From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
---|---|
To: | Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at> |
Cc: | "Mads(dot)Tandrup(at)schneider-electric(dot)com" <Mads(dot)Tandrup(at)schneider-electric(dot)com>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Streaming replication with sync slave, but disconnects due to missing WAL segments |
Date: | 2013-06-05 10:42:57 |
Message-ID: | CAMkU=1wpFx84CTpU3kCL0cUj6VompdDU=L41cpLY5MMLuPhbow@mail.gmail.com |
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Lists: | pgsql-general |
On Wed, Jun 5, 2013 at 1:30 AM, Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>wrote:
> Jeff Janes wrote:
> > On Tue, Jun 4, 2013 at 6:25 AM, <Mads(dot)Tandrup(at)schneider-electric(dot)com>
> wrote:
> >> I have a question about sync streaming replication.
> >>
> >> I have 2 postgresql 9.1 servers set up with streaming replication. On
> the
> >> master node the slave is configured as a synchronous standby. I've
> verified
> >> that pg_stat_replication shows sync_state = sync for the slave node.
> >>
> >> It all seems to work fine. But I have noticed that sometimes when I
> restore
> >> backups created by pg_dump. The slave node will disconnect with the
> message
> >> in the postgresql log:
> >
> > You cannot use pg_dump to set up a database for receiving streaming
> replication.
> >
> > For that it must be a physical copy, not a logical copy which is what
> pg_dump generates.
>
> I think you misunderstood - he restores a dump on
> the *primary* and that makes replication fall over
> because it cannot catch up.
>
Ah, I see. And the synchronization point doesn't help, because it only
occurs at commit-time and if the dump is being loaded in a single
transaction, then the transaction could last for several checkpoints. By
the time it tries to synchronize, it is already too late.
Cheers,
Jeff
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