Re: PostgreSQL Replication with read-only access to standby DB

On Tue, 25 Mar 2008, Jonathan Bond-Caron wrote:

> I know very little about postgreSQL internals but it would be great if:
> - WAL files could be applied while the standby server is operational / allow
> read-only queries

This is the part that requires modifying PostgreSQL, and that progress was
made toward by Florian's GSoC project last summer.

> - Allow master server to send WAL files to standby servers / * WAL traffic
> to be streamed to another server
> - Allow master server to send list of all known standby servers
> - Allow standby server to check if master server is alive and promote itself
> as master (would need to ask / make sure other standby servers do not try
> promote themselves at the same time)

These parts you could build right now, except that there's not too much
value to more than one standby if you're not using them to execute queries
against. People who are using the current warm-standby code are already
grappling with issues like how to coordinate master/slave failover
(including my second favorite acronym, STONITH for "shoot the other node
in the head"). I don't expect handling that sort of thing will ever be
integrated into the PostgreSQL database core. What is happening instead
is that the appropriate interfaces to allow building higher-level tools
are being designed and made available.

(My favorite acronym is TLA)

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD