###############################################################################
# Backport concurrent.futures for python2.7/3.3
#
# author: Thomas Moreau and Olivier Grisel
#
# adapted from concurrent/futures/_base.py (17/02/2017)
# * Do not use yield from
# * Use old super syntax
#
# Copyright 2009 Brian Quinlan. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.
import sys
import time
import logging
import threading
import collections
if sys.version_info[:2] >= (3, 3):
from concurrent.futures import wait, as_completed
from concurrent.futures import TimeoutError, CancelledError
from concurrent.futures import Executor, Future as _BaseFuture
from concurrent.futures import FIRST_EXCEPTION
from concurrent.futures import ALL_COMPLETED, FIRST_COMPLETED
from concurrent.futures._base import LOGGER
from concurrent.futures._base import PENDING, RUNNING, CANCELLED
from concurrent.futures._base import CANCELLED_AND_NOTIFIED, FINISHED
else:
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(_FirstCompletedWaiter, self).add_result(future)
self.event.set()
def add_exception(self, future):
super(_FirstCompletedWaiter, self).add_exception(future)
self.event.set()
def add_cancelled(self, future):
super(_FirstCompletedWaiter, self).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(_AllCompletedWaiter, self).__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(_AllCompletedWaiter, self).add_result(future)
self._decrement_pending_calls()
def add_exception(self, future):
super(_AllCompletedWaiter, self).add_exception(future)
if self.stop_on_exception:
self.event.set()
else:
self._decrement_pending_calls()
def add_cancelled(self, future):
super(_AllCompletedWaiter, self).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:
for future in finished:
yield future
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 _BaseFuture(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 __repr__(self):
with self._condition:
if self._state == FINISHED:
if self._exception:
return '<%s at %#x state=%s raised %s>' % (
self.__class__.__name__,
id(self),
_STATE_TO_DESCRIPTION_MAP[self._state],
self._exception.__class__.__name__)
else:
return '<%s at %#x state=%s returned %s>' % (
self.__class__.__name__,
id(self),
_STATE_TO_DESCRIPTION_MAP[self._state],
self._result.__class__.__name__)
return '<%s at %#x state=%s>' % (
self.__class__.__name__,
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, **kwargs):
"""Returns an 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.
chunksize: The size of the chunks the iterable will be broken
into before being passed to a child process. This argument
is only used by ProcessPoolExecutor; it is ignored by
ThreadPoolExecutor.
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.
"""
timeout = kwargs.get('timeout')
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
# To make loky._base.Future instances awaitable by concurrent.futures.wait,
# derive our custom Future class from _BaseFuture. _invoke_callback is the only
# modification made to this class in loky.
class Future(_BaseFuture):
def _invoke_callbacks(self):
for callback in self._done_callbacks:
try:
callback(self)
except BaseException:
LOGGER.exception('exception calling callback for %r', self)
