which we ignore bgworkers altogether).
*/
- if (Shutdown > NoShutdown ||
+ if (StepDown > NoShutdown ||
(!StartWorkerNeeded && !HaveCrashedWorker))
{
if (AbortStartTime != 0)
@@ -1830,7 +1840,7 @@ ServerLoop(void)
*
* Note we also do this during recovery from a process crash.
*/
- if ((Shutdown >= ImmediateShutdown || (FatalError && !SendStop)) &&
+ if ((StepDown >= ImmediateShutdown || (FatalError && !SendStop)) &&
AbortStartTime != 0 &&
(now - AbortStartTime) >= SIGKILL_CHILDREN_AFTER_SECS)
{
@@ -2305,6 +2315,11 @@ retry1:
(errcode(ERRCODE_CANNOT_CONNECT_NOW),
errmsg("the database system is starting up")));
break;
+ case CAC_DEMOTE:
+ ereport(FATAL,
+ (errcode(ERRCODE_CANNOT_CONNECT_NOW),
+ errmsg("the database system is demoting")));
+ break;
case CAC_SHUTDOWN:
ereport(FATAL,
(errcode(ERRCODE_CANNOT_CONNECT_NOW),
@@ -2436,7 +2451,7 @@ canAcceptConnections(int backend_type)
CAC_state result = CAC_OK;
/*
- * Can't start backends when in startup/shutdown/inconsistent recovery
+ * Can't start backends when in startup/demote/shutdown/inconsistent recovery
* state. We treat autovac workers the same as user backends for this
* purpose. However, bgworkers are excluded from this test; we expect
* bgworker_should_start_now() decided whether the DB state allows them.
@@ -2452,7 +2467,9 @@ canAcceptConnections(int backend_type)
{
if (pmState == PM_WAIT_BACKUP)
result = CAC_WAITBACKUP; /* allow superusers only */
- else if (Shutdown > NoShutdown)
+ else if (StepDown == SmartDemote || StepDown == FastDemote)
+ return CAC_DEMOTE; /* demote is pending */
+ else if (StepDown > NoShutdown)
return CAC_SHUTDOWN; /* shutdown is pending */
else if (!FatalError &&
(pmState == PM_STARTUP ||
@@ -2683,7 +2700,8 @@ SIGHUP_handler(SIGNAL_ARGS)
PG_SETMASK(&BlockSig);
#endif
- if (Shutdown <= SmartShutdown)
+ if (StepDown == NoShutdown || StepDown == SmartShutdown ||
+ StepDown == SmartDemote)
{
ereport(LOG,
(errmsg("received SIGHUP, reloading configuration files")));
@@ -2769,26 +2787,72 @@ pmdie(SIGNAL_ARGS)
(errmsg_internal("postmaster received signal %d",
postgres_signal_arg)));
+ if (CheckDemoteSignal())
+ {
+ if (pmState != PM_RUN)
+ {
+ DemoteSignal = false;
+ unlink(DEMOTE_SIGNAL_FILE);
+ ereport(LOG,
+ (errmsg("ignoring demote signal because already in standby mode")));
+ }
+ else if (postgres_signal_arg == SIGQUIT) {
+ DemoteSignal = false;
+ ereport(WARNING,
+ (errmsg("can not demote in immediate stop mode")));
+ // FIXME: should we abort the shutdown process?
+ }
+ else
+ {
+ FILE *standby_file;
+
+ DemoteSignal = true;
+
+ /* create the standby signal file */
+ standby_file = AllocateFile(STANDBY_SIGNAL_FILE, "w");
+ if (!standby_file)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not create file \"%s\": %m",
+ STANDBY_SIGNAL_FILE)));
+
+ if (FreeFile(standby_file))
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not write file \"%s\": %m",
+ STANDBY_SIGNAL_FILE)));
+ }
+
+ unlink(DEMOTE_SIGNAL_FILE);
+ }
+
switch (postgres_signal_arg)
{
case SIGTERM:
/*
- * Smart Shutdown:
+ * Smart Stepdown:
*
- * Wait for children to end their work, then shut down.
+ * Wait for children to end their work, then shut down or demote.
*/
- if (Shutdown >= SmartShutdown)
+ if (StepDown >= SmartShutdown)
break;
- Shutdown = SmartShutdown;
- ereport(LOG,
- (errmsg("received smart shutdown request")));
- /* Report status */
- AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_STOPPING);
+ if (DemoteSignal) {
+ StepDown = SmartDemote;
+ ereport(LOG, (errmsg("received smart demote request")));
+ /* Report status */
+ AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_DEMOTING);
+ }
+ else {
+ StepDown = SmartShutdown;
+ ereport(LOG, (errmsg("received smart shutdown request")));
+ /* Report status */
+ AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_STOPPING);
#ifdef USE_SYSTEMD
- sd_notify(0, "STOPPING=1");
+ sd_notify(0, "STOPPING=1");
#endif
+ }
if (pmState == PM_RUN || pmState == PM_RECOVERY ||
pmState == PM_HOT_STANDBY || pmState == PM_STARTUP)
@@ -2831,22 +2895,29 @@ pmdie(SIGNAL_ARGS)
case SIGINT:
/*
- * Fast Shutdown:
+ * Fast StepDown:
*
* Abort all children with SIGTERM (rollback active transactions
- * and exit) and shut down when they are gone.
+ * and exit) and shut down or demote when they are gone.
*/
- if (Shutdown >= FastShutdown)
+ if (StepDown >= FastShutdown)
break;
- Shutdown = FastShutdown;
- ereport(LOG,
- (errmsg("received fast shutdown request")));
- /* Report status */
- AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_STOPPING);
+ if (DemoteSignal) {
+ StepDown = FastDemote;
+ ereport(LOG, (errmsg("received fast demote request")));
+ /* Report status */
+ AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_DEMOTING);
+ }
+ else {
+ StepDown = FastShutdown;
+ ereport(LOG, (errmsg("received fast shutdown request")));
+ /* Report status */
+ AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_STOPPING);
#ifdef USE_SYSTEMD
- sd_notify(0, "STOPPING=1");
+ sd_notify(0, "STOPPING=1");
#endif
+ }
if (StartupPID != 0)
signal_child(StartupPID, SIGTERM);
@@ -2903,9 +2974,9 @@ pmdie(SIGNAL_ARGS)
* terminate remaining ones with SIGKILL, then exit without
* attempt to properly shut down the data base system.
*/
- if (Shutdown >= ImmediateShutdown)
+ if (StepDown >= ImmediateShutdown)
break;
- Shutdown = ImmediateShutdown;
+ StepDown = ImmediateShutdown;
ereport(LOG,
(errmsg("received immediate shutdown request")));
@@ -2967,10 +3038,11 @@ reaper(SIGNAL_ARGS)
StartupPID = 0;
/*
- * Startup process exited in response to a shutdown request (or it
- * completed normally regardless of the shutdown request).
+ * Startup process exited in response to a shutdown or demote
+ * request (or it completed normally regardless of the shutdown
+ * request).
*/
- if (Shutdown > NoShutdown &&
+ if (StepDown > NoShutdown &&
(EXIT_STATUS_0(exitstatus) || EXIT_STATUS_1(exitstatus)))
{
StartupStatus = STARTUP_NOT_RUNNING;
@@ -2984,7 +3056,7 @@ reaper(SIGNAL_ARGS)
ereport(LOG,
(errmsg("shutdown at recovery target")));
StartupStatus = STARTUP_NOT_RUNNING;
- Shutdown = SmartShutdown;
+ StepDown = SmartShutdown;
TerminateChildren(SIGTERM);
pmState = PM_WAIT_BACKENDS;
/* PostmasterStateMachine logic does the rest */
@@ -3124,7 +3196,7 @@ reaper(SIGNAL_ARGS)
* archive cycle and quit. Likewise, if we have walsender
* processes, tell them to send any remaining WAL and quit.
*/
- Assert(Shutdown > NoShutdown);
+ Assert(StepDown > NoShutdown);
/* Waken archiver for the last time */
if (PgArchPID != 0)
@@ -3484,7 +3556,7 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
* signaled children, nonzero exit status is to be expected, so don't
* clutter log.
*/
- take_action = !FatalError && Shutdown != ImmediateShutdown;
+ take_action = !FatalError && StepDown != ImmediateShutdown;
if (take_action)
{
@@ -3702,7 +3774,7 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
/* We do NOT restart the syslogger */
- if (Shutdown != ImmediateShutdown)
+ if (StepDown != ImmediateShutdown)
FatalError = true;
/* We now transit into a state of waiting for children to die */
@@ -3845,11 +3917,11 @@ PostmasterStateMachine(void)
WalReceiverPID == 0 &&
BgWriterPID == 0 &&
(CheckpointerPID == 0 ||
- (!FatalError && Shutdown < ImmediateShutdown)) &&
+ (!FatalError && StepDown < ImmediateShutdown)) &&
WalWriterPID == 0 &&
AutoVacPID == 0)
{
- if (Shutdown >= ImmediateShutdown || FatalError)
+ if (StepDown >= ImmediateShutdown || FatalError)
{
/*
* Start waiting for dead_end children to die. This state
@@ -3870,7 +3942,7 @@ PostmasterStateMachine(void)
* the regular children are gone, and it's time to tell the
* checkpointer to do a shutdown checkpoint.
*/
- Assert(Shutdown > NoShutdown);
+ Assert(StepDown > NoShutdown);
/* Start the checkpointer if not running */
if (CheckpointerPID == 0)
CheckpointerPID = StartCheckpointer();
@@ -3958,7 +4030,8 @@ PostmasterStateMachine(void)
* EOF on its input pipe, which happens when there are no more upstream
* processes.
*/
- if (Shutdown > NoShutdown && pmState == PM_NO_CHILDREN)
+ if (pmState == PM_NO_CHILDREN && (StepDown == SmartShutdown ||
+ StepDown == FastShutdown || StepDown == ImmediateShutdown))
{
if (FatalError)
{
@@ -3991,15 +4064,29 @@ PostmasterStateMachine(void)
* startup process fails, because more than likely it will just fail again
* and we will keep trying forever.
*/
- if (pmState == PM_NO_CHILDREN &&
+ if (pmState == PM_NO_CHILDREN && !DemoteSignal &&
(StartupStatus == STARTUP_CRASHED || !restart_after_crash))
ExitPostmaster(1);
+ /* Handle demote signal */
+ if (DemoteSignal && pmState == PM_NO_CHILDREN)
+ {
+ ereport(LOG, (errmsg("all server processes terminated; demoting")));
+
+ // Signal bgworkers?
+
+ StartupPID = StartupDataBase();
+ Assert(StartupPID != 0);
+ StartupStatus = STARTUP_RUNNING;
+ pmState = PM_STARTUP;
+ StepDown = NoShutdown;
+ }
+
/*
* If we need to recover from a crash, wait for all non-syslogger children
* to exit, then reset shmem and StartupDataBase.
*/
- if (FatalError && pmState == PM_NO_CHILDREN)
+ else if (FatalError && pmState == PM_NO_CHILDREN)
{
ereport(LOG,
(errmsg("all server processes terminated; reinitializing")));
@@ -5195,7 +5282,7 @@ sigusr1_handler(SIGNAL_ARGS)
* first. We don't want to go back to recovery in that case.
*/
if (CheckPostmasterSignal(PMSIGNAL_RECOVERY_STARTED) &&
- pmState == PM_STARTUP && Shutdown == NoShutdown)
+ pmState == PM_STARTUP && StepDown == NoShutdown)
{
/* WAL redo has started. We're out of reinitialization. */
FatalError = false;
@@ -5234,7 +5321,7 @@ sigusr1_handler(SIGNAL_ARGS)
pmState = PM_RECOVERY;
}
if (CheckPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY) &&
- pmState == PM_RECOVERY && Shutdown == NoShutdown)
+ pmState == PM_RECOVERY && StepDown == NoShutdown)
{
/*
* Likewise, start other special children as needed.
@@ -5284,7 +5371,7 @@ sigusr1_handler(SIGNAL_ARGS)
}
if (CheckPostmasterSignal(PMSIGNAL_START_AUTOVAC_LAUNCHER) &&
- Shutdown == NoShutdown)
+ StepDown == NoShutdown)
{
/*
* Start one iteration of the autovacuum daemon, even if autovacuuming
@@ -5299,7 +5386,7 @@ sigusr1_handler(SIGNAL_ARGS)
}
if (CheckPostmasterSignal(PMSIGNAL_START_AUTOVAC_WORKER) &&
- Shutdown == NoShutdown)
+ StepDown == NoShutdown)
{
/* The autovacuum launcher wants us to start a worker process. */
StartAutovacuumWorker();
@@ -5644,7 +5731,7 @@ MaybeStartWalReceiver(void)
if (WalReceiverPID == 0 &&
(pmState == PM_STARTUP || pmState == PM_RECOVERY ||
pmState == PM_HOT_STANDBY || pmState == PM_WAIT_READONLY) &&
- Shutdown == NoShutdown)
+ StepDown == NoShutdown)
{
WalReceiverPID = StartWalReceiver();
if (WalReceiverPID != 0)
@@ -6647,3 +6734,18 @@ InitPostmasterDeathWatchHandle(void)
GetLastError())));
#endif /* WIN32 */
}
+
+/*
+ * Check if a promote request appeared. Should be called by postmaster before
+ * shutting down.
+ */
+bool
+CheckDemoteSignal(void)
+{
+ struct stat stat_buf;
+
+ if (stat(DEMOTE_SIGNAL_FILE, &stat_buf) == 0)
+ return true;
+
+ return false;
+}
diff --git a/src/bin/pg_controldata/pg_controldata.c b/src/bin/pg_controldata/pg_controldata.c
index e73639df74..c144cc35d3 100644
--- a/src/bin/pg_controldata/pg_controldata.c
+++ b/src/bin/pg_controldata/pg_controldata.c
@@ -57,6 +57,8 @@ dbState(DBState state)
return _("shut down");
case DB_SHUTDOWNED_IN_RECOVERY:
return _("shut down in recovery");
+ case DB_DEMOTING:
+ return _("demoting");
case DB_SHUTDOWNING:
return _("shutting down");
case DB_IN_CRASH_RECOVERY:
diff --git a/src/bin/pg_ctl/pg_ctl.c b/src/bin/pg_ctl/pg_ctl.c
index 3c03ace7ed..0bb7d69682 100644
--- a/src/bin/pg_ctl/pg_ctl.c
+++ b/src/bin/pg_ctl/pg_ctl.c
@@ -62,6 +62,7 @@ typedef enum
RESTART_COMMAND,
RELOAD_COMMAND,
STATUS_COMMAND,
+ DEMOTE_COMMAND,
PROMOTE_COMMAND,
LOGROTATE_COMMAND,
KILL_COMMAND,
@@ -103,6 +104,7 @@ static char version_file[MAXPGPATH];
static char pid_file[MAXPGPATH];
static char backup_file[MAXPGPATH];
static char promote_file[MAXPGPATH];
+static char demote_file[MAXPGPATH];
static char logrotate_file[MAXPGPATH];
static volatile pgpid_t postmasterPID = -1;
@@ -129,6 +131,7 @@ static void do_stop(void);
static void do_restart(void);
static void do_reload(void);
static void do_status(void);
+static void do_demote(void);
static void do_promote(void);
static void do_logrotate(void);
static void do_kill(pgpid_t pid);
@@ -1029,6 +1032,103 @@ do_stop(void)
}
+static void
+do_demote(void)
+{
+ int cnt;
+ FILE *dmtfile;
+ pgpid_t pid;
+ struct stat statbuf;
+
+ pid = get_pgpid(false);
+
+ if (pid == 0) /* no pid file */
+ {
+ write_stderr(_("%s: PID file \"%s\" does not exist\n"), progname, pid_file);
+ write_stderr(_("Is server running?\n"));
+ exit(1);
+ }
+ else if (pid < 0) /* standalone backend, not postmaster */
+ {
+ pid = -pid;
+ write_stderr(_("%s: cannot demote server; "
+ "single-user server is running (PID: %ld)\n"),
+ progname, pid);
+ exit(1);
+ }
+
+ snprintf(demote_file, MAXPGPATH, "%s/demote", pg_data);
+
+ if ((dmtfile = fopen(demote_file, "w")) == NULL)
+ {
+ write_stderr(_("%s: could not create demote signal file \"%s\": %s\n"),
+ progname, demote_file, strerror(errno));
+ exit(1);
+ }
+ if (fclose(dmtfile))
+ {
+ write_stderr(_("%s: could not write demote signal file \"%s\": %s\n"),
+ progname, demote_file, strerror(errno));
+ exit(1);
+ }
+
+ if (kill((pid_t) pid, sig) != 0)
+ {
+ write_stderr(_("%s: could not send stop signal (PID: %ld): %s\n"), progname, pid,
+ strerror(errno));
+ exit(1);
+ }
+
+ if (!do_wait)
+ {
+ print_msg(_("server demoting\n"));
+ return;
+ }
+ else
+ {
+ /*
+ * If backup_label exists, an online backup is running. Warn the user
+ * that smart demote will wait for it to finish. However, if the
+ * server is in archive recovery, we're recovering from an online
+ * backup instead of performing one.
+ */
+ if (shutdown_mode == SMART_MODE &&
+ stat(backup_file, &statbuf) == 0 &&
+ get_control_dbstate() != DB_IN_ARCHIVE_RECOVERY)
+ {
+ print_msg(_("WARNING: online backup mode is active\n"
+ "Demote will not complete until pg_stop_backup() is called.\n\n"));
+ }
+
+ print_msg(_("waiting for server to demote..."));
+
+ for (cnt = 0; cnt < wait_seconds * WAITS_PER_SEC; cnt++)
+ {
+ if (get_control_dbstate() == DB_IN_ARCHIVE_RECOVERY)
+ break;
+
+ if (cnt % WAITS_PER_SEC == 0)
+ print_msg(".");
+ pg_usleep(USEC_PER_SEC / WAITS_PER_SEC);
+ }
+
+ if (get_control_dbstate() != DB_IN_ARCHIVE_RECOVERY)
+ {
+ print_msg(_(" failed\n"));
+
+ write_stderr(_("%s: server does not demote\n"), progname);
+ if (shutdown_mode == SMART_MODE)
+ write_stderr(_("HINT: The \"-m fast\" option immediately disconnects sessions rather than\n"
+ "waiting for session-initiated disconnection.\n"));
+ exit(1);
+ }
+ print_msg(_(" done\n"));
+
+ print_msg(_("server demoted\n"));
+ }
+}
+
+
/*
* restart/reload routines
*/
@@ -2452,6 +2552,8 @@ main(int argc, char **argv)
ctl_command = RELOAD_COMMAND;
else if (strcmp(argv[optind], "status") == 0)
ctl_command = STATUS_COMMAND;
+ else if (strcmp(argv[optind], "demote") == 0)
+ ctl_command = DEMOTE_COMMAND;
else if (strcmp(argv[optind], "promote") == 0)
ctl_command = PROMOTE_COMMAND;
else if (strcmp(argv[optind], "logrotate") == 0)
@@ -2559,6 +2661,9 @@ main(int argc, char **argv)
case RELOAD_COMMAND:
do_reload();
break;
+ case DEMOTE_COMMAND:
+ do_demote();
+ break;
case PROMOTE_COMMAND:
do_promote();
break;
diff --git a/src/include/catalog/pg_control.h b/src/include/catalog/pg_control.h
index de5670e538..f529f8c7bd 100644
--- a/src/include/catalog/pg_control.h
+++ b/src/include/catalog/pg_control.h
@@ -87,6 +87,7 @@ typedef enum DBState
DB_STARTUP = 0,
DB_SHUTDOWNED,
DB_SHUTDOWNED_IN_RECOVERY,
+ DB_DEMOTING,
DB_SHUTDOWNING,
DB_IN_CRASH_RECOVERY,
DB_IN_ARCHIVE_RECOVERY,
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index 179ebaa104..a9e27f009e 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -70,7 +70,12 @@ typedef struct
typedef enum CAC_state
{
- CAC_OK, CAC_STARTUP, CAC_SHUTDOWN, CAC_RECOVERY, CAC_TOOMANY,
+ CAC_OK,
+ CAC_STARTUP,
+ CAC_DEMOTE,
+ CAC_SHUTDOWN,
+ CAC_RECOVERY,
+ CAC_TOOMANY,
CAC_WAITBACKUP
} CAC_state;
diff --git a/src/include/utils/pidfile.h b/src/include/utils/pidfile.h
index 63fefe5c4c..f761d2c4ef 100644
--- a/src/include/utils/pidfile.h
+++ b/src/include/utils/pidfile.h
@@ -50,6 +50,7 @@
*/
#define PM_STATUS_STARTING "starting" /* still starting up */
#define PM_STATUS_STOPPING "stopping" /* in shutdown sequence */
+#define PM_STATUS_DEMOTING "demoting" /* demote sequence */
#define PM_STATUS_READY "ready " /* ready for connections */
#define PM_STATUS_STANDBY "standby " /* up, won't accept connections */
--
2.20.1
