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From "Wm.A.Stafford" <staff...@marine.rutgers.edu>
Subject Re: Can two Tomcat web apps deadlock each other?
Date Thu, 06 Sep 2007 13:07:53 GMT
Alexey,
    Thanks for taking the time to reply.  I'll try all your suggestions 
but I wanted to investigate the windows vs linux possibilities.  Does 
the fact that this Tomcat behavior does not occur on the windows-based 
development server offer any clue as to  what may be happening on the 
linux server when Tomcat hangs?

Thanks again,
-=bill

Alexey Solofnenko wrote:
> There can be a simple problem with locking - see 
> http://tomcat.apache.org/faq/windows.html#lock . On Linux the files 
> are usually not locked, so you can get "class not found exception" 
> when a jar file is replaced with a new one.
>
> Ask administrators to get the stack trace (and check if CPU is at 100% 
> or not - maybe it is not a deadlock). Otherwise you can look for a 
> problem for a very long time.
>
> You can also add try/catch with finite number of retries  around 
> connection code. Please  also check that your application shuts down 
> cleanly - no exceptions are thrown during shutdown (but they should be 
> logged) and preferably there are no finally() methods.
>
> Wm.A.Stafford wrote:
>> Thanks Alexey.  Unfortunately, the server in question is not ours and 
>> we do not even have log in on it, so any kind of sane analysis is 
>> probably out of the question.
>> All we can do is try deploying another version with changes that will 
>> either fix the problem (we hope) or yield some more information about 
>> what is going on.
>>
>>
>> -=bill
>>
>> Alexey Solofnenko wrote:
>>> Everything is possible, but unlikely. Please try running server 
>>> stack trace from 
>>> http://tmitevski.users.mcs2.netarray.com/stacktrace/app/launch.jnlp 
>>> to get a thread dump. It will show the list of threads and what 
>>> locks they have acquired and what locks they are waiting for.
>>>
>>> - Alexey.
>>>
>>> Wm.A.Stafford wrote:
>>>> We are deploying a newer version of a web app to run in the same 
>>>> Tomcat instance (1.4.31) as the existing version.  On our 
>>>> development servers, winXP,  if the new version encounters a 
>>>> startup problem the production app will start and only the new 
>>>> version will fail.
>>>>
>>>> On the production server, which is linux, Tomcat seems to 'hang' on 
>>>> the first failure encountered when starting the new app and nothing 
>>>> further happens. Tomcat has to be restarted after deleting the new 
>>>> app when it enters this state.  In the localhost log the last log 
>>>> entry is the exception logged from the new app and there is no 
>>>> further logging.  Since we have been doing some database changes 
>>>> the usual error that causes this is Jakarta DBCP connection failure 
>>>> but we have also seen it for a missing class file.  So I  don't 
>>>> think the error per se is at the root of the problem.
>>>>
>>>> To me this looks like a deadlock.  Is it possible for one Tomcat 
>>>> web application to deadlock with another? An obvious difference is 
>>>> windows vs linux servers.  Could there be some config issue for 
>>>> Tomcat on linux that would lead to this behavior?
>>>>
>>>> We are completely stumped by this, any ideas or suggestions would 
>>>> be appreciated.
>>>>
>>>> -=bill
>>>>
>>>>
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>>>
>>
>>
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