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From DE VITO Dominique <dominique.dev...@thalesgroup.com>
Subject RE: sending notifications through data replication on remote clusters
Date Mon, 10 Mar 2014 14:06:04 GMT
> On 03/10/2014 07:49 AM, DE VITO Dominique wrote:
> > If I update a data on DC1, I just want apps "connected-first" to DC2 
> > to be informed when this data is available on DC2 after replication.
> 
> If I run a SELECT, I'm going to receive the latest data per the read conditions (ONE,
TWO, QUORUM), regardless of location of the client connection. If using > network aware
topology, you'll get the most current data in that DC.
> 
> > When using Thrift, one way could be to modify CassandraServer class, 
> > to send notification to apps according to data coming in into the 
> > coordinator node of DC2.
> >
> > Is it "common" (~ the way to do it) ?
> >
> > Is there another way to do so ?
> >
> > When using CQL, is there a precise "src code" place to modify for the 
> > same purpose ?
> 
> Notifying connected clients about random INSERT or UPDATE statements that ran somewhere
seems to be far, far outside the scope of storing data. Just configure your client to SELECT
in the manner that you need.
> 
> I may not fully understand your problem and could be simplifying things in my head, so
feel free to expand.
> 
> --
> Michael

First of all, thanks for you answer and your attention.

I know about SELECT.
The idea, here, is to avoid doing POLLING regularly, as it could be easily a performance nightmare.
The idea is to replace POLLING with PUSH, just like in many cases like SEDA architecture,
or CQRS architecture, or continuous querying with some data stores.

So, following this PUSH idea, it would be nice to inform apps connected to a preferred DC
that some new data have been replicated, and is now "available". 

I hope it's clearer.

Dominique



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