On Mar 15, 2007, at 9:02 PM, Glenn Owen wrote:
I'm sure I should have learned this in MDB 101, but I'll ask here
anyway.
I have an MDB that reads incoming messages, does a bunch of work, and
then writes data to another outgoing JMS Queue.
As the load increases, Geronimo will create multiple instances of the
MDB and I was getting exceptions after about the 10th instance,
because
I could not get enough outgoing Queue connections.
Originally each MDB was looking up the outgoing connection factory and
queue and creating a connection,session,producer in onMessage().
But since I was getting the above error, I modified it to get the
outgoing connection factory,queue and connection in ejbCreate() and
holding onto those is *static* variables, so all instances of the MDB
shared the same connection.
The onMessage() still gets it's own session and producer.
That solved my problem, but I'm not sure it is "right".
It is OK to share the factory/queue/connection across multiple
instances
of an MDB?
It might possibly work for activemq if you don't use any
transactions, but if you use transactions I would expect it to
completely break and give pretty random behavior. I don't think
there's any reason to expect it to work even without transactions.
I have trouble keeping all the places you can configure sizes
straight, but one way to limit the number of active mdbs is to give
the inbound resource adapter its own thread pool and limit that
size. I think there's a more direct way but don't recall what it is.
If the number of outbound connections is at least the number of mdbs
I would expect you wouldn't run into problems.
Maybe someone with more actual experience can give some more informed
advice.
thanks
david jencks
