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From Rainer Jung <rainer.j...@kippdata.de>
Subject Re: JK and IIS - troubles?
Date Wed, 01 Oct 2008 21:18:08 GMT
br1 schrieb:
> Rainer,
> 
> Thank you for your reply. 
> 
> My main question here is: is it normal that that a faulty application takes
> down the whole site?

Yes, unfortunately that's a common source for trouble. If an app doesn't
finish processinf a request, e.g. because it wais without timeout for
some other service, or runs in a loop, or has a deadlock, then each
broken request will block a thread until finally - maybe after weeks -
all threads are blocked in the buggy requests of the single app.

>> 1) Finding the real reason: Assuming some requests send to your Tomcat 
>> simply get stuck and do not return fast enough, you'll need to take 
>> thread dumps of Tomcat and look at those. Take the dumps when the 
>> problem is there and take more than one, e.g. 3 dumps each 3 seconds 
>> apart from the previous one.
>>
> 
> Thanks. I will give this a try, though my main priority is to have the site
> working, not the single application. I suspect there are some problem
> releasing the db connections, but I am not the developer nor a
> modern-Java-with-tons-of-frameworks developer. :-)

The Thread Dumps are an exciting way of bridging the gap between the
operations people and the developers. Operations people can provide it,
and developers can read it. Actually it is not that hard to read for
operations people too.

>> 2) Making IIS/mod_jk more robust against the problem: Use timeouts as 
>> described on page
>>
>> http://tomcat.apache.org/connectors-doc/generic_howto/timeouts.html
>>
>> Those will not make your app work, when in fact requests in Tomcat get 
>> stuck and block all available connector threads, but it will at least 
>> keep iis/mod_jk running.
>>
> 
> Actually, I was about to try this when I found that restarting Tomcat cured
> the problem. 
> I will try with the suggested timeouts as soon as everyone stops watching. 
> 
> As I was writing above, I am stumped to see a single app stopping the web
> server, because we have a zero timeout on all Tomcats and apps since years,
> and no problems like this. 
> I myself thought this was just not possible, so it took long time to figure
> this out. 

Beware, that the timeouts will shield IIS, but if the Tomcat can't
handle more requests, the timeouts in the IIS plugin will not heal Tomcat.

> BTW, thanks for writing the timeouts page, it was really needed. :-)

Yes it was, sorry that it took that long.

Regards,

Rainer

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