pg.ddx.io pgsql-committers@postgresql.org mailing list archivehelp / color / mirror / Atom feed
pgsql: Remove assertion based on pending_since in pgstat_report_stat() 4+ messages / 1 participants [nested] [flat]
* pgsql: Remove assertion based on pending_since in pgstat_report_stat() @ 2025-04-23 04:55 Michael Paquier <michael@paquier.xyz> 0 siblings, 0 replies; 4+ messages in thread From: Michael Paquier @ 2025-04-23 04:55 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org Remove assertion based on pending_since in pgstat_report_stat() This assertion, based on pending_since (timestamp used to prevent stats reports to be too frequent or should a partial flush happen), is reached when it is found that no data can be flushed but a previous call of pgstat_report_stat() determined that some stats data has been found as in need of a flush. So pending_since is set when some stats data is pending (in non-force mode) or if report attempts are too frequent, and reset to 0 once all stats have been flushed. Since 5cbbe70a9cc6, WAL senders have begun to report their stats on a periodic basis for IO stats in v16~ and backend stats on HEAD, creating some friction with the concurrent pgstat_report_stat() calls that can happen in the context of a WAL sender (shutdown callback doing a final report or backend-related code paths). This problem is the cause of spurious failures in the TAP tests. In theory, this assertion can be also reached in v15, even if that's very unlikely. For example, a process, say a background worker, could do periodic and direct stats flushes with concurrent calls of pgstat_report_stat() that could cause conflicting values of pending_since. This can be done with WAL or SLRU stats flushes using pgstat_flush_wal() or pgstat_slru_flush(). HEAD makes this situation easier to happen with custom cumulative stats. This commit removes the assertion altogether, per discussion, as it is more useful to keep the state of things as they are for the WAL sender. The assertion could use a special state based on for example am_walsender, but I doubt that this would be meaningful in the long run based on the other arguments raised while discussing this issue. Reported-by: Tom Lane <tgl@sss.pgh.pa.us> Reported-by: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/1489124.1744685908@sss.pgh.pa.us Discussion: https://postgr.es/m/dwrkeszz6czvtkxzr5mqlciy652zau5qqnm3cp5f3p2po74ppk@omg4g3cc6dgq Backpatch-through: 15 Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/1f7878c33cab8b741ecb0d145809cdd3000677be Modified Files -------------- src/backend/utils/activity/pgstat.c | 3 --- 1 file changed, 3 deletions(-) ^ permalink raw reply [nested|flat] 4+ messages in thread
* pgsql: Remove assertion based on pending_since in pgstat_report_stat() @ 2025-04-23 04:55 Michael Paquier <michael@paquier.xyz> 0 siblings, 0 replies; 4+ messages in thread From: Michael Paquier @ 2025-04-23 04:55 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org Remove assertion based on pending_since in pgstat_report_stat() This assertion, based on pending_since (timestamp used to prevent stats reports to be too frequent or should a partial flush happen), is reached when it is found that no data can be flushed but a previous call of pgstat_report_stat() determined that some stats data has been found as in need of a flush. So pending_since is set when some stats data is pending (in non-force mode) or if report attempts are too frequent, and reset to 0 once all stats have been flushed. Since 5cbbe70a9cc6, WAL senders have begun to report their stats on a periodic basis for IO stats in v16~ and backend stats on HEAD, creating some friction with the concurrent pgstat_report_stat() calls that can happen in the context of a WAL sender (shutdown callback doing a final report or backend-related code paths). This problem is the cause of spurious failures in the TAP tests. In theory, this assertion can be also reached in v15, even if that's very unlikely. For example, a process, say a background worker, could do periodic and direct stats flushes with concurrent calls of pgstat_report_stat() that could cause conflicting values of pending_since. This can be done with WAL or SLRU stats flushes using pgstat_flush_wal() or pgstat_slru_flush(). HEAD makes this situation easier to happen with custom cumulative stats. This commit removes the assertion altogether, per discussion, as it is more useful to keep the state of things as they are for the WAL sender. The assertion could use a special state based on for example am_walsender, but I doubt that this would be meaningful in the long run based on the other arguments raised while discussing this issue. Reported-by: Tom Lane <tgl@sss.pgh.pa.us> Reported-by: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/1489124.1744685908@sss.pgh.pa.us Discussion: https://postgr.es/m/dwrkeszz6czvtkxzr5mqlciy652zau5qqnm3cp5f3p2po74ppk@omg4g3cc6dgq Backpatch-through: 15 Branch ------ REL_17_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/4b6331e0fd5779f31df640d6f5b08a03d8dfb829 Modified Files -------------- src/backend/utils/activity/pgstat.c | 1 - 1 file changed, 1 deletion(-) ^ permalink raw reply [nested|flat] 4+ messages in thread
* pgsql: Remove assertion based on pending_since in pgstat_report_stat() @ 2025-04-23 04:55 Michael Paquier <michael@paquier.xyz> 0 siblings, 0 replies; 4+ messages in thread From: Michael Paquier @ 2025-04-23 04:55 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org Remove assertion based on pending_since in pgstat_report_stat() This assertion, based on pending_since (timestamp used to prevent stats reports to be too frequent or should a partial flush happen), is reached when it is found that no data can be flushed but a previous call of pgstat_report_stat() determined that some stats data has been found as in need of a flush. So pending_since is set when some stats data is pending (in non-force mode) or if report attempts are too frequent, and reset to 0 once all stats have been flushed. Since 5cbbe70a9cc6, WAL senders have begun to report their stats on a periodic basis for IO stats in v16~ and backend stats on HEAD, creating some friction with the concurrent pgstat_report_stat() calls that can happen in the context of a WAL sender (shutdown callback doing a final report or backend-related code paths). This problem is the cause of spurious failures in the TAP tests. In theory, this assertion can be also reached in v15, even if that's very unlikely. For example, a process, say a background worker, could do periodic and direct stats flushes with concurrent calls of pgstat_report_stat() that could cause conflicting values of pending_since. This can be done with WAL or SLRU stats flushes using pgstat_flush_wal() or pgstat_slru_flush(). HEAD makes this situation easier to happen with custom cumulative stats. This commit removes the assertion altogether, per discussion, as it is more useful to keep the state of things as they are for the WAL sender. The assertion could use a special state based on for example am_walsender, but I doubt that this would be meaningful in the long run based on the other arguments raised while discussing this issue. Reported-by: Tom Lane <tgl@sss.pgh.pa.us> Reported-by: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/1489124.1744685908@sss.pgh.pa.us Discussion: https://postgr.es/m/dwrkeszz6czvtkxzr5mqlciy652zau5qqnm3cp5f3p2po74ppk@omg4g3cc6dgq Backpatch-through: 15 Branch ------ REL_16_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/e9ab8677bfc581bdfbcc1e5d286d7d6269741b90 Modified Files -------------- src/backend/utils/activity/pgstat.c | 1 - 1 file changed, 1 deletion(-) ^ permalink raw reply [nested|flat] 4+ messages in thread
* pgsql: Remove assertion based on pending_since in pgstat_report_stat() @ 2025-04-23 04:55 Michael Paquier <michael@paquier.xyz> 0 siblings, 0 replies; 4+ messages in thread From: Michael Paquier @ 2025-04-23 04:55 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org Remove assertion based on pending_since in pgstat_report_stat() This assertion, based on pending_since (timestamp used to prevent stats reports to be too frequent or should a partial flush happen), is reached when it is found that no data can be flushed but a previous call of pgstat_report_stat() determined that some stats data has been found as in need of a flush. So pending_since is set when some stats data is pending (in non-force mode) or if report attempts are too frequent, and reset to 0 once all stats have been flushed. Since 5cbbe70a9cc6, WAL senders have begun to report their stats on a periodic basis for IO stats in v16~ and backend stats on HEAD, creating some friction with the concurrent pgstat_report_stat() calls that can happen in the context of a WAL sender (shutdown callback doing a final report or backend-related code paths). This problem is the cause of spurious failures in the TAP tests. In theory, this assertion can be also reached in v15, even if that's very unlikely. For example, a process, say a background worker, could do periodic and direct stats flushes with concurrent calls of pgstat_report_stat() that could cause conflicting values of pending_since. This can be done with WAL or SLRU stats flushes using pgstat_flush_wal() or pgstat_slru_flush(). HEAD makes this situation easier to happen with custom cumulative stats. This commit removes the assertion altogether, per discussion, as it is more useful to keep the state of things as they are for the WAL sender. The assertion could use a special state based on for example am_walsender, but I doubt that this would be meaningful in the long run based on the other arguments raised while discussing this issue. Reported-by: Tom Lane <tgl@sss.pgh.pa.us> Reported-by: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/1489124.1744685908@sss.pgh.pa.us Discussion: https://postgr.es/m/dwrkeszz6czvtkxzr5mqlciy652zau5qqnm3cp5f3p2po74ppk@omg4g3cc6dgq Backpatch-through: 15 Branch ------ REL_15_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/c1201ffcfbc1e934b37490a57a528d023230daf7 Modified Files -------------- src/backend/utils/activity/pgstat.c | 1 - 1 file changed, 1 deletion(-) ^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2025-04-23 04:55 UTC | newest] Thread overview: 4+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2025-04-23 04:55 pgsql: Remove assertion based on pending_since in pgstat_report_stat() Michael Paquier <michael@paquier.xyz> 2025-04-23 04:55 pgsql: Remove assertion based on pending_since in pgstat_report_stat() Michael Paquier <michael@paquier.xyz> 2025-04-23 04:55 pgsql: Remove assertion based on pending_since in pgstat_report_stat() Michael Paquier <michael@paquier.xyz> 2025-04-23 04:55 pgsql: Remove assertion based on pending_since in pgstat_report_stat() Michael Paquier <michael@paquier.xyz>
This inbox is served by DDX for PostgreSQL; see mirroring instructions for how to clone and mirror all data and code used for this inbox