Broadcasting a message

[tobysaville]

Hello,

what is the best way to broadcast a message to the ESB, where the broadcasting service doesnt care or know who the recipients are?

I assume this would be done with a service placing a message on a JMS topic, but im not totally clear as to how this is done. I have had a look at the jms-topic quickstart but the sending aspect is not clear to me (the qs uses a courier instead of a ServiceInvoker.

If a service sending a message to a topic is the best way to broadcast, can i see an example of how an Action would be written and configured to get the esb aware message on to the topic.

Also, from the jms-topic quickstart, it looks like the services listening to the topic have to know the topic name. Is it possible to have services "subscribe" to a broadcasting service, instead of a jms topic, thereby abstracting the topic name using the service's category & name.

if there is a better/different way of fulfilling this use case, can you enlighten me?

cheers,
toby

[tfennelly]

Hi Toby. You pretty have it as it is there.

On the delivery side, you could improve it a little bit (perhaps) by creating a "dummy" service that listens on that JMS topic only. You could call this your "Broadcast Service". The "real" services would also listen on the same JMS topic. You can then use the ServiceInvoker or the Routing actions and route the message to the "Broadcast Service", which will result in the message being broadcast on the underlying JMS topic and so being picked up by the other Services listening on that topic. Not idea, but better than using JMS directly.

As far as having a "Broadcast Listener" type thing... it doesn't exist yet. Sorry.

[noel.rocher]

The Event Manager could be what you're looking for : http://wiki.jboss.org/wiki/Wiki.jsp?page=EventManagerAction

[tobysaville]

Hi Tom,

thanks for the reply. i would be happy to develop something like this. is it possible with the framework? what would be involved?

cheers,
toby

[tobysaville]

Thanks Noel, ill take a look.

- tobes

[marklittle]

Yes, the event manager is meant to do just that in a protocol agnostic manner. Obviously if you're only interested in JMS then your favourite JMS implementation already supports something native ;-)

[tobysaville]

Hello,

I had a look at the EventManager action, it looks like what i want, thanks!

One question i have is how to automatically send the subscribe/unsubscribe messages. I guess you would want to send these automatically at deployment/undeployment. How is this possible?

cheers,
toby

[tobysaville]

just had a thought, i guess this is possible from within the initialise and destroy methods of the action. i will try this.

[marklittle]

Yes, that should work. I'd add that to a specific Action personally, rather than all Actions, so you have more control over which services register with the event manager. Just a thought.