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From Jabbar Azam <>
Subject Re: Best approach in Cassandra (+ Spark?) for Continuous Queries?
Date Sat, 03 Jan 2015 17:16:00 GMT

Or you can have a look at akka for event processing and
use cassandra for persistence(Peters suggestion).

On Sat Jan 03 2015 at 11:59:45 AM Peter Lin <> wrote:

> It looks like you're using the wrong tool and architecture.
> If the use case really needs continuous query like event processing, use
> an ESP product to do that. You can still store data in Cassandra for
> persistence .
> The design you want is to have two paths: event stream and persistence. At
> the entry point, the system makes parallel calls. One goes to a messaging
> system that feeds the ESP and a second that calls Cassandra
> Sent from my iPhone
> On Jan 3, 2015, at 5:46 AM, Hugo José Pinto <>
> wrote:
> Hello.
> We're currently using Hazelcast ( as a distributed
> in-memory data grid. That's been working sort-of-well for us, but going
> solely in-memory has exhausted its path in our use case, and we're
> considering porting our application to a NoSQL persistent store. After the
> usual comparisons and evaluations, we're borderline close to picking
> Cassandra, plus eventually Spark for analytics.
> Nonetheless, there is a gap in our architectural needs that we're still
> not grasping how to solve in Cassandra (with or without Spark): Hazelcast
> allows us to create a Continuous Query in that, whenever a row is
> added/removed/modified from the clause's resultset, Hazelcast calls up back
> with the corresponding notification. We use this to continuously update the
> clients via AJAX streaming with the new/changed rows.
> This is probably a conceptual mismatch we're making, so - how to best
> address this use case in Cassandra (with or without Spark's help)? Is there
> something in the API that allows for Continuous Queries on key/clause
> changes (haven't found it)? Is there some other way to get a stream of
> key/clause updates? Events of some sort?
> I'm aware that we could, eventually, periodically poll Cassandra, but in
> our use case, the client is potentially interested in a large number of
> table clause notifications (think "all changes to Ship positions on
> California's coastline"), and iterating out of the store would kill the
> streamer's scalability.
> Hence, the magic question: what are we missing? Is Cassandra the wrong
> tool for the job? Are we not aware of a particular part of the API or
> external library in/outside the apache realm that would allow for this?
> Many thanks for any assistance!
> Hugo

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