Re: [jgroups-users] questions about CENTRAL_LOCK locking service under 3.6.11

Questions/problems related to using JGroups <[email protected]> Thu, 12 Oct 2017 10:12:20 -0400
Newsgroups gmane.comp.java.javagroups.general
Message-ID <mailman.9090.1507817551.14213.javagroups-users@lists.sourceforge.net>
> If you look at the coordinator, does it list all locks?

The coordinator (i-06b66037ffd44d0fb) has the lock in the server and my sections (via printLocks).

	server locks: engradeSynchronizationTask: i-06b66037ffd44d0fb::107
	my locks: engradeSynchronizationTask (i-06b66037ffd44d0fb::107)

1st backup (i-040062a23b224bb64) and 2nd backup (i-0d42875495a3cb64f) has no my locks.

	server locks: engradeSynchronizationTask: i-06b66037ffd44d0fb::107
	my locks: 

Is the my-lock asymmetry expected?  Does it imply that the server is holding the lock or just that it is managing it?

> Note that the lock service in JGroups _can_ lead to multiple owners holding the same lock at the same time in case of a split brain. You'd have to resort to jgroups-raft to enforce at-most-once semantics.

It looks like the cluster members have a consistent view so I think I don't have split brain.

> Take a look at [1] and go from 3.6.12 to 3.6.14

I've gone to 3.6.14 and I believe I'm seeing the same issues.
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