{"id":26059,"date":"2014-06-04T19:00:10","date_gmt":"2014-06-04T16:00:10","guid":{"rendered":"http:\/\/www.javacodegeeks.com\/?p=26059"},"modified":"2014-06-05T10:35:52","modified_gmt":"2014-06-05T07:35:52","slug":"activemq-network-of-brokers-explained-part-4","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2014\/06\/activemq-network-of-brokers-explained-part-4.html","title":{"rendered":"ActiveMQ – Network of Brokers Explained – Part 4"},"content":{"rendered":"

In the previous part 3<\/a> , we have seen how ActiveMQ helps distinguish remote consumers from local consumers which helps in determining shorter routes from message producers to consumers.<\/p>\n

In this part 4, we will look into how to load balance concurrent consumers on remote brokers.<\/p>\n

Let\u2019s consider a bit more advanced configuration to load balance concurrent message consumers on a queue in remote brokers as shown below.
\n 
\n <\/p>\n\n\n\n\n
\"part-4-lb-rcc<\/a><\/td>\n<\/tr>\n
Part 4 – Network of brokers<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

In the above configuration, we have a message producer sending messages into a queue moo.bar on broker-1. Broker-1 establishes network connectors to broker-2 and broker-3. Consumer C1 consumes messages from queue moo.bar on broker-2 while consumers C2 and C3 are concurrent consumers on queue moo.bar on broker-3.<\/p>\n

Let’s see this in action<\/h2>\n

Let’s create three brokers instances…<\/p>\n

    \n
  1. Ashwinis-MacBook-Pro:bin akuntamukkala$ pwd\/Users\/akuntamukkala\/apache-activemq-5.8.0\/bin<\/li>\n
  2. Ashwinis-MacBook-Pro:bin akuntamukkala$.\/activemq-admin create ..\/cluster\/broker-1<\/li>\n
  3. Ashwinis-MacBook-Pro:bin akuntamukkala$.\/activemq-admin create ..\/cluster\/broker-2<\/li>\n
  4. Ashwinis-MacBook-Pro:bin akuntamukkala$.\/activemq-admin create ..\/cluster\/broker-3<\/li>\n
  5. Fix the broker-2 and broker-3 transport, amqp connectors and jetty http port by modifying the corresponding conf\/activemq.xml and conf\/jetty.xml as follows:
    \n <\/p>\n\n\n\n\n\n\n
    Broker<\/th>\nOpenwire Port<\/th>\nJetty HTTP Port<\/th>\nAMQP Port<\/th>\n<\/tr>\n
    broker-1<\/td>\n61616<\/td>\n8161<\/td>\n5672<\/td>\n<\/tr>\n
    broker-2<\/td>\n61626<\/td>\n9161<\/td>\n5682<\/td>\n<\/tr>\n
    broker-3<\/td>\n61636<\/td>\n10161<\/td>\n5692<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

     <\/li>\n

  6. Fix network connector on broker-1 such that messages on queues can be forwarded dynamically to consumers on broker-2 and broker-3. This can be done by adding the following XML snippet into broker-1’s conf\/activemq.xml\n
    <networkConnectors>\r\n    <networkConnector\r\n\r\n      name=\"Q:broker1->broker2\"\r\n\r\n      uri=\"static:(tcp:\/\/localhost:61626)\"\r\n\r\n      duplex=\"false\"\r\n\r\n      decreaseNetworkConsumerPriority=\"true\"\r\n\r\n      networkTTL=\"2\"\r\n\r\n      dynamicOnly=\"true\">\r\n\r\n      <excludedDestinations>\r\n\r\n         <topic physicalName=\">\" \/>\r\n\r\n      <\/excludedDestinations>\r\n    <\/networkConnector><\/pre>\n
        <networkConnector\r\n\r\n       name=\"Q:broker1->broker3\"\r\n\r\n       uri=\"static:(tcp:\/\/localhost:61636)\"\r\n\r\n       duplex=\"false\"\r\n\r\n       decreaseNetworkConsumerPriority=\"true\"\r\n\r\n       networkTTL=\"2\"\r\n\r\n       dynamicOnly=\"true\">\r\n\r\n       <excludedDestinations>\r\n\r\n            <topic physicalName=\">\" \/>\r\n\r\n       <\/excludedDestinations>\r\n\r\n    <\/networkConnector>\r\n\r\n<\/networkConnectors><\/pre>\n<\/li>\n
  7. \u00a0Start broker-2, broker-3 and broker-1. We can start these in any order.\n
      \n
    1. \/apache-activemq-5.8.0\/cluster\/broker-3\/bin$ .\/broker-3 console<\/b><\/li>\n
    2. \/apache-activemq-5.8.0\/cluster\/broker-2\/bin$ .\/broker-2 console<\/b><\/li>\n
    3. \/apache-activemq-5.8.0\/cluster\/broker-1\/bin$ .\/broker-1 console<\/b><\/li>\n<\/ol>\n
    4. Let’s start the consumers C1 on broker-2 and C2, C3 on broker-3 but on the same queue called “moo.bar”\n
        \n
      1. \/apache-activemq-5.8.0\/example$\u00a0ant consumer -Durl=tcp:\/\/localhost:61626 -Dsubject=moo.bar<\/b><\/li>\n
      2. \/apache-activemq-5.8.0\/example$ ant consumer -Durl=tcp:\/\/localhost:61636 -Dsubject=moo.bar -DparallelThreads=2
        \n
        \n
        \nThe consumer subscriptions are forwarded by broker-2 and broker-3 to their neighboring broker-1 which has a network connector established to both broker-2 and broker-3 by the use of advisory messages.\u00a0<\/i>
         
        <\/div> <\/div><\/p>\n<\/blockquote>\n<\/li>\n<\/ol>\n
      3. Let’s review the broker web consoles to see the queues and corresponding consumers.\n
          \n
        1. We find that broker-2’s web console shows one queue “moo.bar” having 1 consumer, broker-3’s web console shows one queue “moo.bar” having 2 concurrent consumers<\/li>\n
        2. Though there are three consumers (C1 on broker-2 and C2,C3 on broker-3), broker-1 sees only two consumers (representing broker-2 and broker-3).\n
           <\/p>\n\n\n\n\n
          \"part4-broker1-wc-cf\"<\/a><\/td>\n<\/tr>\n
          http:\/\/localhost:8161\/admin\/queues.jsp<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
           
          \n\"part4-broker1-consumers\"<\/a><\/li>\n
        3. \n
          \n
          This is because the network connector from broker-1 to broker-2 and to broker-3 by default has a property “conduitSubscriptions” which is true.
          \nDue to which broker-3’s C2 and C3 which consume messages from the same queue “moo.bar” are treated as one consumer in broker-1.<\/i><\/p>\n<\/blockquote>\n<\/li>\n<\/ol>\n
        4. Let’s produce 30 messages into broker-1’s queue moo.bar and see how the messages are divvied among the consumers C1, C2 and C3:
          \n <\/p>\n\n\n\n\n
          \"part4-rcc-cSt\"<\/a><\/td>\n<\/tr>\n
          Shows how the messages were propagated from producer to consumers C1, C2, C3<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/li>\n<\/ol>\n
          As seen above, even though there were three consumers and 30 messages, they didn’t get to process 10 messages each as C2, C3 subscriptions were consolidated into one consumer at broker-1.<\/p>\n
          \n
          conduitSubscriptions=”true” is a useful setting if we were creating subscribers on topics as that would prevent duplicate messages. More on this in part 5.<\/i><\/p>\n<\/blockquote>\n
          So, in order to make C2 and C3 subscriptions on queue moo.bar propagate to broker-1, let’s redo the same steps 6, 7, 8, 9 and 10 after setting conduitSubscriptions=”false” in broker-1’s network connector configuration in conf\/activemq.xml.<\/p>\n
          Here is the new network connector configuration snippet for broker-1:<\/p>\n
           <networkConnectors>\r\n  <networkConnector\r\n    name=\"Q:broker1->broker2\"\r\n    uri=\"static:(tcp:\/\/localhost:61626)\"\r\n    duplex=\"false\"\r\n    decreaseNetworkConsumerPriority=\"true\"\r\n    networkTTL=\"2\"\r\n    conduitSubscriptions=\"false\"\r\n    dynamicOnly=\"true\">\r\n    <excludedDestinations>\r\n       <topic physicalName=\">\" \/>\r\n    <\/excludedDestinations>\r\n  <\/networkConnector>\r\n  <networkConnector\r\n    name=\"Q:broker1->broker3\"\r\n    uri=\"static:(tcp:\/\/localhost:61636)\"\r\n    duplex=\"false\"\r\n    decreaseNetworkConsumerPriority=\"true\"\r\n    networkTTL=\"2\"\r\n    conduitSubscriptions=\"false\"\r\n    dynamicOnly=\"true\">\r\n    <excludedDestinations>\r\n       <topic physicalName=\">\" \/>\r\n    <\/excludedDestinations>\r\n  <\/networkConnector>\r\n<\/networkConnectors><\/pre>\n
          Upon restarting the brokers and consumers C1, C2 and C3 and producing 30 messages into broker-1’s moo.bar queue, we find that all of the three consumer subscriptions are visible at broker-1. As a result broker-1 dispatches 10 messages to each of the consumers in a round-robin fashion to load balance. This is depicted pictorially below.<\/p>\n\n\n\n\n
          \"part4-broker-1-cc\"<\/a><\/td>\n<\/tr>\n
          Shows how the messages were propagated from producer to consumers C1, C2, C3<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
           
          \nBroker-1’s web console @http:\/\/localhost:8161\/admin\/queueConsumers.jsp?JMSDestination=moo.bar shows that broker-1 now sees 3 consumers and dispatches 10 messages to each consumer.<\/p>\n
          \"part4-broker-1\"<\/a><\/p>\n
          Thus in this part 4 of the blog series, we have seen how we can load balance remote concurrent consumers which are consuming messages from a queue.<\/p>\n
          As always, your comments and feedback is appreciated!<\/p>\n
          In the next part 5, we will explore how the same scenario will play out if we were to use a topic instead of a queue. Stay tuned…<\/p>\n
          Resources<\/h2>\n