Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Alexander Lakhin <exclusion@gmail.com>, Jelte Fennema-Nio <postgres@jeltef.nl>, 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>, Daniel Gustafsson <daniel@yesql.se>, Peter Eisentraut <peter@eisentraut.org>, Justin Pryzby <pryzby@telsasoft.com>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Etsuro Fujita <etsuro.fujita@gmail.com>
Date: 2024-11-17T02:33:11Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2024-10-01 15:00:00 +0300, Alexander Lakhin wrote:
>> One month later, treehopper has found a way to break that test: [1].
>> The failure log contains:
>> 2024-09-30 19:35:01.485 UTC [3201033:12] pg_regress/query_cancel WARNING: 
>> could not get result of cancel request due to timeout

> Another failure in CI, that cleared up after a retry:
> +WARNING:  could not get result of cancel request due to timeout

Yeah.  This has been happening off-and-on in the buildfarm ever
since we added that test.  I'm not sure if it's just "the test
is unstable" or if it's telling us there's a problem with the
cancel logic.  Scraping the last 3 months worth of buildfarm
logs finds these instances:

  sysname   |    branch     |      snapshot       |           stage            |                                 l
------------+---------------+---------------------+----------------------------+------------------------------------------------------------------
 adder      | HEAD          | 2024-08-29 10:42:09 | postgres_fdwInstallCheck-C | +WARNING:  could not get result of cancel request due to timeout
 adder      | REL_17_STABLE | 2024-08-29 12:52:00 | postgres_fdwCheck          | +WARNING:  could not get result of cancel request due to timeout
 froghopper | HEAD          | 2024-10-25 08:31:55 | ContribCheck-C             | +WARNING:  could not get result of cancel request due to timeout
 grassquit  | HEAD          | 2024-08-20 19:29:20 | postgres_fdwCheck          | +WARNING:  could not get result of cancel request due to timeout
 mylodon    | HEAD          | 2024-08-30 06:25:46 | postgres_fdwCheck          | +WARNING:  could not get result of cancel request due to timeout
 pipit      | HEAD          | 2024-11-13 01:12:28 | ContribCheck-C             | +WARNING:  could not get result of cancel request due to timeout
 snakefly   | REL_17_STABLE | 2024-08-19 11:30:04 | ContribCheck-C             | +WARNING:  could not get result of cancel request due to timeout
 treehopper | REL_17_STABLE | 2024-09-30 19:21:14 | ContribCheck-C             | +WARNING:  could not get result of cancel request due to timeout
(8 rows)

			regards, tom lane

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.