即使在使用 Vert.x 和 Log4j2 将“isThreadContextMapInheritable”设置为 true 后也没有获取 ThreadContext 值

Question

我正在使用 Vertx 和 Log4j2。

这是Remote.java的代码

public class Remote extends AbstractVerticle {

    @Override
    public void start() throws Exception {
        System.setProperty("isThreadContextMapInheritable", "true");
        ThreadContext.put("1", "Company");
        ThreadContext.put("2", "Sector");
        ThreadContext.put("3", "Address");
        ArrayList<String> arrayList = new ArrayList<>();
        for (int i = 1; i < 4; i++) {
            arrayList.add(String.valueOf(i));
        }
        arrayList.parallelStream().forEach(s -> {
            System.out.println("Key " + s + " Value is " + ThreadContext.get(s) + " Name: " + Thread.currentThread().getName());
        });
        System.out.println("After parallelStream");
    }
}

这是我的StartVerticle.java代码

public class StartVerticle {

    public static void main(String[] args) {
        Vertx vertx = Vertx.vertx();
        vertx.deployVerticle(new Remote());
    }
}

当我运行上面的代码时我的输出是

Key 2 Value is Sector Name: vert.x-eventloop-thread-0
Key 1 Value is null Name: ForkJoinPool.commonPool-worker-3
Key 3 Value is null Name: ForkJoinPool.commonPool-worker-5
After parallelStream

您能帮我获得以下输出吗？

Key 2 Value is Sector Name: vert.x-eventloop-thread-0
Key 1 Value is Company Name: ForkJoinPool.commonPool-worker-3
Key 3 Value is Address Name: ForkJoinPool.commonPool-worker-5
After parallelStream

我还打印了线程名称以供参考。 在不使用 Vertx 的情况下，将isThreadContextMapInheritable 设置为true 后，我能够打印ThreadContext 中的所有内容。

Answer 1

Vertx 和 Parallel Stream 都使用 Fork Join Common Pool。只有在公共池初始化之前设置的线程上下文值在子线程中可用。

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即使没有 Vertx，在第一个并行流之后设置的 ThreadContext 值在子线程中也将不可用。例如，

public static void main(String[] args) throws Exception {
    System.setProperty("isThreadContextMapInheritable", "true");
    IntStream.range(0, 5)
             .parallel()
             .forEach(System.out::println);
    ThreadContext.put("1", "Company");
    ThreadContext.put("2", "Sector");
    ThreadContext.put("3", "Address");

    ArrayList<String> arrayList = new ArrayList<>();
    for (int i = 1; i < 4; i++) {
        arrayList.add(String.valueOf(i));
    }
    arrayList.parallelStream()
             .forEach(s -> {
                 System.out.println("Key " + s + " Value is " + ThreadContext.get(s) + " Name: " + Thread.currentThread()
                                                                                                         .getName());
             });
}

这会打印出来

Key 1 Value is null Name: ForkJoinPool.commonPool-worker-5
Key 3 Value is null Name: ForkJoinPool.commonPool-worker-1
Key 2 Value is Sector Name: main

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在我们的例子中，公共池在Vertx 启动时被初始化。此时，没有设置线程上下文值。
所以一种选择是在启动vertx之前在main()中设置线程上下文。

public static void main(String[] args) {
    System.setProperty("isThreadContextMapInheritable", "true");
    ThreadContext.put("1", "Company");
    ThreadContext.put("2", "Sector");
    ThreadContext.put("3", "Address");
    Vertx vertx = Vertx.vertx();
    vertx.deployVerticle(new Remote());
}

产生输出，

Key 2 Value is Sector Name: vert.x-eventloop-thread-0
Key 3 Value is Address Name: ForkJoinPool.commonPool-worker-2
Key 1 Value is Company Name: ForkJoinPool.commonPool-worker-1
After parallelStream

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