Re: [thredds] THREDDS Garbage Collection Tuning


This is great info.   Two questions:

1.  So what do you guys actually do on your tomcat TDS?
Is the only thing you actually do is to bring -Xms up to the same
value as -Xmx?   No other tricky stuff?

2.  What would be involved with running the TDS on multiple servers
with load balancing?
Is anyone doing that?


On Wed, Jun 1, 2011 at 12:27 PM, Bob Simons <Bob.Simons@xxxxxxxx> wrote:
> Three options:
> Tweak it: Java Garbage Collectors (GC's), and the recommendations for using
> them, have changed several times. I encourage you to find a more recent
> article (e.g.,
> so
> you get the recommendations for the version of Java that you are using. It's
> worth a try.
> Fix it: The ideal approach is to identify why the problem is occurring, not
> just deal with the consequences of the problem. Some of the issues are
> programming related and can be solved or minimized via code changes, but you
> have to have a clear idea of what the problem is. You can use hprof to
> identify what lines of code are generating the most, persistent objects.
> (There are other profilers.)  And you can use -verbose:gc to monitor the GC.
>  I'm sure John Caron has investigated and will continue to investigate
> thoroughly. But you are in a better position to investigate the problems on
> your TDS.
> Restart it: It is hard/impossible to prevent these problems from occurring.
>  The garbage collectors aren't perfect. Sometimes, increasing MaxPermSize
> and Xmx and tweaking the GC settings just forestall the inevitable.
> Sometimes, you just need to acquiesce and restart tomcat or restart the
> computer.  Although the big web services do as much as possible to avoid
> problems like this, they rely on multiple servers and load balancing so that
> a given computer can be restarted when needed.
> Good luck.
> On 6/1/2011 8:24 AM, Rich Signell wrote:
>> THREDDS folk,
>> Have folks played around with Garbage Collection tuning parameters
>> besides "-XX:MaxPermSize" to help tomcat/TDS permgen errors?
>> Our TDS tomcat is throwing "GC overhead limit exceeded" errors again.
>> I know on the Unidata TDS page
>> it says the only thing you can do is increase -XX:MaxPermSize, which
>> only delays the problem, solved only by restarting tomcat.
>> But in this Garbage Collection tuning article
>> they describe many different options, and I'm wondering whether folks
>> have tried using these, or whether they just don't do any good.
>> Thanks,
>> Rich
> --
> Sincerely,
> Bob Simons
> IT Specialist
> Environmental Research Division
> NOAA Southwest Fisheries Science Center
> 1352 Lighthouse Ave
> Pacific Grove, CA 93950-2079
> Phone: (831)658-3205
> Fax:   (831)648-8440
> Email: bob.simons@xxxxxxxx
> The contents of this message are mine personally and
> do not necessarily reflect any position of the
> Government or the National Oceanic and Atmospheric
> Administration.
> <>< <>< <>< <>< <>< <>< <>< <>< <><

Dr. Richard P. Signell   (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598