SpringBoot+MDC實(shí)現(xiàn)全鏈路調(diào)用日志跟蹤，非常實(shí)用！

通過本文將了解到什么是MDC、MDC應(yīng)用中存在的問題、如何解決存在的問題

MDC介紹

簡(jiǎn)介：

MDC（Mapped Diagnostic Context，映射調(diào)試上下文）是 log4j 、logback及l(fā)og4j2 提供的一種方便在多線程條件下記錄日志的功能。MDC 可以看成是一個(gè)與當(dāng)前線程綁定的哈希表，可以往其中添加鍵值對(duì)。MDC 中包含的內(nèi)容可以被同一線程中執(zhí)行的代碼所訪問。

當(dāng)前線程的子線程會(huì)繼承其父線程中的 MDC 的內(nèi)容。當(dāng)需要記錄日志時(shí)，只需要從 MDC 中獲取所需的信息即可。MDC 的內(nèi)容則由程序在適當(dāng)?shù)臅r(shí)候保存進(jìn)去。對(duì)于一個(gè) Web 應(yīng)用來(lái)說，通常是在請(qǐng)求被處理的最開始保存這些數(shù)據(jù)

API說明：

• clear() => 移除所有MDC

• get (String key) => 獲取當(dāng)前線程MDC中指定key的值

• getContext() => 獲取當(dāng)前線程MDC的MDC

• put(String key, Object o) => 往當(dāng)前線程的MDC中存入指定的鍵值對(duì)

• remove(String key) => 刪除當(dāng)前線程MDC中指定的鍵值對(duì)

優(yōu)點(diǎn)：

代碼簡(jiǎn)潔，日志風(fēng)格統(tǒng)一，不需要在log打印中手動(dòng)拼寫traceId，即LOGGER.info("traceId:{} ", traceId)

暫時(shí)只能想到這一點(diǎn)

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?{
????????//調(diào)用結(jié)束后刪除
????????MDC.remove(Constants.TRACE_ID);
????}
}

• 修改日志格式

"pattern">[TRACEID:%X{traceId}]?%d{HH:mm:ss.SSS}?%-5level?%class{-1}.%M()/%L?-?%msg%xEx%n

重點(diǎn)是%X{traceId}，traceId和MDC中的鍵名稱一致

簡(jiǎn)單使用就這么容易，但是在有些情況下traceId將獲取不到

MDC 存在的問題

• 子線程中打印日志丟失traceId

• HTTP調(diào)用丟失traceId

......丟失traceId的情況，來(lái)一個(gè)再解決一個(gè)，絕不提前優(yōu)化

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(duì)于直接new創(chuàng)建線程的情況不考略【實(shí)際應(yīng)用中應(yīng)該避免這種用法】，重寫線程池?zé)o非是對(duì)任務(wù)進(jìn)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?workQueue)?{
????????super(corePoolSize,?maximumPoolSize,?keepAliveTime,?unit,?workQueue);
????}

????public?ThreadPoolExecutorMdcWrapper(int?corePoolSize,?int?maximumPoolSize,?long?keepAliveTime,?TimeUnit?unit,
????????????????????????????????????????BlockingQueue?workQueue,?ThreadFactory?threadFactory)?{
????????super(corePoolSize,?maximumPoolSize,?keepAliveTime,?unit,?workQueue,?threadFactory);
????}

????public?ThreadPoolExecutorMdcWrapper(int?corePoolSize,?int?maximumPoolSize,?long?keepAliveTime,?TimeUnit?unit,
????????????????????????????????????????BlockingQueue?workQueue,?RejectedExecutionHandler?handler)?{
????????super(corePoolSize,?maximumPoolSize,?keepAliveTime,?unit,?workQueue,?handler);
????}

????public?ThreadPoolExecutorMdcWrapper(int?corePoolSize,?int?maximumPoolSize,?long?keepAliveTime,?TimeUnit?unit,
????????????????????????????????????????BlockingQueue?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??Future?submit(Runnable?task,?T?result)?{
????????return?super.submit(ThreadMdcUtil.wrap(task,?MDC.getCopyOfContextMap()),?result);
????}

????@Override
????public??Future?submit(Callable?task)?{
????????return?super.submit(ThreadMdcUtil.wrap(task,?MDC.getCopyOfContextMap()));
????}

????@Override
????public?Future?submit(Runnable?task)?{
????????return?super.submit(ThreadMdcUtil.wrap(task,?MDC.getCopyOfContextMap()));
????}
}

說明：

• 繼承ThreadPoolExecutor類，重新執(zhí)行任務(wù)的方法

• 通過ThreadMdcUtil對(duì)任務(wù)進(jìn)行一次包裝

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??Callable?wrap(final?Callable?callable,?final?Map?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?context)?{
????????return?()?->?{
????????????if?(context?==?null)?{
????????????????MDC.clear();
????????????}?else?{
????????????????MDC.setContextMap(context);
????????????}
????????????setTraceIdIfAbsent();
????????????try?{
????????????????runnable.run();
????????????}?finally?{
????????????????MDC.clear();
????????????}
????????};
????}
}

說明【以封裝Runnable為例】：

• 判斷當(dāng)前線程對(duì)應(yīng)MDC的Map是否存在，存在則設(shè)置
• 設(shè)置MDC中的traceId值，不存在則新生成，針對(duì)不是子線程的情況，如果是子線程，MDC中traceId不為null
• 執(zhí)行run方法

代碼等同于以下寫法，會(huì)更直觀

public?static?Runnable?wrap(final?Runnable?runnable,?final?Map?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(duì)應(yīng)的Map就是一樣的了

• 判斷當(dāng)前線程對(duì)應(yīng)MDC的Map是否存在，存在則設(shè)置

• 設(shè)置MDC中的traceId值，不存在則新生成，針對(duì)不是子線程的情況，如果是子線程，MDC中traceId不為null

• 執(zhí)行run方法

HTTP調(diào)用丟失traceId

在使用HTTP調(diào)用第三方服務(wù)接口時(shí)traceId將丟失，需要對(duì)HTTP調(diào)用工具進(jìn)行改造，在發(fā)送時(shí)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

HttpClient：

• 實(shí)現(xiàn)HttpClient攔截器

public?class?HttpClientTraceIdInterceptor?implements?HttpRequestInterceptor?{
????@Override
????public?void?process(HttpRequest?httpRequest,?HttpContext?httpContext)?throws?HttpException,?IOException?{
????????String?traceId?=?MDC.get(Constants.TRACE_ID);
????????//當(dāng)前線程調(diào)用中有traceId，則將該traceId進(jìn)行透?jìng)?/span>
????????if?(traceId?!=?null)?{
????????????//添加請(qǐng)求體
????????????httpRequest.addHeader(Constants.TRACE_ID,?traceId);
????????}
????}
}

實(shí)現(xiàn)HttpRequestInterceptor接口并重寫process方法

如果調(diào)用線程中含有traceId，則需要將獲取到的traceId通過request中的header向下透?jìng)飨氯?/p>

• 為HttpClient添加攔截器

private?static?CloseableHttpClient?httpClient?=?HttpClientBuilder.create()
????????????.addInterceptorFirst(new?HttpClientTraceIdInterceptor())
????????????.build();

通過addInterceptorFirst方法為HttpClient添加攔截器

OKHttp：

• 實(shí)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(qǐng)求體
????????????request?=?chain.request().newBuilder().addHeader(Constants.TRACE_ID,?traceId).build();
????????}
????????Response?originResponse?=?chain.proceed(request);

????????return?originResponse;
????}
}

實(shí)現(xiàn)Interceptor攔截器，重寫interceptor方法，實(shí)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?jìng)?/p>

• 為OkHttp添加攔截器

??private?static?OkHttpClient?client?=?new?OkHttpClient.Builder()
????????????.addNetworkInterceptor(new?OkHttpTraceIdInterceptor())
????????????.build();

調(diào)用addNetworkInterceptor方法添加攔截器

RestTemplate：

• 實(shí)現(xiàn)RestTemplate攔截器

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);
????}
}

實(shí)現(xiàn)ClientHttpRequestInterceptor接口，并重寫intercept方法，其余邏輯都是一樣的不重復(fù)說明

• 為RestTemplate添加攔截器

restTemplate.setInterceptors(Arrays.asList(new?RestTemplateTraceIdInterceptor()));

調(diào)用setInterceptors方法添加攔截器

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);
????}
}

說明：

• 先從request header中獲取traceId

• 從request header中獲取不到traceId則說明不是第三方調(diào)用，直接生成一個(gè)新的traceId

• 將生成的traceId存入MDC中

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：

?"pattern">[TRACEID:%X{traceId}]?%d{HH:mm:ss.SSS}?%-5level?%class{-1}.%M()/%L?-?%msg%xEx%n

需要添加%X{traceId}

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