[infinispan-issues] [JBoss JIRA] (ISPN-4777) Replace command not atomic in REPL_SYNC cache mode

[Anuj Shah (JIRA)]

Anuj Shah created ISPN-4777:
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             Summary: Replace command not atomic in REPL_SYNC cache mode
                 Key: ISPN-4777
                 URL: https://issues.jboss.org/browse/ISPN-4777
             Project: Infinispan
          Issue Type: Bug
            Reporter: Anuj Shah
            Assignee: Mircea Markus
             Fix For: 5.2.6.Final


This problem was discovered using the Lucene InfinispanDirectory with DistributedSegmentReadLocker. We found after a while of production usage that some Lucene files were randomly removed from the caches, but remained in the file listing entry, which resulted in an unusable index.

We managed to replicate the problem in a test that acquires and releases read lock concurrently and checks for file deletion. We found this fails quickly when using REPL_SYNC mode, but runs for a while with DIST_SYNC.

Some extra logging indicated that the replace command used to increment the lock counter across multiple cluster members, results in an single increment when called concurrently, with both calls reporting success. This eventually causes the file deletion, as we have now mis-counted the number of readers. We also observed the opposite effect of the counter only decrementing by one when releasing. 

Our conclusion is that the replace command fails atomicity when in REPL_SYNC mode, but works in other modes, we tried DIST_SYNC, DIST_ASYNC and REPL_ASYNC.



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