@Override public Builder metrics(CollectorMetrics metrics) {
      if (metrics == null) throw new NullPointerException("metrics == null");
      this.metrics = metrics.forTransport("scribe");
      delegate.metrics(this.metrics);
      return this;
    }
Configuration including defaults needed to receive spans from a Scribe category.
zipkin-collector/scribe/src/main/java/zipkin2/collector/scribe/ScribeCollector.java