Our server does recover (whether JRun or Tomcat), but as Pepijn points
out, the thread management during the behaviour is the main concern.  

I did a thread dump (SIG-QUIT) on both the JRun and Tomcat environments
during the "refresh button load test" and the differences are
significant.  

Between the two environments I observed the following:

Tomcat:  Java CPU% exceeds 80%.  Site becomes unusable.  Thread dump
yields approximately 70 threads, just over half are waiting for the DB.

JRun: Java reaches approximately 42% CPU.  The site is usable and
improves over time.  Thread dump yields only about 18 threads, mostly in
"Object.wait()" state.


I realize this test and its methodology are somewhat arbitrary, but can
ANYONE explain what Tomcat (with mod_jk or mod_jk2) is doing with its
thread management with excessive broken pipes and why the threads pile
up out of control?

PS.  I presumed it was bad form to attach documents, but I do have
thread dumps available if anyone is willing to take a gander.

-- 
Chris Boyce


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