Horton

Re: shared-memory based stats collector - v70

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: andres@anarazel.de
Cc: melanieplageman@gmail.com, pryzby@telsasoft.com, thomas.munro@gmail.com, david.g.johnston@gmail.com, pgsql-hackers@lists.postgresql.org
Date: 2022-04-06T09:11:04Z
Lists: pgsql-hackers 
At Tue, 5 Apr 2022 20:00:08 -0700, Andres Freund <andres@anarazel.de> wrote in 
> Hi,
> 
> Here comes v70:
> - extended / polished the architecture comment based on feedback from Melanie
>   and David
> - other polishing as suggested by David
> - addressed the open issue around pgstat_report_stat(), as described in
>   https://www.postgresql.org/message-id/20220405204019.6yj7ocmpw352c2u5%40alap3.anarazel.de
> - while working on the above point, I noticed that hash_bytes() showed up
>   noticeably in profiles, so I replaced it with a fixed-width function
> - found a few potential regression test instabilities by either *always*
>   flushing in pgstat_report_stat(), or only flushing when force = true.
> - random minor improvements
> - reordered commits some
> 
> I still haven't renamed pg_stat_exists_stat() yet - I'm leaning towards
> pg_stat_have_stats() or pg_stat_exists() right now. But it's an SQL function
> for testing, so it doesn't really matter.
> 
> I think this is basically ready, minus a a few comment adjustments here and
> there. Unless somebody protests I'm planning to start pushing things tomorrow
> morning.
> 
> It'll be a few hours to get to the main commit - but except for 0001 it
> doesn't make sense to push without intending to push later changes too. I
> might squash a few commits togther.
> 
> There's lots that can be done once all this is in place, both simplifying
> pre-existing code and easy new features, but that's for a later release.

I'm not sure it's in time but..

(Sorry in advance for possible duplicate or pointless comments.)

0001: Looks fine.

0002:

All references to "stats collector" or alike looks like eliminated
after all of the 24 patches are applied.  So this seems fine.

0003:

This is just moving around functions and variables. Looks fine.

0004:

I can see padding_pgstat_send and fun:pgstat_send in valgrind.supp

0005:

The function is changed later patch, and it looks fine.

0006:

I'm fine with the categorize for now.

+#define PGSTAT_KIND_LAST PGSTAT_KIND_WAL
+#define PGSTAT_NUM_KINDS (PGSTAT_KIND_LAST + 1)

The number of kinds is 10. And PGSTAT_NUM_KINDS is 11?

+	 * Don't define an INVALID value so switch() statements can warn if some
+	 * cases aren't covered. But define the first member to 1 so that
+	 * uninitialized values can be detected more easily.

FWIW, I like this.


0007:

(mmm no comments)

0008:

+	xact_desc_stats(buf, "", parsed.nstats, parsed.stats);
+	xact_desc_stats(buf, "commit ", parsed.nstats, parsed.stats);
+	xact_desc_stats(buf, "abort ", parsed.nabortstats, parsed.abortstats);

I'm not sure I like this, but I don't object to this..

0009: (skipped)

0010:
(I didn't look this closer. The comments arised while looking other
patches.)

+pgstat_kind_from_str(char *kind_str)

I don't think I like "str" so much.  Don't we spell it as
"pgstat_kind_from_name"?


0011:
  Looks fine.

0012:
  Looks like covering all related parts.


0013:
  Just fine.

0014:
  I bilieve it:p

0015:
  Function attributes seems correct. Looks fine.

0016:
(skipped, but looks fine by a quick look.)

0017:

 I don't find a problem with this.

0018: (skipped)

0019:

+my $og_stats = $datadir . '/' . "pg_stat" . '/' . "pgstat.stat";

It can be "$datadir/pg_stat/pgstat.stat" or $datadir . '/pgstat/pgstat.stat'.
Isn't it simpler?


0020-24:(I believe them:p)

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.