From e4e7df78c059b9c888544918789654ebdde3e2eb Mon Sep 17 00:00:00 2001 From: Masahiro Ikeda Date: Tue, 2 Mar 2021 16:36:17 +0900 Subject: [PATCH 2/2] Makes the wal receiver report WAL statistics This patch makes the WAL receiver report WAL statistics. - fundamentally changes how the stats collector interacts with the WAL receiver. - unifying the logic to collect xlog write stats for the WAL receiver and the others to avoid duplicate logic. Author: Masahiro Ikeda Reviewed-By: Japin Li, Hayato Kuroda, Masahiko Sawada, David Johnston, Fujii Masao Discussion: https://postgr.es/m/0509ad67b585a5b86a83d445dfa75392@oss.nttdata.com --- doc/src/sgml/monitoring.sgml | 4 ++ src/backend/access/transam/xlog.c | 64 +++++++++++++++++---------- src/backend/replication/walreceiver.c | 12 ++++- src/include/access/xlog.h | 1 + 4 files changed, 57 insertions(+), 24 deletions(-) diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index a16be45a71..66525e184f 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -3495,6 +3495,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i Number of times WAL buffers were written out to disk via XLogWrite, which is invoked during an XLogFlush request (see ) + , or WAL data written out to disk by the WAL receiver. @@ -3506,6 +3507,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i Total amount of time spent writing WAL buffers were written out to disk via XLogWrite, which is invoked during an XLogFlush request (see ), + or WAL data written out to disk by the WAL receiver, excluding sync time unless is either open_datasync or open_sync. Units are in milliseconds with microsecond resolution. @@ -3521,6 +3523,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i Number of times WAL files were synced to disk via issue_xlog_fsync, which is invoked during an XLogFlush request (see ) + by backends and background processes including the WAL receiver while was set to one of the "sync at commit" options (i.e., fdatasync, fsync, or fsync_writethrough). @@ -3535,6 +3538,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i Total amount of time spent syncing WAL files to disk via issue_xlog_fsync, which is invoked during an XLogFlush request (see ) + by backends and background processes including the WAL receiver while was set to one of the "sync at commit" options (i.e., fdatasync, fsync, or fsync_writethrough). diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 98f558b4c7..c220b6b776 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -2534,7 +2534,6 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible) Size nbytes; Size nleft; int written; - instr_time start; /* OK to write the page(s) */ from = XLogCtl->pages + startidx * (Size) XLOG_BLCKSZ; @@ -2544,28 +2543,7 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible) { errno = 0; - /* Measure I/O timing to write WAL data */ - if (track_wal_io_timing) - INSTR_TIME_SET_CURRENT(start); - - pgstat_report_wait_start(WAIT_EVENT_WAL_WRITE); - written = pg_pwrite(openLogFile, from, nleft, startoffset); - pgstat_report_wait_end(); - - /* - * Increment the I/O timing and the number of times WAL data - * were written out to disk. - */ - if (track_wal_io_timing) - { - instr_time duration; - - INSTR_TIME_SET_CURRENT(duration); - INSTR_TIME_SUBTRACT(duration, start); - WalStats.m_wal_write_time += INSTR_TIME_GET_MICROSEC(duration); - } - - WalStats.m_wal_write++; + written = XLogWriteFile(openLogFile, from, nleft, startoffset); if (written <= 0) { @@ -2705,6 +2683,46 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible) } } +/* + * Issue pg_pwrite to write an XLOG file. + * + * 'fd' is a file descriptor for the XLOG file to write + * 'buf' is a buffer starting address to write. + * 'nbyte' is a number of max bytes to write up. + * 'offset' is a offset of XLOG file to be set. + */ +int +XLogWriteFile(int fd, const void *buf, size_t nbyte, off_t offset) +{ + int written; + instr_time start; + + /* Measure I/O timing to write WAL data */ + if (track_wal_io_timing) + INSTR_TIME_SET_CURRENT(start); + + pgstat_report_wait_start(WAIT_EVENT_WAL_WRITE); + written = pg_pwrite(fd, buf, nbyte, offset); + pgstat_report_wait_end(); + + /* + * Increment the I/O timing and the number of times WAL data were + * written out to disk. + */ + if (track_wal_io_timing) + { + instr_time duration; + + INSTR_TIME_SET_CURRENT(duration); + INSTR_TIME_SUBTRACT(duration, start); + WalStats.m_wal_write_time += INSTR_TIME_GET_MICROSEC(duration); + } + + WalStats.m_wal_write++; + + return written; +} + /* * Record the LSN for an asynchronous transaction commit/abort * and nudge the WALWriter if there is work for it to do. diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c index 7810ee916c..f9834b8302 100644 --- a/src/backend/replication/walreceiver.c +++ b/src/backend/replication/walreceiver.c @@ -770,6 +770,9 @@ WalRcvDie(int code, Datum arg) /* Ensure that all WAL records received are flushed to disk */ XLogWalRcvFlush(true); + /* Send WAL statistics to the stats collector before terminating */ + pgstat_send_wal(); + /* Mark ourselves inactive in shared memory */ SpinLockAcquire(&walrcv->mutex); Assert(walrcv->walRcvState == WALRCV_STREAMING || @@ -907,6 +910,12 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr) XLogArchiveForceDone(xlogfname); else XLogArchiveNotify(xlogfname); + + /* + * Send WAL statistics to the stats collector when finishing + * the current WAL segment file to avoid overloading it. + */ + pgstat_send_wal(); } recvFile = -1; @@ -928,7 +937,8 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr) /* OK to write the logs */ errno = 0; - byteswritten = pg_pwrite(recvFile, buf, segbytes, (off_t) startoff); + byteswritten = XLogWriteFile(recvFile, buf, segbytes, (off_t) startoff); + if (byteswritten <= 0) { char xlogfname[MAXFNAMELEN]; diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h index 1e53d9d4ca..b345de8a28 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -290,6 +290,7 @@ extern bool XLogBackgroundFlush(void); extern bool XLogNeedsFlush(XLogRecPtr RecPtr); extern int XLogFileInit(XLogSegNo segno, bool *use_existent, bool use_lock); extern int XLogFileOpen(XLogSegNo segno); +extern int XLogWriteFile(int fd, const void *buf, size_t nbyte, off_t offset); extern void CheckXLogRemoved(XLogSegNo segno, TimeLineID tli); extern XLogSegNo XLogGetLastRemovedSegno(void); -- 2.25.1