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From "Shapira, Yoav" <Yoav.Shap...@mpi.com>
Subject RE: help - Tomcat/Linux deployment
Date Mon, 13 Jan 2003 14:00:14 GMT
Howdy,
I can't help much with DBCP, but I noticed your other thread was
hijacked with a "how did you get DBCP to work? ..." question ;)

I did want to comment on something else:

>Also, immediately after I start Tomcat on Linux I see a lot (26) of
java
>processes running. As I understand, they are Tomcat internal threads
>launched as OS processes, because Linux JVMs (I tried both SUN's and
>IBM's) use "green", not native threads.

Be careful interpreting the Linux ps/vmstat command output with regards
to JVM memory consumption and thread usage.  More information on this
issue is available in the list archives, so you may want to search
there.

Tomcat by default will record that it's starting a new request
processing thread in its log.  So you can look there and see how many
request processing threads tomcat has running.  There are only a few
threads on top of that (main, finalizer, timer, etc, the standard JVM
threads).

>Now, as the time goes by, the number of these threads/processes grows,
and

Do you create any threads in your app?  If so, be careful to close them
appropriately.

>when I try next morning to login, the server cannot create extra
processes
>needed to fulfill the client's request, because on Linux/UNIX the
number
>of user processes is limited.

Typically DBCP will not try to create extra threads after its
initialization and definitely not after pool fulfillment.

>Can anybody tell me if I understand this right, and what might be a
>workaround?

A three-pronged approach:

- See if you can increase the number of user processes via something
like ulimit on Solaris,
- Make sure you don't create extra threads, run tomcat with the minimum
number of threads you can afford (this depends on how many concurrent
users you need to support)
- Run your application in the development environment, where everything
works, for a prolonged period of time (> 1 day) and see if the same
error repeats.

Post more information once you have it, and I'm sure we'll be able to
offer more help ;)

Yoav Shapira
Millennium ChemInformatics

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