4 Replies Latest reply on Sep 9, 2001 6:48 AM by Lars Olsson

    Creating destinations on the fly.....

    Lars Olsson Newbie

      The JBOSS manual has the following to say about programmatic creation of destinations:

      > Destinations may also be added on the fly, but the
      > API has changed slightly. In 2.5.x destinations
      > created this way will however only live as long as
      > the server is up. When the JBoss server is rebooted,
      > the dynamically created destinations will be gone.

      I have written my owner deployer client application
      that calls the JMSServer Mbean and the Deployer Mbean
      to create destinations and deploy the application
      using the destinations. The code that calls the
      JMSServer mbean has logic like this:

       1) Parse ejb-jar.xml and extract info about destinations.
       2) For each destination found in ejb-jar.xml DO
       If destination can not be found in JNDI
       Call JMSServer mbean to create it
      


      I want my destinations (queues) to be persistent,
      but the comment in the manual seems to imply that
      I cannot count on the queues being persisten across
      server restarts in the future. Is that really the
      case?

      Will I have to modify my deployer to write into
      the jboss.jcml file?

       1) Parse ejb-jar.xml and extract info about destinations.
       2) For each destination found in ejb-jar.xml DO
       If destination can not be found in JNDI
       Write dest entry to jboss.jcml :-(
       3) Make server re-read jboss.jcml?????
      



        • 1. Re: Creating destinations on the fly.....
          Peter Antman Expert

          The MDB already work this way, if destination does not exist, it is created (and removed when undeployed).

          If nothing has changed recently, destination created through the MBean interface will be removed when server is restarted. Yes. Hiram, is this still correct?

          In 3.0 you will however be able to deploy destinations through the new MLet *.sar deployment chema.

          //Peter

          • 2. Re: Creating destinations on the fly.....
            Lars Olsson Newbie

            I understand that the MDB can be removed when it is not
            consuming messages. That is OK. But I don't want the
            queue itself to go away just because the server is
            stopped and then restarted.

            Assume for the sake of argument that the JBOSS server
            is "empty" - there are no JMS destination in it and there
            are no applications deployed into it.

            If I then run my deployment client application, this
            application will talk to the JMSServer mbean to create
            queues and the Deployer MBean to deploy the actual
            EJB application. Let's say that it consists of a
            stateless session bean A and a message driven bean B
            connected by a queue Q:

             A --> ----> B
             ! !
             ----> Q ---
            


            Initially Q is empty.

            Now a client calls a business method in A. In this
            business method, which uses container managed
            transaction support, a data item is written to the
            queue Q. After the business method returns the
            container will commit the operation so that the data
            item really ends up in the persistent queue Q.
            Then something bad happens (power failure) and the
            JBOSS server is terminated.

            When the JBOSS server is restarted it would be nice
            if the data item was still in the queue so that B
            can consume it. But if I understand the JBOSS docs
            correctly, the queue Q will not even be around anymore
            in Jboss 2.5.x because the queue was created
            programatically.

            Why will Jboss 2.5.x not keep programmatically
            created queues across server restarts?

            Lars


            • 3. Re: Creating destinations on the fly.....
              Hiram Chirino Expert

              The problem is that when when we had the jbossmq.xml file, we would update it to reflect addtions of queues and such. With us getting rid up the jbossmq.xml file and loading all the config info from jboss.jcml, we no longer update the config file to reflect the addition of the queue.

              Long term, I think we will move to creating a *.sar style configuration for configuring queues/topics as that would allows us to add and remove queue configurations verry easily.

              Regards,
              Hiram

              • 4. Re: Creating destinations on the fly.....
                Lars Olsson Newbie

                Thanks for your reply.

                So it seems my deployer app will have to try to update
                the jboss.jcml file. While I am slightly disturbed by
                this I suppose that this can be done. At least it
                should be fairly easy to write code that adds entries
                to jboss.jcml.

                But is this safe? Does the JBOSS server survive
                if this file is changed while the server is running?

                Are there ways to tell a running JBOSS server that
                it should re-read the file to pick up the most
                recent changes? It would be a nuisance to have to
                stop and restart the entire server just because
                one queue / topic entry has been added to the file.

                Lars