private <T> void logMetric(String source, String group, String metricName, T value) {
    String fullMetricName = String.format(FULL_METRIC_FORMAT, source, group, metricName);
    if (this.metricsToLog.matcher(fullMetricName).matches()) {
      doLog(String.format("Metric: %s, Value: %s", fullMetricName, value));
    }
  }
VisibleForTesting so that the logging call can be verified in unit tests.
samza-core/src/main/java/org/apache/samza/metrics/reporter/LoggingMetricsReporter.java