High CPU Usage by Tomcat

Posted on 2014-04-11
Medium Priority
Last Modified: 2014-04-25
Our developer team had just updated a link within our webpage that gives our clients a new look and feel to our webpage. As a sysadmin, I helped with the deploying the jsp.war file (build) to the server. Now, the CPU usage for tomcat has maxed out to 99-100%. Of course restarting the service will bring it down, but eventually it will max out again. The development team has looked at the logs, and cannot pin point what the issue is.  I don't know java, or tomcat at all, but my colleague does, and have add more memory to the permgen, java and we've even added more physical memory and CPU, but to no avail. The developers looked at the codes and find nothing wrong. What is odd is that this high CPU spike has something to do with the change from the developers because it happened right after the update. However, we do not want to point fingers, nor do they. I looked at anything possible from a Windows server standpoint. Again, I am not a java expert or a developer, but can someone here who is provide some sort of theory as to what it can possibly be or provide some advice so i can pass that info to our developers? We use VisualVM to looked for any issues, and already had our DBA look at it from a DB perspective, but still to no avail. The application we use is inhouse (proprietary).
Question by:5itface

Expert Comment

ID: 39995471
Nothing wrong doesn't necessarily mean the code is optimal for the platform it's running on.  Some questions that need to be asked are:

1.  What's the target OS?
2.  What OS specific setting are required or recommended to get best performance out of the application?
3.  What are the hardware requirements/recommendations for the application (processor, storage, memory, and network)?
4.  What web server (Tomcat in this case) version is required and are  specific settings required or recommended to get best performance out of the application?
5.  How many users (sessions) will the application support using the recommended hardware, OS, and web server configurations?
6.  What members of the development, systems administration, and database administration teams will be responsible for addressing any issues?

As you get more experience you'll likely have a number of other questions that need to be answered before putting a new application into production but I'd recommend using these as a minimum.

But that's for future applications.  Right now you're stuck with having a poorly performing one in production.  You're very right about not pointing fingers as it's not likely to get you anywhere.  Instead I ask something like, "Who can I work with on the development team to help find out what's going on?"  

As to what's happening there's just too many possibilities to guess but if I had to I'd start by looking at refresh intervals for any active content (particularly calculated data and data driven visual content - graphs, charts, etc.).  In your place I'd start by trying to get the development team to share responsibility for finding a solution and getting answers to the above questions.

Good luck.
LVL 28

Assisted Solution

dpearson earned 500 total points
ID: 39995476
We use VisualVM to looked for any issues...

What did VisualVM show?  It should be able to indicate where the 100% CPU usage is going (i.e. which methods are causing the CPU load) and then you would need to decide whether that's appropriate behavior or not.

Profiling tools like this are definitely the way to go as that's exactly what they're designed to help solve - figuring out where the cycles are being spent in an app.

BTW since it came after an update it's 99% likely to be an issue introduced by the development team - just some unexpected situation that has come up in production that wasn't anticipated.  But the profiler should be able to identify what is using the CPU.

Author Comment

ID: 39997024
The CPU is consumed by the Tomcat process.
LVL 16

Accepted Solution

Valeri earned 500 total points
ID: 39998555
it looks like there are blocked threads. There is a piece of code which is not synchronized.
make thread dumbs and check for blocked threaqds.
this can help you: http://middlewaremagic.com/weblogic/?p=2281

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