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From "Dejan Bosanac (JIRA)" <j...@apache.org>
Subject [jira] Commented: (AMQ-2149) Shared Filesystem Master Slave: missing messages
Date Fri, 13 Mar 2009 14:10:39 GMT

    [ https://issues.apache.org/activemq/browse/AMQ-2149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=50519#action_50519
] 

Dejan Bosanac commented on AMQ-2149:
------------------------------------

Hi Aaron,

I'm not sure why it happens in this case and it definitely should not send messages processed
long time ago. All I can recommend at the moment is that if you receive duplicates in your
real-world application, you should deal with them in your consumer. Shutting down the master
every 20 sec or so, after all, isn't something you'll have in your production environment.
We'll of course try get to the root of the problem and make it work even in this use case.

> 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
>         Attachments: activemq.log, activemq.log.2009_03_12_1, activemq.log.2009_03_12_2,
activemq.xml, AMQ-2149.zip, MasterSlaveTest.java, MasterSlaveTestWithTransactions.java, run_master_slave_brokers.sh
>
>
> I'm finding occasionally messages are not delivered in 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 for test.queue.3 received message 630 after the slave broker
took over and 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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