Tomcat performance break-in under load, zero response, servicetermitated

[SSL <st...@synlogic.ch>]

Hello there, 

we have a problem with an intranet tomcat server.
Under high load*** the performance completely breaks in, or the tomcat
totally fails (service terminated unexpectedly).
The break in first seemed to be a complete collapse, but the tomcat
magically recovered after some time, 
but never reacheed its full capacity again.
The processor load was then at about 0%-40% , not 85%-98% as before when it
was running fine.

***high load
User training with about 20 client pcs.
Reconstructing the failure by running 12 concurrent HTTracks to fetch the
pages. 

Tomcat 5.5.9 also 5.5.17 using jre 1.5.0_04 
768 MB initial 1,5 GB max memory (but not nearly used says lambdaProbe )
lambdaProbe says not running more than 40 running Threats out of max 70 , we
would keep about 50 threats

Windows 2003 Server SP1 4GB 3.2 Ghz dual 
accessing an Oracle 9.2 database on a different server using direct JDBC
also running an IIS on the server

Our Application is essentially a Servlet generating some kind of report
pages.
The pages are XSLT transformed XML data which is fetched from the db.
The pages including large grafics (generated jpg ca 1000x2000px) are
generated on the fly, because of the variations.
We got some NullpointerExecptions instead of expected database result sets, 
but then the servlet will simply not serve the complete page correctly, or
would it have other consequences?

The database logged no errors or problems and the database server could
handle the load easily with about 30% prozessor load.

It seems to me that the memory increase (over initial mem) posses an extreme
problem.
Can anybody confirm this ? would it be useful to set initial mem to a gig or
more?

What can we do or try?
If anybody has some tips to share? please ;-)

We also experienced this bug, but only sometimes
http://issues.apache.org/bugzilla/show_bug.cgi?id=38898

Thanks
Stefan


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