Spring Boot 3.0.2微服务TraceId未从父服务传播至子服务求助

问题场景 #

父服务通过WebClient调用子服务时，子服务未接收到父服务的TraceId，而是生成了新的Observation对象，导致链路追踪断裂。

父服务调用代码 #

public Mono<Product> productFromIntegrator() {

        String url = "http://localhost:8282/product";

    return Mono.deferContextual(contextView -> {
        try (ContextSnapshot.Scope scope = ContextSnapshot.setThreadLocalsFrom(contextView,
                ObservationThreadLocalAccessor.KEY)) {
            LOG.info("<ACCEPTANCE_TEST> <TRACE:{}> Hello from producer", tracer.currentSpan().context().traceId());
            LOG.info("Service Called");
            return webClient.get().uri(url)
                    .retrieve().bodyToMono(Product.class).log(LOG.getName(), Level.FINE)
                    .onErrorMap(WebClientException.class, ex -> {
                        LOG.warn("Error retrieving Product");
                        return ex;
                    });
        }
    });
}

子服务Controller代码 #

@Autowired
private final Service service;
private final Tracer tracer;

public Controller(Service service, Tracer tracer) {
    this.service = service;
    this.tracer = tracer;
}

@GetMapping(value = "/product")
public Mono<Product> getProduct() {

    return Mono.deferContextual(contextView -> {
        try (ContextSnapshot.Scope scope = ContextSnapshot.setThreadLocalsFrom(contextView,
                ObservationThreadLocalAccessor.KEY)) {
            LOG.info("<ACCEPTANCE_TEST> <TRACE:{}> Hello from producer", tracer.currentSpan().context().traceId());
            LOG.info("Service Called");
            return this.service.getProduct();
        }
    });
}

解决建议 #

1. 正确配置WebClient的Observation支持 #

Spring Boot 3.x中，WebClient需要绑定ObservationRegistry来自动传播Trace信息，让框架自动管理上下文：

@Bean
public WebClient webClient(ObservationRegistry observationRegistry) {
    return WebClient.builder()
            .observationRegistry(observationRegistry)
            .build();
}

2. 移除手动ContextSnapshot处理代码 #

手动调用ContextSnapshot.setThreadLocalsFrom会干扰Reactor上下文的自动传播逻辑，Reactor会自动携带Observation信息，无需手动绑定线程本地变量。修改父服务代码：

public Mono<Product> productFromIntegrator() {
    String url = "http://localhost:8282/product";
    
    LOG.info("<ACCEPTANCE_TEST> <TRACE:{}> Hello from producer", tracer.currentSpan().context().traceId());
    LOG.info("Service Called");
    
    return webClient.get().uri(url)
            .retrieve().bodyToMono(Product.class).log(LOG.getName(), Level.FINE)
            .onErrorMap(WebClientException.class, ex -> {
                LOG.warn("Error retrieving Product");
                return ex;
            });
}

3. 子服务简化上下文处理 #

子服务的Controller无需手动处理ContextSnapshot，Spring WebFlux会自动从请求头中提取Trace信息并绑定到上下文：

@GetMapping(value = "/product")
public Mono<Product> getProduct() {
    LOG.info("<ACCEPTANCE_TEST> <TRACE:{}> Hello from producer", tracer.currentSpan().context().traceId());
    LOG.info("Service Called");
    return this.service.getProduct();
}

4. 确保依赖完整 #

检查项目依赖是否包含Micrometer Trace核心组件：
Maven

<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-tracing-bridge-brave</artifactId>
</dependency>
<dependency>
    <groupId>io.zipkin.reporter2</groupId>
    <artifactId>zipkin-reporter-brave</artifactId>
</dependency>

Gradle

implementation 'io.micrometer:micrometer-tracing-bridge-brave'
implementation 'io.zipkin.reporter2:zipkin-reporter-brave'

5. 配置Trace传播格式 #

可通过配置文件指定Trace信息的传播格式（默认使用b3格式）：

management:
  tracing:
    propagation:
      type: b3

6. 验证请求头传播 #

在父服务中添加日志，确认请求头是否携带X-B3-TraceId、X-B3-SpanId等Trace字段：

return webClient.get().uri(url)
        .exchangeToMono(response -> {
            LOG.info("Sent request headers: {}", response.request().headers());
            return response.bodyToMono(Product.class);
        })
        .onErrorMap(WebClientException.class, ex -> {
            LOG.warn("Error retrieving Product");
            return ex;
        });

内容的提问来源于stack exchange，提问作者msuzuki