1 Reply Latest reply on Oct 5, 2005 2:02 PM by Tim Fox

    Issues with message delivery

    Tim Fox Master

      We have a set of fairly major issues in the way message delivery and redelivery is currently implemented in JBoss Messaging.

      I have captured the issues in a set of tests, TransactedSessionTest, testRedel 1-6

      They are probably the best description of the problems.

      One of the issues is a follows:

      1. Send 3 messages m1, m2, m3 in a transacted session

      2. Receive m1 only in the same session using consumer1

      3. commit the session

      4. Try and receive m2, m3 in the same session using new consumer2.

      Expected result is that m2 and m3 are received, in fact they're not.

      This is because messages m2 and m3 are left sitting in the client side callbackhandler buffer.
      When the tx commits, deliveries are left hanging in the corresponding severconsumerdelegate.

      All the other issues are related but subtly different.

      In order to resolve this, we need to do something like the following:

      On commit:

      1. Process acks and sends as normal

      2. Any outstanding deliveries remaining any any serverconsumerdelegates enlisted in the tx represent messages that were either received by the client and not acked OR got sent to the client side message callbackhandler but never got received by the client. (I.e. they just sat in the buffer).
      These should all be cancelled.

      3. Clear the client side message callbackhandler buffers for any consumers enlisted in the tx.

      4. Call deliver() on the channel.

      On rollback/recover:

      We must redeliver any messages that were received by the client but not acked by the client.
      This set is given by the set of deliveries in the serverconsumerdelegate MINUS the messages in the messagecallbackhandler buffer - we do not want to redeliver these.

      1. Cancel only the deliveries corresponding to the message still remaining in the messagecallbackhandler buffers.

      2. Any remaining deliveries represent those received by the client but not acked. These must be redelivered (NOTE we are NOT calling channel.deliver() since this delivers any unacked messages).
      Unfortunately the current redeliver() method only redelivers to the same receiver, but in our case it may be a different receiver - we need to change this.

      3. Now call deliver() this will cause the messages that were in the client side buffer to be redelivered.

      NOTE we may have a message ordering problem here.





        • 1. Re: Issues with message delivery
          Tim Fox Master

          So, in more detail, to fix this we need to:

          Maintain a set of the receivers receiving ("enlisted") in the tx in JBossXAResource.

          This can be added to the set when the messagecallbackhandler is created by adding a new method registerReceiverID(String) to the sessoin delegate.

          This can be intercepted by the tx interceptor who can add it to the set.

          The TxInfo class should be extended to support ONE_PHASE_ROLLBACK which currently does not cause a server call, we need to change it so it does.

          We need to extend the TxState to include the set of receiver ids

          We need to amend JBossConnectionConsumer to register the receiving sessions privelged receiver with the tx.

          We can get rid of getAsfReceiverID - no longer required.

          We need to amend SessionDelegate.redeliver to take a set of receiver ids as a parameter

          We need to remove the calls to redeliver that are currently made explicitly from the client side.

          We need to add code to inspect the message consumer buffers and send that info in the tx request too.

          We need to amend serverconnectiondelegate to cancel, redeliver, deliver as appropriate.

          And probably a few other little bits and pieces.

          We need to amennd the deliveryobserver.redeliver method.