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https://issues.jboss.org/browse/JGRP-2234?page=com.atlassian.jira.plugin....
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Bram Klein Gunnewiek commented on JGRP-2234:
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Not sure how it can be solved, but during a merge of [A,B] and [C,D] there are basically
two locktables (of [A,B] and [C,D]). When merging those lock tables you can detect that
both lock tables have an owner for lockX (lets say A and C both locked lockX). Lets say B
is the new coordinator of the merged cluster. You could implement it so that B saves both
A and C as lockowner and only grants new lock() requests for lockX when both A and C
performed an unlock();
I don't think its possible to take away locks, the only thing you could do is
implement some sort of event system that fires an event when it detects that a lock has
multiple holders after a cluster merge. This could be handled (or ignored) by the
application using JGroups, I don't think its something JGroups itself can solve.
Unlocked locks stay locked forever
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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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