We develop NMS product that has been deployed by couple of telecom operators. Our application (uses ActiveMQ) will publish Fault notifications to the Fault Queue, the messages are set to be persistent. These messages are consumed by third party JMS clients. Not all the customers will have a notification client to consume the events(some of the deployments will not have any subscriptions). The question is, does ActiveMQ persist the messages if the queue never had a subscriber connected to the Queue?.
The Broker will persist messages to a Queue regardless of the presence of consumers when the message is tagged as persistent. That is the general contract of the Queue model.
Related
I am running multiple instances of the same Spring Boot 2.0.4 Application, for scaling purposes, that consume messages from an ActiveMQ queue using the following:
#JmsListener(destination = "myQ")
Only the first consumer receives messages and if I stop the first consumer the second instance starts receiving the messages. I want each consumer to consume a message, not the same message, in a round robin fashion. But only the first consumer consumes messages.
It sounds like you want a JMS Topic rather than a Queue. You should also research durable subscriptions, shared subscriptions, and durable topics before you settle on the configuration you need for your setup.
See:
JMS API Programming Model (Search for JMS Message Consumers)
Queues vs Topics
Durable Queues and Topics
What I would like is to run a Message Driven Bean that listens onto a (Websphere MQ7) topic. I would like to deploy my application on a Websphere 8.5.5 Cluster containing two cluster members.
If a message for the topic arrives I would expect that only one of my two MDBs gets the message and process it.
IBM states that I should set identically ClientIds and Subscription Names to ensure that only one instance is able to process a message on a Topic:
http://www-01.ibm.com/support/docview.wss?uid=swg21442559
Will the second MDB receive the mentioned MQRC_SUBSCRIPTION_IN_USE Exception, or will the cluster take care that one and only one MDB in the cluster will consume the topic-message?
Maybe someone can point me to the IBM Documentation where this behaviour is defined.
To allow multiple concurrent instances of an MDB to access the same subscription on an MQ queue manager you can enable "Allow cloned durable subscriptions" in the activation spec for the MDB.
https://www-01.ibm.com/support/knowledgecenter/SSAW57_8.5.5/com.ibm.websphere.nd.doc/ae/umj_pasm.html
Running like this means both instances of the MDB will start (no IN_USE errors) and each message for that single subscription will be processed by one instance of the MDB. You would use this to workload balance messages across the multiple WAS servers.
This is only true for durable subscriptions. And only when the MDB instances are connected to the same queue manager.
We all know using EJB MDB we can consume the messages through Pub/Sub or with P2P. When i saw the comparision usually according to JMS specification, Pub/Sub is using push model and P2P is using Pull model.
Is it true, can't i consume the P2P messages in MDB using push model? Should we do any configuration changes or it is purely an server providers implementation or both.
thanks
You are speaking about difference between Topic and QUeue. So, Pub/Sub it is Topic and P2P it is Queue. Implementing push or pull model depends of server and you cannot change that behavior.
The difference between Pub/Sub and P2P is how the messages are distributed. A message sent to a topic (via Pub/Sub) is distributed to every consumer. A message sent via P2P is sent to one consumer.
The MDB programming model is a push one. Whether this is implemented as push vs pull is down to how the Resource Adapter and messaging system is implemented. WebSphere MQ and the WebSphere Application Server default messaging provider are both able to push messages to the application server for both Pub/Sub and P2P.
I am using a distributed jms queue and weblogic is my app server. There are three jms servers deployed in my clustered enviroment. The producers just send the message using name of queue jndi lookup 'udq' for example. Now I have associated a consumer for each jms server and I was able to consume the message, no problem so far.
Here is question, can I have a single consumer to consume the messages from the 3 jms servers. The weblogic allows jndi naming for destination lookup with following syntax #
qsession1 = qcon1.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
qsession2 = qcon2.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
qsession3 = qcon3.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
queue1 = (Queue)ctx.lookup("JMSServer-1#UDQ");
queue2 = (Queue)ctx.lookup("JMSServer-2#UDQ");
queue3 = (Queue)ctx.lookup("JMSServer-3#UDQ");
qreceiver1 = qsession1.createReceiver(queue1);
qreceiver2 = qsession2.createReceiver(queue2);
qreceiver3 = qsession3.createReceiver(queue3);
qreceiver1.setMessageListener(this);
qreceiver2.setMessageListener(this);
qreceiver3.setMessageListener(this);
qcon1.start();
qcon2.start();
qcon3.start();
I have only one OnMessage implemented for the above consumer. This does not work. Any suggestions please..
No, you can't have a consumer receiving messages from more than one JMS server. A consumer can receive messages from only one JMS server. You need to create multiple consumers to receive messages from multiple JMS servers.
you can use "Queue Forwarding" function.
From online documentation of wls 10.3:
"Queue members can forward messages to other queue members by configuring the Forward Delay attribute in the Administration Console, which is disabled by default. This attribute defines the amount of time, in seconds, that a distributed queue member with messages, but which has no consumers, will wait before forwarding its messages to other queue members that do have consumers."
here a link: http://docs.oracle.com/cd/E13222_01/wls/docs103/jms/dds.html#wp1260816
You can configure this feature from administration of each single queue.
I need to implemt a pulling consumer.
Most of the examples I see are the producer pushing a message to the consumer; Assuming consumer is always up.
I want the producer to push messages to a queue and the consumer to consume those messages on its own schedule.
My consumer has a off hours calender and cannot process requests during off hours.
How would I configure that in spring.
TIA
Raghu
Use message driven POJOs and JMS.
The onMessage is a server push, The message is processed as soon as it is delivered to the client. I want the client to decide when it wants to pull the message and process it.