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From Joe Fernandez <joe.fernan...@ttmsolutions.com>
Subject Re: Question about Queue destinations in network of brokers
Date Wed, 07 Oct 2009 01:48:17 GMT

Hi Farshad,

You may have encountered the following problem:
http://issues.apache.org/activemq/browse/AMQ-2135

It is a rather nasty problem where messages become stuck in one of the NoB's
brokers. That is, a broker does not forward the messages to other brokers in
the NoB that have valid subscriptions. 

Not until you connect a consumer to one of the brokers that houses the stuck
messages, will the broker  dispatch  the message to the consumer. It has to
do with subscription management. 

There is this patch that addresses the problem, but only for
'fully-connected' NoB topologies. 

http://issues.apache.org/activemq/secure/attachment/17800/AMQ-2135-Patch-03182009.patch

If you're using a ring or line topology, the patch won't work and may make
matters worse. 

You may also encounter a situation where some of the brokers’ transport
threads are parked (stuck) on a Java CountDownLatch object and are thus
unable to service their respective transport. A transport in this case is
used to connect two brokers and the message broker assigns a worker thread
to service that transport. When this occurs, the NoB is compromised. Here
are some relevant links for this problem. 

http://www.nabble.com/Network-connector-failover-problems-td10224971.html#a10275742
http://issues.apache.org/activemq/browse/AMQ-1827

Our testing indicated that the above 'parked thread' problem only occurs
with the failover connector. We were never able to reproduce it with the
static connector. 

I would also recommend moving to 5.3 when possible. 

Joe
http://www.ttmsolutions.com


farshad wrote:
> 
> Hi Joe,
> 
> Thank you for your reply.  So, I set dynamicOnly to "true" and networkTTL
> to 4.  The sender code puts messages in the queue and the receiver code
> connects and sometimes it gets all the messages and somtimes it gets some
> of them.  I have to reconnect to get the rest of them.  Also, if I shut
> down the broker that the messages were sent thru, no messages can be
> received.  In my activemq.xml I have one broker definition and then copy
> the same config file into the all broker machines.  Should each broker
> have its own unique broker definition?  What is the use of
> staticallyIncludedQuues?
> 
> Here's my config file:
> 
>  <destinations>
>            <queue physicalName="Document.QUEUE" />
>  </destinations>
> 
> <networkConnector name="myHosts"
> uri="static://(tcp://host1:61616,tcp://host2:61616,tcp://host3:61616,tcp://host4:61616)">
>              networkTTL=4
>              dynamicOnly=true
> </networkConnector>
> 
> <transportConnectors>
>       <transportConnector name="openwire" uri="tcp://localhost:61616"
> discoveryUri="multicast://default"/>
> </transportConnectors>
> 
> Thank you,
> FarshadK
> 
> 
> Joe Fernandez wrote:
>> 
>> You should use the static and not failover connector to configure your
>> network of brokers. Also make sure that you have the appropriate values
>> assigned to the networkTTL and dynamicOnly parameters.  
>> 
>> http://activemq.apache.org/networks-of-brokers.html
>> 
>> Joe
>> http://www.ttmsolutions.com
>> 
>> 
>> 
>> farshad wrote:
>>> 
>>> I have a network of 4 brokers configuration with
>>> failover://(tcp://host1:61616,tcp://host2:61616,...) defined.  My first
>>> piece of java code connects to one of these hosts (randomly) and puts
>>> some messages in a queue destination (e.g. Document.QUEUE).  A second
>>> piece of java code connects to another one of these hosts and fails to
>>> read the messages.  Is this expected behaviour?  If I connect to one
>>> host and put messages in a queue and the host goes down what do I have
>>> to do to receive my messages connecting to another host in the network?
>>> 
>>> Thank you in advance,
>>> FarshadK
>>> 
>> 
>> 
> 
> 

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