From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr> |
Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Magnus Hagander <magnus(at)hagander(dot)net>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Peter Eisentraut <peter_e(at)gmx(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: pg_basebackup for streaming base backups |
Date: | 2011-01-20 19:51:27 |
Message-ID: | AANLkTi=96cPWR7NBGodwHwdJZD9208JA0mcvywntt9Ns@mail.gmail.com |
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On Thu, Jan 20, 2011 at 2:10 PM, Dimitri Fontaine
<dimitri(at)2ndquadrant(dot)fr> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)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. Right now, the backends get the value through
>> the GUC machinery, and so there's no particular bound on how long it
>> could take for them to pick up the new value. I think if we could
>> find some way of making sure that the backends got the new value in a
>> reasonably timely fashion, we'd be pretty close to being able to do
>> this. But it's hard to see how to do that.
>
> 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.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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