private void updateMetrics(long startProcessing, boolean isOutput, long endProcessing) {
      inputEvents.inc();
      if (isOutput) {
        outputEvents.inc();
      } else {
        filteredOutEvents.inc();
      }
      processingTime.update(endProcessing - startProcessing);
    }
Updates the MetricsRegistery of this operator
@param startProcessing = begin processing of the message
@param endProcessing = end of processing
samza-sql/src/main/java/org/apache/samza/sql/translator/FilterTranslator.java