Re: IPC::Run accepts bug reports

On Mon, Jun 17, 2024 at 11:11:17AM -0700, Andres Freund wrote:
> On 2024-06-15 16:48:24 -0700, Noah Misch wrote:
> > On Sat, Jun 15, 2024 at 01:26:57PM -0400, Robert Haas wrote:
> > > The one
> > > thing I know about that *I* think is a pretty big problem about Perl
> > > is that IPC::Run is not really maintained.
> >
> > I don't see in https://github.com/cpan-authors/IPC-Run/issues anything
> > affecting PostgreSQL. If you know of IPC::Run defects, please report them.
> > If I knew of an IPC::Run defect affecting PostgreSQL, I likely would work on
> > it before absurdity like https://github.com/cpan-authors/IPC-Run/issues/175
> > NetBSD-10-specific behavior coping.
>
> 1) Sometimes hangs hard on windows if started processes have not been shut
> down before script exits. I've mostly encountered this via the buildfarm /
> CI, so I never had a good way of narrowing this down. It's very painful
> because things seem to often just get stuck once that happens.

That's bad. Do you have a link to a log, a thread discussing it, or even just
one of the test names experiencing it?

> 2) If a subprocess dies in an inopportune moment, IPC::Run dies with "ack
> Broken pipe:" (in _do_filters()). There's plenty reports of this on the
> list, and I've hit this several times personally. It seems to be timing
> dependent, I've encountered it after seemingly irrelevant ordering changes.
>
> I suspect I could create a reproducer with a bit of time.

I've seen that one. If the harness has data to write to a child, the child
exiting before the write is one way to reach that. Perhaps before exec(),
IPC::Run should do a non-blocking write from each pending IO. That way, small
writes never experience the timing-dependent behavior.

> 3) It's very slow on windows (in addition to the windows process
> slowness). That got to be fixable to some degree.

Agreed. For the next release, today's git has some optimizations. There are
other known-possible Windows optimizations not implemented.