Date: Fri, 20 Sep 2019 19:06:20 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andres Freund <andres@anarazel.de>,
	Andrew Dunstan <andrew@dunslane.net>,
	Kuntal Ghosh <kuntalghosh.2007@gmail.com>,
	Michael Paquier <michael@paquier.xyz>,
	Tomas Vondra <tomas.vondra@2ndquadrant.com>,
	Robert Haas <robertmhaas@gmail.com>,
	Thomas Munro <thomas.munro@enterprisedb.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: subscriptionCheck failures on nightjar
Message-ID: <20190920220620.GA5214@alvherre.pgsql>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <2636.1569016167@sss.pgh.pa.us>
User-Agent: Mutt/1.9.4 (2018-02-28)
Precedence: bulk

On 2019-Sep-20, Tom Lane wrote:

> Actually, what I did was as attached [1], and I am getting traces like
> [2].  The problem seems to occur only when there are two or three
> processes concurrently creating the same snapshot file.  It's not
> obvious from the debug trace, but the snapshot file *does* exist
> after the music stops.

Uh .. I didn't think it was possible that we would build the same
snapshot file more than once.  Isn't that a waste of time anyway?  Maybe
we can fix the symptom by just not doing that in the first place?
I don't have a strategy to do that, but seems worth considering before
retiring the bf animals.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services