Ok, if that's the case I seem to have completely missed the point of Message Grouping. It states that the following semantics are applied according to the description in the "Impliations" section here http://activemq.apache.org/message-groups.html.
# partioning the traffic # load balancing of message groups across consumers Doesn't this mean that I can have multiple instances of my MDBs, each in its own thread, consuming a message off of the queue? In other words, won't Active MQ give the next message to whatever consumer requests a message? So, can't I have message 1 read from the queue, and while that transaction is processing, another node reads and begins processing message 2 BEFORE the transaction commits for the message 1 read? Otherwise, it becomes a sequential consumer, which I don't want. I need the ability to process multiple messages concurrently across multiple nodes, but just have them ordered in the same way on the output queue as they were when they were inserted into the input queue. Ordering off of the input queue is not as important, only that they end up in order when they are put in the output queue, which I thought I could do by copying the message sequence number. I guess my problem boils down to I'm having trouble distinguishing between normal grid processing where multiple MDB instances read from a JMS queue, and multiple MDB instances attempting to read from the same queue group in Active MQ. Here would be my current understanding of what you described. Thank you for your patience with me, I'll eventually get this through my thick skull, if I only had a virtual white board this would be much easier.... What I thought the documentation said. FileReader1 -> Creates message on input queue group named "Biz1-ISODate" --> Multiple MDB threads processing at the same time, but each MDB thread gets a new message AFTER the previous message has been read by an MDB (so we get concurrent processing)-> Creates message on output queue group named "Biz1-ISODate" --> Single threaded consumer receives messages in order. What I understand from your post. FileReader1 -> Creates message on input queue group named "Biz1-ISODate" --> A single MDB thread processing one message at a time sequentially (for single threaded processing) -> Creates message on output queue group named "Biz1-ISODate" --> Single threaded consumer receives messages in order. Which one is correct? Thanks again for your help. Todd James.Strachan wrote: > > On 4/12/07, tnine <[EMAIL PROTECTED]> wrote: >> >> Let me give a clearer example. Lets say I have 4 "real" messages, that >> contain data. I have a 5th message that contains no data but closes the >> group on the input queue. I need to replicate the order of items from >> the >> input queue to the order on the output queue because the consumer of the >> output queue needs to know when the group is finished in order to flush >> the >> output file to the system. Here is the scenario I was describing >> explained >> a bit clearer, (I hope since I included a bit of source) >> >> Step 1: messages 1 through 3 are processed normally and put on the output >> queue. >> Step 2: message 4 begins processing, then message 5, the "close group" >> message gets processed simultaneously. Message 5 will most likely be >> inserted on the output queue before message 4 since there will be no >> processing of the closing message. > > > So here's the cool thing about Message Groups. The contract is 1 > thread in the entire cluster of processes & threads gets the messages > for a single message group. So you will always process message 4 > first, then message 5. So there will be no out-of-order issues. Cool > eh? :) > > -- > > James > ------- > http://radio.weblogs.com/0112098/ > > -- View this message in context: http://www.nabble.com/Input-queue-and-output-queue-grouping-and-sequences-question-tf3554541s2354.html#a9964482 Sent from the ActiveMQ - User mailing list archive at Nabble.com.
