Horton

Re: shared-memory based stats collector

Tomas Vondra <tomas.vondra@2ndquadrant.com>

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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>, ah@cybertec.at, magnus@hagander.net, robertmhaas@gmail.com, tgl@sss.pgh.pa.us, pgsql-hackers@postgresql.org
Date: 2019-01-01T19:14:25Z
Lists: pgsql-hackers 

On 1/1/19 7:03 PM, Andres Freund wrote:
> Hi,
> 
> On 2019-01-01 18:39:12 +0100, Tomas Vondra wrote:
>> On 11/29/18 1:18 PM, Alvaro Herrera wrote:
>>> On 2018-Nov-28, Tomas Vondra wrote:
>>>
>>>>> v10-0004-Shared-memory-based-stats-collector.patch
>>>>>   updated not to touch guc.
>>>>> v10-0005-Remove-the-GUC-stats_temp_directory.patch
>>>>>   collected all guc-related changes.
>>>>>   updated not to break other programs.
>>>>> v10-0006-Split-out-backend-status-monitor-part-from-pgstat.patch
>>>>>   basebackup.c requires both bestats.h and pgstat.h
>>>>> v10-0007-Documentation-update.patch
>>>>>   small change related to 0005.
>>>>
>>>> I need to do a more thorough review of part 0006, but these patches
>>>> seems quite fine to me. I'd however merge 0007 into the other relevant
>>>> parts (it seems like a mix of docs changes for 0004, 0005 and 0006).
>>>
>>> Looking at 0001 - 0003 it seems OK to keep each as separate commits, but
>>> I suggest to have 0004+0006 be a single commit, mostly because
>>> introducing a bunch of "new" code in 0004 and then moving it over to
>>> bestatus.c in 0006 makes "git blame" doubly painful.  And I think
>>> committing 0005 and not 0007 makes the documentation temporarily buggy,
>>> so I see no reason to think of this as two commits, one being 0004+0006
>>> and the other 0005+0007.  And even those could conceivably be pushed
>>> together instead of as a single patch.  (But be sure to push very early
>>> in your work day, to have plenty of time to deal with any resulting
>>> buildfarm problems.)
>>>
>>
>> Kyotaro-san, do you agree with committing the patch the way Alvaro
>> proposed? That is, 0001-0003 as separate commits, and 0004+0006 and
>> 0005+0007 together. The plan seems reasonable to me.
> 
> Do you guys think these patches are ready already? I'm a bit doubtful, and
> failures here could have quite wide-ranging symptoms.
> 

I agree it's a sensitive part of the code, so additional reviews would
be welcome of course. I've done as much review and testing as possible,
and overall it seems in a fairly good shape. Do you have any particular
concerns / ideas what to look for?

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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.