[infinispan-dev] X-datacentre replication: design suggestions

[Bela Ban]

On 2/13/12 12:22 PM, Sanne Grinovero wrote:

> I have two transactions, run in sequence:
> - TX1 updates A
> - TX2 deletes A
>
> If you send them both in async to the other datacenter, you'll have to
> make sure they are not reordered. I know JGroups can provide that
> guarantee, just wondering if it's the plan to do this via JGroups, or
> if we have an own buffer that we can still guarantee the order, or
> even better merge changes on the same keys like we do with the async CacheStore.


This use case cannot be supported by option #3 AFAICS: the bridge 
between LON and SFO is completely asynchronous and doesn't know anything 
about sync or async RPCs, so TX2 can be applied in SFO before TX1.

With option #2, if you run with SYNC, then the TX1 will complete before 
TX2 is started. Unless, of course, the 2 transactions are started on 
different nodes: then,  it depends on which TX acquires the locks first, 
but this is the same behavior as in a local cluster.

Hmm, how does option #3 handle TXs anyway ? Does a PUT on B and C not 
trigger anything until the TX has been completed successfully, and then 
we forward the outcome of the TX to A, which forwards it to X ? How does 
X then apply it ? Special operation or a set of PUT and REMOVES ?

-- 
Bela Ban
Lead JGroups (http://www.jgroups.org)
JBoss / Red Hat