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 {

    /**
     * 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 ignore) {}
                    catch (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 ignore) {}
                    catch (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:	1.49
Committed:	Wed Dec 3 23:53:45 2014 UTC (9 years, 6 months ago) by jsr166
Branch:	MAIN
Changes since 1.48:	+37 -37 lines
Log Message:	improve implementation of invokeAll
#	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	import java.util.ArrayList;
11	import java.util.Collection;
12	import java.util.Iterator;
13	import java.util.List;
14
15	/**
16	* Provides default implementations of {@link ExecutorService}
17	* execution methods. This class implements the {@code submit},
18	* {@code invokeAny} and {@code invokeAll} methods using a
19	* {@link RunnableFuture} returned by {@code newTaskFor}, which defaults
20	* to the {@link FutureTask} class provided in this package. For example,
21	* the implementation of {@code submit(Runnable)} creates an
22	* associated {@code RunnableFuture} that is executed and
23	* returned. Subclasses may override the {@code newTaskFor} methods
24	* to return {@code RunnableFuture} implementations other than
25	* {@code FutureTask}.
26	*
27	* <p><b>Extension example</b>. Here is a sketch of a class
28	* that customizes {@link ThreadPoolExecutor} to use
29	* a {@code CustomTask} class instead of the default {@code FutureTask}:
30	* <pre> {@code
31	* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
32	*
33	* static class CustomTask<V> implements RunnableFuture<V> {...}
34	*
35	* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
36	* return new CustomTask<V>(c);
37	* }
38	* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
39	* return new CustomTask<V>(r, v);
40	* }
41	* // ... add constructors, etc.
42	* }}</pre>
43	*
44	* @since 1.5
45	* @author Doug Lea
46	*/
47	public abstract class AbstractExecutorService implements ExecutorService {
48
49	/**
50	* Returns a {@code RunnableFuture} for the given runnable and default
51	* value.
52	*
53	* @param runnable the runnable task being wrapped
54	* @param value the default value for the returned future
55	* @param <T> the type of the given value
56	* @return a {@code RunnableFuture} which, when run, will run the
57	* underlying runnable and which, as a {@code Future}, will yield
58	* the given value as its result and provide for cancellation of
59	* the underlying task
60	* @since 1.6
61	*/
62	protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
63	return new FutureTask<T>(runnable, value);
64	}
65
66	/**
67	* Returns a {@code RunnableFuture} for the given callable task.
68	*
69	* @param callable the callable task being wrapped
70	* @param <T> the type of the callable's result
71	* @return a {@code RunnableFuture} which, when run, will call the
72	* underlying callable and which, as a {@code Future}, will yield
73	* the callable's result as its result and provide for
74	* cancellation of the underlying task
75	* @since 1.6
76	*/
77	protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
78	return new FutureTask<T>(callable);
79	}
80
81	/**
82	* @throws RejectedExecutionException {@inheritDoc}
83	* @throws NullPointerException {@inheritDoc}
84	*/
85	public Future<?> submit(Runnable task) {
86	if (task == null) throw new NullPointerException();
87	RunnableFuture<Void> ftask = newTaskFor(task, null);
88	execute(ftask);
89	return ftask;
90	}
91
92	/**
93	* @throws RejectedExecutionException {@inheritDoc}
94	* @throws NullPointerException {@inheritDoc}
95	*/
96	public <T> Future<T> submit(Runnable task, T result) {
97	if (task == null) throw new NullPointerException();
98	RunnableFuture<T> ftask = newTaskFor(task, result);
99	execute(ftask);
100	return ftask;
101	}
102
103	/**
104	* @throws RejectedExecutionException {@inheritDoc}
105	* @throws NullPointerException {@inheritDoc}
106	*/
107	public <T> Future<T> submit(Callable<T> task) {
108	if (task == null) throw new NullPointerException();
109	RunnableFuture<T> ftask = newTaskFor(task);
110	execute(ftask);
111	return ftask;
112	}
113
114	/**
115	* the main mechanics of invokeAny.
116	*/
117	private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
118	boolean timed, long nanos)
119	throws InterruptedException, ExecutionException, TimeoutException {
120	if (tasks == null)
121	throw new NullPointerException();
122	int ntasks = tasks.size();
123	if (ntasks == 0)
124	throw new IllegalArgumentException();
125	ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
126	ExecutorCompletionService<T> ecs =
127	new ExecutorCompletionService<T>(this);
128
129	// For efficiency, especially in executors with limited
130	// parallelism, check to see if previously submitted tasks are
131	// done before submitting more of them. This interleaving
132	// plus the exception mechanics account for messiness of main
133	// loop.
134
135	try {
136	// Record exceptions so that if we fail to obtain any
137	// result, we can throw the last exception we got.
138	ExecutionException ee = null;
139	final long deadline = timed ? System.nanoTime() + nanos : 0L;
140	Iterator<? extends Callable<T>> it = tasks.iterator();
141
142	// Start one task for sure; the rest incrementally
143	futures.add(ecs.submit(it.next()));
144	--ntasks;
145	int active = 1;
146
147	for (;;) {
148	Future<T> f = ecs.poll();
149	if (f == null) {
150	if (ntasks > 0) {
151	--ntasks;
152	futures.add(ecs.submit(it.next()));
153	++active;
154	}
155	else if (active == 0)
156	break;
157	else if (timed) {
158	f = ecs.poll(nanos, NANOSECONDS);
159	if (f == null)
160	throw new TimeoutException();
161	nanos = deadline - System.nanoTime();
162	}
163	else
164	f = ecs.take();
165	}
166	if (f != null) {
167	--active;
168	try {
169	return f.get();
170	} catch (ExecutionException eex) {
171	ee = eex;
172	} catch (RuntimeException rex) {
173	ee = new ExecutionException(rex);
174	}
175	}
176	}
177
178	if (ee == null)
179	ee = new ExecutionException();
180	throw ee;
181
182	} finally {
183	cancelAll(futures);
184	}
185	}
186
187	public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
188	throws InterruptedException, ExecutionException {
189	try {
190	return doInvokeAny(tasks, false, 0);
191	} catch (TimeoutException cannotHappen) {
192	assert false;
193	return null;
194	}
195	}
196
197	public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
198	long timeout, TimeUnit unit)
199	throws InterruptedException, ExecutionException, TimeoutException {
200	return doInvokeAny(tasks, true, unit.toNanos(timeout));
201	}
202
203	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
204	throws InterruptedException {
205	if (tasks == null)
206	throw new NullPointerException();
207	ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
208	try {
209	for (Callable<T> t : tasks) {
210	RunnableFuture<T> f = newTaskFor(t);
211	futures.add(f);
212	execute(f);
213	}
214	for (int i = 0, size = futures.size(); i < size; i++) {
215	Future<T> f = futures.get(i);
216	if (!f.isDone()) {
217	try { f.get(); }
218	catch (CancellationException ignore) {}
219	catch (ExecutionException ignore) {}
220	}
221	}
222	return futures;
223	} catch (Throwable t) {
224	cancelAll(futures);
225	throw t;
226	}
227	}
228
229	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
230	long timeout, TimeUnit unit)
231	throws InterruptedException {
232	if (tasks == null)
233	throw new NullPointerException();
234	final long nanos = unit.toNanos(timeout);
235	final long deadline = System.nanoTime() + nanos;
236	ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
237	int j = 0;
238	timedOut: try {
239	for (Callable<T> t : tasks)
240	futures.add(newTaskFor(t));
241
242	final int size = futures.size();
243
244	// Interleave time checks and calls to execute in case
245	// executor doesn't have any/much parallelism.
246	for (int i = 0; i < size; i++) {
247	if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
248	break timedOut;
249	execute((Runnable)futures.get(i));
250	}
251
252	for (; j < size; j++) {
253	Future<T> f = futures.get(j);
254	if (!f.isDone()) {
255	try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
256	catch (CancellationException ignore) {}
257	catch (ExecutionException ignore) {}
258	catch (TimeoutException timedOut) {
259	break timedOut;
260	}
261	}
262	}
263	return futures;
264	} catch (Throwable t) {
265	cancelAll(futures);
266	throw t;
267	}
268	// Timed out before all the tasks could be completed; cancel remaining
269	cancelAll(futures, j);
270	return futures;
271	}
272
273	private static <T> void cancelAll(ArrayList<Future<T>> futures) {
274	cancelAll(futures, 0);
275	}
276
277	/** Cancels all futures with index at least j. */
278	private static <T> void cancelAll(ArrayList<Future<T>> futures, int j) {
279	for (int size = futures.size(); j < size; j++)
280	futures.get(j).cancel(true);
281	}
282	}