Horton

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

Jelte Fennema <me@jeltef.nl>

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From: Jelte Fennema <me@jeltef.nl>
To: Jelte Fennema <Jelte.Fennema@microsoft.com>
Cc: Daniel Gustafsson <daniel@yesql.se>, Peter Eisentraut <peter@eisentraut.org>, Jacob Champion <jchampion@timescale.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, Justin Pryzby <pryzby@telsasoft.com>, Robert Haas <robertmhaas@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2023-01-19T11:10:01Z
Lists: pgsql-hackers 
Is there anything that is currently blocking this patch? I'd quite
like it to get into PG16.

Especially since I ran into another use case that I would want to use
this patch for recently: Adding an async cancel function to Python
it's psycopg3 library. This library exposes both a Connection class
and an AsyncConnection class (using python its asyncio feature). But
one downside of the AsyncConnection type is that it doesn't have a
cancel method.

I ran into this while changing the PgBouncer tests to use python. And
the cancellation tests were the only tests that required me to use a
ThreadPoolExecutor instead of simply being able to use async-await
style programming:
https://github.com/pgbouncer/pgbouncer/blob/master/test/test_cancel.py#LL9C17-L9C17

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.