Samuel Tannous [https://community.jboss.org/people/stannous] created the discussion "EJBException: Failed to acquire the pool semaphore" To view the discussion, visit: https://community.jboss.org/message/731246#731246 -------------------------------------------------------------- Hi Guys, I see that this problem's come up a few times in the past but our scenario is different so I'll raise it again. We're using ActiveMQ in JBoss 6 and are seeing intermittent errors dispatching messages which causes them to be lost (the JMX consolde shows that they've been dequeued but the listener never gets them). There's a good explanation of the "Failed to acquire the pool semaphore" error here: http://stackoverflow.com/questions/7015583/ejbexception-failed-to-acquire... http://stackoverflow.com/questions/7015583/ejbexception-failed-to-acquire... And it sounds simple enough except we're not using prefetch... so my question is, how can this error occur when messages are being polled instead of batched? Our embedded broker url is: vm://myBroker?create=false&*jms.prefetchPolicy.all=0*&jms.alwaysSyncSend=true The ejb3-interceptors-aop.xml MDB config is default (@org.jboss.ejb3.annotation.Pool (value="StrictMaxPool", maxSize=15, timeout=10000)) The message listener is annotated with: @MessageDriven(name = "MyListener", messageListenerInterface = javax.jms.MessageListener.class, activationConfig = {         @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"),         @ActivationConfigProperty(propertyName = "maxSessions", propertyValue = "20"),         @ActivationConfigProperty(propertyName = "destination", propertyValue = "queue/com.myorg.MyQueue") }) The stack's attached: Any help will be greatly appreciated. Cheers Sam -------------------------------------------------------------- Reply to this message by going to Community [https://community.jboss.org/message/731246#731246] Start a new discussion in JBoss Messaging at Community [https://community.jboss.org/choose-container!input.jspa?contentType=1&...]