Whilst reviewing the draft spec I came across this issue. Although I hope this s simply a recognition of current
practice it represents a spec change and so is worth highlighting more formally and asking for views.
If possible I'd like to include this in JMS 2.0.
-------- Original Message --------
http://java.net/jira/browse/JMS_SPEC-115
Remove the statement that portable applications should only have one consumer per queue
The JMS 1.1 specification, in section 4.4.9 "Multiple Sessions" states that
For PTP, JMS does not specify the semantics of concurrent QueueReceivers for
the same Queue; however, JMS does not prohibit a provider from supporting
this. Therefore, message delivery to multiple QueueReceivers will depend on the
JMS provider's implementation. Applications that depend on delivery to
multiple QueueReceivers are not portable
This means that a JMS provider is not required to support multiple consumers on the same queue, and that although JMS
providers are allowed to do so, any application which depends on this is not portable.
I think that statement is obsolete now that all modern JMS providers allow multiple consumers on a queue. It is also
anomalous now that JMS 2.0 requires shared subscriptions to allow multiple consumers.
It is therefore proposed that the section above be reworded to state that a queue may have multiple consumers, but that
JMS does not define how messages from a queue are distributed amongst multiple consumers (i.e. there is no requirement
for load-balancing etc).