Re: Postgres 9.0 Streaming Replication and Load Balancing?

From: Paulo Correia <paulo(dot)correia(at)pdmfc(dot)com>
To: pgsql <pgsql-general(at)postgresql(dot)org>
Subject: Re: Postgres 9.0 Streaming Replication and Load Balancing?
Date: 2012-05-17 15:10:17
Message-ID: 4FB514D9.4040403@pdmfc.com
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Yes, that was the results of our tests ...

It seems we'll have to do a lot of work on the application to separate
the queries in order to achieve the load-balancing.

Thanks anyway,

Best regards,
Paulo Correia

On 17/05/12 09:32, Sumit Raja wrote:
> Unsure you can achieve this without a read only and a read write
> application set up, I've always had RW application servers separate
> from RO ones.
>
> You could disable the application connection pool completely and let
> pg-pool do the pooling for you (not sure of performance impact, if
> any) as the session needs to be terminated after an insert for pg-pool
> to load balance correctly (see
> http://www.pgpool.net/mediawiki/index.php/FAQ, 5th one down for more
> details).
>
> - Sumit
>
>
> On 16 May 2012 16:34, Paulo Correia<paulo(dot)correia(at)pdmfc(dot)com> wrote:
>> Hello Sumit,
>>
>> At the given point there are no exceptions since the tests for using
>> pgPool-II with the application using a master and a slave resulted in all
>> connections being done on the master and none on the slave.
>>
>> As the application as it's own connection pool, eventually all connections
>> will have a RW operation and as so all these connections will be linked to
>> the master.
>>
>> As so, I cannot benefit from load balancing since all my connections will be
>> redirected to the master by pgPool-II, even if they are RO.
>>
>> Is it possible to have pgPool-II making only load balance with no connection
>> pool?
>>
>> Best regards,
>> Paulo Correia
>>
>> On 15/05/12 09:01, Sumit Raja wrote:
>>> On 14 May 2012 17:28, Paulo Correia<paulo(dot)correia(at)pdmfc(dot)com> wrote:
>>>> Hello all!
>>>> Having a Postgres 9.0 with assynchronous streaming replication to a
>>>> hot-standby slave, both with CentOs 5.6, how can I use both DB instances
>>>> for
>>>> query load balancing?
>>>> I've tried with pgPool-II but the pooling mechanism is disruptive with
>>>> the
>>>> existing pool on the application servers.
>>> Is the application RW or read only? What is the disruption being
>>> caused? Are you seeing specific exceptions?
>>>
>>> - Sumit
>>>
>>
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