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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: Recover from SEVERE: All threads (400) are currently busy, waiting. Increase maxThreads (400) or check the servlet status
Date Tue, 06 Apr 2010 15:59:05 GMT
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Kapilok,

On 4/6/2010 11:19 AM, kapilok wrote:
> Does Tomcat guarantee recovery in case of this Error?

The JVM/Tomcat should "recover" in the sense that service threads that
complete their work should go back into the thread pool and accept new
requests.

Unfortunately, your webapp can significantly impact the ability for
those threads to complete their request handling.

> Can you point me to the documentation?

There is no documentation that covers this "recovery": it's just a
feature of using thread pools.

> Please suggest a way to test / validate the recovery.

First, figure out what the real problem is. The symptom is obvious (see
your subject line).

To see what those threads are doing, allow this situation to occur, then
do the following:

1. Perform whatever magic you need to "solve" the "database overload" issue

2. Wait a minute or two to give your webapp a chance to breathe

3. Perform a thread dump on your webapp
(http://wiki.apache.org/tomcat/HowTo#How_do_I_obtain_a_thread_dump_of_my_running_webapp_.3F)

4. Wait 30 seconds

5. Perform another thread dump on your webapp

6. Inspect the thread dump(s) to see what your threads are stuck doing.
If they're stuck in your webapp's code, go fix that and try again. If
they're stuck in Tomcat's code, post back and we'll take a look.

- -chris
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