Я решил эту проблему в общих чертах, создав Исполнителя, который может "задушить" задачи.
Задачи (Runnables) помещаются в DelayQueue, откуда Scheduler-Thread берет и выполняет их. Последнее запланированное задание также запоминается в переменной, поэтому, если планировщик получает новое задание из очереди, он проверяет, является ли это последнее задание, которое было запланировано. Если это так, он выполняет его, если нет - пропускает.
Я использую String-идентификатор для проверки того, какие задачи считаются принадлежащими одному «газу».
Это код, он также включает в себя обычные возможности планирования, но вы можете проверить здесь важные биты.
package org.uilib.util;
import com.google.common.collect.Maps;
import java.util.Map;
import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public final class SmartExecutor implements Throttle, Executor {
//~ Static fields/initializers -------------------------------------------------------------------------------------
private static final Logger L = LoggerFactory.getLogger(SmartExecutor.class);
//~ Instance fields ------------------------------------------------------------------------------------------------
private final ExecutorService executor = Executors.newCachedThreadPool();
private final DelayQueue<DelayedRunnable> taskQueue = new DelayQueue<DelayedRunnable>();
private final Map<String, ThrottledRunnable> throttledTasks = Maps.newHashMap();
//~ Constructors ---------------------------------------------------------------------------------------------------
/* schedule a Runnable to be executed a fixed period of time after it was scheduled
* if a new Runnable with the same throttleName is scheduled before this one was called, it will overwrite this */
public SmartExecutor() {
this.executor.execute(new Scheduler());
}
//~ Methods --------------------------------------------------------------------------------------------------------
/* execute a Runnable once */
@Override
public void execute(final Runnable runnable) {
this.executor.execute(runnable);
}
/* schedule a Runnable to be executed after a fixed period of time */
public void schedule(final long delay, final TimeUnit timeUnit, final Runnable runnable) {
this.taskQueue.put(new DelayedRunnable(runnable, delay, timeUnit));
}
/* schedule a Runnable to be executed using a fixed delay between the end of a run and the start of the next one */
public void scheduleAtFixedRate(final long period, final TimeUnit timeUnit, final Runnable runnable) {
this.taskQueue.put(new RepeatingRunnable(runnable, period, timeUnit));
}
/* shut the the executor down */
public void shutdown() {
this.executor.shutdownNow();
}
@Override
public void throttle(final String throttleName, final long delay, final TimeUnit timeUnit, final Runnable runnable) {
final ThrottledRunnable thrRunnable = new ThrottledRunnable(runnable, throttleName, delay, timeUnit);
this.throttledTasks.put(throttleName, thrRunnable);
this.taskQueue.put(thrRunnable);
}
//~ Inner Classes --------------------------------------------------------------------------------------------------
private static class DelayedRunnable implements Delayed, Runnable {
protected final Runnable runnable;
private final long endOfDelay;
public DelayedRunnable(final Runnable runnable, final long delay, final TimeUnit delayUnit) {
this.runnable = runnable;
this.endOfDelay = delayUnit.toMillis(delay) + System.currentTimeMillis();
}
@Override
public int compareTo(final Delayed other) {
final Long delay1 = this.getDelay(TimeUnit.MILLISECONDS);
final Long delay2 = other.getDelay(TimeUnit.MILLISECONDS);
return delay1.compareTo(delay2);
}
@Override
public long getDelay(final TimeUnit unit) {
return unit.convert(this.endOfDelay - System.currentTimeMillis(), TimeUnit.MILLISECONDS);
}
@Override
public void run() {
this.runnable.run();
}
}
private static final class RepeatingRunnable extends DelayedRunnable {
private final long periodInMillis;
public RepeatingRunnable(final Runnable runnable, final long period, final TimeUnit delayUnit) {
super(runnable, period, delayUnit);
this.periodInMillis = delayUnit.convert(period, TimeUnit.MILLISECONDS);
}
public RepeatingRunnable reschedule() {
return new RepeatingRunnable(this.runnable, this.periodInMillis, TimeUnit.MILLISECONDS);
}
}
private final class Scheduler implements Runnable {
@Override
public void run() {
while (true) {
try {
/* wait for the next runnable to become available */
final DelayedRunnable task = SmartExecutor.this.taskQueue.take();
if (task instanceof RepeatingRunnable) {
/* tell executor to run the action and reschedule it afterwards */
SmartExecutor.this.executor.execute(
new Runnable() {
@Override
public void run() {
task.run();
SmartExecutor.this.taskQueue.put(((RepeatingRunnable) task).reschedule());
}
});
} else if (task instanceof ThrottledRunnable) {
final ThrottledRunnable thrTask = (ThrottledRunnable) task;
/* run only if this is the latest task in given throttle, otherwise skip execution */
if (SmartExecutor.this.throttledTasks.get(thrTask.getThrottleName()) == thrTask) {
SmartExecutor.this.executor.execute(task);
}
} else {
/* tell the executor to just run the action */
SmartExecutor.this.executor.execute(task);
}
} catch (final InterruptedException e) {
SmartExecutor.L.debug("scheduler interrupted (shutting down)");
return;
}
}
}
}
private static final class ThrottledRunnable extends DelayedRunnable {
private final String throttleName;
public ThrottledRunnable(final Runnable runnable, final String throttleName, final long period,
final TimeUnit delayUnit) {
super(runnable, period, delayUnit);
this.throttleName = throttleName;
}
public String getThrottleName() {
return this.throttleName;
}
}
}