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webMathematica KernelTimeLimit question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg121160] webMathematica KernelTimeLimit question
  • From: Darryl Bragdon <darryl.bragdon at fairchildsemi.com>
  • Date: Thu, 1 Sep 2011 06:03:39 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Hello,

We have been running into issues where our Web Server has been unable
to process requests and we had been restarting the Web Server to
resume processing. After looking into it, it appears that this issue
is occurring when computations are taking longer than the
KernelTimeLimit setting. When this happens, most of the time, it
appears that the system tries to open another Kernel thread and that
runs into the following error: Kernel could not obtain a license. We
currently only have one Kernel license. When I look on the server, I
can see a Mathematica process continues to run after this time limit.

So I tried increasing the time limit to the time that the Mathematica
process was taking and after re-running the computation, there was no
issue. So from my perspective, it appears that the KernelTimeLimit
does not actually stop the computation. But when this time limit is
reached, the system stops the existing Kernel (I see Kernel 0 stopped
in log) and starts a new Kernel process which is unable to obtain a
license because the current process is still running and holding that
license.

I just want to confirm my understanding of the issue and if there is
any easy workaround besides increasing time limits or setting time
limits in the individual computations themselves. I would like for the
process to stop when the KernelTimeLimit is reached and not cause the
License error so that further processing can occur - but this is just
a desire. I apologize for my ignorance as I am trying to help merely
from an IT perspective.

Excerpt from log:
2011-08-29 01:32:08,494 com.wolfram.kerneltools.KernelPool <General
kernelThread-0 > [INFO ] Kernel 1 started
2011-08-29 16:43:49,015 com.wolfram.kerneltools.state.StateMachine
<General Timer-1 1> [ERROR] Evaluation did not complete within the
allowed time limit
2011-08-29 16:43:49,016 com.wolfram.msp.MSPKernelRequest <General
http-8080-1 1> [INFO ] Setting HTTP error 403
2011-08-29 16:43:49,518 com.wolfram.kerneltools.KernelPool <General
kernelThread-0 > [INFO ] Kernel 1 stopped
2011-08-29 16:43:49,519 com.wolfram.kerneltools.KernelPool <General
kernelThread-0 > [INFO ] Kernel 2 started
2011-08-29 16:43:49,648 com.wolfram.kerneltools.state.StateMachine <
Thread-19 > [ERROR] Kernel could not obtain a license.
2011-08-29 16:43:50,150 com.wolfram.kerneltools.KernelPool <General
kernelThread-0 > [INFO ] Kernel 2 stopped
2011-08-29 16:44:06,113 com.wolfram.msp.tags.el.ELStatics <General
http-8080-1 > [ERROR] KernelException thrown while initializing the EL
functions
com.wolfram.kerneltools.KernelException: Kernel could not obtain a
license.
        at com.wolfram.kerneltools.Kernel.initialize1(Kernel.java:386)
        at com.wolfram.kerneltools.Kernel.initialize(Kernel.java:247)
        at com.wolfram.kerneltools.KernelPool
$KernelRunnable.run(KernelPool.java:933)
        at java.lang.Thread.run(Unknown Source)


Thank you.




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