public void markCallbackProcessingEnd() {
    logger.trace("Callback for {} of {} finished", metrics.operationType, context);
    long processingTime = System.currentTimeMillis() - processingStartTime;
    metrics.callbackProcessingTimeInMs.update(processingTime);
  }
Marks that the  callback processing has ended.
ambry-utils/src/main/java/com/github/ambry/utils/AsyncOperationTracker.java