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From Phil Yang <ud1...@gmail.com>
Subject Re: Counters 2.1 Accuracy
Date Wed, 24 Jun 2015 09:31:16 GMT
IMO, the main concern of C*'s counter is, it is not idempotent. For
example, if you add a counter and get a timeout error, you can not know
whether it is successful. For non-counter writes, they are idempotent so
you can just retry, but if you retry in counter, there may be a double
write.

2015-06-23 12:23 GMT+08:00 Mike Trienis <mike.trienis@orcsol.com>:

>
> Hi All,
>
> I'm fairly new to Cassandra and am planning on using it as a datastore for
> an Apache Spark cluster.
>
> The use case is fairly simple, read the raw data and perform aggregates
> and push the rolled up data back to Cassandra. The data models will use
> counters pretty heavily so I'd like to understand what kind of accuracy
> should I expect from Cassandra 2.1 when increment the counters.
>
>    -
>    http://www.datastax.com/dev/blog/whats-new-in-cassandra-2-1-a-better-implementation-of-counters
>
> The blog post above states that the new counter implementations are
> "safer" although I'm not sure what that means in practice. Will the
> counters be 99.99% accurate? How often will they be over or under counted?
>
> Thanks, Mike.
>



-- 
Thanks,
Phil Yang

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