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From Milt Epstein <>
Subject RE: "Naive question" thread
Date Fri, 20 Dec 2002 20:15:54 GMT
On Thu, 19 Dec 2002, Denise Mangano wrote:

> Hi all :)
> In response, I was running ps -ef to view what was running.  I
> haven't had a chance to read the man on ps, but I did quickly try
> pstree -aup as you suggested.  It looks like (if I am reading the
> tree right) there is only one java process, with a number of threads
> branching off.  The same for the httpd process.
> Just out of curiousity, why would so many threads be spawned just
> after starting the services before doing anything?

There are several things those threads could be created for.  First of
all, tomcat is set up to do one request per thread, and it typically
creates a pool of request processing threads to handle requests (you
can control this somewhat because most/all Connector's have
minProcessors and maxProcessors attributes).  So, initially, some
minimum number of such threads are created right away.  There will be
other threads for bookkeeping kinds of things, like perhaps to
invalidate sessions.  I'm not really sure what other things other
threads would be for.  I think someone (Craig McClanahan?) recently
posted about what some of those threads are doing, if you're really
curious, you can look that up in the archives.

> -----Original Message-----
> From: jon wingfield
> To: Tomcat Users List
> Sent: 12/19/2002 1:47 PM
> Subject: RE: "Naive question" thread
> i use pstree -aup.
> Very useful with multiple java apps running on one server :)
> -----Original Message-----
> From: Milt Epstein []
> Sent: 18 December 2002 20:15
> To: Tomcat Users List
> Subject: "Naive question" thread
> Saw a post in the "naive question" thread earlier today that I wanted
> to respond to, but my quick "delete" finger got to it before I got
> around to it.  This was a thread in which John Turner, Denise Mangano,
> and some others had been participating.
> Anyway, Denise posted the output of ps that had a whole bunch of java
> processes listed.  I'd be concerned about the number of such
> processes, because normally there shouldn't be so many -- in fact,
> most typically (i.e. one tomcat instance), there should be just one.
> Now, Denise said she's using linux, and it's my understanding that ps
> under linux will list threads, not just processes.  So it's possible
> all those java listings were all the threads running in one java
> process.  And I think there's an option to ps to cause it list actual
> processes, not threads.  So you might try that and see what the output
> looks like.

Milt Epstein
Research Programmer
Integration and Software Engineering (ISE)
Campus Information Technologies and Educational Services (CITES)
University of Illinois at Urbana-Champaign (UIUC)

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