[Pgpool-general] Feedback on production system in master / slave mode

[Brad Nicholson]

Philippe MOREAU wrote:

>Anyone having a feedback on pgpool being used in such a production
>environment ?
>
>. slony-I used for database replication
>. pgpool in master / slave configuration
>. READ operations load-balanced two both servers
>. WRITE operations only on primary node
>  
>

A couple of potential issues of the top of my head. 

First, consider this scenario

1)write to the slony master
2)read, pgpool balancer sends read to subscriber.
3)Event from 1) propagates via slony to subscriber

This could be a very bad situation, depending on your application.  The 
data from step 1 has been written to the db, but the read in step 2 will 
not find it. 

The other scenario, if you master database fails, pgpool will direct all 
the transactions to the subscriber.  All write transacations will fail 
(slony puts triggers on all subscribers to deny writes).

This automatic failover may be good or bad, depending on your perspective.

-- 
Brad Nicholson  416-673-4106 
Database Administrator, Afilias Canada Corp.