Hi Jakub, Thanks for your reply. Yes I did find the prefetch model and reran my test and now ran into another issue.
I set the prefetch to 1 and ran the same test described in my earlier mail. In this case the behavior I see is, The 1st consumer gets the 1st message and works on it for a while, the 2nd consumer consumes 8 messages and then does nothing(even though there was 1 more unconsumed message). When the first consumer completed its long running message it got around and consumed the remaining 1 message. However, I was expecting the 2nd consumer to dequeue all 9 messages(the number of remaining messages) while the 1st consumer was busy working on the long message. Then, I thought, perhaps the prefetch count meant that, when a consumer is working on a message, another message in the queue is prefetched to the consumer from the persistant store as my prefetch count is 1. That could explain why I saw the behavior as above. What i wanted to achieve was to actually turn of any kinda prefetching (Yeah, I'm ok with taking the throughput hit) So I re ran my test now with prefetch = 0, and saw a really weird result. With prefetch 0, the 1st consumer gets the 1st message and works on it for a while, which the 2nd consumer consumes 7 messages(why 7?) and then does nothing(even though there were 2 more unconsumed messages). When the 1st consumer completed processing it's message it got to consume the remaining two messages too. (Did it kinda prefetch 2?) Can someone please tell me if Is this a bug or am I doing something completely wrong? I'm using the latest Java Broker & client (from trunk) with DerbyMessageStore for my tests. Also, can someone please tell me what'd be the best way to turn off prefetching? Thanks a lot, Praveen On Wed, Oct 26, 2011 at 3:45 AM, Jakub Scholz <[email protected]> wrote: > Hi Praveen, > > Have you set the capacity / prefetch for the receivers to one message? > I believe the capacity defines how many messages can be "buffered" by > the client API in background while you are still processing the first > message. That may cause that both your clients receive 5 messages, > even when the processing in the first client takes a longer time. > > Regards > Jakub > > On Wed, Oct 26, 2011 at 03:02, Praveen M <[email protected]> wrote: > > Hi, > > > > I ran the following test > > > > 1) I created 1 Queue > > 2) Registered 2 consumers to the queue > > 3) Enqueued 10 messages to the Queue. [ The first enqueued message is > long > > running. I simulated such that the first message on consumption takes > about > > 50 seconds to be processed] > > 4) Once the enqueue is committed, the 2 consumers each pick a message. > > 5) The 1st consumer that got the long running message works on it for a > long > > time while the second consumer that got the second message keeps > processing > > and going to the next message, but only goes as far until it processes 5 > of > > the 10 messages enqueued. Then the 2nd consumer gives up processing. > > 6) When the 1st consumer with the long running message completes, it > then > > ends up processing the remaining messages and my test completes. > > > > So it seems like the two consumers were trying to take a fair share of > > messages that they were processing immaterial of the time it takes to > > process individual messages. Enqueued message = 10, Consumer 1 share of 5 > > messages were processed by it, and Consumer 2's share of 5 messages were > > processed by it. > > > > > > This is kinda against the behavior that I'd like to see. The desired > > behavior in my case is that of each consumer keeps going on if it's done > and > > has other messages to process. > > > > In the above test, I'd expect as consumer 1 is working on the long > message, > > the second consumer should work its way through all the remaining > messages. > > > > Is there some config that I'm missing that could cause this effect?? Any > > advice on tackling this will be great. > > > > Also, Can someone please explain in what order are messages delivered to > the > > consumers in the following cases? > > > > Case 1) > > There is a single Queue with more than 1 message in it and multiple > > consumers registered to it. > > > > Case 2) > > There are multiple queues each with more than 1 message in it, and has > > multiple consumers registered to it. > > > > > > > > Thank you, > > -- > > -Praveen > > > > --------------------------------------------------------------------- > Apache Qpid - AMQP Messaging Implementation > Project: http://qpid.apache.org > Use/Interact: mailto:[email protected] > > -- -Praveen
