Date: Thu, 4 Apr 2019 07:53:19 -0700
From: Noah Misch <noah@leadboat.com>
To: Daniel Gustafsson <daniel@yesql.se>
Cc: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>,
	"9erthalion6@gmail.com" <9erthalion6@gmail.com>,
	"sfrost@snowman.net" <sfrost@snowman.net>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Weaker shmem interlock w/o postmaster.pid
Message-ID: <20190404145319.GA1720877@rfd.leadboat.com>
References: 
 <CA+q6zcV4r+oS27G-nYqonG+q7442BOA350s3jeRtA-Oqx4vDWg@mail.gmail.com>
 <20181130065140.GB2774301@rfd.leadboat.com>
 <20181203004106.GA2860387@rfd.leadboat.com>
 <20190304.180420.139624607.horiguchi.kyotaro@lab.ntt.co.jp>
 <20190307032422.GB1797215@rfd.leadboat.com>
 <20190309071610.GA2039121@rfd.leadboat.com>
 <GrdLgAdUK9FdyZg8VIcTDKVOkys122ZINEb3CjjoySfGj2KyPiMKTh1zqtRp0TAD7FJ27G-OBB3eplxIB5GhcQH5o8zzGZfp0MuJaXJxVxk=@yesql.se>
 <20190331224233.GC891537@rfd.leadboat.com>
 <eUPnXaH0-lP5UPgJAeBbpVF-9I3A9TzxXyQOAsTBO4jmB1sFTzFs6vSwaRAnHTmoDo0wJ-EtuHeyM0vn1LO0xm6NPc_dR0dwOzg8dJrLqhU=@yesql.se>
 <20190404020543.GA1319573@rfd.leadboat.com>
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On Wed, Apr 03, 2019 at 07:05:43PM -0700, Noah Misch wrote:
> On Mon, Apr 01, 2019 at 08:19:56AM +0000, Daniel Gustafsson wrote:
> > On Monday, April 1, 2019 12:42 AM, Noah Misch <noah@leadboat.com> wrote:
> > > On Fri, Mar 29, 2019 at 09:53:51AM +0000, Daniel Gustafsson wrote:
> > 
> > > > This seems like a case where it would be useful to log a shmdt() error or do
> > > > an Assert() around the success of the operation perhaps?
> > >
> > > I'll add the same elog(LOG) we have at other shmdt() sites. I can't think of
> > > a site where we Assert() about the results of a system call. While shmdt()
> > > might be a justified exception, elog(LOG) seems reasonable.
> > 
> > Agreed, seems reasonable.
> 
> Pushed, but that broke two buildfarm members:
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=idiacanthus&dt=2019-04-04%2000%3A33%3A14
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=komodoensis&dt=2019-04-04%2000%3A33%3A13
> 
> I think the problem arose because these animals run on the same machine, and
> their test execution was synchronized to the second.  Two copies of the new
> test ran concurrently.  It doesn't tolerate that, owing to expectations about
> which shared memory keys are in use.  My initial thought is to fix this by
> having a third postmaster that runs throughout the test and represents
> ownership of a given port.  If that postmaster gets something other than the
> first shm key pertaining to its port, switch ports and try again.
> 
> I'll also include fixes for the warnings Andres reported on the
> pgsql-committers thread.

This thread's 2019-04-03 patches still break buildfarm members in multiple
ways.  I plan to revert them.  I'll wait a day or two before doing that, in
case more failure types show up.