public static void setDefaults(MetricRegistry metricRegistry) {
    defaultMetrics = new RestRequestMetrics(RestRequestMetricsTracker.class, DEFAULT_REQUEST_TYPE, metricRegistry);
  }
Creates a default {@link RestRequestMetrics} in case {@link #injectMetrics(RestRequestMetrics)} is never
called on an instance of {@link RestRequestMetricsTracker}.
@param metricRegistry the {@link MetricRegistry} to use to register the created metrics.
ambry-api/src/main/java/com/github/ambry/rest/RestRequestMetricsTracker.java