Class Rescheduler

core/src/main/java/io/grpc/internal/Rescheduler.java:29–116

Reschedules a runnable lazily.

 * Reschedules a runnable lazily.
 */
final class Rescheduler {

  // deps
  private final ScheduledExecutorService scheduler;
  private final Executor serializingExecutor;
  private final Runnable runnable;

  // state
  private final Stopwatch stopwatch;
  private long runAtNanos;
  private boolean enabled;
  private ScheduledFuture<?> wakeUp;

  Rescheduler(
      Runnable r,
      Executor serializingExecutor,
      ScheduledExecutorService scheduler,
      Stopwatch stopwatch) {
    this.runnable = r;
    this.serializingExecutor = serializingExecutor;
    this.scheduler = scheduler;
    this.stopwatch = stopwatch;
    stopwatch.start();
  }

  /* must be called from the {@link #serializingExecutor} originally passed in. */
  void reschedule(long delay, TimeUnit timeUnit) {
    long delayNanos = timeUnit.toNanos(delay);
    long newRunAtNanos = nanoTime() + delayNanos;
    enabled = true;
    if (newRunAtNanos - runAtNanos < 0 || wakeUp == null) {
      if (wakeUp != null) {
        wakeUp.cancel(false);
      }
      wakeUp = scheduler.schedule(new FutureRunnable(), delayNanos, TimeUnit.NANOSECONDS);
    }
    runAtNanos = newRunAtNanos;
  }

  // must be called from channel executor
  void cancel(boolean permanent) {
    enabled = false;
    if (permanent && wakeUp != null) {
      wakeUp.cancel(false);
      wakeUp = null;
    }
  }

  private final class FutureRunnable implements Runnable {
    @Override
    public void run() {
      Rescheduler.this.serializingExecutor.execute(new ChannelFutureRunnable());
    }

    private boolean isEnabled() {
      return Rescheduler.this.enabled;
    }
  }