Re: pgpool

> John Cunningham wrote:
> > concerned that if I drop the number of connections to less than the
> > number of databases I have, that pgpool would open the limit of
> > connections, hold them open and not allow any connections to the
> > remaining databases. Is this a concern? If I set up pgpool will I
> > have to have the same number of connections as I have databases?
>
> That depends on how you configure pgpool. pgpool is not aware of the
> connection limit count in the PostgreSQL server, so it will happily
> open connections until there are no more slots available.
>
> pgpool will require max_pool * num_init_children connection slots.
>
> max_pool should be the number of database/user combinations you use
> (300 in your case, assuming only one database user account),

Not really. If a user connects to pgpool and all onnection slots are
already full, then pgpool will release the oldest connection slot and
reuse it for the new connection. So even if there are 300
database/user combinations, it's ok to set max_pool as low as, for
example, 4. Of course this will have unwanted side effect in that
connection caches are not very well kept, though.
--
Tatsuo Ishii

> and
> num_init_children should be on the order of how many concurrent
> connections you expect to each combination ("several" in your case).
> So you should have at least 300 * several PostgreSQL connection slots,
> which is probably more than the 1000 or so that is the default.
>
> --
> Peter Eisentraut
> http://developer.postgresql.org/~petere/
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
>