@Override protected void doEnqueue(Callback<Void> callback) {
      try {
        callback.onSuccess(doExecute());
      } catch (Throwable t) {
        propagateIfFatal(t);
        callback.onError(t);
      }
    }
This is an index of {@link Span#remoteServiceName()} by {@link Endpoint#serviceName() service
name}
zipkin/src/main/java/zipkin2/storage/InMemoryStorage.java