On Wed, 2004-02-04 at 20:02, Barlow, Dustin wrote:
> Adrian Brock wrote:
> > The key contraint is the <MaximumSize> in the proxy config. This
> > configures a pool of jms sessions that deliver messages to the mdb
> > container. Once these are all used, no messages will be delivered
> > until an mdb finishes its invocation/transaction.
> 
> One other thing I forgot to mention in my last post is that <MaximumSize> on
> the proxy-invoker doesn't appear to be the only thing that constrains
> invocations of MDBs.  A while back, you and I had a discussion here about
> doing a singleton MDB.  Setting the MaxSize and MaxMessages to 1 in the
> proxy-binding wasn't enough to ensure that only one MDB fires at time and
> that the next message on the queue only fires when the prior fully commits
> it's work.
> 
> The behaviour actually was that if the container-configuration wasn't set
> the pool size to 1, then a MDB would fire even though the prior MDB had not
> fully committed the transaction yet.  This had to do with the read-ahead
> optimization done by the container and could basically be choked off by
> setting the container-configuration pools to 1 as well.
> 

I remember the discussion, but I don't remember that conclusion.
The MDB instance is returned to the pool after onMessage() completes,
which is before the jms session is made available to the next message. 
I don't see how it would have an affect?

jms -> session pooling -> session -> invoker -> mdb pooling -> mdb

We were discussing why limiting the mdb pool didn't work.

> So I'm wondering read-ahead optimization is why 100 is the default size
> container-config pool instead of mirroring the 15 max setting of the
> proxy-invoker.
> 

That is probably just historical. The MDB container config is very
similar to stateless session beans and was probably copied from it.

Typically only 15 mdb instances will be used. I say typically because
you can attach multiple invoker-proxy-bindings to a container and
deliver messages from multiple jms destinations.

Regards,
Adrian

> Dustin
> 
> 
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