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POActiveMQ - Consumers not sharing the load
 

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    <p>Let's say I have a queue called notifications and I post 1000 messages to that queue. I also have 20 consumers of that queue. I'd like each of those consumers to take one message from the queue, process it, then get the next available message. </p> <p>What is happening now is that a few of the consumers grab a lot of the messages and process them while other consumers do nothing.</p> <p>Below is a complete test case that demonstrates what I'm seeing. In reality the consumers are all separate processes on separate machines, but this duplicates the behavior exactly:</p> <pre><code>using System; using System.Threading; using Apache.NMS; using Apache.NMS.ActiveMQ; using Spring.Messaging.Nms.Core; namespace QueueTest { class Program { private static object _syncObj = new object(); private static int _row; static void Main() { var connectionFactory = new ConnectionFactory("tcp://localhost:61616"); var template = new NmsTemplate(connectionFactory); for (int i = 0; i &lt; 500; i++) { template.ConvertAndSend("notifications", "hello"); } for (int i = 0; i &lt; 10; i++) { ThreadPool.QueueUserWorkItem(Spawn, i); } Console.ReadKey(); } static void Spawn(object o) { int count = 0; int threadId = (int)o; var ts = new TimeSpan(0,0,0,5); while (true) { var connectionFactory = new ConnectionFactory( "tcp://localhost:61616" + "?nms.PrefetchPolicy.QueuePrefetch=1", String.Format("{0}:{1}:{2}", Environment.MachineName, threadId, "notifications")); using (var conn = connectionFactory.CreateConnection()) { conn.ClientId = String.Format("{0}:{1}:{2}", Environment.MachineName, threadId, "notifications"); conn.Start(); using (var session = conn.CreateSession()) { var queue = session.GetQueue("notifications"); using (var consumer = session.CreateConsumer(queue)) { IMessage msg = consumer.Receive(ts); while (msg != null) { lock (_syncObj) { Interlocked.Increment(ref _row); Console.WriteLine("{0}. {1} processed {2}", _row, threadId, ++count); if (_row == 500) { Environment.Exit(0); } } Thread.Sleep(1000); msg = consumer.Receive(ts); } Console.WriteLine("{0} nothing to process", threadId); } } conn.Stop(); } } } } } </code></pre> <p>How do I get it to spread out the messages to all of the consumers more evenly?</p>
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