微服务分布式架构中，如何实现日志链路跟踪？
Logback 背景
Logback是由log4j创始人设计的另一个开源日志组件,官方网站：http://logback.qos.ch。它当前分为下面下个模块：
logback-core：其它两个模块的基础模块
logback-classic：它是log4j的一个改良版本，同时它完整实现了slf4j API使你可以很方便地更换成其它日志系统如log4j或JDK14 Logging
logback-access：访问模块与Servlet容器集成提供通过Http来访问日志的功能
▐ 普通debug日志
▐ SQL执行日志
Logback 配置案例
日志级别排序为：TRACE < DEBUG < INFO < WARN < ERROR
%d：表示日期
%n：换行
%thread：表示线程名
%level：日志级别
%msg：日志消息
%file：表示文件名
%class：表示文件名
%logger：Java类名（含包名，这里设定了36位，若超过36位，包名会精简为类似a.b.c.JavaBean)
%line：Java类的行号
%-4relative %d{yyyy-MM-dd HH:mm:ss.SSS} [%thread][%X{TRACE_ID}] %-5level %logger{100}.%M\(%line\) - %msg%n▐ 案例
3452487 2021-08-03 15:19:36.940 [thread-monitor-daemon][] WARN com.xxxx.common.util.MonitorLogger.warn(27) - 发现超时线程notify-replay-consumer...由于案例中是守护线程thread-monitor-daemon，所以不记录链路ID。
回归正题比如下面的例子中记录了请求的链路ID
19006989 2021-08-04 22:35:25.776 [http-nio-0.0.0.0-8010-exec-10][1fc8pebmgwukw863w2p342rp2936a3r157w0:0:] INFO com.xxx.framework.eureka.core.listener.EurekaStateChangeListener.listen(58) - 服务实例[XX-PAAS]注册成功,当前服务器已注册服务实例数量[3]链路ID设计
▐ 第一种
▐ 第二种
public static class ThreadTraceListener implements ThreadListener {@Overridepublic void onThreadBegin(HttpServletRequest request) {String traceToken = ThreadLocalUtil.getTranVar(TRACE_ID);String fromServer = ThreadLocalUtil.getTranVar(FROM_SERVER);int deep;String traceId;if (StringUtils.isBlank(traceToken)) {traceId = IDGenerator.generateID();deep = 0;traceToken = StringHelper.join(traceId, ":0");} else {int index = traceToken.lastIndexOf(':');traceId = traceToken.substring(0, index);deep = Integer.valueOf(traceToken.substring(index + 1));}ThreadLocalUtil.setLocalVar(TRACE_ID, traceId);ThreadLocalUtil.setLocalVar(TRACE_DEEP, deep);ThreadLocalUtil.setTranVar(TRACE_ID, StringHelper.join(traceId, ":", deep + 1));ThreadLocalUtil.setLocalVar(FROM_SERVER, fromServer);ThreadLocalUtil.setTranVar(FROM_SERVER, getCurrentServer());MDC.put(TRACE_ID, StringHelper.join(traceToken, ":", fromServer));}@Overridepublic void onThreadEnd(HttpServletRequest request) {MDC.remove(TRACE_ID);}}
protected void doFilterInternal(HttpServletRequest request,HttpServletResponse response,FilterChain chain) throws ServletException, IOException {long startTime = System.currentTimeMillis();// 从Header中装载传递过来的变量Map<String, Object> tranVar = new HashMap<String, Object>();Enumeration<String> headers = request.getHeaderNames();while (headers.hasMoreElements()) {String key = headers.nextElement();if (!StringUtils.isEmpty(key)&& key.startsWith(ThreadLocalUtil.TRAN_PREFIX)) {tranVar.put(key.substring(ThreadLocalUtil.TRAN_PREFIX.length()),request.getHeader(key));}}ThreadLocalHolder.begin(tranVar, request);try {if (isGateway) {response.addHeader("X-TRACE-ID", TraceUtil.getTraceId());}// 检查RPC调用深度checkRpcDeep(request, response);// 业务处理chain.doFilter(request, response);// 记录RPC调用次数logRpcCount(request, response);} catch (Throwable ex) {// 错误处理Response<?> result = ExceptionUtil.toResponse(ex);Determine determine = ExceptionUtil.determineType(ex);ExceptionUtil.doLog(result, determine.getStatus(), ex);response.setStatus(determine.getStatus().value());response.setCharacterEncoding("UTF-8");response.setContentType(MediaType.APPLICATION_JSON_UTF8_VALUE);response.getWriter().write(JsonUtil.toJsonString(result));} finally {try {doMonitor(request, response, startTime);if (TraceUtil.isTraceLoggerOn()) {log.warn(StringHelper.join("TRACE-HTTP-", request.getMethod()," URI:", request.getRequestURI(),", dt:", System.currentTimeMillis() - startTime,", rpc:", TraceUtil.getRpcCount(),", status:", response.getStatus()));} else if (log.isTraceEnabled()) {log.trace(StringHelper.join(request.getMethod()," URI:", request.getRequestURI(),", dt:", System.currentTimeMillis() - startTime,", rpc:", TraceUtil.getRpcCount(),", status:", response.getStatus()));}} finally {ThreadLocalHolder.end(request);}}}
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