...

I also propose to add following two metrics measuring the latency to emit final and number of records emitted for emit final:

...

Each exposed metric will have the following tags:

• thread-id = [thread ID],
• task-id = [task ID]
• processor-node-id = [node ID]

The following metrics will be exposed in the Kafka Streams' metrics

• emit-final-latency-max
• emit-final-latency-avg
• emit-final-records-rate
• emit-final-records-total

The recording level for all metrics will be DEBUG and their group will be stream-processor-node-metrics.

Proposed Changes

We introduce several options of API changes discussed above to support output final result for windowed aggregations. We also introduce two metrics to measure the emit final latency as well as the number of records emitted.

...