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https://issues.jboss.org/browse/JGRP-2234?page=com.atlassian.jira.plugin....
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Bela Ban commented on JGRP-2234:
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Yes, I guess my solution would require lock acquire/release acks to be sent back to the
requesters only after successfully copying to the backup member(s). This increases latency
quite a bit, and that's why I tend to favor your proposal.
If you read my comment dated Jan 23, this is actually what I had in mind with
reconciliation protocol I mentioned. This would reduce latency for lock
acquisition/release, which is critical, at the cost of a more involved reconciliation
protocol when the coord changes. I do like the tradeoff though...
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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