Guozhang Wang commented on KAFKA-6645:

Hi Giridhar, could you share with us a bit more on your usage pattern for a 
complete restart? As Matthias mentioned, since Kafka Streams library always 
looks into the specified state directory for existing task ids from the 
previous runs and encode that information in the rebalance protocol, 
"stickiness" should be auto-applied already, and if you did not observe this is 
the case, we'd like to investigate further.

> Host Affinity to facilitate faster restarts of kafka streams applications
> -------------------------------------------------------------------------
>                 Key: KAFKA-6645
>                 URL: https://issues.apache.org/jira/browse/KAFKA-6645
>             Project: Kafka
>          Issue Type: New Feature
>          Components: streams
>            Reporter: Giridhar Addepalli
>            Priority: Major
> Since Kafka Streams applications have lot of state in the stores in general, 
> it would be good to remember the assignment of partitions to machines. So 
> that when whole application is restarted for some reason, there is a way to 
> use past assignment of partitions to machines and there won't be need to 
> build up whole state by reading off of changelog kafka topic. This would 
> result in faster start-up.
> Samza has support for Host Affinity 
> ([https://samza.apache.org/learn/documentation/0.14/yarn/yarn-host-affinity.html])
> KIP-54 
> ([https://cwiki.apache.org/confluence/display/KAFKA/KIP-54+-+Sticky+Partition+Assignment+Strategy)]
>  , handles cases where some members of consumer group goes down / comes up, 
> and KIP-54 ensures there is minimal diff between assignments before and after 
> rebalance. 
> But to handle whole restart use case, we need to remember past assignment 
> somewhere, and use it after restart.
> Please let us know if this is already solved problem / some cleaner way of 
> achieving this objective

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