Horton

Re: [EXTERNAL] Re: Add non-blocking version of PQcancel

Alexander Law <exclusion@gmail.com>

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From: Alexander Lakhin <exclusion@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>, Jelte Fennema-Nio <postgres@jeltef.nl>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Noah Misch <noah@leadboat.com>, Jacob Champion <jacob.champion@enterprisedb.com>, Denis Laxalde <denis.laxalde@dalibo.com>, vignesh C <vignesh21@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Greg Stark <stark@mit.edu>, "Gregory Stark (as CFM)" <stark.cfm@gmail.com>, Jelte Fennema <Jelte.Fennema@microsoft.com>, Daniel Gustafsson <daniel@yesql.se>, Peter Eisentraut <peter@eisentraut.org>, Andres Freund <andres@anarazel.de>, Justin Pryzby <pryzby@telsasoft.com>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Etsuro Fujita <etsuro.fujita@gmail.com>
Date: 2024-08-31T04:04:04Z
Lists: pgsql-hackers 
Hello Tom,

30.08.2024 23:55, Tom Lane wrote:
> Pushed with that addition and some comment-tweaking.  We'll see
> whether that actually makes things more stable, but I don't think
> it could make it worse.

Thank you for fixing that issue!

I've tested your fix with the modification I proposed upthread:
              idle_session_timeout_enabled = false;
          }
+if (rand() % 10 == 0) pg_usleep(10000);
          /*
           * (5) disable async signal conditions again.

and can confirm that the issue is gone. On 8749d850f~1, the test failed
on iterations 3, 3. 12 for me, but on current REL_17_STABLE, 100 test
iterations succeeded.

At the same time, mylodon confirmed my other finding at [1] and failed [2] with:
-ERROR:  canceling statement due to statement timeout
+ERROR:  canceling statement due to user request

[1] https://www.postgresql.org/message-id/4db099c8-4a52-3cc4-e970-14539a319466%40gmail.com
[2] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=mylodon&dt=2024-08-30%2023%3A03%3A31

Best regards,
Alexander

Commits

  1. postgres_fdw: re-issue cancel requests a few times if necessary.

  2. Make postgres_fdw's query_cancel test less flaky.

  3. postgres_fdw: Split out the query_cancel test to its own file

  4. Fix copy-paste mistake in PQcancelCreate

  5. Make libpqsrv_cancel's return const char *, not char *

  6. Stabilize postgres_fdw test

  7. libpq-be-fe-helpers.h: wrap new cancel APIs

  8. dblink/isolationtester/fe_utils: Use new cancel API

  9. Put libpq_pipeline cancel test back

  10. Hopefully make libpq_pipeline's new cancel test more reliable

  11. libpq: Add encrypted and non-blocking query cancellation routines

  12. libpq: Move pg_cancel to fe-cancel.c

  13. Add tests for libpq query cancellation APIs

  14. Add missing connection statuses to docs

  15. libpq: Change some static functions to extern

  16. libpq: Add pqReleaseConnHosts function

  17. libpq: Move cancellation related functions to fe-cancel.c

  18. Make spelling of cancelled/cancellation consistent

  19. Be more wary about OpenSSL not setting errno on error.

  20. libpq: Use modern socket flags, if available.

  21. Drop test view when done with it.

  22. Doc: add some doco about using the libpq_pipeline test module.

  23. postgres_fdw: Allow cancellation of transaction control commands.