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From Stefan Richter <s.rich...@data-artisans.com>
Subject Re: Get which key groups are assigned to an operator
Date Tue, 20 Feb 2018 13:42:30 GMT
Hi,

from what I read, I get the impression that you attempt to implement you own "keyed state"
with a hashmap? Why not using the keyed state that is already provided by Flink and gives
you efficient rescaling etc. out of the box? Please see [1] for the details.

[1] https://ci.apache.org/projects/flink/flink-docs-master/dev/stream/state/state.html#using-managed-keyed-state
<https://ci.apache.org/projects/flink/flink-docs-master/dev/stream/state/state.html#using-managed-keyed-state>

> Am 20.02.2018 um 13:44 schrieb gerardg <gerard@talaia.io>:
> 
> Hello,
> 
> To improve performance we have " keyed state" in the operator's memory,
> basically we keep a Map which contains the state per each of the keys. The
> problem comes when we want to restore the state after a failure or after
> rescaling the operator. What we are doing is sending the concatenation of
> all the state to every operator using an union redistribution and then we
> restore the "in memory state" every time we see a new key. Then, after a
> while, we just clear the redistributed state. This is somewhat complex and
> prone to errors so we would like to find an alternative way of doing this.
> 
> As far as I know Flink knows which keys belong to each operator
> (distributing key groups) so I guess it would be possible to somehow
> calculate the key id from each of the stored keys and restore the in memory
> state at once if we could access to the key groups mapping. Is that
> possible? We could patch Flink if necessary to access that information. 
> 
> Thanks, 
> 
> Gerard
> 
> 
> 
> --
> Sent from: http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/


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