Hello Cedric,
I see your point but I do not completely agree.
> > Nevertheless, in the cases where the sequence is of first
> importance, MDBs
> > are false friends!
>
> If you need sequencing, you should not use JMS at all, as order
> of devivery of
> messages is "not significant" (to quote [4.4.12]).
The spec states the rules when the sequence is preserved and when it may not
be. Nevertheless, it is still possible to enforce a specific policy for a
particular application keeping the sequence i.e. messages of a same client
(i.e. sent from the same session) should arrive to a particular destination
in the good sequence. All messages must have the same priority and sent in
persistant mode. In this case (it is just an example of a possible global
policiy choice), my own usage of JMS keeps the sequence OK. Why sould then
MDB loose this sequence?
Why can't the MDB preserve the semantic selected in JMS in this case? We can
"tune" JMS but not MDB.
> > Don't you think that the spec should incorporate the use of a
> "flag" which
> > would indicate if the messages original sequence needs to be
> preserved or if
> > it may be changed in order to speed up the processing?
>
> This flag could hardly be enforced because delivery of messages
> can become quite
> complex (for example, a consumer might receive old messages sent
> from a persistent
> topic, or higher priority messages can jump ahead lesser priority ones).
OK. This is a particular case i.e a particular choice of semantic. If I
choose another semantic (policy) keeping the sequence, MDBs cannot follow
me.
Don't you think so? what would you use then?
Cheers,
Sacha
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