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From "Andy Moller" <andymol...@gmail.com>
Subject Tomcat 4.x (Major Problem)
Date Fri, 19 Jan 2007 18:13:37 GMT
Hi All,

I have a strange problem that I think Tomcat is causing it, and I need to
confirm if my assumptions are correct.



We have a Tomcat-Standalone (Apache Tomcat/4.0.3) running as a service, we
have been working with that version of tomcat for quite sometime with
different applications. Most of the applications we used that server for
were client server applications that do not perform much data updates
(mostly about data pulls and display), and with limited number of concurrent
users. However, the recent application that de deployed on the same Tomcat
version had a major difference in which there are high frequency of
concurrent users and also high rate of data manipulations. The application
did not show problems initially, but after couple of months of actual usage,
we started noticing strange database discrepancy problems. For example:
there are two tables with one to many relationship, the records should be
(A1, B1_1), (A1, B1_2) / (A2, B2_1), (A2, B2_2)…etc. For an unknown reason,
There are occasional mal-updates that create wrong relationships in the
database, so the records might look like (A1, B2_1), (A3, B1_2)



We tried to tackle the problem from different perspectives. We performed
code inspections, application design inspections, The JDBC Data Bridge used
and the database software. The static checks all passed and the semantics
appeared ok, it must be some runtime behavior that results in this. I
started suspecting Tomcat for the next reason: a bug was reported about an
operation that failed to insert in the database. While debugging the
database query logs, the reason was that the field type is integer, while
the passed value was a "string", we went and inspected the code design and
semantics and it was an impossible case that the used "Variable" could have
been used in that SQL query. For some reason, at the runtime, a variable
reference was switched in the JVM, which suggests a memory leak and a HUGE
problem with that version of Tomcat, and that also confirmed to a certain
extent the discrepancy problem that occurs with a high volume of user
sessions in the recent application.



I would appreciate it if someone confirms that suspicion, and whether Tomcat
is a reliable server for a high demanding application.

Thank you,

Andy

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