Question

我使用ScheduledThreadPoolBasedExecutor来安排和执行callable。根据{{3}}：它以FIFO顺序执行具有给定延迟的任务或（如果延迟相等）。为此，它甚至在实现中包含AtomicLong音序器。

我写了测试，提交了许多计算素数的任务。

public class MyCallable implements Callable<Boolean> {
    private static AtomicInteger counter = new AtomicInteger(0);
    private final long prNumber;
    private long callNanoTime;
    private LocalDateTime callLocalDateTime;
    private boolean isCalled = false;

    public MyCallable(long number) {
        this.prNumber = number;
    }

    public Boolean call() {
        callNanoTime = System.nanoTime();
        callLocalDateTime = LocalDateTime.now();
        isCalled = true;
        return isPrime(this.prNumber);
    }

    public boolean isCalled() {..}

    public long getCallNanoTime() {..}

    public LocalDateTime getCallLocalDateTime() {..}

    private boolean isPrime(long n) {..}
}

我以这种方式提交任务： 1）获取间隔（从现在开始的2秒到现在的6秒） 2）生成4000个任务并按统一分布（实际每毫秒）安排它们

我按计划时间排序了callables，并检查callNanoTime是否为非增加（显然它必须为true）但实际上没有，我的测试输出结果如下：

Callable scheduled to: '2018-01-28T14:04:13.866' was called in: '61665400763727', but callable scheduled to: '2018-01-28T14:04:13.868' was called in: '61665397242047'

实际上，调度计划到以后的时间才执行。如果我增加粒度（让任务之间的间隔为5-10毫秒），一切都很好。

初始化和日程安排：

public class ScheduledThreadPoolBasedExecutor implements Executor {
    private ScheduledExecutorService scheduledExecutorService;
    private AtomicLong counter = new AtomicLong(0);

    public ScheduledThreadPoolBasedExecutor() {
        scheduledExecutorService = Executors.newScheduledThreadPool(1);
    }

    @Override
    public void schedule(Callable callable, LocalDateTime localDateTime) {
        long value = counter.incrementAndGet();
        if (value % 100 == 0) {
            System.out.println(String.format("Schedule callable #%s", value));
        }
        long delay = ChronoUnit.MILLIS.between(LocalDateTime.now(), localDateTime);
        scheduledExecutorService.schedule(callable, delay, TimeUnit.MILLISECONDS);
    }
}

操作系统和ScheduledThreadPoolBasedExecutor引起的这种1-3ms不一致是否不能保证此类时间的顺序？或者我错误地使用它？

ScheduledThreadPoolBasedExecutor

0 个答案: