Source

cpython_sandbox / Lib / concurrent / futures / _base.py

Full commit
  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
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
# Copyright 2009 Brian Quinlan. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.

__author__ = 'Brian Quinlan (brian@sweetapp.com)'

import collections
import logging
import threading
import time

FIRST_COMPLETED = 'FIRST_COMPLETED'
FIRST_EXCEPTION = 'FIRST_EXCEPTION'
ALL_COMPLETED = 'ALL_COMPLETED'
_AS_COMPLETED = '_AS_COMPLETED'

# Possible future states (for internal use by the futures package).
PENDING = 'PENDING'
RUNNING = 'RUNNING'
# The future was cancelled by the user...
CANCELLED = 'CANCELLED'
# ...and _Waiter.add_cancelled() was called by a worker.
CANCELLED_AND_NOTIFIED = 'CANCELLED_AND_NOTIFIED'
FINISHED = 'FINISHED'

_FUTURE_STATES = [
    PENDING,
    RUNNING,
    CANCELLED,
    CANCELLED_AND_NOTIFIED,
    FINISHED
]

_STATE_TO_DESCRIPTION_MAP = {
    PENDING: "pending",
    RUNNING: "running",
    CANCELLED: "cancelled",
    CANCELLED_AND_NOTIFIED: "cancelled",
    FINISHED: "finished"
}

# Logger for internal use by the futures package.
LOGGER = logging.getLogger("concurrent.futures")

class Error(Exception):
    """Base class for all future-related exceptions."""
    pass

class CancelledError(Error):
    """The Future was cancelled."""
    pass

class TimeoutError(Error):
    """The operation exceeded the given deadline."""
    pass

class _Waiter(object):
    """Provides the event that wait() and as_completed() block on."""
    def __init__(self):
        self.event = threading.Event()
        self.finished_futures = []

    def add_result(self, future):
        self.finished_futures.append(future)

    def add_exception(self, future):
        self.finished_futures.append(future)

    def add_cancelled(self, future):
        self.finished_futures.append(future)

class _AsCompletedWaiter(_Waiter):
    """Used by as_completed()."""

    def __init__(self):
        super(_AsCompletedWaiter, self).__init__()
        self.lock = threading.Lock()

    def add_result(self, future):
        with self.lock:
            super(_AsCompletedWaiter, self).add_result(future)
            self.event.set()

    def add_exception(self, future):
        with self.lock:
            super(_AsCompletedWaiter, self).add_exception(future)
            self.event.set()

    def add_cancelled(self, future):
        with self.lock:
            super(_AsCompletedWaiter, self).add_cancelled(future)
            self.event.set()

class _FirstCompletedWaiter(_Waiter):
    """Used by wait(return_when=FIRST_COMPLETED)."""

    def add_result(self, future):
        super().add_result(future)
        self.event.set()

    def add_exception(self, future):
        super().add_exception(future)
        self.event.set()

    def add_cancelled(self, future):
        super().add_cancelled(future)
        self.event.set()

class _AllCompletedWaiter(_Waiter):
    """Used by wait(return_when=FIRST_EXCEPTION and ALL_COMPLETED)."""

    def __init__(self, num_pending_calls, stop_on_exception):
        self.num_pending_calls = num_pending_calls
        self.stop_on_exception = stop_on_exception
        self.lock = threading.Lock()
        super().__init__()

    def _decrement_pending_calls(self):
        with self.lock:
            self.num_pending_calls -= 1
            if not self.num_pending_calls:
                self.event.set()

    def add_result(self, future):
        super().add_result(future)
        self._decrement_pending_calls()

    def add_exception(self, future):
        super().add_exception(future)
        if self.stop_on_exception:
            self.event.set()
        else:
            self._decrement_pending_calls()

    def add_cancelled(self, future):
        super().add_cancelled(future)
        self._decrement_pending_calls()

class _AcquireFutures(object):
    """A context manager that does an ordered acquire of Future conditions."""

    def __init__(self, futures):
        self.futures = sorted(futures, key=id)

    def __enter__(self):
        for future in self.futures:
            future._condition.acquire()

    def __exit__(self, *args):
        for future in self.futures:
            future._condition.release()

def _create_and_install_waiters(fs, return_when):
    if return_when == _AS_COMPLETED:
        waiter = _AsCompletedWaiter()
    elif return_when == FIRST_COMPLETED:
        waiter = _FirstCompletedWaiter()
    else:
        pending_count = sum(
                f._state not in [CANCELLED_AND_NOTIFIED, FINISHED] for f in fs)

        if return_when == FIRST_EXCEPTION:
            waiter = _AllCompletedWaiter(pending_count, stop_on_exception=True)
        elif return_when == ALL_COMPLETED:
            waiter = _AllCompletedWaiter(pending_count, stop_on_exception=False)
        else:
            raise ValueError("Invalid return condition: %r" % return_when)

    for f in fs:
        f._waiters.append(waiter)

    return waiter

def as_completed(fs, timeout=None):
    """An iterator over the given futures that yields each as it completes.

    Args:
        fs: The sequence of Futures (possibly created by different Executors) to
            iterate over.
        timeout: The maximum number of seconds to wait. If None, then there
            is no limit on the wait time.

    Returns:
        An iterator that yields the given Futures as they complete (finished or
        cancelled).

    Raises:
        TimeoutError: If the entire result iterator could not be generated
            before the given timeout.
    """
    if timeout is not None:
        end_time = timeout + time.time()

    with _AcquireFutures(fs):
        finished = set(
                f for f in fs
                if f._state in [CANCELLED_AND_NOTIFIED, FINISHED])
        pending = set(fs) - finished
        waiter = _create_and_install_waiters(fs, _AS_COMPLETED)

    try:
        yield from finished

        while pending:
            if timeout is None:
                wait_timeout = None
            else:
                wait_timeout = end_time - time.time()
                if wait_timeout < 0:
                    raise TimeoutError(
                            '%d (of %d) futures unfinished' % (
                            len(pending), len(fs)))

            waiter.event.wait(wait_timeout)

            with waiter.lock:
                finished = waiter.finished_futures
                waiter.finished_futures = []
                waiter.event.clear()

            for future in finished:
                yield future
                pending.remove(future)

    finally:
        for f in fs:
            f._waiters.remove(waiter)

DoneAndNotDoneFutures = collections.namedtuple(
        'DoneAndNotDoneFutures', 'done not_done')
def wait(fs, timeout=None, return_when=ALL_COMPLETED):
    """Wait for the futures in the given sequence to complete.

    Args:
        fs: The sequence of Futures (possibly created by different Executors) to
            wait upon.
        timeout: The maximum number of seconds to wait. If None, then there
            is no limit on the wait time.
        return_when: Indicates when this function should return. The options
            are:

            FIRST_COMPLETED - Return when any future finishes or is
                              cancelled.
            FIRST_EXCEPTION - Return when any future finishes by raising an
                              exception. If no future raises an exception
                              then it is equivalent to ALL_COMPLETED.
            ALL_COMPLETED -   Return when all futures finish or are cancelled.

    Returns:
        A named 2-tuple of sets. The first set, named 'done', contains the
        futures that completed (is finished or cancelled) before the wait
        completed. The second set, named 'not_done', contains uncompleted
        futures.
    """
    with _AcquireFutures(fs):
        done = set(f for f in fs
                   if f._state in [CANCELLED_AND_NOTIFIED, FINISHED])
        not_done = set(fs) - done

        if (return_when == FIRST_COMPLETED) and done:
            return DoneAndNotDoneFutures(done, not_done)
        elif (return_when == FIRST_EXCEPTION) and done:
            if any(f for f in done
                   if not f.cancelled() and f.exception() is not None):
                return DoneAndNotDoneFutures(done, not_done)

        if len(done) == len(fs):
            return DoneAndNotDoneFutures(done, not_done)

        waiter = _create_and_install_waiters(fs, return_when)

    waiter.event.wait(timeout)
    for f in fs:
        f._waiters.remove(waiter)

    done.update(waiter.finished_futures)
    return DoneAndNotDoneFutures(done, set(fs) - done)

class Future(object):
    """Represents the result of an asynchronous computation."""

    def __init__(self):
        """Initializes the future. Should not be called by clients."""
        self._condition = threading.Condition()
        self._state = PENDING
        self._result = None
        self._exception = None
        self._waiters = []
        self._done_callbacks = []

    def _invoke_callbacks(self):
        for callback in self._done_callbacks:
            try:
                callback(self)
            except Exception:
                LOGGER.exception('exception calling callback for %r', self)

    def __repr__(self):
        with self._condition:
            if self._state == FINISHED:
                if self._exception:
                    return '<Future at %s state=%s raised %s>' % (
                        hex(id(self)),
                        _STATE_TO_DESCRIPTION_MAP[self._state],
                        self._exception.__class__.__name__)
                else:
                    return '<Future at %s state=%s returned %s>' % (
                        hex(id(self)),
                        _STATE_TO_DESCRIPTION_MAP[self._state],
                        self._result.__class__.__name__)
            return '<Future at %s state=%s>' % (
                    hex(id(self)),
                   _STATE_TO_DESCRIPTION_MAP[self._state])

    def cancel(self):
        """Cancel the future if possible.

        Returns True if the future was cancelled, False otherwise. A future
        cannot be cancelled if it is running or has already completed.
        """
        with self._condition:
            if self._state in [RUNNING, FINISHED]:
                return False

            if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]:
                return True

            self._state = CANCELLED
            self._condition.notify_all()

        self._invoke_callbacks()
        return True

    def cancelled(self):
        """Return True if the future was cancelled."""
        with self._condition:
            return self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]

    def running(self):
        """Return True if the future is currently executing."""
        with self._condition:
            return self._state == RUNNING

    def done(self):
        """Return True of the future was cancelled or finished executing."""
        with self._condition:
            return self._state in [CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED]

    def __get_result(self):
        if self._exception:
            raise self._exception
        else:
            return self._result

    def add_done_callback(self, fn):
        """Attaches a callable that will be called when the future finishes.

        Args:
            fn: A callable that will be called with this future as its only
                argument when the future completes or is cancelled. The callable
                will always be called by a thread in the same process in which
                it was added. If the future has already completed or been
                cancelled then the callable will be called immediately. These
                callables are called in the order that they were added.
        """
        with self._condition:
            if self._state not in [CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED]:
                self._done_callbacks.append(fn)
                return
        fn(self)

    def result(self, timeout=None):
        """Return the result of the call that the future represents.

        Args:
            timeout: The number of seconds to wait for the result if the future
                isn't done. If None, then there is no limit on the wait time.

        Returns:
            The result of the call that the future represents.

        Raises:
            CancelledError: If the future was cancelled.
            TimeoutError: If the future didn't finish executing before the given
                timeout.
            Exception: If the call raised then that exception will be raised.
        """
        with self._condition:
            if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]:
                raise CancelledError()
            elif self._state == FINISHED:
                return self.__get_result()

            self._condition.wait(timeout)

            if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]:
                raise CancelledError()
            elif self._state == FINISHED:
                return self.__get_result()
            else:
                raise TimeoutError()

    def exception(self, timeout=None):
        """Return the exception raised by the call that the future represents.

        Args:
            timeout: The number of seconds to wait for the exception if the
                future isn't done. If None, then there is no limit on the wait
                time.

        Returns:
            The exception raised by the call that the future represents or None
            if the call completed without raising.

        Raises:
            CancelledError: If the future was cancelled.
            TimeoutError: If the future didn't finish executing before the given
                timeout.
        """

        with self._condition:
            if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]:
                raise CancelledError()
            elif self._state == FINISHED:
                return self._exception

            self._condition.wait(timeout)

            if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]:
                raise CancelledError()
            elif self._state == FINISHED:
                return self._exception
            else:
                raise TimeoutError()

    # The following methods should only be used by Executors and in tests.
    def set_running_or_notify_cancel(self):
        """Mark the future as running or process any cancel notifications.

        Should only be used by Executor implementations and unit tests.

        If the future has been cancelled (cancel() was called and returned
        True) then any threads waiting on the future completing (though calls
        to as_completed() or wait()) are notified and False is returned.

        If the future was not cancelled then it is put in the running state
        (future calls to running() will return True) and True is returned.

        This method should be called by Executor implementations before
        executing the work associated with this future. If this method returns
        False then the work should not be executed.

        Returns:
            False if the Future was cancelled, True otherwise.

        Raises:
            RuntimeError: if this method was already called or if set_result()
                or set_exception() was called.
        """
        with self._condition:
            if self._state == CANCELLED:
                self._state = CANCELLED_AND_NOTIFIED
                for waiter in self._waiters:
                    waiter.add_cancelled(self)
                # self._condition.notify_all() is not necessary because
                # self.cancel() triggers a notification.
                return False
            elif self._state == PENDING:
                self._state = RUNNING
                return True
            else:
                LOGGER.critical('Future %s in unexpected state: %s',
                                id(self),
                                self._state)
                raise RuntimeError('Future in unexpected state')

    def set_result(self, result):
        """Sets the return value of work associated with the future.

        Should only be used by Executor implementations and unit tests.
        """
        with self._condition:
            self._result = result
            self._state = FINISHED
            for waiter in self._waiters:
                waiter.add_result(self)
            self._condition.notify_all()
        self._invoke_callbacks()

    def set_exception(self, exception):
        """Sets the result of the future as being the given exception.

        Should only be used by Executor implementations and unit tests.
        """
        with self._condition:
            self._exception = exception
            self._state = FINISHED
            for waiter in self._waiters:
                waiter.add_exception(self)
            self._condition.notify_all()
        self._invoke_callbacks()

class Executor(object):
    """This is an abstract base class for concrete asynchronous executors."""

    def submit(self, fn, *args, **kwargs):
        """Submits a callable to be executed with the given arguments.

        Schedules the callable to be executed as fn(*args, **kwargs) and returns
        a Future instance representing the execution of the callable.

        Returns:
            A Future representing the given call.
        """
        raise NotImplementedError()

    def map(self, fn, *iterables, timeout=None):
        """Returns a iterator equivalent to map(fn, iter).

        Args:
            fn: A callable that will take as many arguments as there are
                passed iterables.
            timeout: The maximum number of seconds to wait. If None, then there
                is no limit on the wait time.

        Returns:
            An iterator equivalent to: map(func, *iterables) but the calls may
            be evaluated out-of-order.

        Raises:
            TimeoutError: If the entire result iterator could not be generated
                before the given timeout.
            Exception: If fn(*args) raises for any values.
        """
        if timeout is not None:
            end_time = timeout + time.time()

        fs = [self.submit(fn, *args) for args in zip(*iterables)]

        # Yield must be hidden in closure so that the futures are submitted
        # before the first iterator value is required.
        def result_iterator():
            try:
                for future in fs:
                    if timeout is None:
                        yield future.result()
                    else:
                        yield future.result(end_time - time.time())
            finally:
                for future in fs:
                    future.cancel()
        return result_iterator()

    def shutdown(self, wait=True):
        """Clean-up the resources associated with the Executor.

        It is safe to call this method several times. Otherwise, no other
        methods can be called after this one.

        Args:
            wait: If True then shutdown will not return until all running
                futures have finished executing and the resources used by the
                executor have been reclaimed.
        """
        pass

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.shutdown(wait=True)
        return False