[infinispan-dev] ISPN-777 and dealing with stale locks

[Manik Surtani]

Mircea's initial fix [1] for ISPN-777 was on the right track but incomplete, as witnessed by comments here [2]:

I've made a few more changes [3] to this which will now be in 4.2.0.CR3.  Anyway, the purpose of this email is to summarise my changes:

* Transactions self-destructing was only present on LockingInterceptor.visitLockControlCommand() [4].  This should also be on visiting prepare commands since this is the other place that locks can be acquired and a remote node disappearing.
* The check above is still not enough.  There is a race between conducting the check on a transaction and actually acquiring a lock.  E.g., a remote transaction may seem valid in [4] but by the time the thread acquires the lock, the node could have died rendering its transaction stale.  For this purpose, I have added a validity field to RemoteTransaction [5] which is flagged whenever a RollbackCommand is invoked [6] [7].  This allows the stale transaction cleanup task to flag such transactions as invalid even if they are being processed on the fly.  Finally, I have a check for this flag whenever locks are acquired and entries written to [8] and appropriate lock release if this is the case [9].
* I've also added a stress test that demonstrates this problem better (much more repeatable), based on the original test submitted by the reporter.
* Some other minor tweaks like better logging and toString() impls.  :-)

Cheers
Manik

[1] https://github.com/infinispan/infinispan/commit/51257cb
[2] http://community.jboss.org/thread/158844?tstart=0
[3] https://github.com/infinispan/infinispan/commit/ca0b28f314bb0a59edc0dfa7453f66fcd9162b26
[4] https://github.com/infinispan/infinispan/commit/51257cb#L1R148
[5] https://github.com/infinispan/infinispan/commit/ca0b28f314bb0a59edc0dfa7453f66fcd9162b26#L8R34
[6] https://github.com/infinispan/infinispan/commit/ca0b28f314bb0a59edc0dfa7453f66fcd9162b26#L4R56
[7] https://github.com/infinispan/infinispan/commit/ca0b28f314bb0a59edc0dfa7453f66fcd9162b26#L1R83
[9] https://github.com/infinispan/infinispan/commit/ca0b28f314bb0a59edc0dfa7453f66fcd9162b26#L8R74
[10] https://github.com/infinispan/infinispan/commit/ca0b28f314bb0a59edc0dfa7453f66fcd9162b26#diff-11
--
Manik Surtani
manik at jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org




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