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From Roy Wilson <>
Subject Catalina and Valve versus Interceptor
Date Fri, 21 Jul 2000 18:19:40 GMT
In an earlier email, Criag McClanahan noted that the Valve mechanism "has lower
runtime overhead than the current Tomcat approach (RequestInterceptors)".

I've seen Craig's JavaOne slide presentation and dug up a reference to the Valve
design pattern in an RM-ODP document (forgot what acronym stands for), but
nothing I could get a handle on (but that's just me :-)). Two questions:

(1) Who collected the overhead data, where, (more-or-less) how, etc.?

(2) What source provides (IYHO) the most direct and detailed description of the
valve pattern? I wonder if I'm not making this more difficult than it is: the
JavaOne slide suggests a pipeline (of sorts).

(3) The debate between Valve versus Interceptor could be (as someone else noted,
partially) framed in terms of performance. Of course, the throughput and
response of the pipeline critically depends on the request mix (Hennessy,
Gibson, etc.) as well as the characteristics of the implementing  hardware. The
idea that the Valve is going to be realized in hard/firmware (if I read the
JavaOne slides correctly) suggests some studies have already been done. If so,
can they be looked at (assuming sanitizing is needed)?

Roy Wilson

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