SpringBoot项目traceId生成/日志打印

前言

查看服务日志时，当服务被调过于频繁，日志刷新太快，会影响到联调、测试、线上问题的排查效率，能不能为每一个请求的日志打一个唯一标识呢？后面使用该表示去匹配，直接检索出该请求的日志？引入本文的正题，“traceId”。

MDC

MDC定义 Mapped Diagnostic Context，即：映射诊断环境。

MDC是 log4j 和 logback 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的使用方法

向MDC设置值：MDC.put(key, value);

从MDC中取值：MDC.get(key);

将MDC中的内容打印到日志中：%X{key};

初始化TraceId并向MDC设置值

这里主要是利用切面，方法执行前设置MDC，方法执行后擦除MDC。具体实现方式有很多，如过滤器、拦截器、AOP等等。个人比较推荐Filter实现，因为Filter是请求最先碰到的，也是响应给前端前最后一个碰到的。

过滤器实现

@Slf4j
@WebFilter(filterName = "traceIdFilter", urlPatterns = "/*")
@Order(0)
@Component
public class TraceIdFilter implements Filter {
    /**
     * 日志跟踪标识
     */
    public static final String TRACE_ID = "TRACE_ID";

    @Override
    public void init(FilterConfig filterConfig) {
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
            throws IOException, ServletException {
        MDC.put(TRACE_ID, UUID.randomUUID().toString());
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {
        MDC.clear();
    }
}

拦截器实现

@Component
public class TraceIdInterceptor extends HandlerInterceptorAdapter {
    private static final String TRACE_ID = "TRACE_ID";

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        MDC.put(TRACE_ID, UUID.randomUUID().toString());
        return true;
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) {
        MDC.clear();
    }
}

@Configuration
public class WebConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new TraceIdInterceptor());
    }
}

日志打印配置pattern中配置traceId

与之前的相比只是添加了[%X{TRACE_ID}]， [%X{***}]是一个模板，中间属性名是我们使用MDC put进去的。

%d{yyyy-MM-dd} [%thread] %-5level %logger{50} - [%X{TRACE_ID}] - %msg%n

异步方法的日志打印traceId

异步方法会开启一个新线程，我们想要是异步方法和主线程共用同一个traceId，首先先新建一个任务适配器MdcTaskDecorator。

public class MdcTaskDecorator implements TaskDecorator {
    @Override
    public Runnable decorate(Runnable runnable) {
        Map<String, String> map = MDC.getCopyOfContextMap();
        return () -> {
            try {
                MDC.setContextMap(map);
                String traceId = MDC.get(TRACE_ID);
                if (StringUtils.isBlank(traceId)) {
                    traceId = UUID.randomUUID().toString();
                    MDC.put(TRACE_ID, traceId);
                }
                runnable.run();
            } finally {
                MDC.clear();
            }
        };
    }
}

在线程池配置中增加executor.setTaskDecorator(new MdcTaskDecorator())的设置

@EnableAsync
@Configuration
public class ThreadPoolConfig {
    private int corePoolSize = Runtime.getRuntime().availableProcessors() + 1;
    private int maxPoolSize = corePoolSize * 2;
    private static final int queueCapacity = 50;
    private static final int keepAliveSeconds = 30;

    @Bean(name = "threadPoolTaskExecutor")
    public ThreadPoolTaskExecutor threadPoolTaskExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setMaxPoolSize(maxPoolSize);
        executor.setCorePoolSize(corePoolSize);
        executor.setQueueCapacity(queueCapacity);
        executor.setKeepAliveSeconds(keepAliveSeconds);
        executor.setTaskDecorator(new MdcTaskDecorator());
        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        return executor;
    }
}

使用指定的线程池执行业务代码

@Async("threadPoolTaskExecutor")
public void testThreadPoolTaskExecutor(){
    log.info("Async 测试一下");
}

在响应DTO中返回traceId

@Data
@AllArgsConstructor
public class RetResult<T> {

    private Integer code;

    private String msg;

    private T data;

    private String traceId;

    public RetResult(Integer code, String msg, T data) {
        this.code = code;
        this.msg = msg;
        this.data = data;
        this.traceId = MDC.get(TRACE_ID);
    }

    public static <T> RetResult<T> success(T t) {
        return new RetResult<>(RetCode.SUCCESS.getCode(), "ok", t);
    }

    public static <T> RetResult<T> success() {
        return new RetResult<>(RetCode.SUCCESS.getCode(), "ok", null);
    }

    public static <T> RetResult<T> fail() {
        return new RetResult<>(RetCode.FAIL.getCode(), "fail", null);
    }

    public static <T> RetResult<T> fail(String msg) {
        return new RetResult<>(RetCode.FAIL.getCode(), msg, null);
    }

    public static <T> RetResult<T> fail(Integer code, String msg) {
        return new RetResult<>(code, msg, null);
    }

}