| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Review: Hot standby |
| Date: | 2008-11-28 17:31:35 |
| Message-ID: | 1227893495.20796.218.camel@hp_dx2400_1 |
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| Lists: | pgsql-hackers |
On Fri, 2008-11-28 at 11:44 -0500, Tom Lane wrote:
> Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> > On Fri, 2008-11-28 at 11:14 -0500, Tom Lane wrote:
> >> The sinval queue is an *utterly* inappropriate
> >> mechanism for such a thing.
>
> > To be honest, it did seem quite a neat solution. Any particular
> > direction of thought you'd like me to pursue instead?
>
> I hadn't been following the discussion closely enough to know what the
> problem is.
When we replay an AccessExclusiveLock on the standby we need to kick off
any current lock holders, after a configurable grace period. Current
lock holders may include some read-only backends that are
idle-in-transaction. SIGINT, which is what the current patch uses, is
not sufficient to dislodge the idle backends.
So we need to send a signal to the idle backends and then have them
react. We could use a multi-meaning approach for SIGUSR1 as we do for
pmsignal, or ...
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support
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