[infinispan-dev] [Cloudtm-discussion] CloudTM: Additional Atomic broadcast based replication mechanism integrated in Infinispan

[Manik Surtani]

On 20 Apr 2011, at 18:18, Paolo Romano wrote:

> On 4/17/11 7:55 PM, Manik Surtani wrote:
>> Excellent stuff, Paolo and Pedro.  My comments below, inline.  Cc'ing infinispan-dev as well.
> Thanks Manik!
>> On 16 Apr 2011, at 21:47, Paolo Romano wrote:
>> 
>> ...
>> I presume this implementation still plays nice with XA/JTA?  In that transactions marked for rollback, etc are respected?
> Kind of :)
> 
> We didn't really polish the code to have it fully integrated with 
> XA/JTA, but this could be done without too many problems.
> 
> Basically, if Infinispan is the only resource in a distributed xact, and 
> it is configured to work in replicated mode, then it could externalize a 
> 1 phase commit interface. In this case, the output of the commit phase 
> would be that of the AB-based certification, avoiding totally 2PC.
> 
> If on the other hand, Infinispan (replicated) needs to be enlisted in a 
> distributed transaction encompassing other resources, 2PC is 
> unavoidable. In this case, when an (replicated) Infinispan node receives 
> a prepare message from some external coordinator it could i) AB-cast the 
> prepare message to the other replicas, and ii) do the lock acquisition 
> and write-skew validation to determine the vote to be sent back to the 
> external coordinator. (Note that all replicas are guaranteed to 
> determine the same outcome here, given the total order guarantees of the 
> ABcast and that the certification procedure is deterministic.) The 
> write-back and lock release should instead be done upon receipt of the 
> final decision (2nd phase of the 2PC) from the coordinator.
> 
> Does this answer your question?

Yes.  Is there any benefit then of participating in a distributed transaction (with other resources using 2PC) while Infinispan uses AB?  We still have the network roundtrips and hold locks for the entire duration... 

--
Manik Surtani
manik at jboss.org
twitter.com/maniksurtani

Lead, Infinispan
http://www.infinispan.org