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From Levent Guendogdu <levo...@gmx.de>
Subject Some pitfalls in JDBCAccessLogValve ;)
Date Fri, 24 Oct 2003 23:26:54 GMT
Hi people,

I'm beginning to deploy the JDBCAccessLogValve among my web applications
until I noticed, that there are some considerations to be made. IMHO
there have to be made some adaptations to prohibit that database errors
or -slowness interferes with tomcat and thus disturbs or even prohibts
the user experience.

So decoupling adding and storing of the log entry should lead to a much
faster (to user experience) asynchronous model.

1.) Speed: I think including a queue to which the calling thread just
appends the log record and then continues serving the user is much more
efficient than the current implementation. Without this the user has to
wait for the database to finish writing the access log. On a heavily
used system or a multi user system this can be long time, as this method
is called for each http access and the database access itself is
synchronized, too.

2.) Scalability and error handling: If the database connection fails or
drops for a short period of time  (for example due to a database
restart), then the valve's connection will be either closed or in an
invalid state, so the prepared statements and they will will never
recover. Thus Tomcat becomes totally unresponsive and won't serve any
HTTP requests anymore, as all requests are interrupted by the database
exceptions caused by inconsistent connection and pstmt objects.

Thanks for any insight

Bye,
 Lev.



-- 
Levent Guendogdu <levomat@gmx.de>


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