code: protected void regenerateMetrics() {
      if (isInstrumentationEnabled()) {
        this.readRecordsMeter = Optional.of(this.metricContext.meter(MetricNames.ExtractorMetrics.RECORDS_READ_METER));
        this.dataRecordExceptionsMeter =
            Optional.of(this.metricContext.meter(MetricNames.ExtractorMetrics.RECORDS_FAILED_METER));
        this.extractorTimer = Optional.<Timer>of(this.metricContext.timer(MetricNames.ExtractorMetrics.EXTRACT_TIMER));
      } else {
        this.readRecordsMeter = Optional.absent();
        this.dataRecordExceptionsMeter = Optional.absent();
        this.extractorTimer = Optional.absent();
      }
    }
docs: Generates metrics for the instrumentation of this class.