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From "Aaron Riekenberg (JIRA)" <j...@apache.org>
Subject [jira] Created: (AMQ-2149) Shared Filesystem Master Slave: missing messages
Date Fri, 06 Mar 2009 18:04:44 GMT
Shared Filesystem Master Slave: missing messages
------------------------------------------------

                 Key: AMQ-2149
                 URL: https://issues.apache.org/activemq/browse/AMQ-2149
             Project: ActiveMQ
          Issue Type: Bug
    Affects Versions: 5.2.0
         Environment: Ubuntu Linux 8.10 AMD64, Sun JDK 1.6.0.10
            Reporter: Aaron Riekenberg


I'm finding occasionally messages are delivered out-of-order in a shared filesystem master
slave setup when the master fails and the slave takes over.  I'm running a simple test on
one physical machine where the shared filesystem is on a single disk (no SAN currently involved).

I'm attaching a shell script (run_master_slave_brokers.sh) that starts a master and slave
broker in the same directory, sleeps 20 seconds, kills the master, sleeps 20 seconds, starts
a new slave, sleeps 20 seconds, kills the master, etc.

Also attached is a small java test program (MasterSlaveTest.java)  The program starts 10 JMS
senders that send 75kb text messages every 25 ms to unique queues.  These messages contain
a sequence number header (a long).  The program also starts 10 receivers (1 for each queue)
that keep track of the next expected sequence number and validate each incoming sequence number.
 If a receiver gets an unexpected sequence number, the test program exits (System.exit(1)).
 Both the senders and receivers use the failover transport to connect to the broker.  Messages
being sent are persistent, so in theory there should be no message loss when the master fails
and slave takes over.

I run the script to start the brokers, then run my test program.  Most times when the script
kills the master and the slave is promoted, things work fine - the test program reconnects,
and messages continue to be delivered in order.  If I run this long enough though, eventually
my test program fails just after a slave broker is promoted to master with output similar
to this:


Mar 6, 2009 11:58:12 AM org.apache.activemq.transport.failover.FailoverTransport doReconnect
INFO: Successfully reconnected to tcp://localhost:61616
Mar 6, 2009 11:58:12 AM org.aaron.MasterSlaveTest$Receiver onMessage
WARNING: test.queue.3 received 630 expected 629


This indicates the receiver received message 630 after the slave broker took over.  This means
the receiver missed message 629.

This seems to happen more often when more senders and receivers are running and more queues
are in use.  If I run a single sender/receiver pair on 1 queue, it is very difficult to make
this happen.

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