Skip to main content
aboutsummaryrefslogtreecommitdiffstats
blob: 23eb0cc4714c89abe53904985ec6a6d90d898c8a (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
/*
 * Copyright (c) OSGi Alliance (2017, 2018). All Rights Reserved.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.osgi.util.promise;

import static java.util.Objects.requireNonNull;
import static org.osgi.util.promise.PromiseImpl.uncaughtException;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.RunnableScheduledFuture;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

import org.osgi.annotation.versioning.ConsumerType;
import org.osgi.util.promise.PromiseImpl.Result;

/**
 * Promise factory to create Deferred and Promise objects.
 * <p>
 * Instances of this class can be used to create Deferred and Promise objects
 * which use the executors used to construct this object for any callback or
 * scheduled operation execution.
 * 
 * @Immutable
 * @author $Id$
 * @since 1.1
 */
@ConsumerType
public class PromiseFactory {
	/**
	 * The default factory which uses the default callback executor and default
	 * scheduled executor.
	 */
	final static PromiseFactory				defaultFactory	= new PromiseFactory(
			null, null);

	/**
	 * The executor to use for callbacks. If {@code null}, the default callback
	 * executor is used.
	 */
	private final Executor					callbackExecutor;
	/**
	 * The executor to use for scheduled operations. If {@code null}, the
	 * default scheduled executor is used.
	 */
	private final ScheduledExecutorService	scheduledExecutor;

	private final boolean					allowCurrentThread;

	/**
	 * Create a new PromiseFactory with the specified callback executor.
	 * <p>
	 * The default scheduled executor will be used.
	 * 
	 * @param callbackExecutor The executor to use for callbacks. {@code null}
	 *            can be specified for the default callback executor.
	 */
	public PromiseFactory(Executor callbackExecutor) {
		this(callbackExecutor, null);
	}

	/**
	 * Create a new PromiseFactory with the specified callback executor and
	 * specified scheduled executor.
	 * 
	 * @param callbackExecutor The executor to use for callbacks. {@code null}
	 *            can be specified for the default callback executor.
	 * @param scheduledExecutor The scheduled executor for use for scheduled
	 *            operations. {@code null} can be specified for the default
	 *            scheduled executor.
	 */
	public PromiseFactory(Executor callbackExecutor,
			ScheduledExecutorService scheduledExecutor) {
		this.callbackExecutor = callbackExecutor;
		this.scheduledExecutor = scheduledExecutor;
		allowCurrentThread = Boolean.parseBoolean(System.getProperty(
				"org.osgi.util.promise.allowCurrentThread",
				Boolean.TRUE.toString()));

	}

	/**
	 * Returns the executor to use for callbacks.
	 * 
	 * @return The executor to use for callbacks. This will be the default
	 *         callback executor if {@code null} was specified for the callback
	 *         executor when this PromiseFactory was created.
	 */
	public Executor executor() {
		if (callbackExecutor == null) {
			return DefaultExecutors.callbackExecutor();
		}
		return callbackExecutor;
	}

	/**
	 * Returns the scheduled executor to use for scheduled operations.
	 * 
	 * @return The scheduled executor to use for scheduled operations. This will
	 *         be the default scheduled executor if {@code null} was specified
	 *         for the scheduled executor when this PromiseFactory was created.
	 */
	public ScheduledExecutorService scheduledExecutor() {
		if (scheduledExecutor == null) {
			return DefaultExecutors.scheduledExecutor();
		}
		return scheduledExecutor;
	}

	/**
	 * Create a new Deferred with the callback executor and scheduled executor
	 * of this PromiseFactory object.
	 * <p>
	 * Use this method instead of {@link Deferred#Deferred()} to create a new
	 * {@link Deferred} whose associated Promise uses executors other than the
	 * default executors.
	 * 
	 * @param <T> The value type associated with the returned Deferred.
	 * @return A new {@link Deferred} with the callback and scheduled executors
	 *         of this PromiseFactory object
	 */
	public <T> Deferred<T> deferred() {
		return new Deferred<>(this);
	}

	/**
	 * Returns a new Promise that has been resolved with the specified value.
	 * <p>
	 * The returned Promise uses the callback executor and scheduled executor of
	 * this PromiseFactory object.
	 * <p>
	 * Use this method instead of {@link Promises#resolved(Object)} to create a
	 * Promise which uses executors other than the default executors.
	 * 
	 * @param <T> The value type associated with the returned Promise.
	 * @param value The value of the resolved Promise.
	 * @return A new Promise that has been resolved with the specified value.
	 */
	public <T> Promise<T> resolved(T value) {
		return new ResolvedPromiseImpl<>(value, this);
	}

	/**
	 * Returns a new Promise that has been resolved with the specified failure.
	 * <p>
	 * The returned Promise uses the callback executor and scheduled executor of
	 * this PromiseFactory object.
	 * <p>
	 * Use this method instead of {@link Promises#failed(Throwable)} to create a
	 * Promise which uses executors other than the default executors.
	 * 
	 * @param <T> The value type associated with the returned Promise.
	 * @param failure The failure of the resolved Promise. Must not be
	 *            {@code null}.
	 * @return A new Promise that has been resolved with the specified failure.
	 */
	public <T> Promise<T> failed(Throwable failure) {
		return new FailedPromiseImpl<>(failure, this);
	}

	/**
	 * Returns a new Promise that will hold the result of the specified task.
	 * <p>
	 * The returned Promise uses the callback executor and scheduled executor of
	 * this PromiseFactory object.
	 * <p>
	 * The specified task will be executed on the {@link #executor() callback
	 * executor}.
	 * 
	 * @param <T> The value type associated with the returned Promise.
	 * @param task The task whose result will be available from the returned
	 *            Promise.
	 * @return A new Promise that will hold the result of the specified task.
	 */
	public <T> Promise<T> submit(Callable< ? extends T> task) {
		DeferredPromiseImpl<T> promise = new DeferredPromiseImpl<>(this);
		Runnable submit = promise.new Submit(task);
		try {
			executor().execute(submit);
		} catch (Exception t) {
			promise.tryResolve(null, t);
		}
		return promise.orDone();
	}

	/**
	 * Returns a new Promise that is a latch on the resolution of the specified
	 * Promises.
	 * <p>
	 * The returned Promise uses the callback executor and scheduled executor of
	 * this PromiseFactory object.
	 * <p>
	 * The returned Promise acts as a gate and must be resolved after all of the
	 * specified Promises are resolved.
	 * 
	 * @param <T> The value type of the List value associated with the returned
	 *            Promise.
	 * @param <S> A subtype of the value type of the List value associated with
	 *            the returned Promise.
	 * @param promises The Promises which must be resolved before the returned
	 *            Promise must be resolved. Must not be {@code null} and all of
	 *            the elements in the collection must not be {@code null}.
	 * @return A Promise that must be successfully resolved with a List of the
	 *         values in the order of the specified Promises if all the
	 *         specified Promises are successfully resolved. The List in the
	 *         returned Promise is the property of the caller and is modifiable.
	 *         The returned Promise must be resolved with a failure of
	 *         {@link FailedPromisesException} if any of the specified Promises
	 *         are resolved with a failure. The failure
	 *         {@link FailedPromisesException} must contain all of the specified
	 *         Promises which resolved with a failure.
	 */
	public <T, S extends T> Promise<List<T>> all(
			Collection<Promise<S>> promises) {
		if (promises.isEmpty()) {
			List<T> value = new ArrayList<>();
			return resolved(value);
		}

		/* make a copy and capture the ordering */
		List<Promise<S>> list = new ArrayList<>(promises);

		DeferredPromiseImpl<List<T>> chained = new DeferredPromiseImpl<>(this);
		All<T,S> all = new All<>(chained, list);
		for (Promise<S> p : list) {
			p.onResolve(all);
		}
		return chained.orDone();
	}

	/**
	 * A callback used to resolve the specified Promise when the specified list
	 * of Promises are resolved for the {@link PromiseFactory#all(Collection)}
	 * method.
	 * 
	 * @ThreadSafe
	 */
	private static final class All<T, S extends T> implements Runnable {
		private final DeferredPromiseImpl<List<T>>	chained;
		private final List<Promise<S>>				promises;
		private final AtomicInteger					promiseCount;

		All(DeferredPromiseImpl<List<T>> chained, List<Promise<S>> promises) {
			this.chained = requireNonNull(chained);
			this.promises = requireNonNull(promises);
			this.promiseCount = new AtomicInteger(promises.size());
		}

		@Override
		public void run() {
			if (promiseCount.decrementAndGet() != 0) {
				return;
			}
			List<T> value = new ArrayList<>(promises.size());
			List<Promise< ? >> failed = new ArrayList<>(promises.size());
			Throwable cause = null;
			for (Promise<S> p : promises) {
				Result<S> result = PromiseImpl.collect(p);
				if (result.fail != null) {
					failed.add(p);
					if (cause == null) {
						cause = result.fail;
					}
				} else {
					value.add(result.value);
				}
			}
			if (failed.isEmpty()) {
				chained.tryResolve(value, null);
			} else {
				chained.tryResolve(null,
						new FailedPromisesException(failed, cause));
			}
		}
	}

	/**
	 * Returns an Executor implementation that executes tasks immediately on the
	 * thread calling the {@code Executor.execute} method.
	 * 
	 * @return An Executor implementation that executes tasks immediately on the
	 *         thread calling the {@code Executor.execute} method.
	 */
	public static Executor inlineExecutor() {
		return new InlineExecutor();
	}

	boolean allowCurrentThread() {
		return allowCurrentThread;
	}

	/**
	 * An Executor implementation which executes the task immediately on the
	 * thread calling the {@code Executor.execute} method.
	 * 
	 * @Immutable
	 */
	private static final class InlineExecutor implements Executor {
		InlineExecutor() {}

		@Override
		public void execute(Runnable callback) {
			callback.run();
		}
	}

	/**
	 * Default executors for Promises.
	 * 
	 * @Immutable
	 */
	private static final class DefaultExecutors
			implements ThreadFactory, RejectedExecutionHandler, Runnable {
		private static final DefaultExecutors	callbacks;
		private static final ScheduledExecutor	scheduledExecutor;
		private static final ThreadPoolExecutor	callbackExecutor;
		static {
			callbacks = new DefaultExecutors();
			scheduledExecutor = new ScheduledExecutor(2, callbacks);
			callbackExecutor = new ThreadPoolExecutor(0, 64, 60L,
					TimeUnit.SECONDS, new SynchronousQueue<Runnable>(),
					callbacks, callbacks);
		}

		static Executor callbackExecutor() {
			return callbackExecutor;
		}

		static ScheduledExecutorService scheduledExecutor() {
			return scheduledExecutor;
		}

		private final AtomicBoolean	shutdownHookInstalled;
		private final ThreadFactory	delegateThreadFactory;

		private DefaultExecutors() {
			shutdownHookInstalled = new AtomicBoolean();
			delegateThreadFactory = Executors.defaultThreadFactory();
		}

		/**
		 * Executor threads should not prevent VM from exiting.
		 */
		@Override
		public Thread newThread(Runnable r) {
			if (shutdownHookInstalled.compareAndSet(false, true)) {
				Thread shutdownThread = delegateThreadFactory.newThread(this);
				shutdownThread.setName(
						"ExecutorShutdownHook," + shutdownThread.getName());
				try {
					Runtime.getRuntime().addShutdownHook(shutdownThread);
				} catch (IllegalStateException e) {
					// VM is already shutting down...
					callbackExecutor.shutdown();
					scheduledExecutor.shutdown();
				}
			}
			Thread t = delegateThreadFactory.newThread(r);
			t.setName("PromiseFactory," + t.getName());
			t.setDaemon(true);
			return t;
		}

		/**
		 * Call the callback using the caller's thread because the thread pool
		 * rejected the execution.
		 */
		@Override
		public void rejectedExecution(Runnable callback,
				ThreadPoolExecutor executor) {
			try {
				callback.run();
			} catch (Throwable t) {
				uncaughtException(t);
			}
		}

		/**
		 * Shutdown hook
		 */
		@Override
		public void run() {
			// limit new thread creation
			callbackExecutor.setMaximumPoolSize(
					Math.max(1, callbackExecutor.getPoolSize()));
			// Run all delayed callbacks now
			scheduledExecutor.shutdown();
			BlockingQueue<Runnable> queue = scheduledExecutor.getQueue();
			if (!queue.isEmpty()) {
				for (Object r : queue.toArray()) {
					if (r instanceof RunnableScheduledFuture< ? >) {
						RunnableScheduledFuture< ? > future = (RunnableScheduledFuture< ? >) r;
						if ((future.getDelay(TimeUnit.NANOSECONDS) > 0L)
								&& queue.remove(future)) {
							future.run();
							scheduledExecutor.afterExecute(future, null);
						}
					}
				}
				scheduledExecutor.shutdown();
			}
			try {
				scheduledExecutor.awaitTermination(20, TimeUnit.SECONDS);
			} catch (InterruptedException e) {
				Thread.currentThread().interrupt();
			}
			// Shutdown callback executor
			callbackExecutor.shutdown();
			try {
				callbackExecutor.awaitTermination(20, TimeUnit.SECONDS);
			} catch (InterruptedException e) {
				Thread.currentThread().interrupt();
			}
		}

		/**
		 * ScheduledThreadPoolExecutor for scheduled execution.
		 * 
		 * @ThreadSafe
		 */
		private static final class ScheduledExecutor
				extends ScheduledThreadPoolExecutor {
			ScheduledExecutor(int corePoolSize, ThreadFactory threadFactory) {
				super(corePoolSize, threadFactory);
			}

			/**
			 * Handle uncaught exceptions
			 */
			@Override
			protected void afterExecute(Runnable r, Throwable t) {
				super.afterExecute(r, t);
				if ((t == null) && (r instanceof Future< ? >)) {
					boolean interrupted = Thread.interrupted();
					try {
						((Future< ? >) r).get();
					} catch (CancellationException e) {
						// ignore
					} catch (InterruptedException e) {
						interrupted = true;
					} catch (ExecutionException e) {
						t = e.getCause();
					} finally {
						if (interrupted) { // restore interrupt status
							Thread.currentThread().interrupt();
						}
					}
				}
				if (t != null) {
					uncaughtException(t);
				}
			}
		}
	}
}

Back to the top