Horton

Re: BackgroundPsql swallowing errors on windows

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Noah Misch <noah@leadboat.com>
Cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@postgresql.org
Date: 2025-02-16T23:18:44Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. tests: BackgroundPsql: Fix potential for lost errors on windows

  2. Improve handling of empty query results in BackgroundPsql::query()

  3. Extend Cluster.pm's background_psql() to be able to start asynchronously

Noah Misch <noah@leadboat.com> writes:
> From the slow proxy's perspective, it can't rule out the program under test
> having done those two write() calls.  The proxy doesn't have enough
> information to reconstruct the original four write() calls.  What prevents
> that anomaly?

Yeah, I think it's hopeless to expect that we can disambiguate the
order of writes to two different pipes.  For the problem at hand,
though, it seems like we don't really need to do that.  Rather, the
question is "when we detect that the program-under-test has exited,
can we be sure we have collected all of its output?".  I think that
IPC::Run may be screwing up here, because I have seen non-Windows
CI failures that look like it didn't read all the stderr output.
For example, this pgbench test failure on macOS from [1]:

# Running: pgbench -n -t 1 -Dfoo=bla -Dnull=null -Dtrue=true -Done=1 -Dzero=0.0 -Dbadtrue=trueXXX -Dmaxint=9223372036854775807 -Dminint=-9223372036854775808 -M prepared -f /Users/admin/pgsql/build/testrun/pgbench/001_pgbench_with_server/data/t_001_pgbench_with_server_main_data/001_pgbench_error_shell_bad_command
[17:27:47.408](0.061s) ok 273 - pgbench script error: shell bad command status (got 2 vs expected 2)
[17:27:47.409](0.000s) ok 274 - pgbench script error: shell bad command stdout /(?^:processed: 0/1)/
[17:27:47.409](0.000s) not ok 275 - pgbench script error: shell bad command stderr /(?^:\(shell\) .* meta-command failed)/
[17:27:47.409](0.000s) #   Failed test 'pgbench script error: shell bad command stderr /(?^:\(shell\) .* meta-command failed)/'
#   at /Users/admin/pgsql/src/bin/pgbench/t/001_pgbench_with_server.pl line 1466.
#                   ''
#     doesn't match '(?^:\(shell\) .* meta-command failed)'

The program's exited with a failure code as expected, and we saw (some
of?) the expected stdout output, but stderr output is reported to be
empty.

			regards, tom lane

[1] https://cirrus-ci.com/task/6221238034497536