线程池中出现数据丢失或数据重用的情况

[HuangDayu]

你好，使用场景是这样的。业务上存在一个或者多个线程池，每一个线程池的任务会创建新的线程任务，任务可能是跨线程池的，也可能是在同一个线程池中。问题是出现了数据丢失或者旧数据重用的情况，在任务多的情况下出现的更加频繁。

public class TTLTest {

    static TransmittableThreadLocal<String> transmittableThreadLocal = new TransmittableThreadLocal<>();
    static Executor executorService1;

    @Before
    public void init() {
        executorService1 = eventBusExecutor();
        TtlExecutors.getTtlExecutor(executorService1);
    }

    @Test
    public void run() throws InterruptedException {
        for (int i = 0; i < 10; i++) {
            transmittableThreadLocal.set(i + " - " + UUID.randomUUID().toString());
            execute1();
            System.out.println();
            TimeUnit.MILLISECONDS.sleep(2);
        }
    }


    public void execute1() {
        executorService1.execute(() -> {
            System.out.println("execute1 -> " + transmittableThreadLocal.get());
            execute2();
            try {
                TimeUnit.MILLISECONDS.sleep(2);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
    }

    public void execute2() {
        executorService1.execute(() -> {
            System.out.println("execute2 -> " + transmittableThreadLocal.get());
        });
    }


    public Executor eventBusExecutor() {
        int processors = Runtime.getRuntime().availableProcessors();
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(processors);
        executor.setMaxPoolSize(processors * 4);
        executor.setQueueCapacity(processors * 8);
        executor.setThreadNamePrefix("Context-");
        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        executor.initialize();
        return executor;
    }

}

这个输出结果：

execute1 -> 0 - f424790a-3695-46be-8fa9-bebb4adbe257
execute2 -> 0 - f424790a-3695-46be-8fa9-bebb4adbe257

execute1 -> 1 - 73e441f2-8e96-4dac-af82-f2ffec92b363
execute2 -> 1 - 73e441f2-8e96-4dac-af82-f2ffec92b363

execute1 -> 2 - dc092e47-e14d-458a-b52c-8ac275adcd9b
execute2 -> 2 - dc092e47-e14d-458a-b52c-8ac275adcd9b

execute1 -> 3 - 80700d0d-5c27-45de-a9e2-8a182e1fabf1
execute2 -> 3 - 80700d0d-5c27-45de-a9e2-8a182e1fabf1

execute1 -> 4 - 4b1ebbc9-88da-47ad-87a9-442f2f046b17
execute2 -> 4 - 4b1ebbc9-88da-47ad-87a9-442f2f046b17

execute1 -> 5 - 4bbc084d-0d60-4471-b5f5-e374cbdc1f1c
execute2 -> 5 - 4bbc084d-0d60-4471-b5f5-e374cbdc1f1c

execute1 -> 6 - 0d289dd2-6cd7-4c74-8e3a-747b058ab11b
execute2 -> 6 - 0d289dd2-6cd7-4c74-8e3a-747b058ab11b

execute1 -> 7 - 2f46b88a-9d42-4b07-bc66-e0f9e59811b1
execute2 -> 7 - 2f46b88a-9d42-4b07-bc66-e0f9e59811b1

execute1 -> 0 - f424790a-3695-46be-8fa9-bebb4adbe257
execute2 -> 0 - f424790a-3695-46be-8fa9-bebb4adbe257

execute1 -> 1 - 73e441f2-8e96-4dac-af82-f2ffec92b363
execute2 -> 1 - 73e441f2-8e96-4dac-af82-f2ffec92b363

可以看到，第0次和第1次的数据被重用了，而第8次和第9次的数据则丢失了。

execute1 -> 0 - feaf48cc-b69a-45a9-8fe0-1cb6a1f011fc
execute2 -> 0 - feaf48cc-b69a-45a9-8fe0-1cb6a1f011fc

execute1 -> 1 - be5d923a-a8df-4637-9401-920f48fea82d
execute2 -> 1 - be5d923a-a8df-4637-9401-920f48fea82d

execute1 -> 2 - a61872d1-abc1-4d69-9c93-dd108486642d
execute2 -> 2 - a61872d1-abc1-4d69-9c93-dd108486642d

execute1 -> 3 - f208f099-3a42-4d68-9672-bd22f183564a
execute2 -> 3 - f208f099-3a42-4d68-9672-bd22f183564a

execute1 -> 4 - c09511ad-ab35-4c2a-a83d-f5021c9ec48d
execute2 -> 4 - c09511ad-ab35-4c2a-a83d-f5021c9ec48d

execute1 -> 5 - 85e05522-5685-46e0-9163-26129e4ca262
execute2 -> 5 - 85e05522-5685-46e0-9163-26129e4ca262

execute1 -> 6 - a0c5e2c5-a28e-49b1-ac51-4209f7138423
execute2 -> 6 - a0c5e2c5-a28e-49b1-ac51-4209f7138423

execute1 -> 7 - ecb16d9f-34db-47ca-9d9d-bd0f39872150
execute2 -> 7 - ecb16d9f-34db-47ca-9d9d-bd0f39872150

execute1 -> 0 - feaf48cc-b69a-45a9-8fe0-1cb6a1f011fc
execute2 -> 1 - be5d923a-a8df-4637-9401-920f48fea82d

execute1 -> 0 - feaf48cc-b69a-45a9-8fe0-1cb6a1f011fc
execute2 -> 1 - be5d923a-a8df-4637-9401-920f48fea82d

这一次结果也可以看到，第0次和第1次的数据交叉重用，而第8次和第9次的数据也丢失了。

这似乎是一个必现的问题，是不是我没有手动remove的问题，还是使用的方式存在问题，请赐教，谢谢。

[HuangDayu]

找到了问题的原因，在于没有使用装饰后的线程池对象，而是使用了旧的对象。

    @Before
    public void init() {

        //executorService1 = eventBusExecutor();
        //TtlExecutors.getTtlExecutor(executorService1);

        executorService1 = TtlExecutors.getTtlExecutor(eventBusExecutor());
    }

建议在文档中显著表明一下。:wink:

[oldratlee]

找到了问题的原因，在于没有使用装饰后的线程池对象，而是使用了旧的对象。

    @Before
    public void init() {

        //executorService1 = eventBusExecutor();
        //TtlExecutors.getTtlExecutor(executorService1);

        executorService1 = TtlExecutors.getTtlExecutor(eventBusExecutor());
    }

建议在文档中显著表明一下。😉

@HuangDayu 加了一个代码优化： a545558，发布在 v2.13.2
https://github.com/alibaba/transmittable-thread-local/releases/tag/v2.13.2

上面错误的使用方式，在IntelliJ IDEA中，会有警告出来：✅ 😋

之前的TTL版本，IntelliJ IDEA并不能有警告提示：❌ 😖