[GitHub] [kafka] mingaliu opened a new pull request #10674: KAFKA-12713: Report the real fetch latency by removing the wait-time in purgatory.

[GitBox <gi...@apache.org>]

mingaliu opened a new pull request #10674:
URL: https://github.com/apache/kafka/pull/10674


   This is to help monitor the 'real' fetch latency by removing the waitTime when FetchRequest is in purgatory.
   The changes include:
   1. Add waitTimeMs in FetchResponse()
   2. In Kafka API handler (in handleFetchRequest() function),  when creating FetchResponse(),  set the waitTimeMs as the time spent in purgatory
   3. In Follower broker processFetchRequest(),  it tracks the real latency of fetch requests by minus the waitTimeMs from FetchResponse.
   4. In FetcherStats, we will add a new histogram to track this calculated "true" fetch latency.
   


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