util/concurrent/AbstractExecutorService.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util.concurrent;

import static java.util.concurrent.TimeUnit.NANOSECONDS;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

/**
 * Provides default implementations of {@link ExecutorService}
 * execution methods. This class implements the {@code submit},
 * {@code invokeAny} and {@code invokeAll} methods using a
 * {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
 * to the {@link FutureTask} class provided in this package.  For example,
 * the implementation of {@code submit(Runnable)} creates an
 * associated {@code RunnableFuture} that is executed and
 * returned. Subclasses may override the {@code newTaskFor} methods
 * to return {@code RunnableFuture} implementations other than
 * {@code FutureTask}.
 *
 * <p><b>Extension example.</b> Here is a sketch of a class
 * that customizes {@link ThreadPoolExecutor} to use
 * a {@code CustomTask} class instead of the default {@code FutureTask}:
 * <pre> {@code
 * public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
 *
 *   static class CustomTask<V> implements RunnableFuture<V> { ... }
 *
 *   protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
 *       return new CustomTask<V>(c);
 *   }
 *   protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
 *       return new CustomTask<V>(r, v);
 *   }
 *   // ... add constructors, etc.
 * }}</pre>
 *
 * @since 1.5
 * @author Doug Lea
 */
public abstract class AbstractExecutorService implements ExecutorService {

    /**
     * Constructor for subclasses to call.
     */
    public AbstractExecutorService() {}

    /**
     * Returns a {@code RunnableFuture} for the given runnable and default
     * value.
     *
     * @param runnable the runnable task being wrapped
     * @param value the default value for the returned future
     * @param <T> the type of the given value
     * @return a {@code RunnableFuture} which, when run, will run the
     * underlying runnable and which, as a {@code Future}, will yield
     * the given value as its result and provide for cancellation of
     * the underlying task
     * @since 1.6
     */
    protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
        return new FutureTask<T>(runnable, value);
    }

    /**
     * Returns a {@code RunnableFuture} for the given callable task.
     *
     * @param callable the callable task being wrapped
     * @param <T> the type of the callable's result
     * @return a {@code RunnableFuture} which, when run, will call the
     * underlying callable and which, as a {@code Future}, will yield
     * the callable's result as its result and provide for
     * cancellation of the underlying task
     * @since 1.6
     */
    protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
        return new FutureTask<T>(callable);
    }

    /**
     * @throws RejectedExecutionException {@inheritDoc}
     * @throws NullPointerException       {@inheritDoc}
     */
    public Future<?> submit(Runnable task) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<Void> ftask = newTaskFor(task, null);
        execute(ftask);
        return ftask;
    }

    /**
     * @throws RejectedExecutionException {@inheritDoc}
     * @throws NullPointerException       {@inheritDoc}
     */
    public <T> Future<T> submit(Runnable task, T result) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<T> ftask = newTaskFor(task, result);
        execute(ftask);
        return ftask;
    }

    /**
     * @throws RejectedExecutionException {@inheritDoc}
     * @throws NullPointerException       {@inheritDoc}
     */
    public <T> Future<T> submit(Callable<T> task) {
        if (task == null) throw new NullPointerException();
        RunnableFuture<T> ftask = newTaskFor(task);
        execute(ftask);
        return ftask;
    }

    /**
     * the main mechanics of invokeAny.
     */
    private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
                              boolean timed, long nanos)
        throws InterruptedException, ExecutionException, TimeoutException {
        if (tasks == null)
            throw new NullPointerException();
        int ntasks = tasks.size();
        if (ntasks == 0)
            throw new IllegalArgumentException();
        ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
        ExecutorCompletionService<T> ecs =
            new ExecutorCompletionService<T>(this);

        // For efficiency, especially in executors with limited
        // parallelism, check to see if previously submitted tasks are
        // done before submitting more of them. This interleaving
        // plus the exception mechanics account for messiness of main
        // loop.

        try {
            // Record exceptions so that if we fail to obtain any
            // result, we can throw the last exception we got.
            ExecutionException ee = null;
            final long deadline = timed ? System.nanoTime() + nanos : 0L;
            Iterator<? extends Callable<T>> it = tasks.iterator();

            // Start one task for sure; the rest incrementally
            futures.add(ecs.submit(it.next()));
            --ntasks;
            int active = 1;

            for (;;) {
                Future<T> f = ecs.poll();
                if (f == null) {
                    if (ntasks > 0) {
                        --ntasks;
                        futures.add(ecs.submit(it.next()));
                        ++active;
                    }
                    else if (active == 0)
                        break;
                    else if (timed) {
                        f = ecs.poll(nanos, NANOSECONDS);
                        if (f == null)
                            throw new TimeoutException();
                        nanos = deadline - System.nanoTime();
                    }
                    else
                        f = ecs.take();
                }
                if (f != null) {
                    --active;
                    try {
                        return f.get();
                    } catch (ExecutionException eex) {
                        ee = eex;
                    } catch (RuntimeException rex) {
                        ee = new ExecutionException(rex);
                    }
                }
            }

            if (ee == null)
                ee = new ExecutionException();
            throw ee;

        } finally {
            cancelAll(futures);
        }
    }

    public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
        throws InterruptedException, ExecutionException {
        try {
            return doInvokeAny(tasks, false, 0);
        } catch (TimeoutException cannotHappen) {
            assert false;
            return null;
        }
    }

    public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
                           long timeout, TimeUnit unit)
        throws InterruptedException, ExecutionException, TimeoutException {
        return doInvokeAny(tasks, true, unit.toNanos(timeout));
    }

    public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
        throws InterruptedException {
        if (tasks == null)
            throw new NullPointerException();
        ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
        try {
            for (Callable<T> t : tasks) {
                RunnableFuture<T> f = newTaskFor(t);
                futures.add(f);
                execute(f);
            }
            for (int i = 0, size = futures.size(); i < size; i++) {
                Future<T> f = futures.get(i);
                if (!f.isDone()) {
                    try { f.get(); }
                    catch (CancellationException | ExecutionException ignore) {}
                }
            }
            return futures;
        } catch (Throwable t) {
            cancelAll(futures);
            throw t;
        }
    }

    public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
                                         long timeout, TimeUnit unit)
        throws InterruptedException {
        if (tasks == null)
            throw new NullPointerException();
        final long nanos = unit.toNanos(timeout);
        final long deadline = System.nanoTime() + nanos;
        ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
        int j = 0;
        timedOut: try {
            for (Callable<T> t : tasks)
                futures.add(newTaskFor(t));

            final int size = futures.size();

            // Interleave time checks and calls to execute in case
            // executor doesn't have any/much parallelism.
            for (int i = 0; i < size; i++) {
                if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
                    break timedOut;
                execute((Runnable)futures.get(i));
            }

            for (; j < size; j++) {
                Future<T> f = futures.get(j);
                if (!f.isDone()) {
                    try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
                    catch (CancellationException | ExecutionException ignore) {}
                    catch (TimeoutException timedOut) {
                        break timedOut;
                    }
                }
            }
            return futures;
        } catch (Throwable t) {
            cancelAll(futures);
            throw t;
        }
        // Timed out before all the tasks could be completed; cancel remaining
        cancelAll(futures, j);
        return futures;
    }

    private static <T> void cancelAll(ArrayList<Future<T>> futures) {
        cancelAll(futures, 0);
    }

    /** Cancels all futures with index at least j. */
    private static <T> void cancelAll(ArrayList<Future<T>> futures, int j) {
        for (int size = futures.size(); j < size; j++)
            futures.get(j).cancel(true);
    }
}
Revision:	1.54
Committed:	Fri Nov 27 17:41:59 2020 UTC (3 years, 5 months ago) by dl
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.53:	+2 -2 lines
Log Message:	Incorporate snippets code improvements from Pavel Rappo
#	Content
1	/*
2	* Written by Doug Lea with assistance from members of JCP JSR-166
3	* Expert Group and released to the public domain, as explained at
4	* http://creativecommons.org/publicdomain/zero/1.0/
5	*/
6
7	package java.util.concurrent;
8
9	import static java.util.concurrent.TimeUnit.NANOSECONDS;
10
11	import java.util.ArrayList;
12	import java.util.Collection;
13	import java.util.Iterator;
14	import java.util.List;
15
16	/**
17	* Provides default implementations of {@link ExecutorService}
18	* execution methods. This class implements the {@code submit},
19	* {@code invokeAny} and {@code invokeAll} methods using a
20	* {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
21	* to the {@link FutureTask} class provided in this package. For example,
22	* the implementation of {@code submit(Runnable)} creates an
23	* associated {@code RunnableFuture} that is executed and
24	* returned. Subclasses may override the {@code newTaskFor} methods
25	* to return {@code RunnableFuture} implementations other than
26	* {@code FutureTask}.
27	*
28	* <p><b>Extension example.</b> Here is a sketch of a class
29	* that customizes {@link ThreadPoolExecutor} to use
30	* a {@code CustomTask} class instead of the default {@code FutureTask}:
31	* <pre> {@code
32	* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
33	*
34	* static class CustomTask<V> implements RunnableFuture<V> { ... }
35	*
36	* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
37	* return new CustomTask<V>(c);
38	* }
39	* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
40	* return new CustomTask<V>(r, v);
41	* }
42	* // ... add constructors, etc.
43	* }}</pre>
44	*
45	* @since 1.5
46	* @author Doug Lea
47	*/
48	public abstract class AbstractExecutorService implements ExecutorService {
49
50	/**
51	* Constructor for subclasses to call.
52	*/
53	public AbstractExecutorService() {}
54
55	/**
56	* Returns a {@code RunnableFuture} for the given runnable and default
57	* value.
58	*
59	* @param runnable the runnable task being wrapped
60	* @param value the default value for the returned future
61	* @param <T> the type of the given value
62	* @return a {@code RunnableFuture} which, when run, will run the
63	* underlying runnable and which, as a {@code Future}, will yield
64	* the given value as its result and provide for cancellation of
65	* the underlying task
66	* @since 1.6
67	*/
68	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
69	return new FutureTask<T>(runnable, value);
70	}
71
72	/**
73	* Returns a {@code RunnableFuture} for the given callable task.
74	*
75	* @param callable the callable task being wrapped
76	* @param <T> the type of the callable's result
77	* @return a {@code RunnableFuture} which, when run, will call the
78	* underlying callable and which, as a {@code Future}, will yield
79	* the callable's result as its result and provide for
80	* cancellation of the underlying task
81	* @since 1.6
82	*/
83	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
84	return new FutureTask<T>(callable);
85	}
86
87	/**
88	* @throws RejectedExecutionException {@inheritDoc}
89	* @throws NullPointerException {@inheritDoc}
90	*/
91	public Future<?> submit(Runnable task) {
92	if (task == null) throw new NullPointerException();
93	RunnableFuture<Void> ftask = newTaskFor(task, null);
94	execute(ftask);
95	return ftask;
96	}
97
98	/**
99	* @throws RejectedExecutionException {@inheritDoc}
100	* @throws NullPointerException {@inheritDoc}
101	*/
102	public <T> Future<T> submit(Runnable task, T result) {
103	if (task == null) throw new NullPointerException();
104	RunnableFuture<T> ftask = newTaskFor(task, result);
105	execute(ftask);
106	return ftask;
107	}
108
109	/**
110	* @throws RejectedExecutionException {@inheritDoc}
111	* @throws NullPointerException {@inheritDoc}
112	*/
113	public <T> Future<T> submit(Callable<T> task) {
114	if (task == null) throw new NullPointerException();
115	RunnableFuture<T> ftask = newTaskFor(task);
116	execute(ftask);
117	return ftask;
118	}
119
120	/**
121	* the main mechanics of invokeAny.
122	*/
123	private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
124	boolean timed, long nanos)
125	throws InterruptedException, ExecutionException, TimeoutException {
126	if (tasks == null)
127	throw new NullPointerException();
128	int ntasks = tasks.size();
129	if (ntasks == 0)
130	throw new IllegalArgumentException();
131	ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
132	ExecutorCompletionService<T> ecs =
133	new ExecutorCompletionService<T>(this);
134
135	// For efficiency, especially in executors with limited
136	// parallelism, check to see if previously submitted tasks are
137	// done before submitting more of them. This interleaving
138	// plus the exception mechanics account for messiness of main
139	// loop.
140
141	try {
142	// Record exceptions so that if we fail to obtain any
143	// result, we can throw the last exception we got.
144	ExecutionException ee = null;
145	final long deadline = timed ? System.nanoTime() + nanos : 0L;
146	Iterator<? extends Callable<T>> it = tasks.iterator();
147
148	// Start one task for sure; the rest incrementally
149	futures.add(ecs.submit(it.next()));
150	--ntasks;
151	int active = 1;
152
153	for (;;) {
154	Future<T> f = ecs.poll();
155	if (f == null) {
156	if (ntasks > 0) {
157	--ntasks;
158	futures.add(ecs.submit(it.next()));
159	++active;
160	}
161	else if (active == 0)
162	break;
163	else if (timed) {
164	f = ecs.poll(nanos, NANOSECONDS);
165	if (f == null)
166	throw new TimeoutException();
167	nanos = deadline - System.nanoTime();
168	}
169	else
170	f = ecs.take();
171	}
172	if (f != null) {
173	--active;
174	try {
175	return f.get();
176	} catch (ExecutionException eex) {
177	ee = eex;
178	} catch (RuntimeException rex) {
179	ee = new ExecutionException(rex);
180	}
181	}
182	}
183
184	if (ee == null)
185	ee = new ExecutionException();
186	throw ee;
187
188	} finally {
189	cancelAll(futures);
190	}
191	}
192
193	public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
194	throws InterruptedException, ExecutionException {
195	try {
196	return doInvokeAny(tasks, false, 0);
197	} catch (TimeoutException cannotHappen) {
198	assert false;
199	return null;
200	}
201	}
202
203	public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
204	long timeout, TimeUnit unit)
205	throws InterruptedException, ExecutionException, TimeoutException {
206	return doInvokeAny(tasks, true, unit.toNanos(timeout));
207	}
208
209	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
210	throws InterruptedException {
211	if (tasks == null)
212	throw new NullPointerException();
213	ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
214	try {
215	for (Callable<T> t : tasks) {
216	RunnableFuture<T> f = newTaskFor(t);
217	futures.add(f);
218	execute(f);
219	}
220	for (int i = 0, size = futures.size(); i < size; i++) {
221	Future<T> f = futures.get(i);
222	if (!f.isDone()) {
223	try { f.get(); }
224	catch (CancellationException \| ExecutionException ignore) {}
225	}
226	}
227	return futures;
228	} catch (Throwable t) {
229	cancelAll(futures);
230	throw t;
231	}
232	}
233
234	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
235	long timeout, TimeUnit unit)
236	throws InterruptedException {
237	if (tasks == null)
238	throw new NullPointerException();
239	final long nanos = unit.toNanos(timeout);
240	final long deadline = System.nanoTime() + nanos;
241	ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
242	int j = 0;
243	timedOut: try {
244	for (Callable<T> t : tasks)
245	futures.add(newTaskFor(t));
246
247	final int size = futures.size();
248
249	// Interleave time checks and calls to execute in case
250	// executor doesn't have any/much parallelism.
251	for (int i = 0; i < size; i++) {
252	if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
253	break timedOut;
254	execute((Runnable)futures.get(i));
255	}
256
257	for (; j < size; j++) {
258	Future<T> f = futures.get(j);
259	if (!f.isDone()) {
260	try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
261	catch (CancellationException \| ExecutionException ignore) {}
262	catch (TimeoutException timedOut) {
263	break timedOut;
264	}
265	}
266	}
267	return futures;
268	} catch (Throwable t) {
269	cancelAll(futures);
270	throw t;
271	}
272	// Timed out before all the tasks could be completed; cancel remaining
273	cancelAll(futures, j);
274	return futures;
275	}
276
277	private static <T> void cancelAll(ArrayList<Future<T>> futures) {
278	cancelAll(futures, 0);
279	}
280
281	/** Cancels all futures with index at least j. */
282	private static <T> void cancelAll(ArrayList<Future<T>> futures, int j) {
283	for (int size = futures.size(); j < size; j++)
284	futures.get(j).cancel(true);
285	}
286	}