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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: Tomcat 5.5.26 hangs
Date Wed, 14 Oct 2009 16:58:22 GMT
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Peter,

On 10/14/2009 10:48 AM, conrad-tomcat.users.2009@tivano.de wrote:
> Currently, they're using Tomcat-5.5.26 on SUN's jdk 1.5.0_10 (64 bit)
> and mod_jk 1.2.28. Over the years, we have seen the same situation since
> before Tomcat-5.5.12.
> 
> Most of the time, things work nicely. Occasionally, though, the whole
> system comes to a complete halt. A post-mortem thread dump shows all (!)
> worker threads on all instances waiting for input from the Apache servers,
> e. g.:
> 
> "TP-Processor2432" daemon prio=10 tid=0x00b2f258 nid=0x9f1 runnable [0x7cfbf000.
> .0x7cfbfa70]
>         at java.net.SocketInputStream.socketRead0(Native Method)

Although those threads say "runnable", they're really blocked at the OS
level waiting to receive data from the mod_jk connector. These threads
are actually idle, waiting for requests from httpd to come through the pipe.

You can probably confirm this by checking with 'top' to see that Tomcat
isn't using any CPU time, because it's just waiting.

> Usually, the situation can be resolved by restarting Apache and/or
> (some) Tomcat servers, which makes DOS attacks unlikely, IMO.

If restarting Apache httpd solves the problem, this may be an httpd problem.

Is it feasible to remove httpd from the equation? Tomcat 5.5 can easily
compete with httpd for static file delivery if that's all your using it for.

If you could post your httpd configuration for your worker/prefork stuff
AND your mod_jk configuration, it might be helpful.

- -chris
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