* are treated as not a crash but approximately normal termination;
* the walsender will exit quickly without sending any more XLOG records.
*
- * If the server is shut down, postmaster sends us SIGUSR2 after all
- * regular backends have exited and the shutdown checkpoint has been written.
- * This instructs walsender to send any outstanding WAL, including the
- * shutdown checkpoint record, wait for it to be replicated to the standby,
- * and then exit.
+ * If the server is shut down, postmaster sends us SIGUSR2 after all regular
+ * backends have exited. This causes the walsender to switch to the "stopping"
+ * state. In this state, the walsender will reject any replication command
+ * that may generate WAL activity. The checkpointer begins the shutdown
+ * checkpoint once all walsenders are confirmed as stopping. When the shutdown
+ * checkpoint finishes, the postmaster sends us SIGINT. This instructs
+ * walsender to send any outstanding WAL, including the shutdown checkpoint
+ * record, wait for it to be replicated to the standby, and then exit.
*
*
* Portions Copyright (c) 2010-2017, PostgreSQL Global Development Group
/* Flags set by signal handlers for later service in main loop */
static volatile sig_atomic_t got_SIGHUP = false;
-static volatile sig_atomic_t walsender_ready_to_stop = false;
+static volatile sig_atomic_t got_SIGINT = false;
+static volatile sig_atomic_t got_SIGUSR2 = false;
/*
- * This is set while we are streaming. When not set, SIGUSR2 signal will be
+ * This is set while we are streaming. When not set, SIGINT signal will be
* handled like SIGTERM. When set, the main loop is responsible for checking
- * walsender_ready_to_stop and terminating when it's set (after streaming any
- * remaining WAL).
+ * got_SIGINT and terminating when it's set (after streaming any remaining
+ * WAL).
*/
static volatile sig_atomic_t replication_active = false;
/* Signal handlers */
static void WalSndSigHupHandler(SIGNAL_ARGS);
static void WalSndXLogSendHandler(SIGNAL_ARGS);
+static void WalSndSwitchStopping(SIGNAL_ARGS);
static void WalSndLastCycleHandler(SIGNAL_ARGS);
/* Prototypes for private functions */
ReplicationSlotCleanup();
replication_active = false;
- if (walsender_ready_to_stop)
+ if (got_SIGINT)
proc_exit(0);
/* Revert back to startup state */
WalSndSetState(WALSNDSTATE_STARTUP);
+
+ if (got_SIGUSR2)
+ WalSndSetState(WALSNDSTATE_STOPPING);
}
/*
WalSndLoop(XLogSendPhysical);
replication_active = false;
- if (walsender_ready_to_stop)
+ if (got_SIGINT)
proc_exit(0);
WalSndSetState(WALSNDSTATE_STARTUP);
{
ereport(LOG,
(errmsg("terminating walsender process after promotion")));
- walsender_ready_to_stop = true;
+ got_SIGINT = true;
}
WalSndSetState(WALSNDSTATE_CATCHUP);
ReplicationSlotRelease();
replication_active = false;
- if (walsender_ready_to_stop)
+ if (got_SIGINT)
proc_exit(0);
WalSndSetState(WALSNDSTATE_STARTUP);
else
RecentFlushPtr = GetXLogReplayRecPtr(NULL);
+ /*
+ * If postmaster asked us to switch to the stopping state, do so.
+ * Shutdown is in progress and this will allow the checkpointer to
+ * move on with the shutdown checkpoint.
+ */
+ if (got_SIGUSR2)
+ WalSndSetState(WALSNDSTATE_STOPPING);
+
/*
* If postmaster asked us to stop, don't wait here anymore. This will
* cause the xlogreader to return without reading a full record, which
* RecentFlushPtr, so we can send all remaining data before shutting
* down.
*/
- if (walsender_ready_to_stop)
+ if (got_SIGINT)
break;
/*
MemoryContext cmd_context;
MemoryContext old_context;
+ /*
+ * If WAL sender has been told that shutdown is getting close, switch its
+ * status accordingly to handle the next replication commands correctly.
+ */
+ if (got_SIGUSR2)
+ WalSndSetState(WALSNDSTATE_STOPPING);
+
+ /*
+ * Throw error if in stopping mode. We need prevent commands that could
+ * generate WAL while the shutdown checkpoint is being written. To be
+ * safe, we just prohibit all new commands.
+ */
+ if (MyWalSnd->state == WALSNDSTATE_STOPPING)
+ ereport(ERROR,
+ (errmsg("cannot execute new commands while WAL sender is in stopping mode")));
+
/*
* CREATE_REPLICATION_SLOT ... LOGICAL exports a snapshot until the next
* command arrives. Clean up the old stuff if there's anything.
}
/*
- * When SIGUSR2 arrives, we send any outstanding logs up to the
+ * At the reception of SIGUSR2, switch the WAL sender to the stopping
+ * state.
+ */
+ if (got_SIGUSR2)
+ WalSndSetState(WALSNDSTATE_STOPPING);
+
+ /*
+ * When SIGINT arrives, we send any outstanding logs up to the
* shutdown checkpoint record (i.e., the latest record), wait for
* them to be replicated to the standby, and exit. This may be a
* normal termination at shutdown, or a promotion, the walsender
* is not sure which.
*/
- if (walsender_ready_to_stop)
+ if (got_SIGINT)
WalSndDone(send_data);
}
errno = save_errno;
}
-/* SIGUSR2: set flag to do a last cycle and shut down afterwards */
+/* SIGUSR2: set flag to switch to stopping state */
+static void
+WalSndSwitchStopping(SIGNAL_ARGS)
+{
+ int save_errno = errno;
+
+ got_SIGUSR2 = true;
+ SetLatch(MyLatch);
+
+ errno = save_errno;
+}
+
+/*
+ * SIGINT: set flag to do a last cycle and shut down afterwards. The WAL
+ * sender should already have been switched to WALSNDSTATE_STOPPING at
+ * this point.
+ */
static void
WalSndLastCycleHandler(SIGNAL_ARGS)
{
if (!replication_active)
kill(MyProcPid, SIGTERM);
- walsender_ready_to_stop = true;
+ got_SIGINT = true;
SetLatch(MyLatch);
errno = save_errno;
/* Set up signal handlers */
pqsignal(SIGHUP, WalSndSigHupHandler); /* set flag to read config
* file */
- pqsignal(SIGINT, SIG_IGN); /* not used */
+ pqsignal(SIGINT, WalSndLastCycleHandler); /* request a last cycle and
+ * shutdown */
pqsignal(SIGTERM, die); /* request shutdown */
pqsignal(SIGQUIT, quickdie); /* hard crash time */
InitializeTimeouts(); /* establishes SIGALRM handler */
pqsignal(SIGPIPE, SIG_IGN);
pqsignal(SIGUSR1, WalSndXLogSendHandler); /* request WAL sending */
- pqsignal(SIGUSR2, WalSndLastCycleHandler); /* request a last cycle and
- * shutdown */
+ pqsignal(SIGUSR2, WalSndSwitchStopping); /* switch to stopping state */
/* Reset some signals that are accepted by postmaster but not here */
pqsignal(SIGCHLD, SIG_DFL);
}
}
+/*
+ * Wait that all the WAL senders have reached the stopping state. This is
+ * used by the checkpointer to control when shutdown checkpoints can
+ * safely begin.
+ */
+void
+WalSndWaitStopping(void)
+{
+ for (;;)
+ {
+ int i;
+ bool all_stopped = true;
+
+ for (i = 0; i < max_wal_senders; i++)
+ {
+ WalSndState state;
+ WalSnd *walsnd = &WalSndCtl->walsnds[i];
+
+ SpinLockAcquire(&walsnd->mutex);
+
+ if (walsnd->pid == 0)
+ {
+ SpinLockRelease(&walsnd->mutex);
+ continue;
+ }
+
+ state = walsnd->state;
+ SpinLockRelease(&walsnd->mutex);
+
+ if (state != WALSNDSTATE_STOPPING)
+ {
+ all_stopped = false;
+ break;
+ }
+ }
+
+ /* safe to leave if confirmation is done for all WAL senders */
+ if (all_stopped)
+ return;
+
+ pg_usleep(10000L); /* wait for 10 msec */
+ }
+}
+
/* Set state for current walsender (only called in walsender) */
void
WalSndSetState(WalSndState state)
return "catchup";
case WALSNDSTATE_STREAMING:
return "streaming";
+ case WALSNDSTATE_STOPPING:
+ return "stopping";
}
return "UNKNOWN";
}
projects / postgresql / commitdiff