postmaster: Update pmState via a wrapper function

This makes logging of state changes easier - state transitions are now logged
at DEBUG1. Without that logging it was surprisingly hard to understand the
current state of the system while debugging.

Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://postgr.es/m/kgng5nrvnlv335evmsuvpnh354rw7qyazl73kdysev2cr2v5zu@m3cfzxicm5kp

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 0a915dac4f76ddd0b8edc0754ab3fbe5b45eec6c..3a9ad897837fed80327e7e1791517bd96178c8bf 100644 (file)
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -411,6 +411,7 @@ static void HandleChildCrash(int pid, int exitstatus, const char *procname);
 static void LogChildExit(int lev, const char *procname,
                         int pid, int exitstatus);
 static void PostmasterStateMachine(void);
+static void UpdatePMState(PMState newState);
 
 static void ExitPostmaster(int status) pg_attribute_noreturn();
 static int ServerLoop(void);
@@ -1363,7 +1364,7 @@ PostmasterMain(int argc, char *argv[])
    StartupPMChild = StartChildProcess(B_STARTUP);
    Assert(StartupPMChild != NULL);
    StartupStatus = STARTUP_RUNNING;
-   pmState = PM_STARTUP;
+   UpdatePMState(PM_STARTUP);
 
    /* Some workers may be scheduled to start now */
    maybe_start_bgworkers();
@@ -2099,7 +2100,7 @@ process_pm_shutdown_request(void)
            else if (pmState == PM_STARTUP || pmState == PM_RECOVERY)
            {
                /* There should be no clients, so proceed to stop children */
-               pmState = PM_STOP_BACKENDS;
+               UpdatePMState(PM_STOP_BACKENDS);
            }
 
            /*
@@ -2133,7 +2134,7 @@ process_pm_shutdown_request(void)
            if (pmState == PM_STARTUP || pmState == PM_RECOVERY)
            {
                /* Just shut down background processes silently */
-               pmState = PM_STOP_BACKENDS;
+               UpdatePMState(PM_STOP_BACKENDS);
            }
            else if (pmState == PM_RUN ||
                     pmState == PM_HOT_STANDBY)
@@ -2141,7 +2142,7 @@ process_pm_shutdown_request(void)
                /* Report that we're about to zap live client sessions */
                ereport(LOG,
                        (errmsg("aborting any active transactions")));
-               pmState = PM_STOP_BACKENDS;
+               UpdatePMState(PM_STOP_BACKENDS);
            }
 
            /*
@@ -2176,7 +2177,7 @@ process_pm_shutdown_request(void)
            /* (note we don't apply send_abort_for_crash here) */
            SetQuitSignalReason(PMQUIT_FOR_STOP);
            TerminateChildren(SIGQUIT);
-           pmState = PM_WAIT_BACKENDS;
+           UpdatePMState(PM_WAIT_BACKENDS);
 
            /* set stopwatch for them to die */
            AbortStartTime = time(NULL);
@@ -2231,7 +2232,7 @@ process_pm_child_exit(void)
                (EXIT_STATUS_0(exitstatus) || EXIT_STATUS_1(exitstatus)))
            {
                StartupStatus = STARTUP_NOT_RUNNING;
-               pmState = PM_WAIT_BACKENDS;
+               UpdatePMState(PM_WAIT_BACKENDS);
                /* PostmasterStateMachine logic does the rest */
                continue;
            }
@@ -2243,7 +2244,7 @@ process_pm_child_exit(void)
                StartupStatus = STARTUP_NOT_RUNNING;
                Shutdown = Max(Shutdown, SmartShutdown);
                TerminateChildren(SIGTERM);
-               pmState = PM_WAIT_BACKENDS;
+               UpdatePMState(PM_WAIT_BACKENDS);
                /* PostmasterStateMachine logic does the rest */
                continue;
            }
@@ -2288,7 +2289,7 @@ process_pm_child_exit(void)
                {
                    StartupStatus = STARTUP_NOT_RUNNING;
                    if (pmState == PM_STARTUP)
-                       pmState = PM_WAIT_BACKENDS;
+                       UpdatePMState(PM_WAIT_BACKENDS);
                }
                else
                    StartupStatus = STARTUP_CRASHED;
@@ -2304,7 +2305,7 @@ process_pm_child_exit(void)
            FatalError = false;
            AbortStartTime = 0;
            ReachedNormalRunning = true;
-           pmState = PM_RUN;
+           UpdatePMState(PM_RUN);
            connsAllowed = true;
 
            /*
@@ -2377,7 +2378,7 @@ process_pm_child_exit(void)
                 */
                SignalChildren(SIGUSR2, btmask(B_WAL_SENDER));
 
-               pmState = PM_SHUTDOWN_2;
+               UpdatePMState(PM_SHUTDOWN_2);
            }
            else
            {
@@ -2729,7 +2730,7 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
        pmState == PM_RUN ||
        pmState == PM_STOP_BACKENDS ||
        pmState == PM_SHUTDOWN)
-       pmState = PM_WAIT_BACKENDS;
+       UpdatePMState(PM_WAIT_BACKENDS);
 
    /*
     * .. and if this doesn't happen quickly enough, now the clock is ticking
@@ -2821,7 +2822,7 @@ PostmasterStateMachine(void)
             * Then we're ready to stop other children.
             */
            if (CountChildren(btmask(B_BACKEND)) == 0)
-               pmState = PM_STOP_BACKENDS;
+               UpdatePMState(PM_STOP_BACKENDS);
        }
    }
 
@@ -2909,7 +2910,7 @@ PostmasterStateMachine(void)
 
            SignalChildren(SIGTERM, targetMask);
 
-           pmState = PM_WAIT_BACKENDS;
+           UpdatePMState(PM_WAIT_BACKENDS);
        }
 
        /* Are any of the target processes still running? */
@@ -2920,7 +2921,7 @@ PostmasterStateMachine(void)
                /*
                 * Stop any dead-end children and stop creating new ones.
                 */
-               pmState = PM_WAIT_DEAD_END;
+               UpdatePMState(PM_WAIT_DEAD_END);
                ConfigurePostmasterWaitSet(false);
                SignalChildren(SIGQUIT, btmask(B_DEAD_END_BACKEND));
 
@@ -2945,7 +2946,7 @@ PostmasterStateMachine(void)
                if (CheckpointerPMChild != NULL)
                {
                    signal_child(CheckpointerPMChild, SIGUSR2);
-                   pmState = PM_SHUTDOWN;
+                   UpdatePMState(PM_SHUTDOWN);
                }
                else
                {
@@ -2960,7 +2961,7 @@ PostmasterStateMachine(void)
                     * for checkpointer fork failure.
                     */
                    FatalError = true;
-                   pmState = PM_WAIT_DEAD_END;
+                   UpdatePMState(PM_WAIT_DEAD_END);
                    ConfigurePostmasterWaitSet(false);
 
                    /* Kill the walsenders and archiver too */
@@ -2980,7 +2981,7 @@ PostmasterStateMachine(void)
         */
        if (CountChildren(btmask_all_except2(B_LOGGER, B_DEAD_END_BACKEND)) == 0)
        {
-           pmState = PM_WAIT_DEAD_END;
+           UpdatePMState(PM_WAIT_DEAD_END);
            ConfigurePostmasterWaitSet(false);
            SignalChildren(SIGTERM, btmask_all_except(B_LOGGER));
        }
@@ -3013,7 +3014,7 @@ PostmasterStateMachine(void)
            Assert(AutoVacLauncherPMChild == NULL);
            Assert(SlotSyncWorkerPMChild == NULL);
            /* syslogger is not considered here */
-           pmState = PM_NO_CHILDREN;
+           UpdatePMState(PM_NO_CHILDREN);
        }
    }
 
@@ -3097,7 +3098,7 @@ PostmasterStateMachine(void)
        StartupPMChild = StartChildProcess(B_STARTUP);
        Assert(StartupPMChild != NULL);
        StartupStatus = STARTUP_RUNNING;
-       pmState = PM_STARTUP;
+       UpdatePMState(PM_STARTUP);
        /* crash recovery started, reset SIGKILL flag */
        AbortStartTime = 0;
 
@@ -3106,6 +3107,42 @@ PostmasterStateMachine(void)
    }
 }
 
+static const char *
+pmstate_name(PMState state)
+{
+#define PM_TOSTR_CASE(sym) case sym: return #sym
+   switch (state)
+   {
+           PM_TOSTR_CASE(PM_INIT);
+           PM_TOSTR_CASE(PM_STARTUP);
+           PM_TOSTR_CASE(PM_RECOVERY);
+           PM_TOSTR_CASE(PM_HOT_STANDBY);
+           PM_TOSTR_CASE(PM_RUN);
+           PM_TOSTR_CASE(PM_STOP_BACKENDS);
+           PM_TOSTR_CASE(PM_WAIT_BACKENDS);
+           PM_TOSTR_CASE(PM_SHUTDOWN);
+           PM_TOSTR_CASE(PM_SHUTDOWN_2);
+           PM_TOSTR_CASE(PM_WAIT_DEAD_END);
+           PM_TOSTR_CASE(PM_NO_CHILDREN);
+   }
+#undef PM_TOSTR_CASE
+
+   pg_unreachable();
+   return "";                  /* silence compiler */
+}
+
+/*
+ * Simple wrapper for updating pmState. The main reason to have this wrapper
+ * is that it makes it easy to log all state transitions.
+ */
+static void
+UpdatePMState(PMState newState)
+{
+   elog(DEBUG1, "updating PMState from %s to %s",
+        pmstate_name(pmState), pmstate_name(newState));
+   pmState = newState;
+}
+
 /*
  * Launch background processes after state change, or relaunch after an
  * existing process has exited.
@@ -3524,7 +3561,7 @@ process_pm_pmsignal(void)
 #endif
        }
 
-       pmState = PM_RECOVERY;
+       UpdatePMState(PM_RECOVERY);
    }
 
    if (CheckPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY) &&
@@ -3539,7 +3576,7 @@ process_pm_pmsignal(void)
        sd_notify(0, "READY=1");
 #endif
 
-       pmState = PM_HOT_STANDBY;
+       UpdatePMState(PM_HOT_STANDBY);
        connsAllowed = true;
 
        /* Some workers may be scheduled to start now */