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: masao.fujii@oss.nttdata.com
Cc: gkokolatos@protonmail.com, pgsql-hackers@lists.postgresql.org
Date: 2021-03-11T00:47:49Z
Lists: pgsql-hackers 
At Wed, 10 Mar 2021 21:47:51 +0900, Fujii Masao <masao.fujii@oss.nttdata.com> wrote in 
> Attached is the updated version of the 0003 patch. Barring any
> objection,
> I will commit this patch.
> 
> 
> -#include "storage/latch.h"
> -#include "storage/proc.h"
> 
> I removed these because they are no longer necessary.

Mmm. Sorry for the garbage.

>         <literal>logical replication worker</literal>,
>         <literal>parallel worker</literal>, <literal>background
>         writer</literal>,
>         <literal>client backend</literal>, <literal>checkpointer</literal>,
> +       <literal>archiver</literal>,
>         <literal>startup</literal>, <literal>walreceiver</literal>,
>         <literal>walsender</literal> and <literal>walwriter</literal>.
> 
> In the document about pg_stat_activity, possible values in
> backend_type
> column are all listed. I added "archiver" into the list.
> 
> BTW, those values were originally listed in alphabetical order,
> but ISTM that they were gotten out of order at a certain moment.
> So they should be listed in alphabetical order again. This should
> be implemented as a separate patch.

Thanks for adding it.

They are also mildly sorted by function or characteristics. I'm not
sure which is better, but anyway they should be the order based on a
clear criteria.

> -PgArchData *PgArch = NULL;
> +static PgArchData *PgArch = NULL;
> 
> I marked PgArchData as static because it's used only in pgarch.c.

Right.

> -		ShmemInitStruct("Archiver ", PgArchShmemSize(), &found);
> + ShmemInitStruct("Archiver Data", PgArchShmemSize(), &found);
> 
> I found that the original shmem name ended with unnecessary space
> character.
> I replaced it with "Archiver Data".

Oops. The trailing space is where I stopped writing the string and try
to find a better word, then in the meanwhile, my mind have been
attracted to something else and left.  I don't object to "Archiver
Data".  Thanks for completing it.

> In reaper(), I moved the code block for archiver to the original
> location.

Agreed.

> I ran pgindent for the files that the patch modifies.

Yeah, I forgot to add the new struct into typedefs.list.  I
intentionally omitted clearing newly-acquired shared memory but it
doesn't matter to do that.

So, I'm fine with it. Thanks for taking this.

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.