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From Rainer Jung <rainer.j...@kippdata.de>
Subject Re: JK and IIS - troubles?
Date Wed, 01 Oct 2008 12:00:44 GMT
br1 wrote:
> Dear all,
> 
> I am experiencing a weird problem happening between IIS and Tomcat: it seems
> that the JK connector is hanging IIS. 
> 
> A badly behaving Tomcat app is filling up AJP connections due to some DB
> connection problems. Nothing strange so far, we had these kinds of problems
> already, but this time this is causing IIS to hang. 
> Simply restarting the failing app's Tomcat instance causes IIS to start
> again like it was simply frozen. 
> Instead, restarting IIS makes obviously the whole site restart, except for
> the failing application. 
> 
> I struggled with this problem for the past months on two servers, and just
> configured an additional IIS on our dedicated Tomcat machine with the same
> results. Configuration is as follows:
> IIS 5
> JK 1.2.26 (/maybe some other 1.2.2x version but cannot be sure)

You and we need to be sure. Set you JK log level to at least info. All 
relatively new JK versions will log their version in the log file during 
startup.

> Tomcat 5.5.9 / 5.5.27
> JDK 1.5.0_12 / 1.5.0_16 / 1.6.0_07
> About 40 workers and Tomcats
> 
> Since we use Tomcat since version 3 and Jk since before year 2k - sorry
> Linux guys - on Windows platforms without a single serious problem, I am a
> bit sorry not to be able to solve this one by myself now.
> Clearly the application needs patching, and the affected Tomcat is
> restarting hourly now, but to me the JK connector should be fixed if it is
> causing this problem. 
> 
> Kindly let me know what should  I provide in order to investigate about
> this. 

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.

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.

Regards,

Rainer

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