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From "James Strachan" <>
Subject Re: Messages in AMQ are randomly not sent?
Date Mon, 16 Apr 2007 07:49:12 GMT
You might want to try synchronizing on the producer just in case.
Otherwise could it just be the timeouts are running out? i.e. your
boxes are running too slowly to be able to deal with the request
timeouts you've got?

On 4/13/07, Luciano Mollea <> wrote:
> Hi all.
> We're experiencing a strange situation here. It seems that randomly AMQ does
> not send a message, this happens depending on the load, this problem seems
> to happen more frequently as more threads concurrently send messages on the
> same queue.
> We're using ActiveMQ 4.1.0 as a standalone process, with AMQ 4.0.2 libraries
> on the client side. This problem has been verified also with 4.1.0
> libraries.
> Our usage scenario is as follows:
> Messages are sent on a single queue; the messages represents requests for
> which a response is expected; there is a timeout for the response; replies
> are waited on a temp-queue. The temp queue is created when the
> connection/session is started the first time; on the temp queue messages are
> consumed via a single MessageListener.
> When the client sends a request, it associates to the JMS Message:
> - a correlation ID (created via a string representing the client name+a
> sequence number <-- this id is created in a synchronized method)
> - the JMSReplyTo setting it to the temp queue.
> The client then insert (synchronizing on the map) the request into an
> hashmap<String, message>, the String key is the correlation id.
> The client then synchronizes on the message and sends the message [*] then
> waits for the reply for a configured timeout.
> When the message listener receives a message from the temp queue, extracts
> the correlation ID (left unchanged by the server) from the message received
> and looks up in the map the pending request, if it finds that, it changes
> the message in the association <correlationid, message> with the reply
> message and then issues a notify on the request message, thus waking up the
> waiting client. If the Message Listener does not find anything in the
> pending map for the correlation id, it simply discard the message.
> The client, when woken up (from a notify of from a wait timeout), removes
> (synchronizedly) from the map the object associated with the correlation id.
> If it's the same message he put before the send, then it is a timeout (no
> response has arrived) and returns with an error, otherwise it extracts the
> response from the message received and returns the result.
> We have used this mechanism some time, but only now when the number of
> requests have increased significantly (300k / hour) as the number of
> concurrent threads sending messages (30-40) we are experiencing a 3-4%
> message loss (timeouts).
> We noticed that the consumer of the request queue does not receive the
> messages that go time-out. I mean: if I send 5000 messages and get 4
> timeouts, i will see that the consumer on the request queue gets only 4996
> messages.
> Any idea about the reason of this problem?
> [*] a thought about this: the send is not synchronized on the sender object
> (that is used multi-threaded) but on the sent message.. could this be the
> cause?
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