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Date: Tue, 17 Jan 2012 17:54:04 -0800
From: Manoj Govindassamy <manoj@nimblestorage.com>
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To: Fujii Masao <masao.fujii@gmail.com>
CC: <pgsql-general@postgresql.org>, <pgsql-admin@postgresql.org>
Subject: Re: PG synchronous replication and unresponsive slave
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I am aware of pgpool-II and its features. Just that my requirements are 
little different.  I have a System (PG runs on it) which already has 
Failover mechanism to another System and I want PG to be part of this 
cluster and not clustered on its own. Mean, PG has to be running in 
Master system and in synchronous replication mode with another slave 
system, but the failover is driven from the higher level and not just on 
PG's failure.

So, whenever PG's slave node is unresponsive, we better let the 
replication cutoff and run the master system independently. So, we need 
better mechanism to detect when Master PG's synchronous replication not 
working as expected or when the slave PG is going unresponsive.  If not, 
master PG is held back by the slave PG and so the whole clustered system 
is stuck. Hope, I am making some sense here. Let me know if there are 
easy ways to detect Master PG's replication not working (via libpq would 
be more preferable).

thanks,
Manoj


On 01/17/2012 05:04 PM, Fujii Masao wrote:
> On Wed, Jan 18, 2012 at 6:37 AM, Manoj Govindassamy
> <manoj@nimblestorage.com>  wrote:
>> (2) We are not comfortable moving to PGPool just for automatic failback mode
>> on hot-standby failure.
> Hmm.. my reply might be misleading. What I meant was to use pgpool-II
> as a clusterware for PostgreSQL built-in replication, not as a replication
> itself. You can health-check, do failover if necessary and manage the
> PostgreSQL replication by using pgpool-II. AFAIK pgpool-II has such an
> operation mode. But you are still not comfortable in using pgpool-II in
> that way?
>
> Regards,
>