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From Tony Wei <tony19920...@gmail.com>
Subject How to use operator list state like a HashMap?
Date Tue, 19 Sep 2017 13:58:28 GMT
Hi,

I have a basic streaming job that continuously persist data from Kafka to
S3.
Those data would be grouped by some dimensions and a limited amount.

Originally, I used 'keyBy' and key state to fulfill the requirement.
However, because the data is extremely skewed, I turned to use map function
to aggregate data for some partitions only, so that I can balance the
amount of data in each sub tasks.

I used a HashMap to store data by different dimensions inner map function
and convert it to operator list state when 'snapshot()' is called.
But, that makes another problem. Because I can't access operator list state
directly like using key state in KeyedStream, I have to use heap space to
store those state. It leads to the limitation of the amount that I can
cache in map function.

I was wondering if there is any good suggestion to deal with this problem
or how to use operator list state like this scenario with a better manner.
Thank you.


Best Regards,
Tony Wei

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