[Pgpool-hackers] Automatic reattachment of the node in connection pooling mode

[Guillaume Lelarge]

Le 28/01/2011 01:16, Tatsuo Ishii a écrit :
>> One of my customers asks me today why pgpool doesn't check, from time to
>> time, that the backend is now available in connection pool mode.
>>
>> Here is what we did with a pgpool 3.0.1, configured only for connection
>> pooling and health checking:
>>
>>  * start postgresql (pg_ctl start)
>>  * start pgpool (pgpool -f etc/pgpool.conf start)
>>  * every connection works fine
>>  * stop postgresql (pg_ctl start)
>>  * health check detects the unavailability of the backend
>>    and changes status of node 0 to 3
>>  * no connection, which is good because backend is unavailable
>>  * start postgresql (pg_ctl start)
>>  * and the node still remains in status 3.
>>
>> What I would like to have is a way to check if the backend is now
>> available. And reattach it if it is. All intern to pgpool. Any reason
>> why not to do so?
>>
>> I can have misread the documentation, and I understand why this cannot
>> happen in replication mode or master/slave mode. But in connection
>> pooling only mode, I don't get it.
>>
>> If it seems to be a nice feature to have, I'm interested in working on this.
> 
> I'm not sure if it's good feature. Say you have 2 DB servers and one
> of their network connections goes shakey. It continues to up and down
> every 10 seconds. If pgpool has such a feature, pgpool repeatedly does
> failover every 10 seconds, which will break existing client connection
> every 10 seconds. I'm sure the user is not happy with this situation.

You can use two PostgreSQL servers in pooling mode? how does that work?

I'm speaking only of the pooling mode, without replication and load
balancing. In this case, if the network goes up and down continuously,
you continuously loose the connection and have to reattach node 0.


-- 
Guillaume
 http://www.postgresql.fr
 http://dalibo.com