Я реализовал минимальный рабочий пример, который в основном делает то, что, я думаю, вы хотите.
Интерфейс Task (очень похож на интерфейс runnable, только с переданным Context для выполнения ожидания)
package io.medev.stackoverflow;
import java.util.concurrent.TimeUnit;
import java.util.function.BooleanSupplier;
public interface Task {
/**
* Wraps the given runnable into a Task with a not guessable execution time (meaning guessExecutionTime always returns Long.MAX_VALUE)
* @param runnable The runnable to wrap
* @return a Task wrapping this runnable
*/
static Task wrap(Runnable runnable) {
return wrap(runnable, Long.MAX_VALUE);
}
/**
* Wraps the given runnable using the given guessedExecutionTimeMillis
* @param runnable The runnable to wrap
* @param guessedExecutionTimeMillis The guessed execution time in millis for this runnable
* @return a Task wrapping this runnable
*/
static Task wrap(Runnable runnable, long guessedExecutionTimeMillis) {
return new Task() {
@Override
public long guessExecutionTimeMillis() {
return guessedExecutionTimeMillis;
}
@Override
public void run(Context context) {
runnable.run();
}
};
}
/**
* Should more or less guess how long this task will run
* @return The execution time of this Task in milliseconds
*/
long guessExecutionTimeMillis();
void run(Context context);
interface Context {
/**
* Block until the condition is met, giving other Tasks time to execute
* @param condition the condition to check
* @throws InterruptedException if the current thread is interrupted
*/
void idle(BooleanSupplier condition) throws InterruptedException;
/**
* Blocks at least for the given duration, giving other Tasks time to execute
* @param timeout
* @param timeUnit
* @throws InterruptedException if the current thread is interrupted
*/
void idle(long timeout, TimeUnit timeUnit) throws InterruptedException;
/**
* Blocks until the condition is met or the timeout expires, giving other Tasks time to execute
* @param condition the condition to check
* @param timeout
* @param timeUnit
* @throws InterruptedException if the current thread is interrupted
*/
void idle(BooleanSupplier condition, long timeout, TimeUnit timeUnit) throws InterruptedException;
}
}
И базовый фиксированный исполнитель пула потоков - но вы должны зависеть от конкретной реализации здесь:
package io.medev.stackoverflow;
import java.util.Comparator;
import java.util.concurrent.*;
import java.util.function.BooleanSupplier;
public class TimeEfficientExecutor implements Executor {
private final BlockingQueue<Task> taskQueue;
private final CountDownLatch latch;
private volatile boolean alive;
public TimeEfficientExecutor(int threads) {
this.taskQueue = new PriorityBlockingQueue<>(10, Comparator.comparingLong(Task::guessExecutionTimeMillis));
this.latch = new CountDownLatch(threads);
this.alive = true;
for (int i = 0; i < threads; i++) {
Thread thread = new Thread(new TimeEfficientExecutorRunnable());
thread.start();
}
}
@Override
public void execute(Runnable runnable) {
execute(Task.wrap(runnable));
}
public void execute(Runnable runnable, long guessedExecutionTimeMillis) {
execute(Task.wrap(runnable, guessedExecutionTimeMillis));
}
public void execute(Task task) {
this.taskQueue.offer(task);
}
public void shutdown() {
this.alive = false;
}
public void awaitShutdown() throws InterruptedException {
this.latch.await();
}
public void awaitShutdown(long timeout, TimeUnit timeUnit) throws InterruptedException {
this.latch.await(timeout, timeUnit);
}
private class TimeEfficientExecutorRunnable implements Runnable {
@Override
public void run() {
try {
while (TimeEfficientExecutor.this.alive) {
Task task = TimeEfficientExecutor.this.taskQueue.poll();
if (task != null) {
try {
task.run(new IdleTaskContext());
} catch (Exception e) {
// TODO: logging
}
}
}
} finally {
TimeEfficientExecutor.this.latch.countDown();
}
}
}
private class IdleTaskContext implements Task.Context {
@Override
public void idle(BooleanSupplier condition) throws InterruptedException {
idle(condition, Long.MAX_VALUE);
}
@Override
public void idle(long timeout, TimeUnit timeUnit) throws InterruptedException {
idle(() -> false, timeout, timeUnit);
}
@Override
public void idle(BooleanSupplier condition, long timeout, TimeUnit timeUnit) throws InterruptedException {
idle(condition, System.currentTimeMillis() + timeUnit.toMillis(timeout));
}
private void idle(BooleanSupplier condition, long idleUntilTs) throws InterruptedException {
long leftMillis = idleUntilTs - System.currentTimeMillis();
while (TimeEfficientExecutor.this.alive && !condition.getAsBoolean() && leftMillis >= 1L) {
Task task = TimeEfficientExecutor.this.taskQueue.poll(leftMillis, TimeUnit.MILLISECONDS);
leftMillis = idleUntilTs - System.currentTimeMillis();
if (task != null) {
if (leftMillis >= 1L && task.guessExecutionTimeMillis() < leftMillis) {
task.run(new IdleTaskContext());
} else {
TimeEfficientExecutor.this.taskQueue.offer(task);
}
}
}
}
}
}
Обратите внимание, что вы не можете просто уйти в стек - и стек привязан кисполняющий поток.Это означает, что невозможно вернуться к основной задаче простоя, если какая-то «подзадача» начинает простаивать.Вы должны «доверять» тому, что каждая задача возвращает в guessExecutionTimeMillis -методе.
Благодаря PriorityQueue, используемому в Executor, очередь всегда будет возвращать задачу с наименьшим временем выполнения.