576 lines
19 KiB
Python
576 lines
19 KiB
Python
# 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). If any given Futures are duplicated, they will be returned
|
|
once.
|
|
|
|
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()
|
|
|
|
fs = set(fs)
|
|
with _AcquireFutures(fs):
|
|
finished = set(
|
|
f for f in fs
|
|
if f._state in [CANCELLED_AND_NOTIFIED, FINISHED])
|
|
pending = 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:
|
|
with f._condition:
|
|
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:
|
|
with f._condition:
|
|
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
|