Re: PG-MQ?

On Jun 19, 2007, at 2:45 PM, Chris Browne wrote:

> I'm seeing some applications where it appears that there would be
> value in introducing asynchronous messaging, ala "message queueing."
> <http://en.wikipedia.org/wiki/Message_queue>

Me too.

> My bias would be to have something that can basically run as a thin
> set of stored procedures atop PostgreSQL :-).  It would be trivial to
> extend that to support SOAP/XML-RPC, if desired.
>
> It would be nice to achieve 'higher availability' by having queues
> where you might replicate the contents (probably using the MQ system
> itself ;-)) to other servers.
>
> There tend to be varying semantics out there:
>
> - Some queues may represent "subscriptions" where a whole bunch of
>   listeners want to get all the messages;
>
> - Sometimes you have the semantics where:
>   - messages need to be delivered at least once
>   - messages need to be delivered no more than once
>   - messages need to be delivered exactly once
>
> Is there any existing work out there on this?  Or should I maybe be
> looking at prototyping something?

The skype tools have some sort of decent-looking publish/subscribe
thing, PgQ, then they layer their replication on top of. It's multi
consumer and producer, with "delivered at least once" semantics.

Looks nice.

Cheers,  Steve