Horton

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

Noah Misch <noah@leadboat.com>

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From: Noah Misch <noah@leadboat.com>
To: Jelte Fennema-Nio <postgres@jeltef.nl>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Alvaro Herrera <alvherre@alvh.no-ip.org>, 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>, pgsql-hackers@lists.postgresql.org, Etsuro Fujita <etsuro.fujita@gmail.com>
Date: 2024-03-29T22:17:24Z
Lists: pgsql-hackers 
On Fri, Mar 29, 2024 at 09:17:55AM +0100, Jelte Fennema-Nio wrote:
> On Thu, 28 Mar 2024 at 19:03, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > Could we make this test bulletproof by using an injection point?
> > If not, I remain of the opinion that we're better off without it.
> 
> Possibly, and if so, I agree that would be better than the currently
> added test. But I honestly don't feel like spending the time on
> creating such a test.

The SQL test is more representative of real applications, and it's way simpler
to understand.  In general, I prefer 6-line SQL tests that catch a problem 10%
of the time over injection point tests that catch it 100% of the time.  For
low detection rate to be exciting, it needs to be low enough to have a serious
chance of all buildfarm members reporting green for the bad commit.  With ~115
buildfarm members running in the last day, 0.1% detection rate would have been
low enough to bother improving, but 4% would be high enough to call it good.

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.