小白都能看得懂的服务调用链路追踪设计与实现

ThreadLocal 由来简介：在 JDK 1.2 的版本中就提供 java.lang.ThreadLocal，ThreadLocal 为解决多线程程序的并发问题提供了一种新的思路。ThreadLocal 并不是一个 Thread，而是 Thread 的局部变量。在 JDK 5.0 中，ThreadLocal 开始支持泛型，使其功能更加灵活强大。
ThreadLocal<T> 类中提供了几个重要方法简介：# 获取当前线程中保存的变量副本1.public T get() { }# 设置当前线程中变量的副本2.public void set(T value) { }# 移除当前线程中变量的副本3.public void remove() { }# 初始化当前线程中变量的副本4.protected T initialValue(){ }
ThreadLocal 应用场景简介：在 Java 的多线程编程中，为保证多个线程对共享变量的安全访问，通常会使用 synchronized 来保证同一时刻只有一个线程对共享变量进行操作。这种情况下可以将类变量放到 ThreadLocal 类型的对象中，使变量在每个线程中都有独立拷贝，不会出现一个线程读取变量时而被另一个线程修改的现象。最常见的 ThreadLocal 使用场景为用来解决数据库连接、Session 管理等。

package com.smart4j.core.logtrack.interceptor;
import org.springframework.stereotype.Component;import org.springframework.web.servlet.HandlerInterceptor;
import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.util.Optional;import java.util.UUID;
/** * @Description: 日志追踪拦截器* @Param:  * @return:  * @Author: Mr.Zhang * @Date: 2020/4/14*/ @Componentpublic class LogTrackInterceptor implements HandlerInterceptor {  /**   * 存储 traceId   */  private static final ThreadLocal<String> TRACE_ID_THREAD_LOCAL = new ThreadLocal<>();
  @Override  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {    /**     * 获取请求头header中传递的trace-id，若没有，则UUID代替     */    String traceId = Optional.ofNullable(request.getHeader("trace-id")).orElse(UUID.randomUUID().toString().replaceAll("-",""));    // 请求前设置    TRACE_ID_THREAD_LOCAL.set(traceId);    return true;  }
  @Override  public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {    // 移除，防止内存泄漏    TRACE_ID_THREAD_LOCAL.remove();  }
  public static String getTraceId() {    return TRACE_ID_THREAD_LOCAL.get();  }
  public static void setTraceId(String traceId){    TRACE_ID_THREAD_LOCAL.set(traceId);  }
}

package com.smart4j.core.logtrack.config;
import com.smart4j.core.logtrack.interceptor.LogTrackInterceptor;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.annotation.Configuration;import org.springframework.web.servlet.config.annotation.InterceptorRegistry;import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/** * @Description: 注册自定义拦截器* @Param:  * @return:  * @Author: Mr.Zhang * @Date: 2020/4/14*/ @Configurationpublic class CustomInterceptorConfig implements WebMvcConfigurer {
  @Autowired  private LogTrackInterceptor logTrackInterceptor;
  @Override  public void addInterceptors(InterceptorRegistry registry) {    registry.addInterceptor(logTrackInterceptor);  }}

package com.smart4j.core.logtrack.config;
import ch.qos.logback.classic.pattern.ClassicConverter;import ch.qos.logback.classic.spi.ILoggingEvent;import com.smart4j.core.logtrack.interceptor.LogTrackInterceptor;import org.springframework.util.StringUtils;

/*** @Description:  自定义日志格式化* @Param:* @return:* @Author: Mr.Zhang* @Date: 2020/4/14*/public class TraceIdPatternConverter extends ClassicConverter {  @Override  public String convert(ILoggingEvent iLoggingEvent) {    String traceId = LogTrackInterceptor.getTraceId();    return StringUtils.isEmpty(traceId) ? "traceId" : traceId;  }}

package com.smart4j.core.logtrack.controller;
import lombok.extern.slf4j.Slf4j;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;
/*** @Description:  测试日志追踪* @Param:* @return:* @Author: Mr.Zhang* @Date: 2020/4/14*/@Slf4j@RestController@RequestMapping("/test")public class LogTrackController {
  @GetMapping("/log")  public String logTrack(){    log.info("-----> 测试 info <-----");    log.warn("-----> 测试 warn <-----");    log.error("-----> 测试 error <-----");    return null;  }
}

<?xml version="1.0" encoding="UTF-8"?><configuration>  <!-- 获取 traceId 配置类-->  <conversionRule conversionWord="traceId" converterClass="com.smart4j.core.logtrack.config.TraceIdPatternConverter" />  <!-- 自定义 logback 日志格式-->  <property name="CUSTOM_LOG_PATTERN"            value="[[[%date{yyyy-MM-dd HH:mm:ss} | %-5level | %traceId | %thread | %file:%line | %logger : %.1000m]]]%n" />
  <!-- 控制台输出 -->  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">    <encoder>        <pattern>${CUSTOM_LOG_PATTERN}</pattern>    </encoder>  </appender>
  <root level="INFO">    <!-- 控制台打印 -->    <appender-ref ref="STDOUT"/>  </root></configuration>

[[[2020-04-14 19:53:41 | INFO  | 6ee9257270474ce38826a8b842adb06f | http-nio-8080-exec-1 | LogTrackController.java:22 | com.smart4j.core.logtrack.controller.LogTrackController : -----> 测试 info <-----]]][[[2020-04-14 19:53:41 | WARN  | 6ee9257270474ce38826a8b842adb06f | http-nio-8080-exec-1 | LogTrackController.java:23 | com.smart4j.core.logtrack.controller.LogTrackController : -----> 测试 warn <-----]]][[[2020-04-14 19:53:41 | ERROR | 6ee9257270474ce38826a8b842adb06f | http-nio-8080-exec-1 | LogTrackController.java:24 | com.smart4j.core.logtrack.controller.LogTrackController : -----> 测试 error <-----]]]