ScheduledThreadPoolExecutor杂乱笔记

 

java.util.concurrent.ScheduledThreadPoolExecutor
public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {
    ...
    delayedExecute(t);
    return t;
}
private void delayedExecute(RunnableScheduledFuture<?> task) {
    ...
        super.getQueue().add(task);
        ...
            ensurePrestart();
    ...
}


java.util.concurrent.ThreadPoolExecutor
void ensurePrestart() {
    int wc = workerCountOf(ctl.get());
    if (wc < corePoolSize)
        addWorker(null, true);
    else if (wc == 0)
        addWorker(null, false);
}
private boolean addWorker(Runnable firstTask, boolean core) {
    ...
    Worker w = null;
    try {
        w = new Worker(firstTask);
        final Thread t = w.thread;
        if (t != null) {
            ... 
                t.start();
                workerStarted = true;
        }
    }
    ...
}


java.util.concurrent.ThreadPoolExecutor.Worker
private final class Worker extends AbstractQueuedSynchronizer implements Runnable
Worker(Runnable firstTask) {
    ...
    // 1.Worker也是Runnable的子类  
    // 2.Runnable的子类run()方法执行逻辑
    // 3.上面Thread t = w.thread;  w.thread实际就是w自己
    this.thread = getThreadFactory().newThread(this);
}
// java.util.concurrent.ThreadPoolExecutor#addWorker中t.start()之后调用Worker#run;
// t.start()的t线程,  实际就是Worker的实例线程
java.util.concurrent.ThreadPoolExecutor.Worker#run
public void run() {
    runWorker(this);
}


java.util.concurrent.ThreadPoolExecutor#runWorker
final void runWorker(Worker w) {
    Thread wt = Thread.currentThread();
    Runnable task = w.firstTask;
    ...
    try {
        while (task != null || (task = getTask()) != null) {
    ...
                    task.run();
    ...
}


java.util.concurrent.ThreadPoolExecutor#getTask
private Runnable getTask() {
    ...
        Runnable r = timed ? workQueue.poll(keepAliveTime, TimeUnit.NANOSECONDS) : workQueue.take();
    ...
}


java.util.concurrent.ScheduledThreadPoolExecutor.DelayedWorkQueue#take
public RunnableScheduledFuture<?> take() throws InterruptedException {
    final ReentrantLock lock = this.lock;
    lock.lockInterruptibly();
    try {
        for (;;) {
            RunnableScheduledFuture<?> first = queue[0];
            if (first == null)
                available.await();
            else {
                // 这里很重要,DelayedWorkQueue通过这个long delay判断是不是要调用task,   for (;;)一直在自旋
                long delay = first.getDelay(NANOSECONDS);
                if (delay <= 0)
                    return finishPoll(first);
    ...
}

// task.run();  
// 1. 执行scheduleWithFixedDelay方法传入的Runnable
// 2.设置下一次的执行时间
// 3.重新建task放回到queue中
java.util.concurrent.ScheduledThreadPoolExecutor.ScheduledFutureTask#run
public void run() {
    ...
    else if (ScheduledFutureTask.super.runAndReset()) {
        setNextRunTime();
        reExecutePeriodic(outerTask);
    }
}