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From Jeffrey Wang <>
Subject DatabaseDescriptor.defsVersion
Date Fri, 15 Apr 2011 23:04:40 GMT
Hey all,

I've been seeing a very rare issue with schema change conflicts on 0.7.3 (I am serializing
all schema changes to a single Cassandra node and waiting for them to finish before continuing).
Occasionally a node in the cluster will never report the correct schema, and I think it may
have to do with synchronization on DatabaseDescriptor.defsVersion.

As far as I can tell, it is a static variable accessed by multiple threads but is not protected
by synchronized/volatile. I was able to write a test in which one thread never reads the modification
done by another thread (as is expected by an unsynchronized variable). Should this be fixed
or is there a higher level reason this does not need to be synchronized (in which case I should
continue looking for the reason why my schemas don't agree)? Thanks.


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