SpringCloud sleuth 应用内 traceId 获取及使用

1. MAVEN

1.1. spring-cloud-starter-sleuth:2.0.0.RELEASE

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-sleuth</artifactId>
    <version>2.0.0.RELEASE</version>
</dependency>
<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-sleuth-core</artifactId>
    <version>2.0.0.RELEASE</version>
</dependency>
<dependency>
	<groupId>io.zipkin.brave</groupId>
	<artifactId>brave-instrumentation-spring-webmvc</artifactId>
	<version>5.1.0</version>
</dependency>
<dependency>
	<groupId>io.zipkin.brave</groupId>
	<artifactId>brave-instrumentation-servlet</artifactId>
	<version>5.1.0</version>
</dependency>

1.2. spring-cloud-starter-sleuth:3.0.0

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-sleuth</artifactId>
    <version>3.0.0</version>
</dependency>
<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-sleuth-brave</artifactId>
    <version>3.0.0</version>
</dependency>
<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-sleuth-instrumentation</artifactId>
    <version>3.0.0</version>
</dependency>

2. ​获取代码

2.1. spring-cloud-starter-sleuth:2.0.0.RELEASE

// ServletServerHttpRequest request
TraceContext traceContext = (TraceContext) request.getServletRequest().getAttribute(TraceContext.class.getName());
String traceId = traceContext.traceIdString();

// HttpServletRequest request
TraceContext traceContext = (TraceContext) request.getAttribute(TraceContext.class.getName());
String traceId = traceContext.traceIdString();

2.2. spring-cloud-starter-sleuth:3.0.0

// ServletServerHttpRequest request
TraceContext traceContext = (TraceContext) request.getServletRequest().getAttribute(TraceContext.class.getName());
String traceId = traceContext.traceId();

// HttpServletRequest request
TraceContext traceContext = (TraceContext) request.getAttribute(TraceContext.class.getName());
String traceId = traceContext.traceId();

3. 为何可以如此获取？

版本	所在 jar	全路径
spring-cloud-starter-sleuth:2.0.0.RELEASE	brave-instrumentation-servlet	brave.servlet.TracingFilter
spring-cloud-starter-sleuth:3.0.0	spring-cloud-sleuth-instrumentation	org.springframework.cloud.sleuth.instrument.web.servlet.TracingFilter

public final class TracingFilter implements Filter {
    final ServletRuntime servlet = ServletRuntime.get();
    final CurrentTraceContext currentTraceContext;
    final HttpServerHandler<HttpServerRequest, HttpServerResponse> handler;

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest)request;
        HttpServletResponse res = this.servlet.httpServletResponse(response);
        TraceContext context = (TraceContext)request.getAttribute(TraceContext.class.getName());
        if (context != null) {
            CurrentTraceContext.Scope scope = this.currentTraceContext.maybeScope(context);

            try {
                chain.doFilter(request, response);
            } finally {
                scope.close();
            }

        } else {
            Span span = this.handler.handleReceive(new HttpServletRequestWrapper(req));
            request.setAttribute(SpanCustomizer.class.getName(), span.customizer());
            // 赋值 traceId 
            request.setAttribute(TraceContext.class.getName(), span.context());
        ...
        ...
            
        }
    }

}

4. 实际项目中使用

package com.zxguan.springcloud2.user.config;

import org.springframework.core.MethodParameter;
import org.springframework.core.annotation.Order;
import org.springframework.http.MediaType;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

@Order(0)
@RestControllerAdvice
public class ApiResponseAdvice implements ResponseBodyAdvice {

    /**
     * 判断需要处理的情况
     *
     * @param methodParameter
     * @param selectedHttpMessageConverter
     *
     * @return boolean true:   false:
     */
    @Override
    public boolean supports(MethodParameter methodParameter, Class selectedHttpMessageConverter) {
        // 
        return false;
    }


    /**
     * 消息体返回前处理
     *
     * @param body                         返回的消息体
     * @param methodParameter              响应类型
     * @param mediaType                    请求的响应 contentType
     * @param selectedHttpMessageConverter 执行序列化的转换器
     * @param request
     * @param response
     *
     * @return Object 返回的消息体
     */
    @Override
    public Object beforeBodyWrite(Object body, MethodParameter methodParameter, MediaType mediaType, Class selectedHttpMessageConverter, ServerHttpRequest request, ServerHttpResponse response) {
        // 此处可以统一添加 traceId 到响应中
        return null;
    }

}

5. 日志中打印 traceId

借助 MDC 机制, 实现 traceId 的打印

<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %X{X-B3-TraceId} %X{X-B3-SpanId}</pattern>

6. 特别注意

MDC 设置 X-B3-TraceId, 可以通过自定义过滤器提前到过滤器级别，但需要注意 过滤器顺序，自定义过滤器需排在 TracingFilter 之后