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From ajls77 <ajlstu...@gmail.com>
Subject Messages appear to get lost
Date Tue, 27 Nov 2007 14:07:38 GMT

I am sending messages to an ActiveMQ broker from an Java5 ExecutorService
thread pool.  Concurrency requirements at the moment require at least 60
MessageProducers - these, along with a Session, live in a thread-safe FIFO
pipe. 

When concurrency hots up, it appears that some messages are being lost -
from the client's perspective it appears to have been delivered, but the
debugging output on the broker does not provide a receipt of the message
(the message delivery is set to PERSISTENT just to get the debugging as
there is no debugging information under NON_PERSISTENT).

To prove that the client thinks the message is delivered I recompiled
activemq-core-4.1.1.jar with extra debugging.  I traced the following
execution flow:

ActiveMQMessageProducer.send()
-> ActiveMQSession.send()
 -> TcpTransport.oneway()
   -> TcpBufferedOutputStream.flush()

The output of which is:

DEBUG: org.apache.activemq.ActiveMQSession - sending message with messageID:
ID:ukedfrog-3905-1196171536066-1:5:1:1:54 Thread:
Thread[pool-1-thread-493,5,main]
DEBUG: org.apache.activemq.ActiveMQSession - Sending message:
ActiveMQTextMessage {commandId = 0, responseRequired = false, messageId =
ID:ukedfrog-3905-1196171536066-1:5:1:1:54, originalDestination = null,
originalTransactionId = null, producerId =
ID:ukedfrog-3905-1196171536066-1:5:1:1, destination =
queue://urn:telelogic:ers:two, transactionId = null, expiration = 0,
timestamp = 1196171643911, arrival = 0, correlationId = null, replyTo =
queue://reply-192.168.68.151@urn:telelogic:ers:two, persistent = true, type
= null, priority = 4, groupID = null, groupSequence = 0, targetConsumerId =
null, compressed = false, userID = null, content = null,
marshalledProperties = null, dataStructure = null, redeliveryCounter = 0,
size = 0, properties = null, readOnlyProperties = true, readOnlyBody = true,
droppable = false, text = messageContent}
DEBUG org.apache.activemq.transport.tcp.TcpBufferedOutputStream calling
flush - messageID: ID:ukedfrog-3905-1196171536066-1:5:1:1:54 count: 116
OutputStream: java.net.SocketOutputStream@94124f
DEBUG org.apache.activemq.transport.tcp.TcpTransport flushing bytes -
messageID:ID:ukedfrog-3905-1196171536066-1:5:1:1:54 Thread:
Thread[pool-1-thread-493,5,main]

(The messageID is propagated to the activemq classes via a ThreadLocal)

My understanding is that after TcpBufferedOutputStream.flush() the TCP
packet is delegated to the underlying operating system and the message has
effectively been "sent".  However, there is no receipt of this message in
the broker, no matter how long we wait.  Is this message "lost" ? or is my
client implementation faulty.

I am using one Connection per JVM and used by each thread (with its own
MessageProducer & Session). After reading 
http://gnodet.blogspot.com/2006/12/over-past-weeks-i-spend-some-times-load.html
this  , I tried using a separate Connection per thread, but the problem
persisted.  This write-up concerns me  (that the broker processes all
messages on a given Connection sequentially)  as this would force the client
implementation to have multiple Connections which does not seem to be
mandated by the JMS spec.  


My ConnectionFactory is configured to use synchronous sending via
"connectionFactory.setUseAsyncSend(false);"

Could anybody explain why these message appear to be "lost"? It seems, from
client perspective, that the message has been delivered, but it never is.

Many thanks
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