[Pgpool-general] Zimbra Detected SpamPgPool replication or Slony

[Pascal Cohen]

Pascal Cohen wrote:
> Hello all
> I am new to PgPool (and also Slony).
> I am currently studying the way to ensure more availability but also 
> load balancing to reduce the load on a single DB whenever we would need it.
> PgPool-II is very nice and is running well in the tests I did and the 
> way to integrate it with PgPool-HA seems nice.
> But I am concerned with the replication between several DBs.
> I can handle that in two ways:
> First use PgPool only as a load balancer and rely on Slony for 
> replication or use PgPool as load balancer and replicator.
> I would like to know what are the drawbacks and the advantages of each 
> solution.
>
> I would like also to get details on the PgPool replication behavior.
> The simplest is probably a dummy example.
> Let's say we have a master DB containing a table A and a transaction 
> updates one row in A. Table A in S is synchronized with M.
> Let's say then that I have two connections that get the updated row in A.
>
> Using PgPool as load balancer between a Master M and a Slave S. I can 
> have the following situation (not necessary much probable but 
> technically possible):
> Update of A in M.
> First request on A goes on M.
> Second request on A goes to S.
> Slony performs synchro between M and S.
> In that case my two requests may return different results.
>
> Can that situation occurs also with PgPool replication like:
> PgPool sends update of A in M .
> First request on A goes on M.
> Second request on A goes to S.
> PgPool sends update to S.
>
> My main concern is in fact that there can be transitional state where we 
> can get different data depending on the targeted DB choosing PgPool 
> replication or Slony replication.
>
> Am I right ?
>
>   
Hello again
Can anybody help me ?
Thanks

Regards

Pascal