Re: pgpool and slony

> Hi,
> This is a newbie pgpool question. I have 2 servers (master-slave) and Slony
> is doing the replication. I had installed pgpool for load balance where i
> had disabled the replication_mode=false and load_balance_mode=true in
> pgpool.conf
>
> pcp_node_info gives this output.
>
> -sh-3.00$pcp_node_info 10 localhost 9898 josh postgres 1
> 172.31.0.67 5432 2 16383.500000
>
> -sh-3.00$ pcp_node_info 10 localhost 9898 josh postgres 0
> 172.31.0.68 5432 2 16383.500000
>
> So does this mean that pgpool is working properly with slony-1.

You need to trun on master_slave_mode. This will ensure that write
queries are sent to only master (remember that Slony's slave does not
accept write queries).

> Also how do
> I test to see if the load balancing with pgpool is working properly. What
> kind of query will help me confirm that it is load balanced ?

Turn on query logging on PostgreSQL and look into the log file.

> Also will pgpool automate failover? How can I test that?

For Slony slave, it's easy. Stop the slave's postmaster using pg_ctl
command. I recommend to use -m f option.

For Slony master, it's a little complicated. In this case Slony
requires user to manualy promote one of slaves to new master (correct
me if I am wrong). While pgpool automaticaly detach the broken master
and chose the second PostgreSQL ("second" means written in the second
place in pgpool.conf") and regard it as a new master. So there needs
some communication between pgpool and Slony. As of pgpool-II 2.0，a
new directive called "failover_command" is added. User can specify
shell command to be executed when a node is detached by pgpool.

You can specify following in the directive:
# special values: %d = node id
# %h = host name
# %p = port number
# %D = database cluster path
# %% = '%' character

So you could invoke some Slony management command by using above to
sync pgpool and Slony(I'm not familiar with Slony, and hope someone
help us in this regard).

> sorry if my question is silly

Not at all. Thanks for testing pgpool.

> thanks
> josh