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
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Mon, 26 Jun 2017 13:33:47 -0700"
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Date: Mon, 26 Jun 2017 16:49:07 -0400
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Andres Freund <andres@anarazel.de> writes:
> Arguably we could and should improve the logic when the server has
> started, right now it's pretty messy because we never treat a standby as
> up if hot_standby is disabled...

True.  If you could tell the difference between "HS disabled" and "HS not
enabled yet" from pg_control, that would make pg_ctl's behavior with
cold-standby servers much cleaner.  Maybe it *is* worth messing with the
contents of pg_control at this late hour.

My inclination for the least invasive fix is to leave the DBState
enum alone and add a separate hot-standby state field with three
values (disabled/not-yet-enabled/enabled).  Then pg_ctl would start
probing the postmaster when it saw either DB_IN_PRODUCTION DBstate
or hot-standby-enabled.  (It'd almost not have to probe the postmaster
at all, except there's a race condition that the startup process
will probably change the field a little before the postmaster gets
the word to open the gates.)  On the other hand, if it saw
DB_IN_ARCHIVE_RECOVERY with hot standby disabled, it'd stop waiting.

Any objections to that design sketch?  Do we need to distinguish
between master and slave servers in the when-to-stop-waiting logic?

			regards, tom lane


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