[jboss-jira] [JBoss JIRA] (JGRP-2234) Unlocked locks stay locked forever

[Bram Klein Gunnewiek (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-2234?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13530930#comment-13530930 ] 

Bram Klein Gunnewiek commented on JGRP-2234:
--------------------------------------------

[~belaban] Thanks for resolving this! Using the testcase provided is fine obviously.

A side note about the "multiple members holding the same lock in a split brain": since JGroups can't prevent these scenario's I would suggest that in case of "multiple locks" the lock should be released again when *all* lock owners have released it. E.G. in a cluster of [A,B,C,D] that splits into [A,B][C,D] where A and C hold the same lock (lock X) and they merge back into one cluster [A,B,C,D] I think think lock X should be 'released' after both A and C unlock it. But that might be something to think about in JGRP-2249.

> Unlocked locks stay locked forever
> ----------------------------------
>
>                 Key: JGRP-2234
>                 URL: https://issues.jboss.org/browse/JGRP-2234
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bram Klein Gunnewiek
>            Assignee: Bela Ban
>             Fix For: 4.0.11
>
>         Attachments: ClusterSplitLockTest.java, jg_clusterlock_output_testfail.txt
>
>
> As discussed in the mailing list we have issues where locks from the central lock protocol stay locked forever when the coordinator of the cluster disconnects. We can reproduce this with the attached ClusterSplitLockTest.java. Its a race condition and we need to run the test a lot of times (sometimes > 20) before we encounter a failure. 
> What we think is happening: 
> In a three node cluster (node A, B and C where node A is the coordinator) unlock requests from B and/or C can be missed when node A leaves and B and/or C don't have the new view installed yet. When, for example, node B takes over coordination it creates the lock table based on the back-ups. Lets say node C has locked the lock with name 'lockX'. Node C performs an unlock of 'lockX' just after node A (gracefully) leaves and sends the unlock request to node A since node C doesn't have the correct view installed yet. Node B has recreated the lock table where 'lockX' is locked by Node C. Node C doesn't resend the unlock request so 'lockX' gets locked forever.
> Attached is the testng test we wrote and the output of a test failure.



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