CPU Spike Every 10 seconds

[Ashraf Mohamed <as...@spanlink.com>]

Hi,

We are running Tomcat 5.5.9 on Windows 2000 Server. Our test involves
500 plus clients sending periodic jsp requests. 

Performance logs show that the tomcat process spikes up to 50% every 10
seconds even AFTER the test has ended and the clients have stopped
sending requests.

Tomcat logs showed the following two statements:

Every 10 seconds:

16:59:46,599 DEBUG (HostConfig.java:960)
[org.apache.catalina.startup.HostConfig::checkResources] - Checking
context[/TUP] redeploy resource D:\Program Files\Tomcat\webapps\TUP

Every 60 seconds:

2007-01-09 16:59:36,532 DEBUG (ManagerBase.java:653)
[org.apache.catalina.session.ManagerBase::processExpires] - Start expire
sessions StandardManager at 1168383576532 sessioncount 0
2007-01-09 16:59:36,563 DEBUG (ManagerBase.java:662)
[org.apache.catalina.session.ManagerBase::processExpires] - End expire
sessions StandardManager processingTime 31 expired sessions: 02007-01-09


I tried turning off autoDeploy. The redeploy log messages went away, but
the cpu remains the same.

I turned on verbose:gc and the GC logs show collection every 90 seconds
or so. So that does not match the cpu spike.

What does Tomcat do that could cause a cpu spike of almost exactly 50%
almost exactly every 10 seconds?

I have spent a couple of days searching the web, tomcat lists and bug
lists without any luck. Appreciate any help anyone can provide. Thanks.

Ash

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RE: CPU Spike Every 10 seconds

["Caldarale, Charles R" <Ch...@unisys.com>]

> From: Ashraf Mohamed [mailto:ashraf.mohamed@spanlink.com] 
> Subject: CPU Spike Every 10 seconds
> 
> What does Tomcat do that could cause a cpu spike of almost exactly 50%
> almost exactly every 10 seconds?

It's most likely the background processor thread for the Catalina
engine; look at the description for backgroundProcessorDelay here:
http://tomcat.apache.org/tomcat-5.5-doc/config/engine.html

It's doing things such as scanning for changes to files specified by
<WatchedResource> declarations.

 - Chuck


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