Spring Boot中WebClient的subscribe/onStatus方法日志缺失Trace ID

在Spring Boot应用中，WebClient调用的onStatus方法回调以及subscribe的回调内生成的日志无法显示Trace ID。已通过Micrometer配置让所有日志包含Trace ID，且WebClient附加的过滤器中日志能正常显示Trace ID，说明追踪配置功能正常，但上述特定位置日志仍缺失该ID。

环境信息 #

• Spring Boot版本：3.3.0
• Java版本：21

依赖配置 #

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-tracing</artifactId>
</dependency>
<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-tracing-bridge-brave</artifactId>
</dependency>

WebClient配置 #

@Bean
public WebClient webclientBean(WebClient.Builder builder) throws SSLException {
    return builder
            .baseUrl(getBaseUrl())
            .exchangeStrategies(ExchangeStrategies
                    .builder()
                    // 以下过滤器中的日志正常，包含trace id 
                    .filter(WebClientFilter.logRequest())  
                    .filter(WebClientFilter.logResponse())  
                    .filter(WebClientFilter.handleError()) 
                    .clientConnector(new ReactorClientHttpConnector(WebClientFilter.httpClient()))
                    .build());
}

主类上下文传播配置 #

@PostConstruct
public void init() {
    Hooks.enableAutomaticContextPropagation();
}

问题代码（WebClient调用逻辑） #

public Object webClientDispatchPost(Object input, String endpoint) {
    return webClient.post().uri(endpoint).body(input != null ? BodyInserters.fromValue(input) : BodyInserters.empty()).retrieve()
            .onStatus(HttpStatusCode::is2xxSuccessful, (r) -> {
                log.info("trace id does not logged here !!!");
                // do something 
            })
            .bodyToMono(Object.class)
            .subscribe(response -> {
                        log.info("trace id does not logged here !!!");
                    },
                    error -> {
                        log.info("trace id does not logged here !!!");
                    },
                    () -> log.info("trace id does not logged here !!!"));
}

已尝试的解决方法 #

• 尝试在subscribe方法中访问MDC，但MDC为空（过滤器中可正常获取Trace ID）
• 添加micrometer-tracing-bridge-otel依赖，无效果

解决方案 #

1. 避免手动调用subscribe（推荐） #

将方法返回类型改为Mono<Object>，使用Reactor的doOnNext、doOnError、doOnComplete操作符替代subscribe的回调逻辑，由上层调用方（如Controller）负责订阅。这样Reactor上下文会自动传播，Trace ID可正常写入日志：

public Mono<Object> webClientDispatchPost(Object input, String endpoint) {
    return webClient.post()
            .uri(endpoint)
            .body(input != null ? BodyInserters.fromValue(input) : BodyInserters.empty())
            .retrieve()
            .onStatus(HttpStatusCode::is2xxSuccessful, (r) -> {
                log.info("trace id should appear here now!!!");
                // do something
                return Mono.empty();
            })
            .bodyToMono(Object.class)
            .doOnNext(response -> log.info("trace id should appear here now!!!"))
            .doOnError(error -> log.info("trace id should appear here now!!!"))
            .doOnComplete(() -> log.info("trace id should appear here now!!!"));
}

2. 若必须手动订阅，手动传播上下文 #

通过Mono.deferContextual获取当前Reactor上下文，在subscribe回调中打开上下文作用域，确保MDC能捕获Trace ID：

public void webClientDispatchPost(Object input, String endpoint) {
    Mono<Object> mono = webClient.post()
            .uri(endpoint)
            .body(input != null ? BodyInserters.fromValue(input) : BodyInserters.empty())
            .retrieve()
            .onStatus(HttpStatusCode::is2xxSuccessful, (r) -> {
                log.info("trace id should appear here now!!!");
                return Mono.empty();
            })
            .bodyToMono(Object.class);

    mono.deferContextual(ctx -> {
        mono.subscribe(
                response -> {
                    try (ContextView.Scope scope = ctx.openScope()) {
                        log.info("trace id should appear here now!!!");
                    }
                },
                error -> {
                    try (ContextView.Scope scope = ctx.openScope()) {
                        log.info("trace id should appear here now!!!");
                    }
                },
                () -> {
                    try (ContextView.Scope scope = ctx.openScope()) {
                        log.info("trace id should appear here now!!!");
                    }
                }
        );
        return Mono.empty();
    }).subscribe();
}

3. 验证日志格式配置 #

确保日志框架（如Logback）的格式配置中包含Trace ID变量，示例Logback配置：

<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
        <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg %X{traceId}%n</pattern>
    </encoder>
</appender>

内容的提问来源于stack exchange，提问作者Ibrahim