You are viewing a plain text version of this content. The canonical link for it is here.
Posted to users@activemq.apache.org by jcm231 <jc...@dynasty.es> on 2007/06/18 17:56:31 UTC

Problem with message groups

Hi! 

I am have a standalone ActiveMQ server and I am sending messages using a
producer. The messages include the JMSXGroupID header with two different
values: "one" and "two". I launch two Consumer objects, both being threads
and implementing the interface MesageListener. The result is that only one
of the two consumers receives all the messages. Sometimes is the first
consumer and sometimes is the second who receives them all. 

What am I doing wrong? It is the first time I use ActiveMQ and I would thank
any help anybody could give me. 


Thanks in advance.
-- 
View this message in context: http://www.nabble.com/Problem-with-message-groups-tf3941180s2354.html#a11178578
Sent from the ActiveMQ - User mailing list archive at Nabble.com.

Re: Problem with message groups

Posted by James Strachan <ja...@gmail.com>.
On 6/19/07, jcm231 <jc...@dynasty.es> wrote:
>
>
>
> James.Strachan wrote:
> >
> > On 6/18/07, jcm231 <jc...@dynasty.es> wrote:
> >>
> >> Hi!
> >>
> >> I am have a standalone ActiveMQ server and I am sending messages using a
> >> producer. The messages include the JMSXGroupID header with two different
> >> values: "one" and "two". I launch two Consumer objects, both being
> >> threads
> >> and implementing the interface MesageListener. The result is that only
> >> one
> >> of the two consumers receives all the messages. Sometimes is the first
> >> consumer and sometimes is the second who receives them all.
> >>
> >> What am I doing wrong? It is the first time I use ActiveMQ and I would
> >> thank
> >> any help anybody could give me.
> >
> > We don't yet guarrentee an exact round-robin dispatch policy on a per
> > message group basis; consumers tend to eagerly grab as many messages
> > as will fit into their pre-fetch buffer.
> > http://activemq.apache.org/what-is-the-prefetch-limit-for.html
> >
> > to mimick round-robin, try setting the prefetch to 1 on both
> > consumers; or try using thousands of messages
> >
> >
> >
> >
> > --
> > James
> > -------
> > http://macstrac.blogspot.com/
> >
> >
>
>
> I have sent 34000 messages but they all get consumed by the same consumer.
>
>
> I tried to specify the prefetchSize as indicated in:
>
> http://activemq.apache.org/what-is-the-prefetch-limit-for.html
>
> but I am not creating the ActiveMQQueue on the consumer's code but on the
> xml file. So I put this on my activemq.xml file:
>
>
>   <!-- Destination -->
>   <bean id="destination" class="org.apache.activemq.command.ActiveMQQueue">
>     <constructor-arg>
>
> <value>example.MyQueue?consumer.prefetchSize=1;consumer.exclusive=false</value>
>     </constructor-arg>
>   </bean>
>
> but it seems not be effective.

Creating a queue does nothing, unless you actually use it in your JMS
client (e.g. to consume from)

If you're struggling to set the prefetch groups; try sending say
50,000 messages to group 1, then start mixing 1 and 2; then the first
consumer will get its pre-fetch buffer filled with the first group; so
it won't grab group 2. (Or have lots of groups)

-- 
James
-------
http://macstrac.blogspot.com/

Re: Problem with message groups

Posted by jcm231 <jc...@dynasty.es>.


James.Strachan wrote:
> 
> On 6/18/07, jcm231 <jc...@dynasty.es> wrote:
>>
>> Hi!
>>
>> I am have a standalone ActiveMQ server and I am sending messages using a
>> producer. The messages include the JMSXGroupID header with two different
>> values: "one" and "two". I launch two Consumer objects, both being
>> threads
>> and implementing the interface MesageListener. The result is that only
>> one
>> of the two consumers receives all the messages. Sometimes is the first
>> consumer and sometimes is the second who receives them all.
>>
>> What am I doing wrong? It is the first time I use ActiveMQ and I would
>> thank
>> any help anybody could give me.
> 
> We don't yet guarrentee an exact round-robin dispatch policy on a per
> message group basis; consumers tend to eagerly grab as many messages
> as will fit into their pre-fetch buffer.
> http://activemq.apache.org/what-is-the-prefetch-limit-for.html
> 
> to mimick round-robin, try setting the prefetch to 1 on both
> consumers; or try using thousands of messages
> 
> 
> 
> 
> -- 
> James
> -------
> http://macstrac.blogspot.com/
> 
> 


I have sent 34000 messages but they all get consumed by the same consumer. 


I tried to specify the prefetchSize as indicated in:

http://activemq.apache.org/what-is-the-prefetch-limit-for.html

but I am not creating the ActiveMQQueue on the consumer's code but on the
xml file. So I put this on my activemq.xml file:


  <!-- Destination -->
  <bean id="destination" class="org.apache.activemq.command.ActiveMQQueue">    
    <constructor-arg>
     
<value>example.MyQueue?consumer.prefetchSize=1;consumer.exclusive=false</value>
    </constructor-arg>    
  </bean>

but it seems not be effective.



On the class that launches the consumers, I am getting the queueReceiver via
JNDI, so maybe the way I indicate the prefetch size is wrong, I do not know:




      try {
        queueConnectionFactory = (QueueConnectionFactory)
jndiContext.lookup("jms/MYQUEUE");
        queue = (Queue) jndiContext.lookup(queueName);
      } catch (NamingException e) {
        System.out.println("JNDI API lookup failed: " + e.getMessage());
        System.exit(1);
      }
      
      
      try {
        queueConnection =
queueConnectionFactory.createQueueConnection("User", "Password");
        queueSession = queueConnection.createQueueSession(false,
Session.AUTO_ACKNOWLEDGE);
        queueReceiver = queueSession.createReceiver(queue);
        
        // Creating two consumers
        Consumer cons1 = new Consumer("cons1");
	Consumer cons2 = new Consumer("cons2");
        
        
        // Setting cons1 as listener
        queueReceiver.setMessageListener(cons1);
        
        
        // Setting cons2 as listener
        queueReceiver.setMessageListener(cons2);
        
        
        
        new Thread(cons1).start();
        new Thread(cons2).start();
            
        queueConnection.start();
        
                
 
      } catch (JMSException e) {
        System.out.println("Exception ocurred: " + e.getMessage());
      } 


cons1 and cons2 implement Runnable and MessageListener but only one of them
is receiving the messages.

The idea is to use the message groups feature of ActiveMQ for our project,
because we need to assure that all the messages with the same id (in the
JMSXGroupId header) are consumed by the same consumer. Could be using
selectors a better aproach? How can I get message groups working?




-- 
View this message in context: http://www.nabble.com/Problem-with-message-groups-tf3941180s2354.html#a11191679
Sent from the ActiveMQ - User mailing list archive at Nabble.com.

Re: Problem with message groups

Posted by James Strachan <ja...@gmail.com>.
On 6/18/07, jcm231 <jc...@dynasty.es> wrote:
>
> Hi!
>
> I am have a standalone ActiveMQ server and I am sending messages using a
> producer. The messages include the JMSXGroupID header with two different
> values: "one" and "two". I launch two Consumer objects, both being threads
> and implementing the interface MesageListener. The result is that only one
> of the two consumers receives all the messages. Sometimes is the first
> consumer and sometimes is the second who receives them all.
>
> What am I doing wrong? It is the first time I use ActiveMQ and I would thank
> any help anybody could give me.

We don't yet guarrentee an exact round-robin dispatch policy on a per
message group basis; consumers tend to eagerly grab as many messages
as will fit into their pre-fetch buffer.
http://activemq.apache.org/what-is-the-prefetch-limit-for.html

to mimick round-robin, try setting the prefetch to 1 on both
consumers; or try using thousands of messages


-- 
James
-------
http://macstrac.blogspot.com/