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From Marco Massenzio <m.massen...@gmail.com>
Subject Re: Customize Cassandra to execute a query multiple times
Date Thu, 27 Jul 2017 07:26:53 GMT
Why not simply have a microservice that does this for you?

It may expose an API that allows to either store queries and/or conditions
that trigger the queries (maybe time elapsed, an alert generated,
whatever...) and it would then connect to Cassandra and execute the stored
query(ies).

Given that there is no client waiting for a response, then latency is not
even a (major) issue, so the extra network hop is probably of little
consequence.

Why would you want this to be an integral part of Cassandra?
(like Jeff I also am struggling to come up with a concrete use case where
this would be desirable)

-- 
*Marco Massenzio*
http://codetrips.com

On Wed, Jul 26, 2017 at 11:06 PM, Ke Wang <klwangke@gmail.com> wrote:

> Hi Jeff,
>
> Thanks for the prompt reply.
>
> I'm sorry I wasn't clear about my use case. Let's say I just want the
> server to execute writes that are not directly generated from clients. It
> can be previously stored queries (the case in my last email), or it can be
> arbitrarily made-up write requests by the server itself.
>
> Can you describe a little bit more on how to implement serializing the
> mutation into the table?
>
> Best,
> Ke
>
> 2017-07-26 22:57 GMT-07:00 Jeff Jirsa <jjirsa@apache.org>:
>
> >
> >
> > On 2017-07-26 22:19 (-0700), Ke Wang <klwangke@gmail.com> wrote:
> > > Hello all,
> > >
> > > Is there a way to customize Cassandra to execute a query multiple
> times?
> > >
> >
> > There's always a way...
> >
> > > My use case is the following. When the Cassandra server receives
> queries
> > > from remote clients, besides executing those queries, the server also
> > > stores the queries. In the future, the server can re-execute stored
> > queries
> > > under certain circumstances.
> > >
> >
> > Seems like an unusual request. Where are you storing the queries? Are
> > these reads or writes? For writes you could just serialize the resulting
> > partitionupdate/mutation into a table a la pre-3.0 hints, and then
> re-play
> > as needed (though tbh I don't really get the use case)?
> >
> >
> >
> > ---------------------------------------------------------------------
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> >
> >
>

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