1 背景

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通常，我们会在日志中，通过 traceId 来进行一次完整请求日志的定位，而 traceId 是保存在 MDC 的本地线程中，当主线程开启了一个异步线程时，traceId 就会丢失。本方案，通过线程池中的装饰器，来将父线程中的traceId传递给子线程，从而保证 traceId 不丢失。

2 实现代码

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/**
 * redis 操作线程池
 */
@Bean(value = "redisOperatorThreadPoolTaskExecutor")
public ThreadPoolTaskExecutor redisOperatorThreadPoolTaskExecutor() {
    // todo 监听线程池使用的情况

    return getThreadPoolTaskExecutor(redisOperatorThreadPoolProperties);
}

/**
 * 根据线程池的属性值获取对应线程的设置
 *
 * @param baseThreadPoolProperties 线程池配置信息
 * @return 线程池
 */
private ThreadPoolTaskExecutor getThreadPoolTaskExecutor(BaseThreadPoolProperties baseThreadPoolProperties) {
    ThreadPoolTaskExecutor threadPoolTaskExecutor = new ThreadPoolTaskExecutor();
    if (StringUtils.isNotBlank(baseThreadPoolProperties.getThreadGroupName())) {
        threadPoolTaskExecutor.setThreadGroupName(baseThreadPoolProperties.getThreadGroupName());
    }
    if (StringUtils.isNotBlank(baseThreadPoolProperties.getThreadNamePrefix())) {
        threadPoolTaskExecutor.setThreadNamePrefix(baseThreadPoolProperties.getThreadNamePrefix());
    }
    if (null != baseThreadPoolProperties.getCorePoolSize() && baseThreadPoolProperties.getCorePoolSize() > 0) {
        threadPoolTaskExecutor.setCorePoolSize(baseThreadPoolProperties.getCorePoolSize());
    }
    if (null != baseThreadPoolProperties.getQueueCapacity() && baseThreadPoolProperties.getQueueCapacity() > 0) {
        threadPoolTaskExecutor.setQueueCapacity(baseThreadPoolProperties.getQueueCapacity());
    }
    if (null != baseThreadPoolProperties.getMaxPoolSize() && baseThreadPoolProperties.getMaxPoolSize() > 0) {
        threadPoolTaskExecutor.setMaxPoolSize(baseThreadPoolProperties.getMaxPoolSize());
    }
    if (null != baseThreadPoolProperties.getKeepAliveSeconds() && baseThreadPoolProperties.getKeepAliveSeconds() > 0) {
        threadPoolTaskExecutor.setKeepAliveSeconds(baseThreadPoolProperties.getKeepAliveSeconds());
    }
    // 设置拒绝策略
    if (StringUtils.isNotBlank(baseThreadPoolProperties.getRejectedPolicy())) {
        ThreadPoolRejectedPolicyEnum threadPoolRejectedPolicyEnum = ThreadPoolRejectedPolicyEnum.toEnum(baseThreadPoolProperties.getRejectedPolicy());
        if (null != threadPoolRejectedPolicyEnum) {
            threadPoolTaskExecutor.setRejectedExecutionHandler(threadPoolRejectedPolicyEnum.getRejectedExecutionHandler());
        } else {
            log.warn("Not exist rejectedPolicy:{}, return threadPoolRejectedPolicyEnum null.", baseThreadPoolProperties.getRejectedPolicy());
        }
    }
    // 设置MdcRunnable
    threadPoolTaskExecutor.setTaskDecorator(new MdcTaskDecorator());
    return threadPoolTaskExecutor;
}

/**
 * 主线程traceId传入到子线程（注意：线程池池化） 核心代码
 */
private static class MdcTaskDecorator implements TaskDecorator {

    @Override
    public Runnable decorate(Runnable runnable) {
        String traceId = MDC.get(TRACE_ID);
        return () -> {
            try {
                MDC.put(TRACE_ID, traceId);
                runnable.run();
            } finally {
                MDC.remove(TRACE_ID);
            }
        };
    }
}

3 效果

异步线程的traceId 和 主线程中的 traceId 一致，从而保证了业务在查看日志时，能够通过 traceId 完成串联一次完整请求的所有日志（包括异步线程中的日志）。