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There is a possibility, however remote, that there could be a chained failure. In this case, either consumer1 or consumer2 will fail. If consumer1 were to fail, we could simply repeat our previous policy, and instantiate another thread to process the intervening lag. However, if consumer2 were to fail, no new processes will be created. This is because the offset range that consumer2 is processing is bounded, so this means that consumer2 does not have to deal with a continuous influx of new records – thus no "lag" technically to speak of. Note that if consumer1 crashes N times, N child processes will be created. Checkpointing will write the progress from these N child processes into N distinct logs, which will merge with one another once their respective process terminates.

Compatibility, Deprecation, and Migration Plan

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