On 2020/11/10 16:17, Kyotaro Horiguchi wrote:
At Sat, 7 Nov 2020 19:31:21 +0530, Bharath Rupireddy
<bharath.rupireddyforpostg...@gmail.com> wrote in
The main reason for having SetLatch() in
SignalHandlerForConfigReload() is to wake up the calling process if
waiting in WaitLatchOrSocket() or WaitLatch() and reload the new
config file and use the reloaded config variables. Maybe we should
give a thought on the scenarios in which the walreceiver process
waits, and what happens in case the latch is set when SIGHUP is
received.
The difference is whether the config file is processed at the next
wakeup (by force-reply-request or SIGTERM) of walreceiver or
immediately. If server-reload happened frequently, say, several times
per second(?), we should consider to reduce the useless reloading, but
actually that's not the case.
So, attached is the patch that makes walreceiver use both standard
SIGTERM and SIGHUP handlers. Currently I've not found any actual
issues by making walreceiver use standard SIGHUP handler, yet.
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
diff --git a/src/backend/replication/walreceiver.c
b/src/backend/replication/walreceiver.c
index bb1d44ccb7..babee386c4 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -104,13 +104,6 @@ static int recvFile = -1;
static TimeLineID recvFileTLI = 0;
static XLogSegNo recvSegNo = 0;
-/*
- * Flags set by interrupt handlers of walreceiver for later service in the
- * main loop.
- */
-static volatile sig_atomic_t got_SIGHUP = false;
-static volatile sig_atomic_t got_SIGTERM = false;
-
/*
* LogstreamResult indicates the byte positions that we have already
* written/fsynced.
@@ -135,11 +128,6 @@ static void XLogWalRcvSendReply(bool force, bool
requestReply);
static void XLogWalRcvSendHSFeedback(bool immed);
static void ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime);
-/* Signal handlers */
-static void WalRcvSigHupHandler(SIGNAL_ARGS);
-static void WalRcvShutdownHandler(SIGNAL_ARGS);
-
-
/*
* Process any interrupts the walreceiver process may have received.
* This should be called any time the process's latch has become set.
@@ -164,7 +152,7 @@ ProcessWalRcvInterrupts(void)
*/
CHECK_FOR_INTERRUPTS();
- if (got_SIGTERM)
+ if (ShutdownRequestPending)
{
ereport(FATAL,
(errcode(ERRCODE_ADMIN_SHUTDOWN),
@@ -267,9 +255,10 @@ WalReceiverMain(void)
on_shmem_exit(WalRcvDie, 0);
/* Properly accept or ignore signals the postmaster might send us */
- pqsignal(SIGHUP, WalRcvSigHupHandler); /* set flag to read config file
*/
+ pqsignal(SIGHUP, SignalHandlerForConfigReload); /* set flag to read
config
+
* file */
pqsignal(SIGINT, SIG_IGN);
- pqsignal(SIGTERM, WalRcvShutdownHandler); /* request shutdown */
+ pqsignal(SIGTERM, SignalHandlerForShutdownRequest); /* request shutdown
*/
/* SIGQUIT handler was already set up by InitPostmasterChild */
pqsignal(SIGALRM, SIG_IGN);
pqsignal(SIGPIPE, SIG_IGN);
@@ -441,9 +430,9 @@ WalReceiverMain(void)
/* Process any requests or signals received
recently */
ProcessWalRcvInterrupts();
- if (got_SIGHUP)
+ if (ConfigReloadPending)
{
- got_SIGHUP = false;
+ ConfigReloadPending = false;
ProcessConfigFile(PGC_SIGHUP);
XLogWalRcvSendHSFeedback(true);
}
@@ -510,7 +499,7 @@ WalReceiverMain(void)
* avoiding some system calls.
*/
Assert(wait_fd != PGINVALID_SOCKET);
- rc = WaitLatchOrSocket(walrcv->latch,
+ rc = WaitLatchOrSocket(MyLatch,
WL_EXIT_ON_PM_DEATH | WL_SOCKET_READABLE |
WL_TIMEOUT | WL_LATCH_SET,
wait_fd,
@@ -518,7 +507,7 @@ WalReceiverMain(void)
WAIT_EVENT_WAL_RECEIVER_MAIN);
if (rc & WL_LATCH_SET)
{
- ResetLatch(walrcv->latch);
+ ResetLatch(MyLatch);
ProcessWalRcvInterrupts();
if (walrcv->force_reply)
@@ -669,7 +658,7 @@ WalRcvWaitForStartPosition(XLogRecPtr *startpoint,
TimeLineID *startpointTLI)
WakeupRecovery();
for (;;)
{
- ResetLatch(walrcv->latch);
+ ResetLatch(MyLatch);
ProcessWalRcvInterrupts();
@@ -701,7 +690,7 @@ WalRcvWaitForStartPosition(XLogRecPtr *startpoint,
TimeLineID *startpointTLI)
}
SpinLockRelease(&walrcv->mutex);
- (void) WaitLatch(walrcv->latch, WL_LATCH_SET |
WL_EXIT_ON_PM_DEATH, 0,
+ (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
WAIT_EVENT_WAL_RECEIVER_WAIT_START);
}
@@ -806,28 +795,6 @@ WalRcvDie(int code, Datum arg)
WakeupRecovery();
}
-/* SIGHUP: set flag to re-read config file at next convenient time */
-static void
-WalRcvSigHupHandler(SIGNAL_ARGS)
-{
- got_SIGHUP = true;
-}
-
-
-/* SIGTERM: set flag for ProcessWalRcvInterrupts */
-static void
-WalRcvShutdownHandler(SIGNAL_ARGS)
-{
- int save_errno = errno;
-
- got_SIGTERM = true;
-
- if (WalRcv->latch)
- SetLatch(WalRcv->latch);
-
- errno = save_errno;
-}
-
/*
* Accept the message from XLOG stream, and process it.
*/
