From 723d0184e2972f21db0f85feef3d35f0cb9b3298 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Wed, 15 Sep 2010 10:35:05 +0000 Subject: [PATCH] Use a latch to make startup process wake up and replay immediately when new WAL arrives via streaming replication. This reduces the latency, and also allows us to use a longer polling interval, which is good for energy efficiency. We still need to poll to check for the appearance of a trigger file, but the interval is now 5 seconds (instead of 100ms), like when waiting for a new WAL segment to appear in WAL archive. --- src/backend/access/transam/xlog.c | 53 ++++++++++++++++++++++++--- src/backend/replication/walreceiver.c | 5 ++- src/include/access/xlog.h | 3 +- 3 files changed, 53 insertions(+), 8 deletions(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index d2d1e9ad5a..7135196b22 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.434 2010/08/30 15:37:41 sriggs Exp $ + * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.435 2010/09/15 10:35:05 heikki Exp $ * *------------------------------------------------------------------------- */ @@ -46,6 +46,7 @@ #include "storage/bufmgr.h" #include "storage/fd.h" #include "storage/ipc.h" +#include "storage/latch.h" #include "storage/pmsignal.h" #include "storage/procarray.h" #include "storage/smgr.h" @@ -392,6 +393,13 @@ typedef struct XLogCtlData */ bool SharedRecoveryInProgress; + /* + * recoveryWakeupLatch is used to wake up the startup process to + * continue WAL replay, if it is waiting for WAL to arrive or failover + * trigger file to appear. + */ + Latch recoveryWakeupLatch; + /* * During recovery, we keep a copy of the latest checkpoint record here. * Used by the background writer when it wants to create a restartpoint. @@ -4840,6 +4848,7 @@ XLOGShmemInit(void) XLogCtl->SharedRecoveryInProgress = true; XLogCtl->Insert.currpage = (XLogPageHeader) (XLogCtl->pages); SpinLockInit(&XLogCtl->info_lck); + InitSharedLatch(&XLogCtl->recoveryWakeupLatch); /* * If we are not in bootstrap mode, pg_control should already exist. Read @@ -5814,6 +5823,13 @@ StartupXLOG(void) (errmsg("starting archive recovery"))); } + /* + * Take ownership of the wakup latch if we're going to sleep during + * recovery. + */ + if (StandbyMode) + OwnLatch(&XLogCtl->recoveryWakeupLatch); + if (read_backup_label(&checkPointLoc)) { /* @@ -6274,6 +6290,13 @@ StartupXLOG(void) if (WalRcvInProgress()) elog(PANIC, "wal receiver still active"); + /* + * We don't need the latch anymore. It's not strictly necessary to disown + * it, but let's do it for the sake of tidyness. + */ + if (StandbyMode) + DisownLatch(&XLogCtl->recoveryWakeupLatch); + /* * We are now done reading the xlog from stream. Turn off streaming * recovery to force fetching the files (which would be required at end of @@ -9139,6 +9162,13 @@ startupproc_quickdie(SIGNAL_ARGS) } +/* SIGUSR1: let latch facility handle the signal */ +static void +StartupProcSigUsr1Handler(SIGNAL_ARGS) +{ + latch_sigusr1_handler(); +} + /* SIGHUP: set flag to re-read config file at next convenient time */ static void StartupProcSigHupHandler(SIGNAL_ARGS) @@ -9213,7 +9243,7 @@ StartupProcessMain(void) else pqsignal(SIGALRM, SIG_IGN); pqsignal(SIGPIPE, SIG_IGN); - pqsignal(SIGUSR1, SIG_IGN); + pqsignal(SIGUSR1, StartupProcSigUsr1Handler); pqsignal(SIGUSR2, SIG_IGN); /* @@ -9397,16 +9427,17 @@ retry: } /* - * Data not here yet, so check for trigger then sleep. + * Data not here yet, so check for trigger then sleep for + * five seconds like in the WAL file polling case below. */ if (CheckForStandbyTrigger()) goto triggered; /* - * When streaming is active, we want to react quickly when - * the next WAL record arrives, so sleep only a bit. + * Wait for more WAL to arrive, or timeout to be reached */ - pg_usleep(100000L); /* 100ms */ + WaitLatch(&XLogCtl->recoveryWakeupLatch, 5000000L); + ResetLatch(&XLogCtl->recoveryWakeupLatch); } else { @@ -9681,3 +9712,13 @@ CheckForStandbyTrigger(void) } return false; } + +/* + * Wake up startup process to replay newly arrived WAL, or to notice that + * failover has been requested. + */ +void +WakeupRecovery(void) +{ + SetLatch(&XLogCtl->recoveryWakeupLatch); +} diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c index 06646ead94..ca5fddaee3 100644 --- a/src/backend/replication/walreceiver.c +++ b/src/backend/replication/walreceiver.c @@ -29,7 +29,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/replication/walreceiver.c,v 1.16 2010/07/06 19:18:57 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/replication/walreceiver.c,v 1.17 2010/09/15 10:35:05 heikki Exp $ * *------------------------------------------------------------------------- */ @@ -529,6 +529,9 @@ XLogWalRcvFlush(void) walrcv->receivedUpto = LogstreamResult.Flush; SpinLockRelease(&walrcv->mutex); + /* Signal the startup process that new WAL has arrived */ + WakeupRecovery(); + /* Report XLOG streaming progress in PS display */ if (update_process_title) { diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h index 3d8ffbba61..ea156d3834 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -6,7 +6,7 @@ * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.116 2010/08/12 23:24:54 rhaas Exp $ + * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.117 2010/09/15 10:35:05 heikki Exp $ */ #ifndef XLOG_H #define XLOG_H @@ -303,5 +303,6 @@ extern TimeLineID GetRecoveryTargetTLI(void); extern void HandleStartupProcInterrupts(void); extern void StartupProcessMain(void); +extern void WakeupRecovery(void); #endif /* XLOG_H */ -- 2.40.0