Horton

Re: shared-memory based stats collector

Artur Zakirov <a.zakirov@postgrespro.ru>

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From: Arthur Zakirov <a.zakirov@postgrespro.ru>
To: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>, alvherre@2ndquadrant.com
Cc: andres@anarazel.de, tomas.vondra@2ndquadrant.com, ah@cybertec.at, magnus@hagander.net, robertmhaas@gmail.com, tgl@sss.pgh.pa.us, pgsql-hackers@postgresql.org
Date: 2019-02-21T14:30:50Z
Lists: pgsql-hackers 
Hello,

On 21.02.2019 10:05, Kyotaro HORIGUCHI wrote:
> Done. This verison 16 looks as if the moving and splitting were
> not happen. Major changes are:
> 
>   - Restored old pgstats_* names. This largily shrinks the patch
>     size to less than a half lines of v15.  More than that, it
>     gets easier to examine differences. (checkpointer.c and
>     bgwriter.c have a bit stale comments but it is an issue for
>     later.)
> 
>   - Removed "oneshot" feature at all. This simplifies pgstat API
>     and let this patch far less simple.
> 
>   - Moved StatsLock to LWTRANCHE_STATS, which is not necessary to
>     be in the main tranche.
> 
>   - Fixed several bugs revealed by the shrinked size of the patch.

I run regression tests. Unfortunately tests didn't pass, failed test is 
'rangetypes':

rangetypes ... FAILED (test process exited with exit code 2)

It seems to me that an autovacuum process terminates because of segfault.

Segfault occurs within get_pgstat_tabentry_relid(). If I'm not mistaken, 
somehow 'dbentry' hasn't valid pointer anymore.

'dbentry' is get in the line in do_autovacuum():

dbentry = pgstat_fetch_stat_dbentry(MyDatabaseId);

'dbentry' becomes invalid after calling pgstat_vacuum_stat().

-- 
Arthur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company

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.