Horton

Re: shared-memory based stats collector

Fujii Masao <masao.fujii@oss.nttdata.com>

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From: Fujii Masao <masao.fujii@oss.nttdata.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: andres@anarazel.de, gkokolatos@protonmail.com, pgsql-hackers@lists.postgresql.org
Date: 2021-03-12T06:13:15Z
Lists: pgsql-hackers 

On 2021/03/12 13:49, Kyotaro Horiguchi wrote:
> At Fri, 12 Mar 2021 10:38:00 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in
>> At Fri, 12 Mar 2021 10:03:31 +0900, Fujii Masao <masao.fujii@oss.nttdata.com> wrote in
>>>> I moved archiver from the current location to next to "walsenders"
>>>> that is to be terminated along with archiver.
>>>> The attached the only 0003 of the new version based on the last one
>>>> from Fujii-san.
>>>
>>> Thanks for updating the patch! But you forgot to add the changes
>>> related to pgprocno into the patch?
>>
>> Although I intentinally didn't do that because "it really doesn't
>> matter", please wait for a while for the new version.  I'm going to
>> make PgArchData have only one member procno instead of replacing the
>> struct with a single variable.
> 
> I noticed that I accidentally removed the launch-suppression feature
> that is to avoid frequent relaunching.  That mechanism is needed on
> the postmaster side. I added PgArchIsSuppressed() to do the same check
> with the old pgarch_start() and make it called as a part of
> PgArchStartupAllowed().

You're right! At least for me the function name PgArchIsSuppressed() sounds not good to me. What about something like PgArchCanRestart()?

This is not fault of this patch. But last_pgarch_start_time should be initialized with zero?

+	if ((curtime - last_pgarch_start_time) < PGARCH_RESTART_INTERVAL)
+		return true;

Why did you remove the cast to unsigned int there?

+	/*
+	 * Advertise our latch that backends can use to wake us up while we're
+	 * sleeping.
+	 */
+	PgArch->pgprocno = MyProc->pgprocno;

The comment should be updated?

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION

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.