Spring Boot + MDC 实现全链路调用日志跟踪
写在前面
通过本文将了解到什么是MDC、MDC应用中存在的问题、如何解决存在的问题
MDC介绍
简介：
MDC（Mapped Diagnostic Context，映射调试上下文）是 log4j 、logback及log4j2 提供的一种方便在多线程条件下记录日志的功能。 MDC 可以看成是一个 与当前线程绑定的哈希表 ，可以往其中添加键值对。MDC 中包含的内容可以 被同一线程中执行的代码所访问 。当前线程的子线程会继承其父线程中的 MDC 的内容。当需要记录日志时，只需要从 MDC 中获取所需的信息即可。MDC 的内容则由程序在适当的时候保存进去。对于一个 Web 应用来说，通常是在请求被处理的最开始保存这些数据
API说明：
- clear() => 移除所有MDC
- get (String key) => 获取当前线程MDC中指定key的值
- getContext() => 获取当前线程MDC的MDC
- put(String key, Object o) => 往当前线程的MDC中存入指定的键值对
- remove(String key) => 删除当前线程MDC中指定的键值对
优点：
- 代码简洁，日志风格统一，不需要在log打印中手动拼写traceId，即LOGGER.info("traceId:{} ", traceId)
暂时只能想到这一点
MDC使用
- 添加拦截器
public class LogInterceptor implements HandlerInterceptor {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
//如果有上层调用就用上层的ID
String traceId = request.getHeader(Constants.TRACE_ID);
if (traceId == null) {
traceId = TraceIdUtil.getTraceId();
MDC.put(Constants.TRACE_ID, traceId);
return true;
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
throws Exception {
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
throws Exception {
//调用结束后删除
MDC.remove(Constants.TRACE_ID);
}- 修改日志格式
<property name="pattern">[TRACEID:%X{traceId}] %d{HH:mm:ss.SSS} %-5level %class{-1}.%M()/%L - %msg%xEx%n</property>重点是%X{traceId}，traceId和MDC中的键名称一致
简单使用就这么容易，但是在有些情况下traceId将获取不到
img
MDC 存在的问题
- 子线程中打印日志丢失traceId
- HTTP调用丢失traceId
丢失traceId的情况，来一个再解决一个，绝不提前优化
解决MDC存在的问题
子线程日志打印丢失traceId
子线程在打印日志的过程中traceId将丢失，解决方式为重写线程池，对于直接new创建线程的情况不考略【实际应用中应该避免这种用法】，重写线程池无非是对任务进行一次封装
- 线程池封装类：ThreadPoolExecutorMdcWrapper.java
public class ThreadPoolExecutorMdcWrapper extends ThreadPoolExecutor {
public ThreadPoolExecutorMdcWrapper(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit,
BlockingQueue<Runnable> workQueue) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
public ThreadPoolExecutorMdcWrapper(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit,
BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory);
public ThreadPoolExecutorMdcWrapper(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit,
BlockingQueue<Runnable> workQueue, RejectedExecutionHandler handler) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler);
public ThreadPoolExecutorMdcWrapper(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit,
BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory,
RejectedExecutionHandler handler) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
@Override
public void execute(Runnable task) {
super.execute(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap()));
@Override
public <T> Future<T> submit(Runnable task, T result) {
return super.submit(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap()), result);
@Override
public <T> Future<T> submit(Callable<T> task) {
return super.submit(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap()));
@Override
public Future<?> submit(Runnable task) {
return super.submit(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap()));
}说明：
- 继承ThreadPoolExecutor类，重新执行任务的方法
- 通过ThreadMdcUtil对任务进行一次包装
- 线程traceId封装工具类：ThreadMdcUtil.java
public class ThreadMdcUtil {
public static void setTraceIdIfAbsent() {
if (MDC.get(Constants.TRACE_ID) == null) {
MDC.put(Constants.TRACE_ID, TraceIdUtil.getTraceId());
public static <T> Callable<T> wrap(final Callable<T> callable, final Map<String, String> context) {
return () -> {
if (context == null) {
MDC.clear();
} else {
MDC.setContextMap(context);
setTraceIdIfAbsent();
try {
return callable.call();
} finally {
MDC.clear();
public static Runnable wrap(final Runnable runnable, final Map<String, String> context) {
return () -> {
if (context == null) {
MDC.clear();
} else {
MDC.setContextMap(context);
setTraceIdIfAbsent();
try {
runnable.run();
} finally {
MDC.clear();
}说明【以封装Runnable为例】：
- 判断当前线程对应MDC的Map是否存在，存在则设置
- 设置MDC中的traceId值，不存在则新生成，针对不是子线程的情况，如果是子线程，MDC中traceId不为null
- 执行run方法
代码等同于以下写法，会更直观
public static Runnable wrap(final Runnable runnable, final Map<String, String> context) {
return new Runnable() {
@Override
public void run() {
if (context == null) {
MDC.clear();
} else {
MDC.setContextMap(context);
setTraceIdIfAbsent();
try {
runnable.run();
} finally {
MDC.clear();
}重新返回的是包装后的Runnable，在该任务执行之前【runnable.run()】先将主线程的Map设置到当前线程中【 即MDC.setContextMap(context)】，这样子线程和主线程MDC对应的Map就是一样的了
HTTP调用丢失traceId
在使用HTTP调用第三方服务接口时traceId将丢失，需要对HTTP调用工具进行改造，在发送时在request header中添加traceId，在下层被调用方添加拦截器获取header中的traceId添加到MDC中
HTTP调用有多种方式，比较常见的有HttpClient、OKHttp、RestTemplate，所以只给出这几种HTTP调用的解决方式
HttpClient：
- 实现HttpClient拦截器
public class HttpClientTraceIdInterceptor implements HttpRequestInterceptor {
@Override
public void process(HttpRequest httpRequest, HttpContext httpContext) throws HttpException, IOException {
String traceId = MDC.get(Constants.TRACE_ID);
//当前线程调用中有traceId，则将该traceId进行透传
if (traceId != null) {
//添加请求体
httpRequest.addHeader(Constants.TRACE_ID, traceId);
复制代码- 实现HttpRequestInterceptor接口并重写process方法
- 如果调用线程中含有traceId，则需要将获取到的traceId通过request中的header向下透传下去
- 为HttpClient添加拦截器
private static CloseableHttpClient httpClient = HttpClientBuilder.create()
.addInterceptorFirst(new HttpClientTraceIdInterceptor())通过addInterceptorFirst方法为HttpClient添加拦截器
OKHttp：
- 实现OKHttp拦截器
public class OkHttpTraceIdInterceptor implements Interceptor {
@Override
public Response intercept(Chain chain) throws IOException {
String traceId = MDC.get(Constants.TRACE_ID);
Request request = null;
if (traceId != null) {
//添加请求体
request = chain.request().newBuilder().addHeader(Constants.TRACE_ID, traceId).build();
Response originResponse = chain.proceed(request);
return originResponse;
}实现Interceptor拦截器，重写interceptor方法，实现逻辑和HttpClient差不多，如果能够获取到当前线程的traceId则向下透传
- 为OkHttp添加拦截器
private static OkHttpClient client = new OkHttpClient.Builder()
.addNetworkInterceptor(new OkHttpTraceIdInterceptor())
.build();调用addNetworkInterceptor方法添加拦截器
RestTemplate：
- 实现RestTemplate拦截器
public class RestTemplateTraceIdInterceptor implements ClientHttpRequestInterceptor {
@Override
public ClientHttpResponse intercept(HttpRequest httpRequest, byte[] bytes, ClientHttpRequestExecution clientHttpRequestExecution) throws IOException {
String traceId = MDC.get(Constants.TRACE_ID);
if (traceId != null) {
httpRequest.getHeaders().add(Constants.TRACE_ID, traceId);
return clientHttpRequestExecution.execute(httpRequest, bytes);
}实现ClientHttpRequestInterceptor接口，并重写intercept方法，其余逻辑都是一样的不重复说明
- 为RestTemplate添加拦截器
restTemplate.setInterceptors(Arrays.asList(new RestTemplateTraceIdInterceptor()));调用setInterceptors方法添加拦截器
第三方服务拦截器：
HTTP调用第三方服务接口全流程traceId需要第三方服务配合，第三方服务需要添加拦截器拿到request header中的traceId并添加到MDC中
public class LogInterceptor implements HandlerInterceptor {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
//如果有上层调用就用上层的ID
String traceId = request.getHeader(Constants.TRACE_ID);
if (traceId == null) {
traceId = TraceIdUtils.getTraceId();
MDC.put("traceId", traceId);
return true;
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
throws Exception {
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
throws Exception {
MDC.remove(Constants.TRACE_ID);