[infinispan-dev] SingleJoinTest#testTransactional failure

[Manik Surtani]

On 24 Nov 2010, at 20:10, Vladimir Blagojevic wrote:

> Here is a JIRA https://jira.jboss.org/browse/ISPN-799

Thanks

> I like option 1 as well. I am interested in details of how this can be done. How do we set lock acquisition timeout for InvalidateL1Command, issue command to abort specific tx etc etc?

Propose a design, we can review it here.

> 
> Cheers.
> 
> On 10-11-24 12:36 PM, Manik Surtani wrote:
>> Right, I've spotted it.  The test failure itself is intermittent due to the way addresses are organised in the hash wheel, so you are correct that it is a timing issue.  Anyway, it still is a very real problem.  Just to re-iterate and to make sure we are talking about the same thing:
>> 
>> 1.  View is {A, B, C}
>> 2.  K is mapped to {A, B}
>> 3.  A tx starts to update K, and is prepared.  Locks now held for K on {A, B}
>> 4.  D joins.  D is placed on the hash wheel between A and B.  So the new view is {A, D, B, C}
>> 5.  As per the test (artificial, I know, but could still happen), the tx waits for a long time before committing.  In the case of the test, artificially waits until D has finished joining before committing, by use of a latch.
>> 6.  D never joins as even though it receives the prepare for the tx and could potentially commit itself (as a new owner), it fails as it is unable to invalidate K on B.
>> 
>> There are a few solutions here:
>> 
>> 1)  This is pretty easy to detect.  Attempt to acquire the lock with a smaller lock acquisition timeout and if the transaction is still stuck, abort the transaction and proceed with the join.
>> 2)  If the blocking node is *not* the transaction originator (as in this case: the tx was started on A), then just force lock removal and tx rollback on B *only*.  Let the tx complete on A, since the new joiner will receive the transactional event and will be able to apply it as a new owner.
>> 
>> My vote is to go for solution 1 - a bit more crude, but 2 would be very complex to implement.  And even then, would only solve for  the invalidation being blocked on a node that did not originate the transaction.  E.g., the tx originated on A but the lock issue was on B.  If, however, the tx originated on B, *and* B no longer owns the entry in question, then 2 is no longer a solution and the only solution would be 1.
>> 
>> Thoughts?
>> 
>> Cheers
>> Manik
>> 
>> PS: Do we have a JIRA for this?
> 

--
Manik Surtani
manik at jboss.org
Lead, Infinispan
Lead, JBoss Cache
http://www.infinispan.org
http://www.jbosscache.org