Spring Boot 3启用分布式追踪配置问题：Trace/Span ID为空

核心排查步骤与解决方案 #

1. 确认依赖完整性

你已引入micrometer-tracing-bridge-brave，但需确保：

• Web应用场景下已引入spring-boot-starter-web（Spring Boot会自动配置Web追踪过滤器，负责初始化Span上下文）
• 若需通过Actuator查看追踪指标，可补充spring-boot-starter-actuator依赖

Maven依赖示例：

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

2. 启用Brave MDC集成

你的日志配置%X{traceId:-},%X{spanId:-}依赖MDC（映射诊断上下文）传递追踪ID，但Brave的MDC默认可能未完全生效，需在application.properties中添加：

brave.mdc.enabled=true
brave.trace-id-continuation.enabled=true

3. 验证追踪上下文是否初始化

在业务代码中手动注入Tracer，检查Span是否正常创建：

import io.micrometer.tracing.Tracer;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestTraceController {
    private final Tracer tracer;

    public TestTraceController(Tracer tracer) {
        this.tracer = tracer;
    }

    @GetMapping("/trace-test")
    public String testTrace() {
        var currentSpan = tracer.currentSpan();
        if (currentSpan != null) {
            System.out.println("Trace ID: " + currentSpan.context().traceId());
            System.out.println("Span ID: " + currentSpan.context().spanId());
        }
        return "trace test completed";
    }
}

如果此处能打印出ID，说明追踪上下文正常，日志未显示可能是MDC传递问题；若打印为空，说明Span未被创建，需检查Web过滤器是否生效。

4. 异步场景的上下文传递

若使用@Async异步方法，需配置任务装饰器将追踪上下文传递到异步线程：

import io.micrometer.tracing.Tracer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.concurrent.Executor;

@Configuration
@EnableAsync
public class AsyncTraceConfig {
    private final Tracer tracer;

    public AsyncTraceConfig(Tracer tracer) {
        this.tracer = tracer;
    }

    @Bean("asyncExecutor")
    public Executor asyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(3);
        executor.setMaxPoolSize(5);
        executor.setQueueCapacity(100);
        executor.setThreadNamePrefix("Async-Trace-");
        // 传递追踪上下文到异步线程
        executor.setTaskDecorator(runnable -> {
            var currentContext = tracer.currentSpan() != null ? tracer.currentSpan().context() : null;
            return () -> {
                if (currentContext != null) {
                    try (var scope = tracer.withSpan(tracer.nextSpan(currentContext))) {
                        runnable.run();
                    }
                } else {
                    runnable.run();
                }
            };
        });
        executor.initialize();
        return executor;
    }
}

5. 排除自定义MDC干扰

检查项目中是否存在自定义的MDC过滤器或拦截器，若有需确保它们不会覆盖Brave写入的traceId和spanId字段。

内容的提问来源于stack exchange，提问作者Ramesh Talapaneni