Matthias J. Sax created KAFKA-12634:
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             Summary: Should checkpoint after restore finished
                 Key: KAFKA-12634
                 URL: https://issues.apache.org/jira/browse/KAFKA-12634
             Project: Kafka
          Issue Type: Improvement
          Components: streams
            Reporter: Matthias J. Sax


For state stores, Kafka Streams maintains local checkpoint files to track the 
offsets of the state store changelog topics. The checkpoint is updated on 
commit or when a task is closed cleanly.

However, after a successful restore, the checkpoint is not written. Thus, if an 
instance crashes after restore but before committing, even if the state is on 
local disk the checkpoint file is missing (indicating that there is no state) 
and thus state would be restored from scratch.

While for most cases, the time between restore end and next commit is small, 
there are cases when this time could be large, for example if there is no new 
input data to be processed (if there is no input data, the commit would be 
skipped).

Thus, we should write the checkpoint file after a successful restore to close 
this gap (or course, only for at-least-once processing).



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