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| UncleAndy |
 Posted: Thu Sep 15, 2005 3:28 am Post subject: Urgent: multi-thread issue with MQ client (C#) |
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Newbie
Joined: 15 Sep 2005
Posts: 7
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Hi,
I am experiencing problems when running multiple threads against my MQ Server. WebSphere MQ v.5.3 (with CSD 10) is installed on a Windows 2000 Server (with decent hardware) and my client is located on a separate box (also Windows 2000 Server). The client is written in C# and communicates over TCP. Each thread creates a new instance of the queue manager, MQ environment and sender/receiver channels. A dummy server is set up to get messages from one queue and place a response on another which is retrieved from the client.
When the traffic load is "high" (10 simultanious threads..) everything works fine until a certain point when things seem to get clogged up. The 10 threads are started simultaniously and perform 1 request each. When all 10 threads have completed, 10 new threads are spawned and does that same operation. The QM object is created successfully, but when I invoke methods (qMgr.Get(), gMgr.MaximumHandles() etc) I get a null pointer exception and it seems like the QM object has lost connection with the server. The server does not recover from this, and I experience more and more threads throwing exceptions until I shut down MQ and restart it to get a fresh start.
I also experience exceptions identified as MQRC_HOBJ_ERROR, which indicates that an object handle is invalid. The corrective action for this is:
| Quote: |
| Ensure that a successful MQOPEN call is performed for this object |
Do I have to put in a check for each time I use the QM object to see if it's still "open"? If so, how can this done?
Single thread works fine, and as mentioned above multiple threads also work fine until a certain point.
This is critical to us right now, and I need to sort this out ASAP. I would appreciate any help!
Thanks!
Andreas |
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| jefflowrey |
| Posted: Thu Sep 15, 2005 8:24 am Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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I'd say you're probably running out of available client connections on the qmgr.
This is a really bad design for your app - you'd never code a database app the same way, I hope.
I would change your code to establish the qmgr connection as a thread-shareable connection, and use exactly one connection for each qmgr you need, and only close it when your program ends or when an error indicates that the qmgr is down.
_________________
I am *not* the model of the modern major general. |
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| UncleAndy |
| Posted: Thu Sep 15, 2005 11:16 pm Post subject: |
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Newbie
Joined: 15 Sep 2005
Posts: 7
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Thank you for you input! The reason why I created a new instance of the QM for each request was that it was actually suggested in one of the IBM eBooks.. (please shoot me if I misunderstood that!  ). I am currently changing the client now to only keep one connection to the QM open at the time.
Let's hope this will solve my issue!
Andreas |
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| UncleAndy |
| Posted: Tue Sep 20, 2005 12:39 am Post subject: |
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Newbie
Joined: 15 Sep 2005
Posts: 7
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I still have problems when traffic is high. What happens is that I get a null pointer exception when I try to access the queues (either through QueueManager.AccessQueues or QueueManager.Get/Put).
Does anyone know the cause of this? Is the MQ Server dropping connections because the number is too high? I have tried to increase the values for:
MaxChannels (1024)
MaxActiveChannels (1024)
MaxInitiators (32)
ListenerBackLog (512)
EntryPoints (100)
- all config settings for the QM available through the MQ Services console.
Any other settings I should look at?
Andreas |
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| jefflowrey |
| Posted: Tue Sep 20, 2005 3:35 am Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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I guess you should confirm that you're not trying to access a null pointer...
If it were an issue with MQ dropping connections, you should get a reason code back that told you something, and there would be error messages in the queue manager system log.
_________________
I am *not* the model of the modern major general. |
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| JasonE |
| Posted: Tue Sep 20, 2005 3:40 am Post subject: |
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Grand Master
Joined: 03 Nov 2003
Posts: 1220
Location: Hursley
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Whats the call stack from the null pointer? Your code, or MQ's?
What version/release of mq? If 5.3, try applying fixpack 10 or 11, registering the amqmdnet.dll into the GAC and seeing if the problem continues
Can you cut the code down to a trivial sample, and post here? |
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