public static String appendSuffix(String serviceName, String serviceNameSuffix) {
    if (serviceNameSuffix == null) throw new NullPointerException("serviceNameSuffix == null");
    if (serviceNameSuffix.isEmpty()) return serviceName;
    return serviceName + "_" + serviceNameSuffix;
  }
Zipkin trace ids are random 64bit numbers. This creates a relatively large input to avoid
flaking out due to PRNG nuance.
zipkin-tests/src/main/java/zipkin2/TestObjects.java