From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Jeff Janes <jeff.janes@gmail.com>,
        Michael Paquier <michael.paquier@gmail.com>,
        PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Subject: Re: Reducing pg_ctl's reaction time
In-reply-to: <20170626213414.ejcesidei2hv4h5x@alap3.anarazel.de>
References: 
 <CAB7nPqTWWBEZ6NN_pbgmU=yn-HZNKGY3nAivvLSuLPe61n1KJw@mail.gmail.com>
 <24992.1498504537@sss.pgh.pa.us>
 <CAMkU=1xJW8e+CTotojOMBd-yzUvD0e_JZu2xHo=MnuZ4__m7Pg@mail.gmail.com>
 <18520.1498508356@sss.pgh.pa.us>
 <20170626202356.qybnpn5li2ke4ioc@alap3.anarazel.de>
 <18890.1498508760@sss.pgh.pa.us>
 <20170626203347.6efkdwiadyt33edy@alap3.anarazel.de>
 <19812.1498510147@sss.pgh.pa.us>
 <20170626205853.ezhnmxpotdy3wokm@alap3.anarazel.de>
 <15166.1498512630@sss.pgh.pa.us>
 <20170626213414.ejcesidei2hv4h5x@alap3.anarazel.de>
Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Mon, 26 Jun 2017 14:34:14 -0700"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <15731.1498513083.1@sss.pgh.pa.us>
Date: Mon, 26 Jun 2017 17:38:03 -0400
Message-ID: <15732.1498513083@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Andres Freund <andres@anarazel.de> writes:
> On 2017-06-26 17:30:30 -0400, Tom Lane wrote:
>> No, I don't like that at all.  Has race conditions against updates
>> coming from the startup process.

> You'd obviously have to take the appropriate locks.  I think the issue
> here is less race conditions, and more that architecturally we'd
> interact with shmem too much.

Uh, we are *not* taking any locks in the postmaster.

>> Yeah, that would be a different way to go at it.  The postmaster would
>> probably just write the state of the hot_standby GUC to the file, and
>> pg_ctl would have to infer things from there.

> I'd actually say we should just mirror the existing
> #ifdef USE_SYSTEMD
> 		if (!EnableHotStandby)
> 			sd_notify(0, "READY=1");
> #endif
> with corresponding pidfile updates - doesn't really seem necessary for
> pg_ctl to do more?

Hm.  Take that a bit further, and we could drop the connection probes
altogether --- just put the whole responsibility on the postmaster to
show in the pidfile whether it's ready for connections or not.

			regards, tom lane


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers