WL 8.1 - JMS Flow Control: How does it work

Question

I have been reading the documenattion on the way weblogic has its Flow
          Control setup. However I still have a few doubts. It would be great
          if some one can help.
          Background: I have a J2EE application deployed on the weblogic server
          (8.1 sp5) which connects as a Consumer to a Topic. On the other side I
          have a plain java application that acts as a producer and sends lots
          of small messages (about 300 bytes) out to the topic using
          MessageProducer.send() method.
          I would like to restrict the flow from this producer so that it waits
          if the consumers are unable to collect all messages from the topic.
          When I enable flow control, I can see log entries in my weblogic
          application that shows that it has beocme armed but it clears off the
          same second. However, I don't see any exceptions being raised at the
          producer side. How can I ensure that the producer is waiting x ms to
          send further messages across. I can't see anything at the producer
          side that would lead me to believe that the flow control is working. I
          also checked the properties for each of teh Session, Connection and
          COnnectionFactory attributes but could not come across any way where I
          could see that the producer knows about the quotas being implemented
          on the queue.
          Can someone throw some light?
          Thanks
          Vikash

Answer 1

Hi,
          Except for the threshold log messages you mention, flow control is silent: no exceptions are thrown when a producer is flow controlled. Flow control simply slows down "send()" calls. You can control how long a flow controlled send() call will take via the connection factory settings. I suppose you can instrument your code to time the send() calls.
          Your statement "When I enable flow control, I can see log entries in my weblogic application that shows that it has beocme armed but it clears off the same second." is likely an indicator that flow control is working. You need to configure your thresholds to be farther apart if you want the flow control condition to last longer, and if you want to reduce the number of transitions in and out of flow-control.
          Tom
          P.S. The threshold settings in 8.1 also control paging. If you upgrade to a new version, then the threshold settings will only control flow-control. You will also likely get much much higher messaging performance - which can reduce the need for flow control.