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https://issues.apache.org/jira/browse/GEODE-8671?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17269580#comment-17269580
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ASF GitHub Bot commented on GEODE-8671:
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upthewaterspout commented on pull request #5925:
URL: https://github.com/apache/geode/pull/5925#issuecomment-764889906
Minor nitpick - can you please provide a description of what you changed and
why in the final commit message. I don't see one in this PR or the individual
commits, but maybe I missed something. Thanks!
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> Two threads calling get and retrieve the same PdxInstance, resulting in
> corruption
> ----------------------------------------------------------------------------------
>
> Key: GEODE-8671
> URL: https://issues.apache.org/jira/browse/GEODE-8671
> Project: Geode
> Issue Type: Improvement
> Components: regions
> Reporter: Dan Smith
> Assignee: Jianxia Chen
> Priority: Major
> Labels: pull-request-available
>
> Even if copy-on-read is set to true, two threads calling get on a partitioned
> region can end up with the same PdxInstance object.
> This is problematic because some PdxInstances methods are not thread safe.
> Although the underlying bytes are immutatable, the PDXInstance has a
> ByteSource with a position field that changes. That means two threads doing
> serialization or calling toString on the PdxInstance could result in one or
> more threads getting a corrupt read.
> It looks like they are ending up with the same instance because of the
> behavior in LocalRegion.optimizedGetObject. We use futures to make sure there
> is only 1 get that goes through, and both threads receive the same value.
>
> Ending up in optimizedGetObject requires a race with the put, because if the
> value was in the cache at the beginning of the get it would be returned
> earlier in the get process.
> I put a test that reproduces this issue here -
> https://github.com/upthewaterspout/geode/pull/new/feature/pdx-instances-shared
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