Re: BUG #14830: Missed NOTIFications, PostgreSQL 9.1.24

On Tue, Oct 10, 2017 at 3:58 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

> Marko Tiikkaja <marko@joh.to> writes:
> > So I managed to accidentally kill and/or restart both servers while
> trying
> > to install debug symbols, but I'm doing a new run now and I noticed
> > something interesting: the listening backend's RecentXmin doesn't seem to
> > ever go forward.  By my reading of this code, that would mean trouble for
> > this piece of code in TransactionIdIsInProgress:
>
> >   if (TransactionIdPrecedes(xid, RecentXmin))
> >       return false;
>
> Hmm ... I suppose it's possible that that happens if the listening
> backend isn't executing any SQL commands but is just sitting.
> While that might describe your test harness, does it describe any
> real-world application?
>

Yes.  It's a service which only does LISTEN and UNLISTEN and forwards
notifications to its clients.


.m