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Message
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| avivo22 |
 Posted: Sun Apr 22, 2012 3:23 am Post subject: MqQueue.Get() "locked" when reading from multiple |
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Newbie
Joined: 22 Apr 2012
Posts: 5
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Hey,
i wrote java client that reads and processes messages from mq.
When i run multiple clients that read from the same queue, in each moment at least one of them is stuck for few seconds while trying to execute queue.get().
What can be the problem?
Here is my code:
| Code: |
mqqueuemanager mgr=new mqqueuemanager(mgr-name);
Mqqueue queue = mgr.accessqueue(queue-name, mqconstants.mqoo_input_as_q_def);
Mqgetmessageoptions gmo=new mqgetmessageoptions();
Gmo.options=mqconstants.mqgmo_fail_if_quiseing | mqconstants.mqgmo_syncpoint;
While(true)
{
Mqmessage msg = new mqmessage();
System.out.println("before get");
Queue.get(msg)
system.out.println("after get");
//process message.....
mgr.commit();
}
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Thanks,
Aviv |
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| Vitor |
| Posted: Sun Apr 22, 2012 4:49 am Post subject: Re: MqQueue.Get() "locked" when reading from multi |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| avivo22 wrote: |
| What can be the problem? |
Almost anything. You've not said what version of the WMQ you're using, what environment you're running the Java under, how the queue manager is configured with particular reference to any consideration for multiple access. You've not even mentioned what OS you're using.
One point is that you're reading messages under syncpoint. If the messages are persistent and if you've got the logging and/or file system set up in a non-optimal way and/or you're running on a slow machine or the queue manager is using XA and the network is slow or the coordinator is slow then that could introduce a delay.
Or it could be 1 of a 100 different things. Perhaps if you gave a few more details (or some details) and what diagnostic steps you've taken.
_________________
Honesty is the best policy.
Insanity is the best defence. |
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| avivo22 |
| Posted: Sun Apr 22, 2012 5:14 am Post subject: |
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Newbie
Joined: 22 Apr 2012
Posts: 5
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Sorry, im kind of new with mq.
I hope the following details will help you to diagnose my problom:
im using WMQ 7.0.1 installed on winServer 2008 R2 with 2GB memory dual core server.
My java app runs in linux (redhat).
Thanks,
Aviv |
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| mqjeff |
| Posted: Sun Apr 22, 2012 6:14 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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| You should also review the options on the queue that get populated when you use mqconstants.mqoo_input_as_q_def. |
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| avivo22 |
| Posted: Sun Apr 22, 2012 6:41 am Post subject: |
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Newbie
Joined: 22 Apr 2012
Posts: 5
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| mqjeff wrote: |
| You should also review the options on the queue that get populated when you use mqconstants.mqoo_input_as_q_def. |
the "default input open option" of the queue set to "input shared". |
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| fjb_saper |
| Posted: Sun Apr 22, 2012 10:13 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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it could also be something completely outside of your specific app but that impacts the qmgr. Are you making extensive use (not in your app but in others) of dynamic temporary queues? What is the message size when this happens. Is it significantly bigger than the average message? 
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| rekarm01 |
| Posted: Sun Apr 22, 2012 3:12 pm Post subject: Re: MqQueue.Get() "locked" when reading from multi |
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Grand Master
Joined: 25 Jun 2008
Posts: 1415
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| avivo22 wrote: |
When i run multiple clients that read from the same queue, in each moment at least one of them is stuck for few seconds while trying to execute queue.get().
What can be the problem? |
The posted code has syntax errors and spelling errors, so there are at least some discrepancies with the code that's actually running. There could be a delay in the running code that's not posted; it's difficult to help with that.
One obvious guess: if the queue is empty and the client enables a wait interval, then the get will block, waiting for the next message.
How is the delay actually measured? If the output stream is buffered, (particularly if it's redirected to a file or piped to some other command), then the apparent delay could be due to the buffering. It might be useful to use System.currentTimeMillis() or similar method to more accurately calculate the elapsed before and after the get. |
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| avivo22 |
| Posted: Sun Apr 22, 2012 10:39 pm Post subject: |
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Newbie
Joined: 22 Apr 2012
Posts: 5
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| fjb_saper wrote: |
| it could also be something completely outside of your specific app but that impacts the qmgr. Are you making extensive use (not in your app but in others) of dynamic temporary queues? What is the message size when this happens. Is it significantly bigger than the average message? |
The answers is No  |
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| avivo22 |
| Posted: Sun Apr 22, 2012 10:46 pm Post subject: Re: MqQueue.Get() "locked" when reading from multi |
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Newbie
Joined: 22 Apr 2012
Posts: 5
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| rekarm01 wrote: |
| avivo22 wrote: |
When i run multiple clients that read from the same queue, in each moment at least one of them is stuck for few seconds while trying to execute queue.get().
What can be the problem? |
The posted code has syntax errors and spelling errors, so there are at least some discrepancies with the code that's actually running. There could be a delay in the running code that's not posted; it's difficult to help with that.
One obvious guess: if the queue is empty and the client enables a wait interval, then the get will block, waiting for the next message.
How is the delay actually measured? If the output stream is buffered, (particularly if it's redirected to a file or piped to some other command), then the apparent delay could be due to the buffering. It might be useful to use System.currentTimeMillis() or similar method to more accurately calculate the elapsed before and after the get. |
This is not the same code, just the idea...the code compiles&run perfect without errors/warnings.
The queue isnt empty. I put 5000 messages in the queue and then start my 3 clients at the same time and i can clearly see "locks" when 2 clients are showing "trying to get message" while the third client reads a lot of messages at the same time.
sometimes there are 2 "active clients" and just one "locked". |
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| Vitor |
| Posted: Mon Apr 23, 2012 4:45 am Post subject: Re: MqQueue.Get() "locked" when reading from multi |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| avivo22 wrote: |
| This is not the same code, just the idea...the code compiles&run perfect without errors/warnings. |
If I'd been allowed to consider code error free when it compiled clean, I'd have got through a lot more COBOL back in the day.... 
The fact that it compiles and doesn't throw errors doesn't mean the code doesn't have problems.
| avivo22 wrote: |
| i can clearly see "locks" when 2 clients are showing "trying to get message" while the third client reads a lot of messages at the same time. |
How do you see this? Where? Is it your code generating this or some kind of Java container?
As I & others have said, this could be nothing to do with your code but a queue manager configuration issue.
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Insanity is the best defence. |
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| mqjeff |
| Posted: Mon Apr 23, 2012 4:58 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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| It could also be as simple as trying to use the same connection to execute multiple gets. |
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| Vitor |
| Posted: Mon Apr 23, 2012 5:20 am Post subject: |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| mqjeff wrote: |
| It could also be as simple as trying to use the same connection to execute multiple gets. |
 
Without the actual code who can say?
Without knowing where these "locks" are being "seen" who can say?
_________________
Honesty is the best policy.
Insanity is the best defence. |
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| fjb_saper |
| Posted: Mon Apr 23, 2012 4:55 pm Post subject: Re: MqQueue.Get() "locked" when reading from multi |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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| avivo22 wrote: |
The queue isnt empty. I put 5000 messages in the queue and then start my 3 clients at the same time and i can clearly see "locks" when 2 clients are showing "trying to get message" while the third client reads a lot of messages at the same time.
sometimes there are 2 "active clients" and just one "locked". |
Sounds like a know problem to me. Upgrade!
What version of WMQ are you on!
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