Tyler DeWitt wrote:
I was curious if anybody knew of some software that tracked the memory
and cpu usage of each servlet that was running on a Tomcat instance. I am
looking to be able to say "Servlet A is using 2%CPU and 10 mb of heap and
Servlet B is using 2% CPU and 200 mb of heap." I need to be able to do this
because the company I work for uses a Tomcat server running 20 servlets.
Occasionally, a servlet will begin consuming huge amounts of resources
(either CPU or memory).
If it is really occasionally, then a continuous metering might not be
that good; more effective would be to be able to gather data when the
abnormal situation arises.
Our only diagnostic tool tells us that Tomcat is consuming resources, it
> does not pinpoint the actual misbehaving servlet.
As for CPU (this depends on platform of course, which you did not
identify):
- you can get a thread dump of the JVM, which will (among other
things) disclose what was running at the time of the thread
dump
- you may be able to see per-thread CPU statistics from the OS
level (this is the platform-dependent part!), and correlate
them with the thread information in the thread dump; this should
give you enough to identify the CPU hog; most of the time when
I've seen issues with Tomcat eating all of the CPU it has been
either a servlet (or something called via a servlet) stuck in
a loop for some oversight in application logic, or alternatively
it has been the garbage collector trying to survive from
an application that leaks memory
Then to memory usage issues; my recommendation is YourKit memory
profiler (http://www.yourkit.com/). YourKit will give you the tools
to take a memory snapshot at the time your application is having
problems with memory usage (or can even take a snapshot by itself
when memory usage exceeds a pre-set threshold). This snapshot can
then be analyzed off-line to find out the object reference graphs
in the running application. A big plus in this way of analyzing
memory issues is the non-intrusiveness - and from that the extremely
low impact (I haven't been able to notice any - something might be
visible if measuring with accurate timing tools) to the runtime
performance (except for the moments when a snapshot is just being
taken; at those point the JVM may freeze completely for a short
while).
No coding, no recompilation required.
--
..Juha
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