public static Span.Builder spanBuilder(String serviceNameSuffix) {
    Endpoint frontend = suffixServiceName(FRONTEND, serviceNameSuffix);
    return SPAN_BUILDER.clone().localEndpoint(frontend).traceId(newTraceId());
  }
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