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From Bruno Cadonna <cado...@apache.org>
Subject Re: State Store Data Retention
Date Mon, 19 Apr 2021 08:57:32 GMT
Hi Upesh,

The answers to your questions are:

The configs cleanup.policy and retention.ms are topic configs. Hence, 
they only affect the changelog of a state store, not the local state 
store in a Kafka Streams client.

Locally, window and session stores remove data they do not need anymore. 
Window and session stores are segmented stores. That means they consist 
of segments that are ordered by the windows they contain. Once the 
segment that contains the oldest windows is not needed anymore, i.e., 
the data exceeded the retention time of the state store, the segment is 

Non-windowed state store will not remove data.

Worth noting here: If you change retention.ms directly on the brokers, 
it will not affect the behavior of local state stores.

Yes, this behavior is the same for in-memory state stores and persistent 
state stores.

Window and session state stores do remove data.


On 18.04.21 18:18, Upesh Desai wrote:
> Hello, I have not been able to find a concrete answer on if/how state 
> stores on a running kafka streams instance remove data when it has 
> passed the configured retention.ms config. So a couple clarification 
> questions:
>  1. If the stores are configured with: cleanup.policy=compact,delete AND
>     retention.ms=N, will the stores remove data automatically over time
>     in the running stream instance stores?
>  2. Is this behavior the same for in-memory stores and persistent
>     rocksdb stores?
>  3. If they do not remove data that has passed the retention.ms period,
>     is there a different way to periodically remove old data from the
>     stores?
> I’m using kafka 2.7.0 components across the board (broker, connect, etc.).
> Thanks in advance,
> Upesh
> <https://www.itrsgroup.com/>
> Upesh Desai​
> Senior Software Developer
> *udesai@itrsgroup.com* <mailto:udesai@itrsgroup.com>
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