private void maybeStopTrackingWaitForChunkTime() {
    if (startTimeForChunkAvailabilityWaitMs != 0) {
      // this is the first point in time since the last wait that a chunk became available for filling.
      waitTimeForCurrentChunkAvailabilityMs = time.milliseconds() - startTimeForChunkAvailabilityWaitMs;
      startTimeForChunkAvailabilityWaitMs = 0;
    }
  }
Called whenever the channel has data and there is a free or building chunk available to be filled.
ambry-router/src/main/java/com/github/ambry/router/PutOperation.java