[pgpool-general: 1401] Re: pgPool Online Recovery Streaming Replication

Tatsuo Ishii ishii at postgresql.org
Sun Feb 17 17:13:26 JST 2013

> Hi all,
> I have the following question regarding the recovery of a filed Primary
> Database Server.
> Question 1: in the documentation, under Streaming Replication Online
> Recovery section.
> http://www.pgpool.net/docs/latest/pgpool-en.html#stream
> in steps 6:
>    1. After completing online recovery, pgpool-II will start PostgreSQL on
>    the standby node. Install the script for this purpose on each DB
> nodes. Sample
>    script <http://www.pgpool.net/docs/latest/pgpool_remote_start> is
>    included in "sample" directory of the source code. This script uses ssh.
>    You need to allow recovery_user to login from the primary node to the
>    standby node without being asked password.
> To my understanding, i think the postgreSQL doesn't not need to be online
> for the recovery process right? Since later on it mentions that
> pgpool_remote_start will start up the DB on the failed node.

Acually standby PostgreSQL node should not be started.

> Question 2: in my configuration, i have 2 pgpool server with two backends.
> Will it work for oneline recovery?

Yes, but online recovery process should be initiated by one of pgpool,
not both. If you enable pgpool-II 3.2's watchdog, it will take care of
neccessary interlocking.

> Question 3: when the failed node comes back online, should i use
> pcp_recovery from DB primary or should i use pcp_attach on the failed node
> to recover the failed system? Actually in my case, both methods do not
> recover my system every time.

I'm confused. Didn't you start the online recovery process by using
pcp_recovery_node?(of course you could do it via pgpoolAdmin).

Anyway pcp_recovery_node automatically attach recovered node, and you
don't need to execute pcp_attach_node.

I suggest you read tutorial:
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp

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