Horton

Re: shared-memory based stats collector

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: andres@anarazel.de
Cc: masao.fujii@oss.nttdata.com, gkokolatos@protonmail.com, pgsql-hackers@lists.postgresql.org
Date: 2021-04-07T03:05:12Z
Lists: pgsql-hackers 
At Tue, 6 Apr 2021 09:32:16 -0700, Andres Freund <andres@anarazel.de> wrote in 
> Hi,
> 
> On 2021-04-05 02:29:14 -0700, Andres Freund wrote:
..
> I'm inclined to push patches
> [PATCH v60 05/17] pgstat: split bgwriter and checkpointer messages.
> [PATCH v60 06/17] pgstat: Split out relation stats handling from AtEO[Sub]Xact_PgStat() etc.
> [PATCH v60 09/17] pgstat: xact level cleanups / consolidation.
> [PATCH v60 10/17] pgstat: Split different types of stats into separate files.
> [PATCH v60 12/17] pgstat: reorder file pgstat.c / pgstat.h contents.

FWIW..

05 is a straight forward code-rearrange and reasonable to apply.

06 is same as above and it seems to make things cleaner.

09 mainly adds ensure_tabtat_xact_level() to remove repeated code
  blocks a straight-forward way. I wonder if
  pgstat_xact_stack_level_get() might better be
  pgstat_get_xact_stack_level(), but I'm fine with the name in the
  patch.

10 I found that the kind in "pgstat_kind" meant the placeholder for
  specific types.  It looks good to separate them into smaller pieces.
  It is also a simple rearrangement of code.

> pgstat.c is very long, and it's hard to find an order that makes sense
> and is likely to be maintained over time. Splitting the different

  I deeply agree to "hard to find an order that makes sense".

12 I'm not sure how it looks after this patch (I failed to apply 09 at
  my hand.), but it is also a simple rearrangement of code blocks.

> to v14. They're just moving things around, so are fairly low risk. But
> they're going to be a pain to maintain. And I think 10 and 12 make
> pgstat.c a lot easier to understand.

I think that pgstat.c doesn't get frequent back-patching.  It seems to
me that at least 10 looks good.

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.