Horton

Re: shared-memory based stats collector

Stephen Frost <sfrost@snowman.net>

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From: Stephen Frost <sfrost@snowman.net>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: alvherre@2ndquadrant.com, andres@anarazel.de, michael@paquier.xyz, thomas.munro@gmail.com, tomas.vondra@2ndquadrant.com, ah@cybertec.at, magnus@hagander.net, robertmhaas@gmail.com, tgl@sss.pgh.pa.us, pgsql-hackers@postgresql.org
Date: 2020-09-03T17:16:59Z
Lists: pgsql-hackers 
Greetings,

* Kyotaro Horiguchi (horikyota.ntt@gmail.com) wrote:
> At Mon, 01 Jun 2020 18:00:01 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in 
> > Rebased on the current HEAD. 36ac359d36 conflicts with this. Tranche
> 
> Hmm. This conflicts with 0fd2a79a63. Reabsed on it.

Thanks for working on this and keeping it updated!

I've started taking a look and at least right off...

> >From 4926e50e7635548f86dcd0d36cbf56d168a5d242 Mon Sep 17 00:00:00 2001
> From: Kyotaro Horiguchi <horikyoga.ntt@gmail.com>
> Date: Mon, 16 Mar 2020 17:15:35 +0900
> Subject: [PATCH v35 1/7] Use standard crash handler in archiver.
> 
> The commit 8e19a82640 changed SIGQUIT handler of almost all processes
> not to run atexit callbacks for safety. Archiver process should behave
> the same way for the same reason. Exit status changes 1 to 2 but that
> doesn't make any behavioral change.

Shouldn't this:

a) be back-patched, as the other change was
b) also include a change to have the stats collector (which I realize is
   removed later on in this patch set, but we're talking about fixing
   existing things..) for the same reason, and because there isn't much
   point in trying to write out the stats after we get a SIGQUIT, since
   we're just going to blow them away again since we're going to go
   through crash recovery..?

Might be good to have a separate thread to address these changes.

I've looked through (some of) this thread and through the patches also
and hope to provide a review of the bits that should be targetting v14
(unlike the above) soon.

Thanks,

Stephen

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.