[jboss-user] [JBoss Messaging] - Re: deleting messages rather than blocking if server down fo

2009-07-08 Thread AdrianWoodhead
We have a thread pool - the problem is, we really *do* need to be able to 
handle thousands of simultaneous request threads. The application in this case 
is an audio streaming server which ideally should only be limited by IO reading 
files from disk. Currently we have this scaling up to a few thousand 
simultaneous users but the idea is for this to go up into the tens of thousands.

I will code up a message queue so message sending happens in one thread. Thanks 
for the input.

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[jboss-user] [JBoss Messaging] - Re: deleting messages rather than blocking if server down fo

2009-07-08 Thread timfox
Perhaps you also need a thread pool in your application to stop potentially 
unlimited number of threads being created for your HTTP requests...

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[jboss-user] [JBoss Messaging] - Re: deleting messages rather than blocking if server down fo

2009-07-08 Thread timfox
"AdrianWoodhead" wrote : The clients are calling send() on the same 
MessageProducer instance, and this isn't synchronized. This hasn't caused any 
noticeable problems in the past (when the MessageProducer was using ActiveMQ) 
or since we started evaluating JBM (although the loads on those 2 servers are 
still very low). This makes me think I really should queue up the messages to 
be sent myself and have one thread call send(), which will also get rid of the 
blocking problem..

+1

You may have just got lucky in the past. All sorts of weird subtle errors might 
start happening if you use a JMS session concurrently with different threads.

http://java.sun.com/javaee/5/docs/api/javax/jms/Session.html

"...A Session object is a single-threaded context for producing and consuming 
messages..."

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[jboss-user] [JBoss Messaging] - Re: deleting messages rather than blocking if server down fo

2009-07-08 Thread AdrianWoodhead
The clients are calling send() on the same MessageProducer instance, and this 
isn't synchronized. This hasn't caused any noticeable problems in the past 
(when the MessageProducer was using ActiveMQ) or since we started evaluating 
JBM (although the loads on those 2 servers are still very low). This makes me 
think I really should queue up the messages to be sent myself and have one 
thread call send(), which will also get rid of the blocking problem.

As for the exception listener stuff - yes, I understand how that works with the 
different re-connect values and it makes sense.

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[jboss-user] [JBoss Messaging] - Re: deleting messages rather than blocking if server down fo

2009-07-08 Thread timfox
Adrian-

Are your client threads calling send() on the same ClientProducer (core ) or 
MessageProducer (JMS) instance? If you do this you would have to synchronize 
access in your client application since neither JMS MessageProducers or core 
ClientProducer instances are designed to be used by more than one thread at a 
time,

Alternatively if you're creating a new MessageProducer for each message sent - 
that would also be frowned upon as an anti-pattern. 
Sessions/Producers/Consumers should always be reused between messages 
sent/consumed (unless you're not worried about performance).

If you enable auto reconnect you do so on the presumption that  your server has 
not really failed but there is a temporary network glitch (like someone has 
pulled out the cable for a while), and when the network comes back the client 
will be able to automatically reconnect its session(s) with the sesssion(s) 
still remaining on the server and carry on as if nothing  had happened (this is 
transparent reconnection). In your case the server has really failed so on 
recovery the server sessions will clearly not be there any more (since the 
server was restarted) and they won't be able to connect. That's why you don't 
get the exception until the client has tried to reconnect and not found the 
session(s) there. If you turn off auto reconnection you'll get the exception 
sooner.



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[jboss-user] [JBoss Messaging] - Re: deleting messages rather than blocking if server down fo

2009-07-08 Thread AdrianWoodhead
The threads are coming from my client application - there is a thread per http 
request and at the end of the request it calls send(). Hundreds of these 
threads are created every minute so if the call to send() blocks then it 
doesn't take long for the blocking to overwhelm the VM. I guess I could 
re-architect my application to put the messages in a queue and have one thread 
pull the messages off and send them, this just feels a bit like I'm 
implementing something which could (should?) be in the messaging client.

As for the ExceptionListener solution, I thought about this too. I have JBM 
setup to auto-reconnect so I don't actually get an exception when the server 
goes down (I just see some warning messages in the logs). From what I can tell 
the sender queues up the messages in the background. When the server comes 
back, only then does my ExceptionListener callback get called, at which point I 
redo the JNDI lookup and recreate the connections and sessions etc. This works 
well. I think if I set JBM not to auto-connect then the ExceptionListener 
callback is called right away when the server goes down, but then I have to do 
my own reconnect logic. I'm happy with this ExceptionListener logic, it would 
just be nice to be able to throw messages away instead of blocking, but maybe I 
should code this up myself.


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[jboss-user] [JBoss Messaging] - Re: deleting messages rather than blocking if server down fo

2009-07-07 Thread timfox
Adrian-

I am trying to get my head around what you're asking here.

if you're referring to command buffering:

http://labs.jboss.com/file-access/default/members/jbossmessaging/freezone/docs/usermanual-2.0.0.beta3/html/command-buffering.html

Then JBM will block by default on send if it hasn't received any acks back from 
the server. As mentioned in the docs you can turn this off by setting the 
ProducerWindowSize param to -1, but do so at your peril! Flow control is there 
to stop the server getting overwhelmed.

BTW JBM won't create any threads here - there will only be as many threads 
blocking as the number of threads from your application that have called 
send(), so I'm not sure how that could bring your application down.

You could also set an ExceptionListener which would be called when a problem 
with the connection is detected.

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[jboss-user] [JBoss Messaging] - Re: deleting messages rather than blocking if server down fo

2009-07-07 Thread ataylor
Currently JBm can't be configured to do this, typically you would have at least 
1 backup server to failover too.

Feel free to add a JIRA for this functionality if you think its worth while.

P.S thanks for all the feedback.

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