@Bean CurrentTraceContext currentTraceContext() {
    return RequestContextCurrentTraceContext.builder()
      .addScopeDecorator(MDCScopeDecorator.get()) // puts trace IDs into logs
      .build();
  }
Configuration for how to buffer spans into messages for Zipkin
zipkin-server/src/main/java/zipkin2/server/internal/brave/ZipkinSelfTracingConfiguration.java