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
#	User	Rev	Content
1	tim	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3	dl	1.17	* Expert Group and released to the public domain, as explained at
4	jsr166	1.35	* http://creativecommons.org/publicdomain/zero/1.0/
5	tim	1.1	*/
6
7			package java.util.concurrent;
8	jsr166	1.48
9	jsr166	1.49	import static java.util.concurrent.TimeUnit.NANOSECONDS;
10	jsr166	1.48	import java.util.ArrayList;
11			import java.util.Collection;
12			import java.util.Iterator;
13			import java.util.List;
14	tim	1.1
15			/**
16	jsr166	1.24	* Provides default implementations of {@link ExecutorService}
17	jsr166	1.40	* 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	peierls	1.21	* to the {@link FutureTask} class provided in this package. For example,
21	jsr166	1.40	* 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	tim	1.1	*
27	jsr166	1.39	* <p><b>Extension example</b>. Here is a sketch of a class
28	dl	1.22	* that customizes {@link ThreadPoolExecutor} to use
29	jsr166	1.40	* a {@code CustomTask} class instead of the default {@code FutureTask}:
30	jsr166	1.32	* <pre> {@code
31	dl	1.22	* public class CustomThreadPoolExecutor extends ThreadPoolExecutor {
32			*
33	jsr166	1.32	* static class CustomTask<V> implements RunnableFuture<V> {...}
34	dl	1.22	*
35	jsr166	1.32	* protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
36			* return new CustomTask<V>(c);
37	jsr166	1.25	* }
38	jsr166	1.32	* protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
39			* return new CustomTask<V>(r, v);
40	jsr166	1.25	* }
41			* // ... add constructors, etc.
42	jsr166	1.32	* }}</pre>
43			*
44	tim	1.1	* @since 1.5
45			* @author Doug Lea
46			*/
47			public abstract class AbstractExecutorService implements ExecutorService {
48
49	peierls	1.21	/**
50	jsr166	1.40	* Returns a {@code RunnableFuture} for the given runnable and default
51	peierls	1.21	* value.
52	jsr166	1.24	*
53	peierls	1.21	* @param runnable the runnable task being wrapped
54			* @param value the default value for the returned future
55	jsr166	1.46	* @param <T> the type of the given value
56	jsr166	1.44	* @return a {@code RunnableFuture} which, when run, will run the
57	jsr166	1.40	* underlying runnable and which, as a {@code Future}, will yield
58	dl	1.22	* the given value as its result and provide for cancellation of
59	jsr166	1.43	* the underlying task
60	dl	1.22	* @since 1.6
61	peierls	1.21	*/
62			protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
63			return new FutureTask<T>(runnable, value);
64			}
65
66			/**
67	jsr166	1.40	* Returns a {@code RunnableFuture} for the given callable task.
68	jsr166	1.24	*
69	peierls	1.21	* @param callable the callable task being wrapped
70	jsr166	1.46	* @param <T> the type of the callable's result
71	jsr166	1.44	* @return a {@code RunnableFuture} which, when run, will call the
72	jsr166	1.40	* underlying callable and which, as a {@code Future}, will yield
73	dl	1.22	* the callable's result as its result and provide for
74	jsr166	1.43	* cancellation of the underlying task
75	dl	1.22	* @since 1.6
76	peierls	1.21	*/
77			protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
78			return new FutureTask<T>(callable);
79			}
80
81	jsr166	1.30	/**
82			* @throws RejectedExecutionException {@inheritDoc}
83			* @throws NullPointerException {@inheritDoc}
84			*/
85	dl	1.11	public Future<?> submit(Runnable task) {
86	dl	1.13	if (task == null) throw new NullPointerException();
87	jsr166	1.33	RunnableFuture<Void> ftask = newTaskFor(task, null);
88	tim	1.1	execute(ftask);
89			return ftask;
90			}
91
92	jsr166	1.30	/**
93			* @throws RejectedExecutionException {@inheritDoc}
94			* @throws NullPointerException {@inheritDoc}
95			*/
96	dl	1.13	public <T> Future<T> submit(Runnable task, T result) {
97			if (task == null) throw new NullPointerException();
98	peierls	1.21	RunnableFuture<T> ftask = newTaskFor(task, result);
99	dl	1.13	execute(ftask);
100			return ftask;
101			}
102
103	jsr166	1.30	/**
104			* @throws RejectedExecutionException {@inheritDoc}
105			* @throws NullPointerException {@inheritDoc}
106			*/
107	tim	1.1	public <T> Future<T> submit(Callable<T> task) {
108	dl	1.13	if (task == null) throw new NullPointerException();
109	peierls	1.21	RunnableFuture<T> ftask = newTaskFor(task);
110	tim	1.1	execute(ftask);
111			return ftask;
112			}
113
114	dl	1.15	/**
115			* the main mechanics of invokeAny.
116			*/
117	jsr166	1.26	private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
118	jsr166	1.36	boolean timed, long nanos)
119	dl	1.15	throws InterruptedException, ExecutionException, TimeoutException {
120	dl	1.3	if (tasks == null)
121			throw new NullPointerException();
122	dl	1.15	int ntasks = tasks.size();
123			if (ntasks == 0)
124	dl	1.7	throw new IllegalArgumentException();
125	jsr166	1.47	ArrayList<Future<T>> futures = new ArrayList<>(ntasks);
126	jsr166	1.20	ExecutorCompletionService<T> ecs =
127	dl	1.7	new ExecutorCompletionService<T>(this);
128	dl	1.15
129			// For efficiency, especially in executors with limited
130			// parallelism, check to see if previously submitted tasks are
131	dl	1.18	// done before submitting more of them. This interleaving
132	dl	1.15	// plus the exception mechanics account for messiness of main
133	dl	1.18	// loop.
134	dl	1.15
135	dl	1.3	try {
136	dl	1.15	// Record exceptions so that if we fail to obtain any
137			// result, we can throw the last exception we got.
138	dl	1.7	ExecutionException ee = null;
139	jsr166	1.37	final long deadline = timed ? System.nanoTime() + nanos : 0L;
140	jsr166	1.26	Iterator<? extends Callable<T>> it = tasks.iterator();
141	dl	1.15
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	jsr166	1.20	Future<T> f = ecs.poll();
149	dl	1.15	if (f == null) {
150			if (ntasks > 0) {
151			--ntasks;
152			futures.add(ecs.submit(it.next()));
153			++active;
154			}
155	jsr166	1.20	else if (active == 0)
156	dl	1.15	break;
157			else if (timed) {
158	jsr166	1.49	f = ecs.poll(nanos, NANOSECONDS);
159	dl	1.15	if (f == null)
160			throw new TimeoutException();
161	jsr166	1.37	nanos = deadline - System.nanoTime();
162	dl	1.15	}
163	jsr166	1.20	else
164	dl	1.15	f = ecs.take();
165			}
166			if (f != null) {
167			--active;
168			try {
169			return f.get();
170	jsr166	1.19	} catch (ExecutionException eex) {
171	dl	1.15	ee = eex;
172	jsr166	1.19	} catch (RuntimeException rex) {
173	dl	1.15	ee = new ExecutionException(rex);
174			}
175	dl	1.7	}
176	jsr166	1.20	}
177	dl	1.15
178			if (ee == null)
179			ee = new ExecutionException();
180			throw ee;
181
182	dl	1.3	} finally {
183	jsr166	1.49	cancelAll(futures);
184	dl	1.3	}
185			}
186
187	jsr166	1.26	public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
188	dl	1.15	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	jsr166	1.26	public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
198	jsr166	1.20	long timeout, TimeUnit unit)
199	dl	1.7	throws InterruptedException, ExecutionException, TimeoutException {
200	dl	1.15	return doInvokeAny(tasks, true, unit.toNanos(timeout));
201	dl	1.3	}
202
203	jsr166	1.26	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
204	dl	1.3	throws InterruptedException {
205			if (tasks == null)
206			throw new NullPointerException();
207	jsr166	1.47	ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
208	dl	1.3	try {
209			for (Callable<T> t : tasks) {
210	peierls	1.21	RunnableFuture<T> f = newTaskFor(t);
211	dl	1.3	futures.add(f);
212			execute(f);
213			}
214	jsr166	1.42	for (int i = 0, size = futures.size(); i < size; i++) {
215			Future<T> f = futures.get(i);
216	dl	1.6	if (!f.isDone()) {
217	jsr166	1.49	try { f.get(); }
218			catch (CancellationException ignore) {}
219			catch (ExecutionException ignore) {}
220	dl	1.6	}
221			}
222	dl	1.3	return futures;
223	jsr166	1.49	} catch (Throwable t) {
224			cancelAll(futures);
225			throw t;
226	dl	1.3	}
227			}
228
229	jsr166	1.26	public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
230	jsr166	1.20	long timeout, TimeUnit unit)
231	dl	1.3	throws InterruptedException {
232	jsr166	1.38	if (tasks == null)
233	dl	1.3	throw new NullPointerException();
234	jsr166	1.49	final long nanos = unit.toNanos(timeout);
235			final long deadline = System.nanoTime() + nanos;
236	jsr166	1.47	ArrayList<Future<T>> futures = new ArrayList<>(tasks.size());
237	jsr166	1.49	int j = 0;
238			timedOut: try {
239	jsr166	1.20	for (Callable<T> t : tasks)
240	peierls	1.21	futures.add(newTaskFor(t));
241	dl	1.16
242	jsr166	1.42	final int size = futures.size();
243	dl	1.16
244			// Interleave time checks and calls to execute in case
245			// executor doesn't have any/much parallelism.
246	jsr166	1.42	for (int i = 0; i < size; i++) {
247	jsr166	1.49	if (((i == 0) ? nanos : deadline - System.nanoTime()) <= 0L)
248			break timedOut;
249	jsr166	1.42	execute((Runnable)futures.get(i));
250	dl	1.3	}
251	dl	1.16
252	jsr166	1.49	for (; j < size; j++) {
253			Future<T> f = futures.get(j);
254	dl	1.6	if (!f.isDone()) {
255	jsr166	1.49	try { f.get(deadline - System.nanoTime(), NANOSECONDS); }
256			catch (CancellationException ignore) {}
257			catch (ExecutionException ignore) {}
258			catch (TimeoutException timedOut) {
259			break timedOut;
260	dl	1.6	}
261			}
262			}
263	dl	1.3	return futures;
264	jsr166	1.49	} catch (Throwable t) {
265			cancelAll(futures);
266			throw t;
267	dl	1.3	}
268	jsr166	1.49	// Timed out before all the tasks could be completed; cancel remaining
269			cancelAll(futures, j);
270			return futures;
271	dl	1.3	}
272
273	jsr166	1.49	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	tim	1.1	}