Cosmetic adjustments for postmaster's handling of checkpointer.

Correct some comments, order some operations a bit more consistently.
No functional changes.

diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 5daf8c6177b624ad928a3fe5029e2d48d345f178..9ad7178aeb8a1ccfb9f70cfd4f18e3fc82e2d15e 100644 (file)
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -15,9 +15,9 @@
  * The bgwriter is started by the postmaster as soon as the startup subprocess
  * finishes, or as soon as recovery begins if we are doing archive recovery.
  * It remains alive until the postmaster commands it to terminate.
- * Normal termination is by SIGUSR2, which instructs the bgwriter to exit(0).
- * Emergency termination is by SIGQUIT; like any
- * backend, the bgwriter will simply abort and exit on SIGQUIT.
+ * Normal termination is by SIGTERM, which instructs the bgwriter to exit(0).
+ * Emergency termination is by SIGQUIT; like any backend, the bgwriter will
+ * simply abort and exit on SIGQUIT.
  *
  * If the bgwriter exits unexpectedly, the postmaster treats that the same
  * as a backend crash: shared memory may be corrupted, so remaining backends

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index d59ee68df549ef8c6d1135e7fe4148b8b37437c4..dd7dd5560faf03443df89f9216a31f2d51ad183f 100644 (file)
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -239,13 +239,13 @@ static bool RecoveryError = false;                /* T if WAL recovery failed */
  * hot standby during archive recovery.
  *
  * When the startup process is ready to start archive recovery, it signals the
- * postmaster, and we switch to PM_RECOVERY state. The background writer is
- * launched, while the startup process continues applying WAL. If Hot Standby
- * is enabled, then, after reaching a consistent point in WAL redo, startup
- * process signals us again, and we switch to PM_HOT_STANDBY state and
- * begin accepting connections to perform read-only queries.  When archive
- * recovery is finished, the startup process exits with exit code 0 and we
- * switch to PM_RUN state.
+ * postmaster, and we switch to PM_RECOVERY state. The background writer and
+ * checkpointer are launched, while the startup process continues applying WAL.
+ * If Hot Standby is enabled, then, after reaching a consistent point in WAL
+ * redo, startup process signals us again, and we switch to PM_HOT_STANDBY
+ * state and begin accepting connections to perform read-only queries.  When
+ * archive recovery is finished, the startup process exits with exit code 0
+ * and we switch to PM_RUN state.
  *
  * Normal child backends can only be launched when we are in PM_RUN or
  * PM_HOT_STANDBY state.  (We also allow launch of normal
@@ -1038,7 +1038,7 @@ PostmasterMain(int argc, char *argv[])
         * handling setup of child processes.  See tcop/postgres.c,
         * bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/walwriter.c,
         * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c,
-        * postmaster/syslogger.c and postmaster/checkpointer.c
+        * postmaster/syslogger.c and postmaster/checkpointer.c.
         */
        pqinitmask();
        PG_SETMASK(&BlockSig);
@@ -1373,10 +1373,10 @@ ServerLoop(void)
                /*
                 * If no background writer process is running, and we are not in a
                 * state that prevents it, start one.  It doesn't matter if this
-                * fails, we'll just try again later.
+                * fails, we'll just try again later.  Likewise for the checkpointer.
                 */
                if (pmState == PM_RUN || pmState == PM_RECOVERY ||
-                        pmState == PM_HOT_STANDBY)
+                       pmState == PM_HOT_STANDBY)
                {
                        if (BgWriterPID == 0)
                                BgWriterPID = StartBackgroundWriter();
@@ -1386,7 +1386,8 @@ ServerLoop(void)
 
                /*
                 * Likewise, if we have lost the walwriter process, try to start a new
-                * one.
+                * one.  But this is needed only in normal operation (else we cannot
+                * be writing any new WAL).
                 */
                if (WalWriterPID == 0 && pmState == PM_RUN)
                        WalWriterPID = StartWalWriter();
@@ -2131,11 +2132,12 @@ pmdie(SIGNAL_ARGS)
                                /* and the autovac launcher too */
                                if (AutoVacPID != 0)
                                        signal_child(AutoVacPID, SIGTERM);
+                               /* and the bgwriter too */
+                               if (BgWriterPID != 0)
+                                       signal_child(BgWriterPID, SIGTERM);
                                /* and the walwriter too */
                                if (WalWriterPID != 0)
                                        signal_child(WalWriterPID, SIGTERM);
-                               if (BgWriterPID != 0)
-                                       signal_child(BgWriterPID, SIGTERM);
 
                                /*
                                 * If we're in recovery, we can't kill the startup process
@@ -2174,13 +2176,17 @@ pmdie(SIGNAL_ARGS)
 
                        if (StartupPID != 0)
                                signal_child(StartupPID, SIGTERM);
-                       if (WalReceiverPID != 0)
-                               signal_child(WalReceiverPID, SIGTERM);
                        if (BgWriterPID != 0)
                                signal_child(BgWriterPID, SIGTERM);
+                       if (WalReceiverPID != 0)
+                               signal_child(WalReceiverPID, SIGTERM);
                        if (pmState == PM_RECOVERY)
                        {
-                               /* only checkpointer is active in this state */
+                               /*
+                                * Only startup, bgwriter, and checkpointer should be active
+                                * in this state; we just signaled the first two, and we don't
+                                * want to kill checkpointer yet.
+                                */
                                pmState = PM_WAIT_BACKENDS;
                        }
                        else if (pmState == PM_RUN ||
@@ -2362,7 +2368,7 @@ reaper(SIGNAL_ARGS)
                        }
 
                        /*
-                        * Crank up background tasks, if we didn't do that already
+                        * Crank up the background tasks, if we didn't do that already
                         * when we entered consistent recovery state.  It doesn't matter
                         * if this fails, we'll just try again later.
                         */
@@ -2370,13 +2376,13 @@ reaper(SIGNAL_ARGS)
                                BgWriterPID = StartBackgroundWriter();
                        if (CheckpointerPID == 0)
                                CheckpointerPID = StartCheckpointer();
+                       if (WalWriterPID == 0)
+                               WalWriterPID = StartWalWriter();
 
                        /*
                         * Likewise, start other special children as needed.  In a restart
                         * situation, some of them may be alive already.
                         */
-                       if (WalWriterPID == 0)
-                               WalWriterPID = StartWalWriter();
                        if (!IsBinaryUpgrade && AutoVacuumingActive() && AutoVacPID == 0)
                                AutoVacPID = StartAutoVacLauncher();
                        if (XLogArchivingActive() && PgArchPID == 0)
@@ -2392,7 +2398,9 @@ reaper(SIGNAL_ARGS)
                }
 
                /*
-                * Was it the bgwriter?
+                * Was it the bgwriter?  Normal exit can be ignored; we'll start a
+                * new one at the next iteration of the postmaster's main loop, if
+                * necessary.  Any other exit condition is treated as a crash.
                 */
                if (pid == BgWriterPID)
                {
@@ -4228,13 +4236,13 @@ sigusr1_handler(SIGNAL_ARGS)
                FatalError = false;
 
                /*
-                * Crank up the background writers.     It doesn't matter if this fails,
+                * Crank up the background tasks.  It doesn't matter if this fails,
                 * we'll just try again later.
                 */
-               Assert(CheckpointerPID == 0);
-               CheckpointerPID = StartCheckpointer();
                Assert(BgWriterPID == 0);
                BgWriterPID = StartBackgroundWriter();
+               Assert(CheckpointerPID == 0);
+               CheckpointerPID = StartCheckpointer();
 
                pmState = PM_RECOVERY;
        }