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From "Tkatcheva, Irina N (388D)" <irina.n.tkatch...@jpl.nasa.gov>
Subject Re: Question about xmlrpc
Date Tue, 21 Feb 2012 17:56:51 GMT
Hi Brian and all,

I have noticed that the system does recover after the "System overload: Maximum number of
concurren trequests (100) exceeded"  message, but usually some jobs stay in 'Waiting on resource
(executing)' condition and never proceed further. I have seen it every time after the overload
messages. I usually run a test that runs a bunch of jobs overnight. If there is no overload
messages, all jobs are completed; if there are overload messages, usually in the morning some
jobs are stuck in  'Waiting on resource (executing)' state. So it looks to me that the system
does not recover completely.

Irina



On Feb 17, 2012, at 9:17 AM, Brian Foster wrote:

Hey Chris,

ya I'm in favor of adding the property but let's make it use 100 by default if the property
is not set and I would even say let's add it to the properties file but comment it out or
something... that's a really advanced flag which only needs to be changed to get rid of that
logging message... CAS works fine even when that message is being thrown... I think it prints
to sndout, otherwise I would have just turned the logging for that off back when I added the
client retry handlers that fixed the issue... oh and this is another thing your probably gonna
want to port to trunk workflow :)

-Brian

"Mattmann, Chris A (388J)" <chris.a.mattmann@jpl.nasa.gov<mailto:chris.a.mattmann@jpl.nasa.gov>>
wrote:

Thanks Brian, I was thinking this too, +1, which is why I cautioned against any number greater
than 256
in terms of thread count in my reply email too, since the risk is either that (a) you have
to increase the
ulimit (which extends the boundaries from devops oriented updates to sysops on the sysadmin
side);
and (b) the JVM will likely start trashing unless there is an inordinate amount of RAM, or
swap space, etc.

I think the best solution here is to simply make it a configurable property and then encourage
projects
to use a sensible default that's not too large...

Cheers,
Chris

On Feb 16, 2012, at 12:52 AM, Brian Foster wrote:

You have to be careful with the number you set that too because you are basically telling
XML-RPC that it is now allowed to create 2000 threads in the same JVM... not a good practice...
I don't remember the exact number but the JVM will crash if it creates a certain number of
threads because there is a limit to the number of threads one process can create and I believe
this is restricted at the operating system level... and i believe this number is less than
2000... The trunk filemgr and wengine already have built-in client retry handling support
and are configurable via java properties (i.e. org.apache.oodt.cas.filemgr.system.xmlrpc.connection.retries
and o.a.o.c.filemger.system.connection.retry.interval.seconds and there are similar ones for
wengine)... The message you are seeing is XML-RPC server logging that it already using a 100
worker threads... you will see this message if you create a 100+ jobs in the RM (e.g. Workflow
Conditions and Tasks) and they all start talking to the workflow manager or file manger at
the same time... the client retry handlers will catch this error and just wait and retry again...
you shouldn't be loosing any data... the only inconvenience I guess is that message is cluttering
the logs

-Brian

On Feb 15, 2012, at 10:42 PM, "Cheng, Cecilia S (388K)" <cecilia.s.cheng@jpl.nasa.gov<mailto:cecilia.s.cheng@jpl.nasa.gov>>
wrote:


Hi Chris,

Sure we can discuss this in dev@oodt.apache.org<mailto:dev@oodt.apache.org>.

If you feel comfortable w/ the 2000 number, of course I can push the patch
upstream into Apache OODT. But what kind of tests, if any, should we do
before we deliver the patch? Our projects are concerned that if we
arbitrarily set a number, we don't know what other problems it might cause.

Thanks,
Cecilia

On 2/15/12 10:07 PM, "Mattmann, Chris A (388J)"
<chris.a.mattmann@jpl.nasa.gov<mailto:chris.a.mattmann@jpl.nasa.gov>> wrote:

Hi Cecilia,

This is really good news!

A couple questions:

1. Do you think you would be willing to push your XML-RPC patches upstream
into Apache OODT so others in the
community could benefit? This would involve filing corresponding JIRA issue(s)
[1], and then letting the dev@oodt.apache.org<mailto:dev@oodt.apache.org>
know.

2. Can we move this conversation onto dev@oodt.apache.org<mailto:dev@oodt.apache.org>?
I think others
could benefit from the answers below.

Thanks and let me know. If you'd like to discuss more, that's fine too, but
I'd urge us to move this onto the public Apache OODT
lists.

Cheers,
Chris

[1] http://issues.apache.org/jira/browse/OODT

On Feb 15, 2012, at 2:31 PM, Cheng, Cecilia S (388K) wrote:

Hi Chris and Paul,

Just want to fill you in on where we are w/ the xmlrpc problem that we see on
ACOS and PEATE and get your advice.

As you might recall, on both projects, and in all 3 components (FM, RM, and
WEngine), we will periodically see the following message in the console:

java.lang.RuntimeException: System overload: Maximum number of concurrent
requests (100) exceeded

when the system is very busy. Since upgrading to the newer version of xmlrpc
seems to be quite involved, we thought that we will just download the source
code and change the hardcoded number of 100 to something bigger, recompile
the jar file and use that in our system.

So I set the number to 2000 and have Lan, Michael and Irina try again. All 3
of them said that it solved their problems, but now that this works, we have
other concerns:

[1] Will setting this number so high (2000 vs. 100)  create other problems?
[2] How can we find out what is a “good” number to use?
[3] What are some ways I can monitor these concurrent requests as they run?
netstat?

Would you please share your thought on this?

Thanks,
Cecilia



++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Chris Mattmann, Ph.D.
Senior Computer Scientist
NASA Jet Propulsion Laboratory Pasadena, CA 91109 USA
Office: 171-266B, Mailstop: 171-246
Email: chris.a.mattmann@nasa.gov<mailto:chris.a.mattmann@nasa.gov>
WWW:   http://sunset.usc.edu/~mattmann/
Phone: +1 (818) 354-8810
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Adjunct Assistant Professor, Computer Science Department
University of Southern California, Los Angeles, CA 90089 USA
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++




++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Chris Mattmann, Ph.D.
Senior Computer Scientist
NASA Jet Propulsion Laboratory Pasadena, CA 91109 USA
Office: 171-266B, Mailstop: 171-246
Email: chris.a.mattmann@nasa.gov<mailto:chris.a.mattmann@nasa.gov>
WWW:   http://sunset.usc.edu/~mattmann/
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Adjunct Assistant Professor, Computer Science Department
University of Southern California, Los Angeles, CA 90089 USA
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++



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