[jboss-dev-forums] [Design of Messaging on JBoss (Messaging/JBoss)] - Client failover redeliveries discussion

[clebert.suconic@jboss.com]

I already have consumers seamlessly reconnecting to a new server during a HA event.

Basically what I do on failover is to create a new consumer on the new server, replace IDs and re-register the Callback handler. The server at this point will think it's a new client coming. In case of durable subscribers/queues and persistent messages you will have the queue refilled

There are some issues that I would like to discuss now:

If the consumer receives a message from CallBack but if it didn't send an ACK yet, after the failover, the server not knowing the message might throw an exception (messageId not known). 

There are a couple of use cases we have to consider.
-   Persistent Messages. (how to treat a redelivery). 
-   Should we send the list of previously ACKs to the server?
-   Should we ignore ACKs for non existent messages on the server?

Second point also:

What to do when a durable subscriber gets the queue refilled?
-   The client will probably receive the message again. I would just ignore redeliveries.

I'm considering having a conference call with developers about these possibilities.


Clebert Suconic

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