Many EXCPs with Tomcat

Nalini · Post by **Nalini** » Wed Nov 30, 2005 12:24 pm

I have Tomcat installed & running fairly happily on the mainframe. At times, I see quite a few EXCP's done by Tomcat. I think that maybe my classpath's are not set optimally. I seem to recall there is a way to see what the search order is for classes?

I have tried all kinds of options in Server.XML and am getting nowhere. Appreciate any help!

Thanks,
Nalini Elkins
Inside Products, Inc.

Post by **dovetail** » Thu Dec 01, 2005 10:50 am

Are you seeing excessive EXCPs at startup? This would probably be classloader stuff. If the EXCPs are happening later, after the container and web applications are initialized, then it might be something else.
What EXCP rate are you seeing that concerns you?

The following Tomcat document explains how its classloaders are set up:

http://tomcat.apache.org/tomcat-5.0-doc ... howto.html

You might try googling "Tomcat tuning" to fine more help on tuning Tomcat. One suggestion is to only configure the webapps that you really need. Default apps like "balancer", "web-dav", "samples", etc you can probably remove.

Also, remember that if you are running z/OS under FLEX/ES (as we do), that the Java JVM really performs poorly

Guest · Post by **Guest** » Thu Dec 01, 2005 11:05 am

This tomcat is running on a real system. When I first bring it up there are about 150,000 excps.

What I did was just bring Tomcat up and do nothing. Left it running all night long and in the morning there were over 6 million EXCPs. I did not even log on to our application or ANY application. What I am thinking is that somehow there must be some background process in Tomcat which is looking for work to do?

I have been googling Tomcat Tuning & quite a few other things to get some ideas. I think that there is a book on Tomcat at Amazon I have heard about. I can play with the number of active or concurrent threads.

Does your tomcat do this kind of thing?

Post by **dovetail** » Thu Dec 01, 2005 12:37 pm

No, I haven't noticed this behavior. A suggestion would be to start Tomcat without any webapps (at all) and let it run... to see if it uses an IO. That way, you can tell if it is the container itself, or one of the webapps. If no problem found with an empty container, then try adding in the webapps until you find which one is doing the IO.

wwwild · Post by **wwwild** » Fri Dec 02, 2005 3:51 am

It looks like my system is similar. We are running Tomcat and are using it for cruisecontrol. Started Tomcat on 23Nov and as of now it has 110 million EXCPs indicated in SDSF. That's about 12 million I/Os per day. I generally only look at the cruisecontrol builder results once in the morning, very little activity.

www

Nalini · Post by **Nalini** » Fri Dec 02, 2005 4:24 pm

I took out all the webapps except JZOS and ROOT. I assume I need JZOS to have Tomcat come up?

I still get a ton of EXCP's. I thought maybe it was the balancer webapp which comes with Tomcat, but seems not.

There has to be some kind of background process. But why do you not see this behaviour?

Post by **dovetail** » Sun Dec 04, 2005 11:58 am

You don't need the JZOS webapp... is just some examples/samples.

When I start a default Tomcat 5.0.28 configuration, I have the following web apps running: (login to the /manager application to see)

/
/admin
/balancer
/jsp-examples
/manager
/servlets-examples
/tomcat-docs
/webdav

It takes less than 200,000 EXCPS to start everything. I never noticed if an "idle" instance with these apps running would continue to consume IO, but I never really payed much attention, so it could be happening. So, I stopped everything -except- manager and see if the system uses any resources.... after a half hour it was up to 300,000.

Try this on your system... It could that one of the default applications is occasionally doing a bunch of stuff. Or, maybe the Catalina container itself is doing it. I know that the container by default does look in the file system for changes that would cause it to deploy/undeploy applications. Maybe that's the cause.

Post by **dovetail** » Sun Dec 04, 2005 12:25 pm

OK, I think I found what was using IO on an "idle" system.

I changed the conf/server.xml, and set autoDeploy="false" on the Host definition.

Then I restarted Tomcat, and from "/manager" stopped all applications except "/manager". The EXCP count now seems to be frozen. It also seems to be using zero CPU cycles.

Apparently it takes some IO to continually check the file system to see if there are new applications to deploy

Regards,
Kirk Wolf

Nalini · Post by **Nalini** » Mon Dec 12, 2005 11:26 am

Thanks, Kirk. I was out of town last week, I will try this out and let you know. Thanks again for all your help.

Nalini

Nalini · Post by **Nalini** » Fri Dec 16, 2005 10:31 am

Kirk,

Your suggestion for autodeploy worked perfectly. No more huge numbers of EXCP's. You are the man!

Thanks for everything,
Nalini

Many EXCPs with Tomcat

Many EXCPs with Tomcat

12 million I/Os per day for our Tomcat