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

[Mircea Markus]

----- Original Message -----
> From: "Sanne Grinovero" <sanne at infinispan.org>
> To: "infinispan -Dev List" <infinispan-dev at lists.jboss.org>
> Sent: Monday, February 13, 2012 8:06:03 AM
> Subject: Re: [infinispan-dev] X-datacentre replication: design suggestions
> 
> On 10 February 2012 19:17, Dan Berindei <dan.berindei at gmail.com>
> wrote:
> > Mircea was saying that we'd only send over committed modifications,
> > so
> > no locking RPCs that need to be synchronous.
> 
> I understand the performance cost would be otherwise high, but is
> this
> not defeating the purpose?
> I would expect as a user that - if I need cross-datacenter
> replication
> - I would get a strong guarantee that committed data is safe in both
> locations, not that some might still need to be sent.
If you configure an *sync* bridge then you'd get the confirmation during the commit. What you don't get by participating in the preapre is consistency guarnatees for two tx writing to same data in different datacenters - but not sure we want to support that?

> So I would expect that - for transactional operations only - the
> other
> locations participate in the prepare phase.
> If we go for async replication, won't we need as well some way to
> guarantee that the other replicas apply changes in the correct order?
Can you please detail on this scenario?

> About the cons in #3, it states
> "the state transfer needs to be customized to send all cluster's
> state
> through the end-point."
> Why? Can't we have each node connect directly? No endpoint -> no
> overloading.
that's what #2 does. Possible, but it has its cons, mainly the number of x-site connections. See bela's comment in a previous email and Erik's comment here: https://community.jboss.org/wiki/CrossDatacenterReplication-Design