KafkaConsumer: triggerCount should specify the exact value for initiating a checkpoint

[cancilla]

In the current implementation of the triggerCount parameter, the value specified by the user will be the minimum number of tuples that will be submitted prior to initiating a checkpoint. This implies that the actual number of tuples that get submitted before the operator is checkpointed is not deterministic.

The KafkaConsumer operator needs to be enhanced so that the value specified for triggerCount represents the exact number of tuples that will be submitted prior to a checkpoint.

[cancilla]

Fixed in v1.2.0

[ddebrunner]

What's the rationale for requiring the number be fixed?

I'm looking at if this change broke the operator at least once guarantee in a consistent region.