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From Andrew ...@starfishzone.com>
Subject Forced spool to Disc Cache
Date Thu, 01 Sep 2005 15:11:48 GMT
Please can you tell me if the following is an appropriate use of JCS.

My application will ultimately be long running and I want all the classic 
features of a memory based cache that spools to disc.  However, I want to 
use JCS during the development cycle and then leave it in-situ ready to be 
used in the finished application.

My application processes data through stages A > B > C > etc and I intend 
storing objects in a cache at the end of each completed stage.  In JCS 
terms, I would give each processing stage its own region.

In development, I am developing the stages sequentially A,B,C... and 
continually stopping and starting the JVM as I develop the later stages of 
the process pipeline.  I want to be able to re-use data successfully 
processed and stored in the cache from earlier stages.

1) My application only runs for a short time, in development, and runs 100% 
cpu.  In my limited testing of JCS so far, I find that any lazy spooling to 
disc does not occur.  Indeed, spooling to a Disc Cache only occurs if 
MaxObjects is exceeded.  What I would like is a command that could be 
executed that spools all memory objects to disc on a blocking-call basis 
(so that the JVM can exit knowing that the spooling is complete)?  I 
suppose this is equivalent to EJB passivation of entity beans when you 
shutdown a server gracefully, or a JSP server that persists sessions.

2) If I change the class signatures of data previously stored at any stage; 
how do you suggest I deal with this?  Are these appropriate: I can remove 
all data from the region (that caches that set of classes), or trap 
IncompatibleClassChangeError type errors as the cache is read.

Andrew.


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