concurrentConsumers for an ActiveMQ queue

Question

I try to consume messages from an ActiveMQ queue in grails. I've configured some spring beans for the connection and everything works great so far.

The problem starts when I try to set the concurrentConsumers above 8. It seems that 8 is set as maximum for one client - if I configure more than 8, the ActiveMQ explorer still shows 8 consumers for the queue. If I configure two listeners for different queues with more than 8 concurrentConsumers , the number of consumers shown by ActiveMQ oszillate, but the sum is always 8.

What am I doing wrong? Configuration examples show concurrentConsumers of up to 50...

Here is my configuration, written as groovy DSL, I guess it is no problem to read it...

jmsFactory(org.apache.activemq.pool.PooledConnectionFactory) { bean ->
    bean.destroyMethod = "stop"
    connectionFactory = { org.apache.activemq.ActiveMQConnectionFactory cf ->
        brokerURL = "tcp://localhost:61616"
    }
}
jmsTemplate(org.springframework.jms.core.JmsTemplate) {
    connectionFactory = jmsFactory
}
jmsMessageListener(org.springframework.jms.listener.adapter.MessageListenerAdapter, ref("messageService")) {
    defaultListenerMethod = "onMessage"
}
jmsContainer(org.springframework.jms.listener.DefaultMessageListenerContainer) {
    connectionFactory = jmsFactory
    concurrency="10"
    concurrentConsumers="15"
    destinationName = "demoQueue"
    messageListener = jmsMessageListener
    transactionManager = ref("transactionManager")
    autoStartup = false
}    
jmsMessageListener2(org.springframework.jms.listener.adapter.MessageListenerAdapter, ref("messageService")) {
    defaultListenerMethod = "onMessage2"
}
jmsContainer2(org.springframework.jms.listener.DefaultMessageListenerContainer) {
    connectionFactory = jmsFactory
    destinationName = "demoQueue2"
    messageListener = jmsMessageListener2
    transactionManager = ref("transactionManager")
    autoStartup = false
}    

Answer 1

Since Petter pointed out that it can't be a problem with the ActiveMQ or Spring configuration, I created a spring consumer in java and tried to find the difference to my grails consumer.

The java consumer works as expected, but doesn't use a transaction manager. So I removed the transaction manager from my grails confid and it works!

I then googled a little bit and found a hint to the cacheLevel setting: http://static.springsource.org/spring/docs/2.0.8/api/org/springframework/jms/listener/DefaultMessageListenerContainer.html#setCacheLevel%28int%29

The cacheLevel is set to none when a transaction manager is used - bingo! If I now set the cacheLevel to CACHE_CONSUMER, everything works as expected...