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From Alex Dean <a...@crackpot.org>
Subject Re: ajax clients must refresh browser to get data
Date Wed, 22 Sep 2010 20:16:39 GMT
Change logging levels and discovered a bit more about the problem.

 1. start broker & start a publisher script
 2. view ajax page in browser.  receiving messages normally
 3. shut down broker
 4. close browser window
 5. start broker
 6. start publisher
 7. view page again in browser

This is what my logs show for the first request after the browser loads in #7 above:

DEBUG | REQUEST /demo/amq on org.eclipse.jetty.server.nio.SelectChannelConnector$2@4cb0f24a
DEBUG | servlet=AjaxServlet
DEBUG | servlet holder=
DEBUG | REQUEST /demo/amq on org.eclipse.jetty.server.nio.SelectChannelConnector$2@7559f3f0
DEBUG | servlet=AjaxServlet
DEBUG | servlet holder=
DEBUG | Got Session ID 3xgrpw116ot7 from cookie
DEBUG | sessionManager=org.eclipse.jetty.server.session.HashSessionManager@576f8789
DEBUG | session=null
DEBUG | chain=
DEBUG | call filter session
DEBUG | Got Session ID 3xgrpw116ot7 from cookie
DEBUG | sessionManager=org.eclipse.jetty.server.session.HashSessionManager@576f8789
DEBUG | session=null
DEBUG | chain=
DEBUG | call filter session
DEBUG | call servlet AjaxServlet
DEBUG | call servlet AjaxServlet
DEBUG | GET client=org.apache.activemq.web.WebClient@513e86ec session=7ly2kihm6481 uri=/demo/amq
query=timeout=45000&d=1285186135767&r=0.6001447476869052
DEBUG | POST client=org.apache.activemq.web.WebClient@600c199f session=sca25cn0nuu3 info=null
contentType=application/x-www-form-urlencoded; charset=UTF-8
DEBUG | doMessage timeout=25000
DEBUG | sensors (topic)
DEBUG | RESPONSE /demo/amq  200
DEBUG | return with suspended request
DEBUG | Setting up new connection id: ID:rutabaga.local-60310-1285186041188-3:1, address:
vm://localhost#2
DEBUG | localhost adding consumer: ID:rutabaga.local-60310-1285186041188-3:1:-1:1 for destination:
topic://ActiveMQ.Advisory.TempQueue,topic://ActiveMQ.Advisory.TempTopic
DEBUG | 0 destination=topic://sensors message=test type=listen
DEBUG | topic://sensors is a org.apache.activemq.command.ActiveMQTopic
DEBUG | localhost adding consumer: ID:rutabaga.local-60310-1285186041188-3:1:1:1 for destination:
topic://sensors
DEBUG | localhost adding destination: topic://ActiveMQ.Advisory.Consumer.Topic.sensors
DEBUG | Subscribed: ActiveMQMessageConsumer { value=ID:rutabaga.local-60310-1285186041188-3:1:1:1,
started=true } to topic://sensors id=test
DEBUG | RESPONSE /demo/amq  200
DEBUG | message for ActiveMQMessageConsumer { value=ID:rutabaga.local-60310-1285186041188-3:1:1:1,
started=true }continuation=null
DEBUG | remove: ID:rutabaga.local-60310-1285186041188-3:1:1:1, lastDeliveredSequenceId:0
DEBUG | localhost removing consumer: ID:rutabaga.local-60310-1285186041188-3:1:1:1 for destination:
topic://sensors

My browser never receives the data which is being published to the topic.  The last line ('removing
consumer...') seems problematic here.

When I close the browser window and open it again, I get...

DEBUG | REQUEST /demo/amq on org.eclipse.jetty.server.nio.SelectChannelConnector$2@7559f3f0
DEBUG | servlet=AjaxServlet
DEBUG | servlet holder=
DEBUG | Got Session ID 7ly2kihm6481 from cookie
DEBUG | sessionManager=org.eclipse.jetty.server.session.HashSessionManager@576f8789
DEBUG | session=org.eclipse.jetty.server.session.HashSessionManager$Session:7ly2kihm6481@496418976
DEBUG | chain=
DEBUG | call filter session
DEBUG | call servlet AjaxServlet
DEBUG | GET client=org.apache.activemq.web.WebClient@17cb0a16 session=7ly2kihm6481 uri=/demo/amq
query=timeout=45000&d=1285186383593&r=0.9412045402828407
DEBUG | doMessage timeout=25000
DEBUG | RESPONSE /demo/amq  200
DEBUG | return with suspended request
DEBUG | REQUEST /demo/amq on org.eclipse.jetty.server.nio.SelectChannelConnector$2@2d11f5f1
DEBUG | servlet=AjaxServlet
DEBUG | servlet holder=
DEBUG | Got Session ID 7ly2kihm6481 from cookie
DEBUG | sessionManager=org.eclipse.jetty.server.session.HashSessionManager@576f8789
DEBUG | session=org.eclipse.jetty.server.session.HashSessionManager$Session:7ly2kihm6481@496418976
DEBUG | chain=
DEBUG | call filter session
DEBUG | call servlet AjaxServlet
DEBUG | POST client=org.apache.activemq.web.WebClient@17cb0a16 session=7ly2kihm6481 info=null
contentType=application/x-www-form-urlencoded; charset=UTF-8
DEBUG | sensors (topic)
DEBUG | Setting up new connection id: ID:rutabaga.local-60310-1285186041188-3:2, address:
vm://localhost#4
DEBUG | localhost adding consumer: ID:rutabaga.local-60310-1285186041188-3:2:-1:1 for destination:
topic://ActiveMQ.Advisory.TempQueue,topic://ActiveMQ.Advisory.TempTopic
DEBUG | 0 destination=topic://sensors message=test type=listen
DEBUG | topic://sensors is a org.apache.activemq.command.ActiveMQTopic
DEBUG | localhost adding consumer: ID:rutabaga.local-60310-1285186041188-3:2:1:1 for destination:
topic://sensors
DEBUG | Subscribed: ActiveMQMessageConsumer { value=ID:rutabaga.local-60310-1285186041188-3:2:1:1,
started=true } to topic://sensors id=test
DEBUG | RESPONSE /demo/amq  200
DEBUG | message for ActiveMQMessageConsumer { value=ID:rutabaga.local-60310-1285186041188-3:2:1:1,
started=true }continuation=org.eclipse.jetty.server.AsyncContinuation@24cc0f9f@ASYNCWAIT
DEBUG | async request
DEBUG | REQUEST /demo/amq on org.eclipse.jetty.server.nio.SelectChannelConnector$2@7559f3f0
DEBUG | servlet=AjaxServlet
DEBUG | servlet holder=
DEBUG | sessionManager=org.eclipse.jetty.server.session.HashSessionManager@576f8789
DEBUG | session=org.eclipse.jetty.server.session.HashSessionManager$Session:7ly2kihm6481@496418976
DEBUG | chain=
DEBUG | call filter session
DEBUG | call servlet AjaxServlet
DEBUG | GET client=org.apache.activemq.web.WebClient@17cb0a16 session=7ly2kihm6481 uri=/demo/amq
query=timeout=45000&d=1285186383593&r=0.9412045402828407
DEBUG | doMessage timeout=25000
DEBUG | RESPONSE /demo/amq  200

At this point, my client is receiving messages normally.  But why do I have to refresh the
page twice in order to make this happen?

thanks,
alex


On Sep 22, 2010, at 1:40 PM, Alex Dean wrote:

> I am trying to track down a problem we see when using activemq+ajax.  Sometimes when
a web page (which uses amq.js) is first loaded, the amq.js POST & GET requests will be
made as normal, but no data is returned even though there are messages being published to
the desired topic.  Each GET just returns with an empty <ajax-response></ajax-response>.
 If we refresh the browser, making no changes to the message publisher or the broker, then
we are able to start receiving messages.
> 
> The most reliable way I'm able to reproduce is as follows:
> - Open a web browser and view a page using amq.js.
> - Restart the broker.  The client will (as expected) get error responses when trying
to contact the dead broker.  The client will wait a few seconds after the error, and then
try again.
> - Restart the message publisher.  Mine (written in Ruby/stomp) always terminates when
the broker shuts down.
> - After the broker is fully started, the client will again get 200 responses to its GET
requests, but no messages will be received. (Although they are being published to the topic.)
> - Refresh the browser.  Again, GET requests will be accepted and appear normal, but no
data is received.
> - Refresh the browser again.  At this point, messages are received normally.
> 
> I have been able to see via Firefox/Firebug that after the server restarts, the client
does get a new JSESSIONID value, which is then sent back to the server with subsequent requests.
 It doesn't surprise me that the client doesn't get messages after the broker restarts, since
I expect the client needs to re-send the 'listen' POST.  But why a simple refresh doesn't
achieve this, I don't know.
> 
> I'm seeing similar behavior if I view data via ajax, then leave that web page for some
amount of time (not sure what the time is, still trying to pin it down more precisely), and
then visit the page again.  The first time I load the page after a prolonged absence, I don't
get any data.  Ajax GET & POST requests are made, and activemq responds with empty <ajax-response>
messages, though there are messages being published to the topic.   No data is received until
I refresh the browser.
> 
> I don't know much about continuations, but could they be involved with this problem?
> 
> thanks,
> alex


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