I have made a change to the client on trunk that should result in it now doing what you want when using prefetch=1 on transacted sessions when using onMessage().
Robbie On 28 October 2011 02:25, Robbie Gemmell <[email protected]> wrote: > Ok, I havent actually tried this yet, but after sneaking a look at the > code I am pretty sure I see a problem in the client specific to > transacted AMQP 0-10 sessions with prefetch=1 that would cause the > behaviour you are seeing. I'll look into it at the weekend. Time for > sleep, before 3am comes along ;) > > Robbie > > On 28 October 2011 01:18, Praveen M <[email protected]> wrote: >> Hi Robbie, >> >> I was testing against trunk, and also, I was calling commit after my >> simulated processing delay, yes. >> >> Thanks, >> Praveen >> >> On Thu, Oct 27, 2011 at 5:11 PM, Robbie Gemmell >> <[email protected]>wrote: >> >>> Just to be clear for when I look at it...were you using trunk or 0.12 >>> for those tests, and presumably you were calling commit after your >>> simulated processing delay? >>> >>> Robbie >>> >>> On 28 October 2011 00:28, Praveen M <[email protected]> wrote: >>> > Hi Robbie, >>> > >>> > I was using asynchronous onMessage delivery with transacted session for >>> my >>> > tests. >>> > >>> > So from your email, I'm afraid it might be an issue. It will be great if >>> you >>> > could investigate a little on this and keep us update. >>> > >>> > Thanks a lot, >>> > Praveen >>> > >>> > On Thu, Oct 27, 2011 at 11:49 AM, Robbie Gemmell >>> > <[email protected]>wrote: >>> > >>> >> From the below, would I be right in thinking you were using receive() >>> >> calls with an AutoAck session? If so then you would see the behaviour >>> >> you observed as the message gets acked just before receive() returns, >>> >> which makes the broker send the next one to the client. That shouldnt >>> >> happen if you were using asynchronous onMessage delivery (since the >>> >> ack gets since when the onMessage() handler returns), or if you you >>> >> used a ClientAck or Transacted session in which you only acknowledged >>> >> the message / commited the session after the processing is complete. >>> >> >>> >> I must admit to having never used the client with prefetch set to 0, >>> >> which should in theory give you what you are looking for even with >>> >> AutoAck but based on your comments appears not to have. I will try and >>> >> take a look into that at the weekend to see if there are any obvious >>> >> issues we can JIRA for fixing. >>> >> >>> >> Robbie >>> >> >>> >> On 26 October 2011 23:48, Praveen M <[email protected]> wrote: >>> >> > 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 >>> >> > >>> >> >>> >> --------------------------------------------------------------------- >>> >> Apache Qpid - AMQP Messaging Implementation >>> >> Project: http://qpid.apache.org >>> >> Use/Interact: mailto:[email protected] >>> >> >>> >> >>> > >>> > >>> > -- >>> > -Praveen >>> > >>> >>> --------------------------------------------------------------------- >>> Apache Qpid - AMQP Messaging Implementation >>> Project: http://qpid.apache.org >>> Use/Interact: mailto:[email protected] >>> >>> >> >> >> -- >> -Praveen >> > --------------------------------------------------------------------- Apache Qpid - AMQP Messaging Implementation Project: http://qpid.apache.org Use/Interact: mailto:[email protected]
