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Re: Stefan's bug (was: max_standby_delay considered harmful)

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Fujii Masao <masao.fujii@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>, Simon Riggs <simon@2ndquadrant.com>, Andres Freund <andres@anarazel.de>, Florian Pflug <fgp@phlo.org>, Dimitri Fontaine <dfontaine@hi-media.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Bruce Momjian <bruce@momjian.us>, Greg Smith <greg@2ndquadrant.com>, Josh Berkus <josh@agliodbs.com>
Date: 2010-05-19T12:21:29Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> On Wed, May 19, 2010 at 1:47 AM, Fujii Masao <masao.fujii@gmail.com> wrote:
>> Yes, but I prefer XLogCtl->SharedRecoveryInProgress, which is the almost
>> same indicator as the boolean you suggested. Thought?

> It feels cleaner and simpler to me to use the information that the
> postmaster already collects rather than having it take locks and check
> shared memory, but I might be wrong.  Why do you prefer doing it that
> way?

The postmaster must absolutely not take locks (once there are competing
processes).  This is non negotiable from a system robustness standpoint.

			regards, tom lane