Re: Hot standby, recovery infra - Mailing list pgsql-hackers

From Fujii Masao
Subject Re: Hot standby, recovery infra
Date
Msg-id 3f0b79eb0901281918s299d3d1cwa335f847bb99bed5@mail.gmail.com
Whole thread Raw
In response to Re: Hot standby, recovery infra  (Fujii Masao <masao.fujii@gmail.com>)
Responses Re: Hot standby, recovery infra  (Simon Riggs <simon@2ndQuadrant.com>)
List pgsql-hackers
Hi,

On Wed, Jan 28, 2009 at 11:19 PM, Fujii Masao <masao.fujii@gmail.com> wrote:
>> I feel quite good about this patch now. Given the amount of code churn, it
>> requires testing, and I'll read it through one more time after sleeping over
>> it. Simon, do you see anything wrong with this?
>
> I also read this patch and found something odd. I apologize if I misread it..

Sorry for my random reply.

Though this is a matter of taste, I think that it's weird that bgwriter
runs with ThisTimeLineID = 0 during recovery. This is because
XLogCtl->ThisTimeLineID is set at the end of recovery. ISTM this will
be a cause of bug in the near future, though this is harmless currently.

> +    /*
> +     * XXX: Should we try to perform restartpoints if we're not in consistent
> +     * recovery? The bgwriter isn't doing it for us in that case.
> +     */

I think yes. This is helpful for the system which it takes a long time to get
a base backup, ie. it also takes a long time to reach a consistent recovery
point.

> +CreateRestartPoint(int flags)
<snip>
> +     * We rely on this lock to ensure that the startup process doesn't exit
> +     * Recovery while we are half way through a restartpoint. XXX ?
>       */
> +    LWLockAcquire(CheckpointLock, LW_EXCLUSIVE);

Is this comment correct? CheckpointLock cannot prevent the startup process
from exiting recovery because the startup process doesn't acquire that lock.

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center


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