MDC使用
- 添加攔截器
public class LogInterceptor implements HandlerInterceptor {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
//如果有上層調(diào)用就用上層的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 {
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>
重點是%X{traceId}，traceId和MDC中的鍵名稱一致
MDC 存在的問題
- 子線程中打印日志丟失traceId
- HTTP調(diào)用丟失traceId
解決MDC存在的問題
- 子線程日志打印丟失traceId
子線程在打印日志的過程中traceId將丟失，解決方式為重寫線程池，對于直接new創(chuàng)建線程的情況不考略【實際應(yīng)用中應(yīng)該避免這種用法】，重寫線程池?zé)o非是對任務(wù)進行一次封裝.
線程池封裝類：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()));
}
}
線程traceId封裝工具類：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();
}
};
}
}
代碼等同于以下寫法，會更直觀
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();
}
}
};
}
重新返回的是包裝后的Runnable，在該任務(wù)執(zhí)行之前【runnable.run()】先將主線程的Map設(shè)置到當(dāng)前線程中【 即MDC.setContextMap(context)】，這樣子線程和主線程MDC對應(yīng)的Map就是一樣的了.
- HTTP調(diào)用丟失traceId
在使用HTTP調(diào)用第三方服務(wù)接口時traceId將丟失，需要對HTTP調(diào)用工具進行改造，在發(fā)送時在request header中添加traceId，在下層被調(diào)用方添加攔截器獲取header中的traceId添加到MDC中
HTTP調(diào)用有多種方式，比較常見的有HttpClient、OKHttp、RestTemplate，所以只給出這幾種HTTP調(diào)用的解決方式, 以okhttp為例：
- 實現(xiàn)OKHttp攔截器*
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) {
//添加請求體
request = chain.request().newBuilder().addHeader(Constants.TRACE_ID, traceId).build();
}
Response originResponse = chain.proceed(request);
return originResponse;
}
}
實現(xiàn)Interceptor攔截器，重寫interceptor方法，實現(xiàn)邏輯和HttpClient差不多，如果能夠獲取到當(dāng)前線程的traceId則向下透傳.
為OkHttp添加攔截器
private static OkHttpClient client = new OkHttpClient.Builder()
.addNetworkInterceptor(new OkHttpTraceIdInterceptor())
.build();
- 第三方服務(wù)攔截器
HTTP調(diào)用第三方服務(wù)接口全流程traceId需要第三方服務(wù)配合，第三方服務(wù)需要添加攔截器拿到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 {
//如果有上層調(diào)用就用上層的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);
}
}
除了需要添加攔截器之外，還需要在日志格式中添加traceId的打印，如下：
<property name="pattern">[TRACEID:%X{traceId}] %d{HH:mm:ss.SSS} %-5level %class{-1}.%M()/%L - %msg%xEx%n</property>
