Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 1 | """A Future class similar to the one in PEP 3148.""" |
| 2 | |
| 3 | __all__ = ['CancelledError', 'TimeoutError', |
| 4 | 'InvalidStateError', |
| 5 | 'Future', 'wrap_future', |
| 6 | ] |
| 7 | |
| 8 | import concurrent.futures._base |
| 9 | import logging |
Victor Stinner | 313a980 | 2014-07-29 12:58:23 +0200 | [diff] [blame] | 10 | import reprlib |
Victor Stinner | 4c3c699 | 2013-12-19 22:42:40 +0100 | [diff] [blame] | 11 | import sys |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 12 | import traceback |
| 13 | |
Victor Stinner | 71080fc | 2015-07-25 02:23:21 +0200 | [diff] [blame] | 14 | from . import compat |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 15 | from . import events |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 16 | |
| 17 | # States for Future. |
| 18 | _PENDING = 'PENDING' |
| 19 | _CANCELLED = 'CANCELLED' |
| 20 | _FINISHED = 'FINISHED' |
| 21 | |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 22 | Error = concurrent.futures._base.Error |
| 23 | CancelledError = concurrent.futures.CancelledError |
| 24 | TimeoutError = concurrent.futures.TimeoutError |
| 25 | |
| 26 | STACK_DEBUG = logging.DEBUG - 1 # heavy-duty debugging |
| 27 | |
| 28 | |
| 29 | class InvalidStateError(Error): |
| 30 | """The operation is not allowed in this state.""" |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 31 | |
| 32 | |
| 33 | class _TracebackLogger: |
| 34 | """Helper to log a traceback upon destruction if not cleared. |
| 35 | |
| 36 | This solves a nasty problem with Futures and Tasks that have an |
| 37 | exception set: if nobody asks for the exception, the exception is |
| 38 | never logged. This violates the Zen of Python: 'Errors should |
| 39 | never pass silently. Unless explicitly silenced.' |
| 40 | |
| 41 | However, we don't want to log the exception as soon as |
| 42 | set_exception() is called: if the calling code is written |
| 43 | properly, it will get the exception and handle it properly. But |
| 44 | we *do* want to log it if result() or exception() was never called |
| 45 | -- otherwise developers waste a lot of time wondering why their |
| 46 | buggy code fails silently. |
| 47 | |
| 48 | An earlier attempt added a __del__() method to the Future class |
| 49 | itself, but this backfired because the presence of __del__() |
| 50 | prevents garbage collection from breaking cycles. A way out of |
| 51 | this catch-22 is to avoid having a __del__() method on the Future |
| 52 | class itself, but instead to have a reference to a helper object |
| 53 | with a __del__() method that logs the traceback, where we ensure |
| 54 | that the helper object doesn't participate in cycles, and only the |
| 55 | Future has a reference to it. |
| 56 | |
| 57 | The helper object is added when set_exception() is called. When |
| 58 | the Future is collected, and the helper is present, the helper |
| 59 | object is also collected, and its __del__() method will log the |
| 60 | traceback. When the Future's result() or exception() method is |
Serhiy Storchaka | 56a6d85 | 2014-12-01 18:28:43 +0200 | [diff] [blame] | 61 | called (and a helper object is present), it removes the helper |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 62 | object, after calling its clear() method to prevent it from |
| 63 | logging. |
| 64 | |
| 65 | One downside is that we do a fair amount of work to extract the |
| 66 | traceback from the exception, even when it is never logged. It |
| 67 | would seem cheaper to just store the exception object, but that |
| 68 | references the traceback, which references stack frames, which may |
| 69 | reference the Future, which references the _TracebackLogger, and |
| 70 | then the _TracebackLogger would be included in a cycle, which is |
| 71 | what we're trying to avoid! As an optimization, we don't |
| 72 | immediately format the exception; we only do the work when |
| 73 | activate() is called, which call is delayed until after all the |
| 74 | Future's callbacks have run. Since usually a Future has at least |
| 75 | one callback (typically set by 'yield from') and usually that |
| 76 | callback extracts the callback, thereby removing the need to |
| 77 | format the exception. |
| 78 | |
| 79 | PS. I don't claim credit for this solution. I first heard of it |
| 80 | in a discussion about closing files when they are collected. |
| 81 | """ |
| 82 | |
Victor Stinner | 80f53aa | 2014-06-27 13:52:20 +0200 | [diff] [blame] | 83 | __slots__ = ('loop', 'source_traceback', 'exc', 'tb') |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 84 | |
Victor Stinner | 80f53aa | 2014-06-27 13:52:20 +0200 | [diff] [blame] | 85 | def __init__(self, future, exc): |
| 86 | self.loop = future._loop |
| 87 | self.source_traceback = future._source_traceback |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 88 | self.exc = exc |
| 89 | self.tb = None |
| 90 | |
| 91 | def activate(self): |
| 92 | exc = self.exc |
| 93 | if exc is not None: |
| 94 | self.exc = None |
| 95 | self.tb = traceback.format_exception(exc.__class__, exc, |
| 96 | exc.__traceback__) |
| 97 | |
| 98 | def clear(self): |
| 99 | self.exc = None |
| 100 | self.tb = None |
| 101 | |
| 102 | def __del__(self): |
| 103 | if self.tb: |
Victor Stinner | 662fd5f | 2014-11-20 14:16:31 +0100 | [diff] [blame] | 104 | msg = 'Future/Task exception was never retrieved\n' |
Victor Stinner | 80f53aa | 2014-06-27 13:52:20 +0200 | [diff] [blame] | 105 | if self.source_traceback: |
Victor Stinner | 662fd5f | 2014-11-20 14:16:31 +0100 | [diff] [blame] | 106 | src = ''.join(traceback.format_list(self.source_traceback)) |
| 107 | msg += 'Future/Task created at (most recent call last):\n' |
| 108 | msg += '%s\n' % src.rstrip() |
Victor Stinner | 80f53aa | 2014-06-27 13:52:20 +0200 | [diff] [blame] | 109 | msg += ''.join(self.tb).rstrip() |
| 110 | self.loop.call_exception_handler({'message': msg}) |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 111 | |
| 112 | |
Guido van Rossum | 7b3b3dc | 2016-09-09 14:26:31 -0700 | [diff] [blame] | 113 | def isfuture(obj): |
| 114 | """Check for a Future. |
| 115 | |
| 116 | This returns True when obj is a Future instance or is advertising |
| 117 | itself as duck-type compatible by setting _asyncio_future_blocking. |
| 118 | See comment in Future for more details. |
| 119 | """ |
| 120 | return getattr(obj, '_asyncio_future_blocking', None) is not None |
| 121 | |
| 122 | |
INADA Naoki | 9e4e38e | 2016-10-09 14:44:47 +0900 | [diff] [blame] | 123 | def _format_callbacks(cb): |
| 124 | """helper function for Future.__repr__""" |
| 125 | size = len(cb) |
| 126 | if not size: |
| 127 | cb = '' |
| 128 | |
| 129 | def format_cb(callback): |
| 130 | return events._format_callback_source(callback, ()) |
| 131 | |
| 132 | if size == 1: |
| 133 | cb = format_cb(cb[0]) |
| 134 | elif size == 2: |
| 135 | cb = '{}, {}'.format(format_cb(cb[0]), format_cb(cb[1])) |
| 136 | elif size > 2: |
| 137 | cb = '{}, <{} more>, {}'.format(format_cb(cb[0]), |
| 138 | size-2, |
| 139 | format_cb(cb[-1])) |
| 140 | return 'cb=[%s]' % cb |
| 141 | |
| 142 | |
| 143 | def _future_repr_info(future): |
| 144 | # (Future) -> str |
| 145 | """helper function for Future.__repr__""" |
| 146 | info = [future._state.lower()] |
| 147 | if future._state == _FINISHED: |
| 148 | if future._exception is not None: |
| 149 | info.append('exception={!r}'.format(future._exception)) |
| 150 | else: |
| 151 | # use reprlib to limit the length of the output, especially |
| 152 | # for very long strings |
| 153 | result = reprlib.repr(future._result) |
| 154 | info.append('result={}'.format(result)) |
| 155 | if future._callbacks: |
| 156 | info.append(_format_callbacks(future._callbacks)) |
| 157 | if future._source_traceback: |
| 158 | frame = future._source_traceback[-1] |
| 159 | info.append('created at %s:%s' % (frame[0], frame[1])) |
| 160 | return info |
| 161 | |
| 162 | |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 163 | class Future: |
| 164 | """This class is *almost* compatible with concurrent.futures.Future. |
| 165 | |
| 166 | Differences: |
| 167 | |
| 168 | - result() and exception() do not take a timeout argument and |
| 169 | raise an exception when the future isn't done yet. |
| 170 | |
| 171 | - Callbacks registered with add_done_callback() are always called |
| 172 | via the event loop's call_soon_threadsafe(). |
| 173 | |
| 174 | - This class is not compatible with the wait() and as_completed() |
| 175 | methods in the concurrent.futures package. |
| 176 | |
| 177 | (In Python 3.4 or later we may be able to unify the implementations.) |
| 178 | """ |
| 179 | |
| 180 | # Class variables serving as defaults for instance variables. |
| 181 | _state = _PENDING |
| 182 | _result = None |
| 183 | _exception = None |
| 184 | _loop = None |
Victor Stinner | fe22e09 | 2014-12-04 23:00:13 +0100 | [diff] [blame] | 185 | _source_traceback = None |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 186 | |
Guido van Rossum | 1140a03 | 2016-09-09 12:54:54 -0700 | [diff] [blame] | 187 | # This field is used for a dual purpose: |
| 188 | # - Its presence is a marker to declare that a class implements |
| 189 | # the Future protocol (i.e. is intended to be duck-type compatible). |
| 190 | # The value must also be not-None, to enable a subclass to declare |
| 191 | # that it is not compatible by setting this to None. |
| 192 | # - It is set by __iter__() below so that Task._step() can tell |
| 193 | # the difference between `yield from Future()` (correct) vs. |
| 194 | # `yield Future()` (incorrect). |
| 195 | _asyncio_future_blocking = False |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 196 | |
Victor Stinner | e40c078 | 2013-12-21 00:19:33 +0100 | [diff] [blame] | 197 | _log_traceback = False # Used for Python 3.4 and later |
| 198 | _tb_logger = None # Used for Python 3.3 only |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 199 | |
| 200 | def __init__(self, *, loop=None): |
| 201 | """Initialize the future. |
| 202 | |
Martin Panter | c04fb56 | 2016-02-10 05:44:01 +0000 | [diff] [blame] | 203 | The optional event_loop argument allows explicitly setting the event |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 204 | loop object used by the future. If it's not provided, the future uses |
| 205 | the default event loop. |
| 206 | """ |
| 207 | if loop is None: |
| 208 | self._loop = events.get_event_loop() |
| 209 | else: |
| 210 | self._loop = loop |
| 211 | self._callbacks = [] |
Victor Stinner | 80f53aa | 2014-06-27 13:52:20 +0200 | [diff] [blame] | 212 | if self._loop.get_debug(): |
| 213 | self._source_traceback = traceback.extract_stack(sys._getframe(1)) |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 214 | |
INADA Naoki | 9e4e38e | 2016-10-09 14:44:47 +0900 | [diff] [blame] | 215 | _repr_info = _future_repr_info |
Victor Stinner | 313a980 | 2014-07-29 12:58:23 +0200 | [diff] [blame] | 216 | |
| 217 | def __repr__(self): |
INADA Naoki | 9e4e38e | 2016-10-09 14:44:47 +0900 | [diff] [blame] | 218 | return '<%s %s>' % (self.__class__.__name__, ' '.join(self._repr_info())) |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 219 | |
Victor Stinner | 978a9af | 2015-01-29 17:50:58 +0100 | [diff] [blame] | 220 | # On Python 3.3 and older, objects with a destructor part of a reference |
| 221 | # cycle are never destroyed. It's not more the case on Python 3.4 thanks |
| 222 | # to the PEP 442. |
Victor Stinner | 71080fc | 2015-07-25 02:23:21 +0200 | [diff] [blame] | 223 | if compat.PY34: |
Victor Stinner | 4c3c699 | 2013-12-19 22:42:40 +0100 | [diff] [blame] | 224 | def __del__(self): |
Victor Stinner | e40c078 | 2013-12-21 00:19:33 +0100 | [diff] [blame] | 225 | if not self._log_traceback: |
| 226 | # set_exception() was not called, or result() or exception() |
| 227 | # has consumed the exception |
| 228 | return |
| 229 | exc = self._exception |
Yury Selivanov | 569efa2 | 2014-02-18 18:02:19 -0500 | [diff] [blame] | 230 | context = { |
Victor Stinner | 80f53aa | 2014-06-27 13:52:20 +0200 | [diff] [blame] | 231 | 'message': ('%s exception was never retrieved' |
| 232 | % self.__class__.__name__), |
Yury Selivanov | 569efa2 | 2014-02-18 18:02:19 -0500 | [diff] [blame] | 233 | 'exception': exc, |
| 234 | 'future': self, |
| 235 | } |
Victor Stinner | 80f53aa | 2014-06-27 13:52:20 +0200 | [diff] [blame] | 236 | if self._source_traceback: |
| 237 | context['source_traceback'] = self._source_traceback |
Yury Selivanov | 569efa2 | 2014-02-18 18:02:19 -0500 | [diff] [blame] | 238 | self._loop.call_exception_handler(context) |
Victor Stinner | 4c3c699 | 2013-12-19 22:42:40 +0100 | [diff] [blame] | 239 | |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 240 | def cancel(self): |
| 241 | """Cancel the future and schedule callbacks. |
| 242 | |
| 243 | If the future is already done or cancelled, return False. Otherwise, |
| 244 | change the future's state to cancelled, schedule the callbacks and |
| 245 | return True. |
| 246 | """ |
| 247 | if self._state != _PENDING: |
| 248 | return False |
| 249 | self._state = _CANCELLED |
| 250 | self._schedule_callbacks() |
| 251 | return True |
| 252 | |
| 253 | def _schedule_callbacks(self): |
| 254 | """Internal: Ask the event loop to call all callbacks. |
| 255 | |
| 256 | The callbacks are scheduled to be called as soon as possible. Also |
| 257 | clears the callback list. |
| 258 | """ |
| 259 | callbacks = self._callbacks[:] |
| 260 | if not callbacks: |
| 261 | return |
| 262 | |
| 263 | self._callbacks[:] = [] |
| 264 | for callback in callbacks: |
| 265 | self._loop.call_soon(callback, self) |
| 266 | |
| 267 | def cancelled(self): |
| 268 | """Return True if the future was cancelled.""" |
| 269 | return self._state == _CANCELLED |
| 270 | |
| 271 | # Don't implement running(); see http://bugs.python.org/issue18699 |
| 272 | |
| 273 | def done(self): |
| 274 | """Return True if the future is done. |
| 275 | |
| 276 | Done means either that a result / exception are available, or that the |
| 277 | future was cancelled. |
| 278 | """ |
| 279 | return self._state != _PENDING |
| 280 | |
| 281 | def result(self): |
| 282 | """Return the result this future represents. |
| 283 | |
| 284 | If the future has been cancelled, raises CancelledError. If the |
| 285 | future's result isn't yet available, raises InvalidStateError. If |
| 286 | the future is done and has an exception set, this exception is raised. |
| 287 | """ |
| 288 | if self._state == _CANCELLED: |
| 289 | raise CancelledError |
| 290 | if self._state != _FINISHED: |
| 291 | raise InvalidStateError('Result is not ready.') |
Victor Stinner | e40c078 | 2013-12-21 00:19:33 +0100 | [diff] [blame] | 292 | self._log_traceback = False |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 293 | if self._tb_logger is not None: |
| 294 | self._tb_logger.clear() |
Victor Stinner | e40c078 | 2013-12-21 00:19:33 +0100 | [diff] [blame] | 295 | self._tb_logger = None |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 296 | if self._exception is not None: |
| 297 | raise self._exception |
| 298 | return self._result |
| 299 | |
| 300 | def exception(self): |
| 301 | """Return the exception that was set on this future. |
| 302 | |
| 303 | The exception (or None if no exception was set) is returned only if |
| 304 | the future is done. If the future has been cancelled, raises |
| 305 | CancelledError. If the future isn't done yet, raises |
| 306 | InvalidStateError. |
| 307 | """ |
| 308 | if self._state == _CANCELLED: |
| 309 | raise CancelledError |
| 310 | if self._state != _FINISHED: |
| 311 | raise InvalidStateError('Exception is not set.') |
Victor Stinner | e40c078 | 2013-12-21 00:19:33 +0100 | [diff] [blame] | 312 | self._log_traceback = False |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 313 | if self._tb_logger is not None: |
| 314 | self._tb_logger.clear() |
Victor Stinner | e40c078 | 2013-12-21 00:19:33 +0100 | [diff] [blame] | 315 | self._tb_logger = None |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 316 | return self._exception |
| 317 | |
| 318 | def add_done_callback(self, fn): |
| 319 | """Add a callback to be run when the future becomes done. |
| 320 | |
| 321 | The callback is called with a single argument - the future object. If |
| 322 | the future is already done when this is called, the callback is |
| 323 | scheduled with call_soon. |
| 324 | """ |
| 325 | if self._state != _PENDING: |
| 326 | self._loop.call_soon(fn, self) |
| 327 | else: |
| 328 | self._callbacks.append(fn) |
| 329 | |
| 330 | # New method not in PEP 3148. |
| 331 | |
| 332 | def remove_done_callback(self, fn): |
| 333 | """Remove all instances of a callback from the "call when done" list. |
| 334 | |
| 335 | Returns the number of callbacks removed. |
| 336 | """ |
| 337 | filtered_callbacks = [f for f in self._callbacks if f != fn] |
| 338 | removed_count = len(self._callbacks) - len(filtered_callbacks) |
| 339 | if removed_count: |
| 340 | self._callbacks[:] = filtered_callbacks |
| 341 | return removed_count |
| 342 | |
| 343 | # So-called internal methods (note: no set_running_or_notify_cancel()). |
| 344 | |
| 345 | def set_result(self, result): |
| 346 | """Mark the future done and set its result. |
| 347 | |
| 348 | If the future is already done when this method is called, raises |
| 349 | InvalidStateError. |
| 350 | """ |
| 351 | if self._state != _PENDING: |
| 352 | raise InvalidStateError('{}: {!r}'.format(self._state, self)) |
| 353 | self._result = result |
| 354 | self._state = _FINISHED |
| 355 | self._schedule_callbacks() |
| 356 | |
| 357 | def set_exception(self, exception): |
| 358 | """Mark the future done and set an exception. |
| 359 | |
| 360 | If the future is already done when this method is called, raises |
| 361 | InvalidStateError. |
| 362 | """ |
| 363 | if self._state != _PENDING: |
| 364 | raise InvalidStateError('{}: {!r}'.format(self._state, self)) |
Victor Stinner | 9572898 | 2014-01-30 16:01:54 -0800 | [diff] [blame] | 365 | if isinstance(exception, type): |
| 366 | exception = exception() |
Yury Selivanov | 1bd0307 | 2016-03-02 11:03:28 -0500 | [diff] [blame] | 367 | if type(exception) is StopIteration: |
| 368 | raise TypeError("StopIteration interacts badly with generators " |
| 369 | "and cannot be raised into a Future") |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 370 | self._exception = exception |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 371 | self._state = _FINISHED |
| 372 | self._schedule_callbacks() |
Victor Stinner | 71080fc | 2015-07-25 02:23:21 +0200 | [diff] [blame] | 373 | if compat.PY34: |
Victor Stinner | e40c078 | 2013-12-21 00:19:33 +0100 | [diff] [blame] | 374 | self._log_traceback = True |
Victor Stinner | 4c3c699 | 2013-12-19 22:42:40 +0100 | [diff] [blame] | 375 | else: |
Victor Stinner | 80f53aa | 2014-06-27 13:52:20 +0200 | [diff] [blame] | 376 | self._tb_logger = _TracebackLogger(self, exception) |
Victor Stinner | 4c3c699 | 2013-12-19 22:42:40 +0100 | [diff] [blame] | 377 | # Arrange for the logger to be activated after all callbacks |
| 378 | # have had a chance to call result() or exception(). |
| 379 | self._loop.call_soon(self._tb_logger.activate) |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 380 | |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 381 | def __iter__(self): |
| 382 | if not self.done(): |
Guido van Rossum | 1140a03 | 2016-09-09 12:54:54 -0700 | [diff] [blame] | 383 | self._asyncio_future_blocking = True |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 384 | yield self # This tells Task to wait for completion. |
| 385 | assert self.done(), "yield from wasn't used with future" |
| 386 | return self.result() # May raise too. |
| 387 | |
Victor Stinner | 71080fc | 2015-07-25 02:23:21 +0200 | [diff] [blame] | 388 | if compat.PY35: |
Yury Selivanov | 1af2bf7 | 2015-05-11 22:27:25 -0400 | [diff] [blame] | 389 | __await__ = __iter__ # make compatible with 'await' expression |
| 390 | |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 391 | |
Yury Selivanov | 5d7e3b6 | 2015-11-17 12:19:41 -0500 | [diff] [blame] | 392 | def _set_result_unless_cancelled(fut, result): |
| 393 | """Helper setting the result only if the future was not cancelled.""" |
| 394 | if fut.cancelled(): |
| 395 | return |
| 396 | fut.set_result(result) |
| 397 | |
| 398 | |
Guido van Rossum | 841d9ee | 2015-10-03 08:31:42 -0700 | [diff] [blame] | 399 | def _set_concurrent_future_state(concurrent, source): |
| 400 | """Copy state from a future to a concurrent.futures.Future.""" |
| 401 | assert source.done() |
| 402 | if source.cancelled(): |
| 403 | concurrent.cancel() |
| 404 | if not concurrent.set_running_or_notify_cancel(): |
| 405 | return |
| 406 | exception = source.exception() |
| 407 | if exception is not None: |
| 408 | concurrent.set_exception(exception) |
| 409 | else: |
| 410 | result = source.result() |
| 411 | concurrent.set_result(result) |
| 412 | |
| 413 | |
Yury Selivanov | 5d7e3b6 | 2015-11-17 12:19:41 -0500 | [diff] [blame] | 414 | def _copy_future_state(source, dest): |
| 415 | """Internal helper to copy state from another Future. |
| 416 | |
| 417 | The other Future may be a concurrent.futures.Future. |
| 418 | """ |
| 419 | assert source.done() |
| 420 | if dest.cancelled(): |
| 421 | return |
| 422 | assert not dest.done() |
| 423 | if source.cancelled(): |
| 424 | dest.cancel() |
| 425 | else: |
| 426 | exception = source.exception() |
| 427 | if exception is not None: |
| 428 | dest.set_exception(exception) |
| 429 | else: |
| 430 | result = source.result() |
| 431 | dest.set_result(result) |
| 432 | |
| 433 | |
Guido van Rossum | 841d9ee | 2015-10-03 08:31:42 -0700 | [diff] [blame] | 434 | def _chain_future(source, destination): |
| 435 | """Chain two futures so that when one completes, so does the other. |
| 436 | |
| 437 | The result (or exception) of source will be copied to destination. |
| 438 | If destination is cancelled, source gets cancelled too. |
| 439 | Compatible with both asyncio.Future and concurrent.futures.Future. |
| 440 | """ |
Guido van Rossum | 7b3b3dc | 2016-09-09 14:26:31 -0700 | [diff] [blame] | 441 | if not isfuture(source) and not isinstance(source, |
| 442 | concurrent.futures.Future): |
Guido van Rossum | 841d9ee | 2015-10-03 08:31:42 -0700 | [diff] [blame] | 443 | raise TypeError('A future is required for source argument') |
Guido van Rossum | 7b3b3dc | 2016-09-09 14:26:31 -0700 | [diff] [blame] | 444 | if not isfuture(destination) and not isinstance(destination, |
| 445 | concurrent.futures.Future): |
Guido van Rossum | 841d9ee | 2015-10-03 08:31:42 -0700 | [diff] [blame] | 446 | raise TypeError('A future is required for destination argument') |
Guido van Rossum | 7b3b3dc | 2016-09-09 14:26:31 -0700 | [diff] [blame] | 447 | source_loop = source._loop if isfuture(source) else None |
| 448 | dest_loop = destination._loop if isfuture(destination) else None |
Guido van Rossum | 841d9ee | 2015-10-03 08:31:42 -0700 | [diff] [blame] | 449 | |
| 450 | def _set_state(future, other): |
Guido van Rossum | 7b3b3dc | 2016-09-09 14:26:31 -0700 | [diff] [blame] | 451 | if isfuture(future): |
Yury Selivanov | 5d7e3b6 | 2015-11-17 12:19:41 -0500 | [diff] [blame] | 452 | _copy_future_state(other, future) |
Guido van Rossum | 841d9ee | 2015-10-03 08:31:42 -0700 | [diff] [blame] | 453 | else: |
| 454 | _set_concurrent_future_state(future, other) |
| 455 | |
| 456 | def _call_check_cancel(destination): |
| 457 | if destination.cancelled(): |
| 458 | if source_loop is None or source_loop is dest_loop: |
| 459 | source.cancel() |
| 460 | else: |
| 461 | source_loop.call_soon_threadsafe(source.cancel) |
| 462 | |
| 463 | def _call_set_state(source): |
| 464 | if dest_loop is None or dest_loop is source_loop: |
| 465 | _set_state(destination, source) |
| 466 | else: |
| 467 | dest_loop.call_soon_threadsafe(_set_state, destination, source) |
| 468 | |
| 469 | destination.add_done_callback(_call_check_cancel) |
| 470 | source.add_done_callback(_call_set_state) |
| 471 | |
| 472 | |
| 473 | def wrap_future(future, *, loop=None): |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 474 | """Wrap concurrent.futures.Future object.""" |
Guido van Rossum | 7b3b3dc | 2016-09-09 14:26:31 -0700 | [diff] [blame] | 475 | if isfuture(future): |
Guido van Rossum | 841d9ee | 2015-10-03 08:31:42 -0700 | [diff] [blame] | 476 | return future |
| 477 | assert isinstance(future, concurrent.futures.Future), \ |
| 478 | 'concurrent.futures.Future is expected, got {!r}'.format(future) |
Yury Selivanov | 7661db6 | 2016-05-16 15:38:39 -0400 | [diff] [blame] | 479 | if loop is None: |
| 480 | loop = events.get_event_loop() |
| 481 | new_future = loop.create_future() |
Guido van Rossum | 841d9ee | 2015-10-03 08:31:42 -0700 | [diff] [blame] | 482 | _chain_future(future, new_future) |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 483 | return new_future |
INADA Naoki | c411a7d | 2016-10-18 11:48:14 +0900 | [diff] [blame^] | 484 | |
| 485 | |
| 486 | try: |
| 487 | import _asyncio |
| 488 | except ImportError: |
| 489 | pass |
| 490 | else: |
| 491 | Future = _asyncio.Future |