I wrote:
> So for some reason, on these machines detection of walsender-initiated
> connection close is unreliable ... or maybe, the walsender didn't close
> the connection, but is somehow still hanging around? Don't have much idea
> where to dig beyond that, but maybe someone else will. I wonder in
> particular if this could be related to our recent discussions about
> whether to use shutdown(2) on Windows --- could we need to do the
> equivalent of 6051857fc/ed52c3707 on walsender connections?
... wait a minute. After some more study of the buildfarm logs,
it was brought home to me that these failures started happening
just after 6051857fc went in:
https://buildfarm.postgresql.org/cgi-bin/show_failures.pl?max_days=90&branch=&member=&stage=module-commit_tsCheck&filter=Submit
The oldest matching failure is jacana's on 2021-12-03.
(The above sweep finds an unrelated-looking failure on 2021-11-11,
but no others before 6051857fc went in on 2021-12-02. Also, it
looks likely that ed52c3707 on 2021-12-07 made the failure more
probable, because jacana's is the only matching failure before 12-07.)
So I'm now thinking it's highly likely that those commits are
causing it somehow, but how?
regards, tom lane