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From "Corin Moss" <Corin.M...@tvnz.co.nz>
Subject JCS Store - new issues
Date Thu, 11 Mar 2004 02:54:51 GMT

Hi Guys,

You may or may not have seen my recent posts about performance with JCS
store, but I've gotten a little further into diagnosing what looks like
a deadlock issue.

After about 30mins of load testing I'm seeing everything lock up (iowait
of ~ 100%) the error log is getting this message repeatedly:

ERROR   (2004-03-11) 15:24.32:587   [core.store.janitor] (Unknown-URI)
Unknown-thread/StoreJanitorImpl: Error in freeMemory()
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
        at java.util.ArrayList.RangeCheck(ArrayList.java:507)
        at java.util.ArrayList.get(ArrayList.java:324)
        at
org.apache.excalibur.store.impl.StoreJanitorImpl.freeMemory(StoreJanitor
Impl.java:383)
        at
org.apache.excalibur.store.impl.StoreJanitorImpl.run(StoreJanitorImpl.ja
va:202)
        at java.lang.Thread.run(Thread.java:534)

Obviously it's getting it every cycle of the Store Janitor.

I'm currently a little confused about it - it seems to me that the only
reason this error could be thrown is if the ArrayList which contains the
available stores is empty.  Is this the case?  If it is, then the next
question is:  what causes the JCS store to fall out of the store list?
Would this happen if JCS threw a fatal exception? I suspect it would,
but I'm not 100% certain.

I have a feeling I know the particular part of JCS that causes the
problem.  It seems to me that the R-W lock mechanism they use is not
quite perfect under load.

So - anyone have any more info on the questions above?

Thanks,

Corin

Corin Moss
Lead Developer
TVNZ Interactive

+64 9 916 7367
+64 21 403 054
corin.moss@tvnz.co.nz




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