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Re: Hot Standby startup with overflowed snapshots

From: Chris Redekop <chris(at)replicon(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Hot Standby startup with overflowed snapshots
Date: 2011-10-27 21:09:40
Message-ID: CAC2SuRJN1+qk0gVzd1mr_e5qoGL6vXY4t-BzpGkqunB1kK7xMw@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
hrmz, still basically the same behaviour.  I think it might be a *little*
better with this patch.  Before when under load it would start up quickly
maybe 2 or 3 times out of 10 attempts....with this patch it might be up to 4
or 5 times out of 10...ish...or maybe it was just fluke *shrug*.  I'm still
only seeing your log statement a single time (I'm running at debug2).  I
have discovered something though - when the standby is in this state if I
force a checkpoint on the primary then the standby comes right up.  Is there
anything I check or try for you to help figure this out?....or is it
actually as designed that it could take 10-ish minutes to start up even
after all clients have disconnected from the primary?


On Thu, Oct 27, 2011 at 11:27 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:

> On Thu, Oct 27, 2011 at 5:26 PM, Chris Redekop <chris(at)replicon(dot)com> wrote:
>
> > Thanks for the patch Simon, but unfortunately it does not resolve the
> issue
> > I am seeing.  The standby still refuses to finish starting up until long
> > after all clients have disconnected from the primary (>10 minutes).  I do
> > see your new log statement on startup, but only once - it does not
> repeat.
> >  Is there any way for me to see  what the oldest xid on the standby is
> via
> > controldata or something like that?  The standby does stream to keep up
> with
> > the primary while the primary has load, and then it becomes idle when the
> > primary becomes idle (when I kill all the connections)....so it appears
> to
> > be current...but it just doesn't finish starting up
> > I'm not sure if it's relevant, but after it has sat idle for a couple
> > minutes I start seeing these statements in the log (with the same offset
> > every time):
> > DEBUG:  skipping restartpoint, already performed at 9/95000020
>
> OK, so it looks like there are 2 opportunities to improve, not just one.
>
> Try this.
>
> --
>  Simon Riggs                   http://www.2ndQuadrant.com/
>  PostgreSQL Development, 24x7 Support, Training & Services
>

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Next:From: Simon RiggsDate: 2011-10-27 22:55:38
Subject: Re: Hot Standby startup with overflowed snapshots
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Subject: Re: (PATCH) Adding CORRESPONDING (NULL error)

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