[Pgpool-hackers] proposal for new feature

[mitani at sraw.co.jp]

Hi Ishii-San,

Thank you for quick response.

In order to implement of redundancy for pgpoll, 
I think three functions are required as follows,
Observation, Take over and Recovery.

How to share the information, 
 that's a key point of this solution.
There are two methods to share the information.
 (1) servers use a data at same data location,
 (2) servers use same contents of data in own storage.
In either case have some pros and cons.

I'm planing to use the (1) method cause it can make simple.
And I'm going to use database as a shared data repository for pgpools.
In that case, the communication protocol also might be based on the libpq.

Anyway, this is still just an idea.
I'd like to have any comments for it.

Thank you.
--
At.Mitani



-- original message --
From: Tatsuo Ishii<ishii at sraoss.co.jp>
To: <mitani at sraw.co.jp>
Cc: <pgpool-hackers at pgfoundry.org>
Sent: Wed, 16 Nov 2011 21:40:53 +0900 (JST)
Subject: Re: [Pgpool-hackers] proposal for new feature

>> Hi all,
>> 
>> I'm a developer of the PGCluster which is a multi-master synchronous replication tool for PogstreSQL.
>> I have used pgpool as a loadbalancer of PGCluster for a long time (about eight years).
>
>Welcome Mitani!
>
>> I would like to propose new features for pgpool-II to bolster an availability.
>>
>> In order to prevent single point of failure, two or more pgpool sets should be put in a system. In this case, there are two type of composition. 
>> (1) Single master and multi slave composition
>> If the master pgpool failed, the slave pgpool might take over it.
>> I know there are some tools which is designed to build redundant system like a Heartbeat, DRBD and Lifekeeper etc. However, these tools are not so easy to build up. And these are not enouth for database redundancy I think.
>> If pgpool-II has this function in it self, user might be pleased to use it.
>> (2) Multi master composition 
>> I know that pgpool-II can be used like a multi master composition.
>> However, if one pgpool execute online backup, other pgpools are not block  sessions.
>> I think that it needs a cooperate action for online backup.
>> 
>> I'll create some patches within a few monthes if nobody oppesed it.
>> I would like to have a comment about it.
>
>All sounds great to me. In the mean time I'm interested in how do you
>design a communication infrastracture between mutiple pgpool instances
>in #1. I'm looking forward to hearing more details from you.
>--
>Tatsuo Ishii
>SRA OSS, Inc. Japan
>English: http://www.sraoss.co.jp/index_en.php
>Japanese: http://www.sraoss.co.jp
>