activemq-users mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Gary Tully <gary.tu...@gmail.com>
Subject Re: Browsing a queue in a distributed broker network sometimes not seeing messages
Date Fri, 11 Dec 2009 12:40:55 GMT
This is expected. A queue browser takes a shapshot of the queue through a
short lived consumer. The network bridge is by default a demand forwarder,
such that messages are only forwarded when there are consumers on other
brokers.

With the browser, the consumer (and hence demand) is transient, so it may
take a snapshot before the forwarding has a chance to kick in. And the
forwarding stops when the consumer goes away once the browse shapshot
completes.

One way to make this more deterministic would be to have a statically
configured destination in the network connector configuration such that
messages for that destination are forwarded irrespective of demand.

2009/12/11 ant elder <ant.elder@gmail.com>

> I'm trying to track down an problem where a queue browser on a VM
> connection to one AMQ broker is sometimes not seeing messages put on a
> queue from a VM connection to another broker in the same network. The
> code below can recreate the problem, running the put() on JVM and the
> browse() on another JVM the first QueueBrowser never sees the message
> but the second QueueBrowser does though sometimes it doesn't without
> the Thread.sleep for a few seconds.
>
> Is there anything obviously wrong with this setup or are there any
> config settings that could help?
>
>   ...ant
>
> The code to put a message on a queue:
>
>    public void put() throws Exception {
>        BrokerService broker1 = new BrokerService();
>        broker1.setBrokerName("default");
>        broker1.setPersistent(false);
>        broker1.setUseJmx(false);
>        TransportConnector tc = broker1.addConnector("tcp://localhost:0");
>        tc.setDiscoveryUri(URI.create("multicast://default"));
>        broker1.addNetworkConnector("multicast://default");
>        broker1.start();
>
>        Connection conn1 = new
> ActiveMQConnectionFactory("vm://default?create=false").createConnection();
>        conn1.start();
>        Session sess1 = conn1.createSession(false, 1);
>        Queue d1 = sess1.createQueue("d1");
>        MessageProducer p1 = sess1.createProducer(d1);
>        TextMessage m1 = sess1.createTextMessage("test");
>        p1.send(m1);
>   }
>
>
> The code to browse the messages on the queue:
>
>    public void browse() throws Exception {
>
>        BrokerService broker2 = new BrokerService();
>        broker2.setBrokerName("default");
>        broker2.setPersistent(false);
>        broker2.setUseJmx(false);
>        TransportConnector tc = broker2.addConnector("tcp://localhost:0");
>        tc.setDiscoveryUri(URI.create("multicast://default"));
>        broker2.addNetworkConnector("multicast://default");
>        broker2.start();
>
>        Connection conn2 = new
> ActiveMQConnectionFactory("vm://default?create=false").createConnection();
>        conn2.start();
>        Session sess2 = conn2.createSession(false, 1);
>        Queue d1 = sess2.createQueue("d1");
>        QueueBrowser b = sess2.createBrowser(d1);
>
>        Enumeration x2 = b.getEnumeration();
>        while (x2.hasMoreElements()) {
>            System.out.println(x2.nextElement()); // this never gets
> the message
>        }
>
>        Thread.sleep(5000);
>
>        b = sess2.createBrowser(d1);
>        Enumeration x2a = b.getEnumeration();
>        while (x2a.hasMoreElements()) {
>            System.out.println(x2a.nextElement()); // this does get the
> message
>        }
>
>    }
>



-- 
http://blog.garytully.com

Open Source Integration
http://fusesource.com

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message