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Report stats when replaying XLOG_RUNNING_XACTS

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Previously stats in the startup process would only get reported during
shutdown of the startup process. It has been that way for a long time, but
became a lot more noticeable with the new pg_stat_io view, which separates out
IO done by different backend types...

While replaying after every XLOG_RUNNING_XACTS isn't the prettiest approach,
it has the advantage of being quite easy. Given that we're well past feature
freeze...

It's not a problem that we don't report stats more frequently with
wal_level=minimal, in that case stats can't be read before the stats process
has shut down.

Besides the above, this commit also changes pgstat_report_stat() to acquire
the timestamp with GetCurrentTimestamp() instead of
GetCurrentTransactionStopTimestamp().

Thanks to Melih Mutlu, Kyotaro Horiguchi for prototypes of other approaches to
solving this issue.

Reported-by: Fujii Masao <masao.fujii@oss.nttdata.com>
Discussion: https://postgr.es/m/5315aedc-fbca-1556-c5de-dc2e00b23a14@oss.nttdata.com
This commit is contained in:
Andres Freund 2023-06-12 15:06:12 -07:00
parent 7398e27224
commit e3cb1a586c
2 changed files with 23 additions and 3 deletions
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9
src/backend/storage/ipc/standby.c
View File

@ -1193,6 +1193,15 @@ standby_redo(XLogReaderState *record)
running.xids = xlrec->xids;
ProcArrayApplyRecoveryInfo(&running);
/*
* The startup process currently has no convenient way to schedule
* stats to be reported. XLOG_RUNNING_XACTS records issued at a
* regular cadence, making this a convenient location to report
* stats. While these records aren't generated with wal_level=minimal,
* stats also cannot be accessed during WAL replay.
*/
pgstat_report_stat(true);
}
else if (info == XLOG_INVALIDATIONS)
{

17
src/backend/utils/activity/pgstat.c
View File

@ -615,10 +615,21 @@ pgstat_report_stat(bool force)
*/
Assert(!pgStatLocal.shmem->is_shutdown);
now = GetCurrentTransactionStopTimestamp();
if (!force)
if (force)
{
/*
* Stats reports are forced either when it's been too long since stats
* have been reported or in processes that force stats reporting to
* happen at specific points (including shutdown). In the former case
* the transaction stop time might be quite old, in the latter it
* would never get cleared.
*/
now = GetCurrentTimestamp();
}
else
{
now = GetCurrentTransactionStopTimestamp();
if (pending_since > 0 &&
TimestampDifferenceExceeds(pending_since, now, PGSTAT_MAX_INTERVAL))
{