[JBoss-dev] [ jboss-Bugs-856983 ] Threading issue with ALL finders in JBoss 3.2.1

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Bugs item #856983, was opened at 2003-12-09 16:54
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Category: JBossCMP
Group: v3.2
>Status: Closed
>Resolution: Out of Date
Priority: 5
Submitted By: Jacy Grannis (jacyg)
Assigned to: Nobody/Anonymous (nobody)
Summary: Threading issue with ALL finders in JBoss 3.2.1

Initial Comment:
The problem is this, when running the finder, if it
uses the ReadAheadCache, it uses addFinderResults().
That method is synchronized, and, the way the system is
coded, there is only one ReadAheadCache instance per
CMP bean-type. So...there's this significant bottleneck
when running multiple threads against the same bean....
This *clearly* can not be good. Now, I wasn't entirely
sure on why there is only a single ReadAheadCache per
bean-type. The read-ahead data itself is stored in the
entity transaction cache. However, the paging data is
stored in a single cache across all transactions. It is
the management of this paging data that led to marking
the method(s) synchronized on ReadAheadCache. Now,
maybe there is a good reason for only having one paging
cache for the whole system, I'm not sure. However, it
MUST not be synchronized. It really causes problems if
you have finders that return lots of results....
So...in order to remedy this, I modified
JDBCStoreManager so that the getReadAheadCache() method
returns different ReadAheadCache instances per
transaction. I don't know if this will cause some
subtler issue that I can't see, but...it certainly
removes an INCREDIBLY significant bottleneck from the
system. Maybe one of JBoss's developers would be able
to come up with a better fix? (I'm simply not ready to
assert that there wasn't a reason for sharing portions
of the cache) but this does seem to remedy the problem
for now.

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Comment By: Bill Burke (patriot1burke)
Date: 2003-12-09 20:46

Message:
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already fixed within 3.2.2.  Synchronization has probably
been removed.  Get back to me if it hasn't, although I
thought I removed it.

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