Mod_JK <> tomcat problem

[Pepijn Palmans - Kangaroot <pe...@kangaroot.net>]

Hi there,

My 'first post' here.  hit reply with appropriate remarks if i'm on the
wrong list please :)

I'm having some troubles with the connection between Mod_JK and Tomcat.
After a while things go wrong.

FYI, I'm using:
- mod_jk-2.0.43.so
- jakarta-tomcat-4.1.29
- suse (SLES 8) linux kernel 2.4.19-64GB-SMP

I have a certain application running on this tomcat instance.  Problems
occur at random moments. (At least, I couldn't find a sequence in it).

Suddenly a certain httpd process starts taking heaps of memory.  With
that, it eats up a lot of CPU also.  It only takes what is available, my
machine doesn't crash on it.  I'm able to work further, but with huge
delays everywhere.

Analyses of this problem gave me this information:

- The httpd process was sending and receiving information on file
descriptor 10 (FD 10). (found out with strace)

- FD 10 is a socket with source localhost port 54500 and destination the
tomcat ajpv13 listener port (netstat -atpen, 54500 is not bound to any
interface/process)

- tcpdump on localhost showed me that there is continues traffic between
both the httpd/mod_jk and the tomcat server (ajpv13).  The traffic is
always the same.  A request from the container (AB|length|6 -> in ajpv13
this means "Get Body Chunk") and a reply from the server (1234|00|00 ->
this is an 'empty packet' telling there is nothing more to be sent).


MY QUESTION:

Why is Tomcat repeating it's request to send more 'body chunk(s)' if
there's nothing more to be sent ?  It's eating my cpu/mem and I have no
idea why.

I know, the first answer should be: monitor until problem happens, then
see for the last packet before this starts and you might have your
problem.  Unfortunately this website is having to much traffic to start
logging for hours and I have no idea when to start/stop monitoring since
it's all occuring at random moments.

Any ideas there out in the wild ?


Kind regards,

Pepijn Palmans
Managing Director

Kangaroot Linux Solutions
Grote Steenweg 91
2600 Berchem, Antwerpen
Tel: +32 3/286.17.17
Fax: +32 3/281.23.49
Email: pepijn@kangaroot.net


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