[Pgpool-general] The forgotten question

[Jaume Sabater]

On Thu, Dec 18, 2008 at 7:53 PM, Marcelo Martins <pglists at zeroaccess.org> wrote:

> In the pgpool page there is section under online recovery that says "A
> recovery target node must have detached before doing online recovery.
> If you wish to add PostgreSQL server dynamically, add backend_*
> parameters and reload pgpool.conf. pgpool-II registers a new node as a
> detached node. ".
>
> How should that "backend_*" be configured in the pgpool.conf file so
> that I could add nodes dynamically when needed. Say I already have 3
> backend_nodes that are already configured and I would like to have the
> option to attache new nodes dynamically without having to edit the
> pgpool.conf file and reload it.

As far as I know, it means that, provided that you have three nodes in
a cluster, attached all of them, or just some of them, you can attach
(add) new nodes to the cluster by editing the pgpool.conf file, adding
the directives for a new backend node (as if pgpool was stopped and
you were at the beginning of the installation and you were adding your
nodes), such as:

backend_hostnameN = 'x.y.z.t'
backend_portN = 5432
backend_weightN = 1
backend_data_directoryN = '/var/lib/postgresql/8.3/main'

And then you would do /etc/init.d/pgpool2 reload or equivalent and
voilá, now the cluster has N nodes. So it does not really have
anything to do with doing an actual online recovery of a previously
attached node (provided it already was in the configuration file), but
adding new nodes without stopping the service.

Hope it helps.

-- 
Jaume Sabater
http://linuxsilo.net/

"Ubi sapientas ibi libertas"