Horton

Re: shared-memory based stats collector

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

View thread View on postgr.es
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: masao.fujii@oss.nttdata.com
Cc: gkokolatos@protonmail.com, pgsql-hackers@lists.postgresql.org
Date: 2021-03-10T08:51:37Z
Lists: pgsql-hackers

Attachments

At Wed, 10 Mar 2021 15:20:43 +0900, Fujii Masao <masao.fujii@oss.nttdata.com> wrote in 
> On 2021/03/10 12:10, Kyotaro Horiguchi wrote:
> > Agreed. The code moved to the original place and added the crash
> > handling code. And I added a phrase to the comment.
> > +		 * Was it the archiver?  If exit status is zero (normal) or one (FATAL
> > +		 * exit), we assume everything is all right just like normal backends
> > +		 * and just try to restart a new one so that we immediately retry
> >                                               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +		 * archiving of remaining files. (If fail, we'll try again in future
> >             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> 
> "of" of "archiving of remaining" should be replaced with "the", or removed?

Either will do.  I don't mind turning the gerund (archiving) into a
gerund phrase (archiving remaining files).

> Just for record. Previously LogChildExit() was called and the following LOG
> message was output when the archiver reported FATAL error. OTOH the patch
> prevents that and the following LOG message is not output at FATAL exit of
> archiver. But I don't think that the following message is required in that
> case
> because FATAL message indicating the similar thing is already output.
> Therefore, I'm ok with the patch.
> 
> LOG:  archiver process (PID 46418) exited with exit code 1

Yeah, that's the same behavor with wal receiver.

> >> I read v50_003 patch.
> >>
> >> When archiver dies, ProcGlobal->archiverLatch should be reset to NULL,
> >> like walreceiver does the similar thing in WalRcvDie()?
> > Differently from walwriter and checkpointer, archiver as well as
> > walreceiver may die while server is running. Leaving the latch pointer
> > alone may lead to nudging a wrong process that took over the same
> > procarray slot. Added pgarch_die() to do that.
> 
> Thanks!
> 
> +	if (IsUnderPostmaster && ProcGlobal->archiverLatch)
> +		SetLatch(ProcGlobal->archiverLatch);
> 
> The latch can be reset to NULL in pgarch_die() between the if-condition and
> SetLatch(), and which would be problematic. Probably we should protect
> the access to the latch by using spinlock, like we do for walreceiver's latch?

Ugg. Right.  I remember about that bug.  I moved the archiverLatch out
of ProcGlobal to a dedicate local struct PgArch and placed a spinlock
together.

Thanks for the review!  v52 is attached.

Other than the archiver fix above, A bug of 0004 in handling of
replication slot stats that leads to a hang is fixed. (It's the cause
of CF-bot failure.)

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

Commits

  1. Improve comment about dropped entries in pgstat.c

  2. Fix temporary memory leak in system table index scans

  3. pgstat: set timestamps of fixed-numbered stats after a crash.

  4. pgstat: Update docs to match the shared memory stats reality.

  5. pgstat: Hide instability in stats.spec with -DCATCACHE_FORCE_RELEASE.

  6. pgstat: add/extend tests for resetting various kinds of stats.

  7. Add minimal tests for recovery conflict handling.

  8. pgstat: test stats interactions with physical replication.

  9. pgstat: add tests for handling of restarts, including crashes.

  10. pgstat: add tests for transaction behaviour, 2PC, function stats.

  11. pgstat: add pg_stat_have_stats() test helper.

  12. pgstat: add pg_stat_force_next_flush(), use it to simplify tests.

  13. pgstat: move pgstat.c to utils/activity.

  14. pgstat: store statistics in shared memory.

  15. pgstat: remove stats_temp_directory.

  16. pgstat: rename STATS_COLLECTOR GUC group to STATS_CUMULATIVE.

  17. pgstat: revise replication slot API in preparation for shared memory stats.

  18. pgstat: scaffolding for transactional stats creation / drop.

  19. pgstat: introduce PgStat_Kind enum.

  20. pgstat: prepare APIs used by pgstatfuncs for shared memory stats.

  21. pgstat: add pgstat_copy_relation_stats().

  22. pgstat: rename some pgstat_send_* functions to pgstat_report_*.

  23. pgstat: stats collector references in comments.

  24. pgstat: move transactional code into pgstat_xact.c.

  25. dsm: allow use in single user mode.

  26. dshash: revise sequential scan support.

  27. pgstat: remove some superflous comments from pgstat.h.

  28. pgstat: reorder pgstat.[ch] contents.

  29. pgstat: split different types of stats into separate files.

  30. pgstat: introduce pgstat_relation_should_count().

  31. pgstat: separate "xact level" handling out of relation specific functions.

  32. pgstat: rename pgstat_initstats() to pgstat_relation_init().

  33. pgstat: split out WAL handling from pgstat_{initialize,report_stat}.

  34. pgstat: run pgindent on pgstat.c/h.

  35. pgstat: split relation, database handling out of pgstat_report_stat().

  36. Move code around in StartupXLOG().

  37. pgstat: Prepare to use mechanism for truncated rels also for droppped rels.

  38. pgstat: Split out relation stats handling from AtEO[Sub]Xact_PgStat() etc.

  39. pgstat: Schedule per-backend pgstat shutdown via before_shmem_exit().

  40. Schedule ShutdownXLOG() in single user mode using before_shmem_exit().

  41. Make parallel worker shutdown complete entirely via before_shmem_exit().

  42. pgstat: Bring up pgstat in BaseInit() to fix uninitialized use of pgstat by AV.

  43. pgstat: split reporting/fetching of bgwriter and checkpointer stats.

  44. Split backend status and progress related functionality out of pgstat.c.

  45. Split wait event related code from pgstat.[ch] into wait_event.[ch].

  46. Make archiver process an auxiliary process.

  47. Force to send remaining WAL stats to the stats collector at walwriter exit.

  48. Add pg_stat_database counters for sessions and session time

  49. Collect statistics about SLRU caches

  50. Don't run atexit callbacks in quickdie signal handlers.

  51. Create a "fast path" for acquiring weak relation locks.