[jira] [Created] (KAFKA-12960) WindowStore and SessionStore do not enforce strict retention time

["Matthias J. Sax (Jira)" <ji...@apache.org>]

Matthias J. Sax created KAFKA-12960:
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             Summary: WindowStore and SessionStore do not enforce strict retention time
                 Key: KAFKA-12960
                 URL: https://issues.apache.org/jira/browse/KAFKA-12960
             Project: Kafka
          Issue Type: Improvement
          Components: streams
            Reporter: Matthias J. Sax


WindowedStore and SessionStore do not implement a strict retention time in general. We should consider to make retention time strict: even if we still have some record in the store (due to the segmented implementation), we might want to filter expired records on-read. This might benefit PAPI users.

Atm, InMemoryWindow store does already enforce a strict retention time.

As an alternative, we could also inject such a filter in the wrapping `MeteredStore` – this might lift the burden from users who implement a custom state store.

As an alternative, we could change all DSL operators to verify if data from a state store is already expired or not. It might be better to push this responsibility into the stores though.

It's especially an issue for stream-stream joins, because the operator relies on the retention time to implement it's grace period.



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