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From Ning Zhang <ning2008w...@gmail.com>
Subject Re: does Kafka exactly-once guarantee also apply to kafka state stores?
Date Fri, 01 Jan 2021 23:26:50 GMT
The physical store behind "state store" is change-log kafka topic. In Kafka stream, if something
fails in the middle, the "state store" is restored back to the state before the event happens
at the first step / beginning of the stream.


On 2020/12/31 08:48:16, Pushkar Deole <pdeole2015@gmail.com> wrote: 
> Hi All,
> We use Kafka streams and may need to use exactly-once configuration for
> some of the use cases. Currently, the application uses either local or
> global state store to store state.
>  So, the application will consume events from source kafka topic, process
> the events, for state stores it will use either local or global state store
> of kafka, then produce events onto the destination topic.
> Question i have is: in the case of exactly-once setting, kafka streams
> guarantees that all actions happen or nothing happens. So, in this case,
> any state stored on the local or global state store will also be counted
> under 'all or nothing' guarantee e.g. if event is consumed and state store
> is updated, however some issue occurs before event is produced on
> destination topic then will state store be restored back to the state
> before it was updated for this event?

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