Flat Tomcat busy threads and thread counts charts

[dthollis]

I've been watching the Tomcat Busy Threads charts and the Thread count
charts and they remain relatively high and constant even with a low
number of active sessions. Is this any indication of an issue or is
this normal behavior?

[Vernat Emeric]

Hi dthollis,

You should probably see the public demo:
http://code.google.com/p/javamelody/wiki/Demo
http://demo.javamelody.cloudbees.net/monitoring

Then click on "Other charts" to see "Threads count" and "Tomcat busy
threads":
http://demo.javamelody.cloudbees.net/monitoring?part=graph&graph=threadCount&period=semaine
http://demo.javamelody.cloudbees.net/monitoring?part=graph&graph=tomcatBusyThreads&period=semaine


You will see in the "Threads count" that it is more or less constant.
This is normal.
A simple Tomcat server may have about 30 threads alive (they are not
always active).
And I have seen highly loaded Tomcat servers with several hundreds of
threads alive. See for example:
http://javamelody.googlecode.com/svn/trunk/javamelody-core/src/site/resources/screenshots/autres_courbes.png

The "Tomcat busy threads" chart shows the number of active threads as
said by the Tomcat server. This count is not supposed to be high at all
times: often 0, sometimes just a few.
And sometimes, a high number of "Active threads" shows a big issue with
"blocked" requests in the webapp as said a few days ago in the users' group:
https://javamelody.googlegroups.com/attach/490d6ea6a50771c9/javaMelodyThreads.jpg?view=1&part=4

Otherwise, do you have Comet, WebSockets, long polling or something like
that in your webapp?
If yes, this may be normal to have many "Tomcat busy threads".

bye,
Emeric


Le 19/04/2012 22:23, dthollis a �crit :