Horton

Re: pg_basebackup for streaming base backups

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: Dimitri Fontaine <dimitri@2ndquadrant.fr>, Bruce Momjian <bruce@momjian.us>, Magnus Hagander <magnus@hagander.net>, Simon Riggs <simon@2ndquadrant.com>, Peter Eisentraut <peter_e@gmx.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2011-01-20T21:08:47Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> On Thu, Jan 20, 2011 at 2:10 PM, Dimitri Fontaine
> <dimitri@2ndquadrant.fr> wrote:
>> Robert Haas <robertmhaas@gmail.com> writes:
>>> I think that the basic problem with wal_level is that to increase it
>>> you need to somehow ensure that all the backends have the new setting,
>>> and then checkpoint.
>> 
>> Well, you just said when to force the "reload" to take effect: at
>> checkpoint time. IIRC we already multiplex SIGUSR1, is that possible to
>> add that behavior here? And signal every backend at checkpoint time
>> when wal_level has changed?

> Sending them a signal seems like a promising approach, but the trick
> is guaranteeing that they've actually acted on it before you start the
> checkpoint.

Have the backends show their current wal_level in their PGPROC entries.
Sleep till they're all reporting the right thing, then fire checkpoint.

			regards, tom lane