Bill Harts created AMQ-4797:
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Summary: Unable to add multiple AJAX listeners for the same topic
in the same browser window
Key: AMQ-4797
URL: https://issues.apache.org/jira/browse/AMQ-4797
Project: ActiveMQ
Issue Type: Bug
Affects Versions: 5.8.0
Environment: Windows Server 2008 R2 on Dell server boxes
Reporter: Bill Harts
I'm using ExtJS to create two separate panels which run in one browser tab.
After loading jquery, amq_jquery_adapter.js and amq.js I call amq_init (only
once). Then each panel calls addlistener like so:
Panel 1 code:
{{ amq.addListener('testconnection1', 'topic://MyApp/IOIs/Simulator',
myHandler1.rcvMessage);}}
Panel 2 code:
{{ amq.addListener('testconnection2', 'topic://MyApp/IOIs/Simulator',
myHandler2.rcvMessage);}}
Note that both are subscribing to the same topic. This is because Panel 1
shows the data in a different format than Panel 2.
*The Problem:*
If I start Panel 1 alone, it receives data from the topic without problems. But
then I start Panel 2 and as soon as it executes the addlistener, Panel 2 starts
receiving data but Panel 1 stops!
So I started tracing into the network traffic and all looks fine, i.e, I can
see each addlistener trigger a 'listen' request with the proper id and topic.
And I see the amq server return data to testconnection1, then stop suddenly
when the 'listen' for testconnection2 is sent. So I turned my attention to the
backend code and enabled a detailed trace. Here's what I found:
When the Panel 1 'listen' is received, the trace shows:
{{2013-10-10 09:10:09,701 | DEBUG | 0 destination=topic://MyApp/IOIs/Simulator
message=testconnection1 type=listen |
org.apache.activemq.web.MessageListenerServlet | qtp2088898587-51 - /demo/amq
2013-10-10 09:10:09,701 | DEBUG | topic://MyApp/IOIs/Simulator is a
org.apache.activemq.command.ActiveMQTopic |
org.apache.activemq.web.MessageListenerServlet | qtp2088898587-51 - /demo/amq
2013-10-10 09:10:09,701 | DEBUG | amq-broker adding consumer:
ID:MYAPPDATA-7392-1381410590247-5:1:1:1 for destination:
topic://MyApp/IOIs/Simulator | org.apache.activemq.broker.region.AbstractRegion
| ActiveMQ VMTransport: vm://localhost#1-2
2013-10-10 09:10:09,701 | DEBUG | amq-broker adding destination:
topic://ActiveMQ.Advisory.Consumer.Topic.MyApp/IOIs/Simulator |
org.apache.activemq.broker.region.AbstractRegion | ActiveMQ VMTransport:
vm://localhost#1-2
2013-10-10 09:10:09,717 | DEBUG | Initialized TaskRunnerFactory[ActiveMQ
Session Task] using ExecutorService:
java.util.concurrent.ThreadPoolExecutor@2e2667db[Running, pool size = 0, active
threads = 0, queued tasks = 0, completed tasks = 0] |
org.apache.activemq.thread.TaskRunnerFactory | qtp2088898587-51 - /demo/amq
2013-10-10 09:10:09,717 | DEBUG | Subscribed: ActiveMQMessageConsumer {
value=ID:MYAPPDATA-7392-1381410590247-5:1:1:1, started=true } to
topic://MyApp/IOIs/Simulator id=testconnection1 |
org.apache.activemq.web.MessageListenerServlet | qtp2088898587-51 - /demo/amq}}
When the Panel 2 'listen' is received, I see this trace:
{{2013-10-10 09:10:09,888 | DEBUG | 0 destination=topic://MyApp/IOIs/Simulator
message=testconnection2 type=listen |
org.apache.activemq.web.MessageListenerServlet | qtp2088898587-53 - /demo/amq
2013-10-10 09:10:09,888 | DEBUG | topic://MyApp/IOIs/Simulator is a
org.apache.activemq.command.ActiveMQTopic |
org.apache.activemq.web.MessageListenerServlet | qtp2088898587-53 - /demo/amq
2013-10-10 09:10:09,888 | DEBUG | remove:
ID:MYAPPDATA-7392-1381410590247-5:1:1:1, lastDeliveredSequenceId:0 |
org.apache.activemq.ActiveMQMessageConsumer | qtp2088898587-53 - /demo/amq
2013-10-10 09:10:09,888 | DEBUG | Unregistering MBean
org.apache.activemq:type=Broker,brokerName=amq-broker,destinationType=Topic,destinationName=MyApp/IOIs/Simulator,endpoint=Consumer,clientId=ID_MYAPPDATA-7392-1381410590247-4_1,consumerId=ID_MYAPPDATA-7392-1381410590247-5_1_1_1
| org.apache.activemq.broker.jmx.ManagementContext | ActiveMQ VMTransport:
vm://localhost#1-2
2013-10-10 09:10:09,888 | DEBUG | amq-broker removing consumer:
ID:MYAPPDATA-7392-1381410590247-5:1:1:1 for destination:
topic://MyApp/IOIs/Simulator | org.apache.activemq.broker.region.AbstractRegion
| ActiveMQ VMTransport: vm://localhost#1-2
2013-10-10 09:10:09,888 | DEBUG | amq-broker adding consumer:
ID:MYAPPDATA-7392-1381410590247-5:1:1:2 for destination:
topic://MyApp/IOIs/Simulator | org.apache.activemq.broker.region.AbstractRegion
| ActiveMQ VMTransport: vm://localhost#1-2
2013-10-10 09:10:09,904 | DEBUG | Subscribed: ActiveMQMessageConsumer {
value=ID:MYAPPDATA-7392-1381410590247-5:1:1:2, started=true } to
topic://MyApp/IOIs/Simulator id=testconnection2 |
org.apache.activemq.web.MessageListenerServlet | qtp2088898587-53 - /demo/amq}}
SO what is happening is that in MessageListenerServlet.js, function doPost,
line 165 is dropping any previous consumer to the same destination:
client.closeConsumer(destination); // drop any existing consumer.
But why? There doesn't seem to be a good reason for doing this--maybe it was
originally put there for cleanup purposes?. Or if there is a good reason,
maybe the behavior should be to not do it if the id of the new destination (in
this case 'testconnection2') is different than the id of the existing
destination ('testconnection1').
I believe this can be fixed by simply removing line 165 from
MessageListenerServlet.js but I'm not sure if this will break something else
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