> From: Evan Ireland [mailto:[EMAIL PROTECTED]]
> No. JMS shouldn't deliver the same message twice (or at least if
> a message is delivered twice in unusual circumstances the JMSRedelivered
> flag should be correctly set).
Agreed, but I think we're misunderstanding each other. I'll be more
specific.
Consider the two following cases:
1) Cluster made of nodes A and B. MDB M1 listens to Topic "quotes" and is
deployed on the cluster (meaning: the user actually only wants one instance
of this MDB, but the server will deploy it on all the nodes for failure and
recovery).
2) No cluster, just two machines A and B. MDB M2 deployed on A and M3
deployed on B, both listening to the Topic "quotes". This time, the user
wants two different MDB's.
The intuitive behavior expected if a message is published on the Topic
"quotes" is:
1) only one instance of M1 receives the message, regardless fthe machine
where it lives
2) both M2 and M3 receive the message
Agreed so far?
What I'm saying is this: it is impossible to get this intuitive behavior
without JMS and EJB sharing some intimate knowledge of each other. Remember
that MDB's are supposed to be "real" JMS listeners, so JMS shouldn't deliver
messages to them differently than to regular listeners.
> An MDB is not an ordinary JMS client.
How so? To JMS, it certainly is a listener like any other.
> I think that you are assuming that an MDB implementation has to use the
> standard JMS interfaces (e.g. connection, session, or the 'application
> server' JMS interfaces). It turns out that there is no such requirement,
> which is a good thing
Agreed. Actually, the current effort goes even further: not mandating the
use of JMS as the underlying transport for MDB's (see for example the recent
renaming of some MDB tags).
> By the way, I do think this ia a great discussion thread! Let's
> hope that we can get a wider discussion going.
Agreed! Let's keep it up.
--
Cedric
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