mirror of
https://github.com/python/cpython.git
synced 2025-11-03 23:21:29 +00:00
660 lines
22 KiB
Python
660 lines
22 KiB
Python
"""Support for tasks, coroutines and the scheduler."""
|
|
|
|
__all__ = ['coroutine', 'Task',
|
|
'iscoroutinefunction', 'iscoroutine',
|
|
'FIRST_COMPLETED', 'FIRST_EXCEPTION', 'ALL_COMPLETED',
|
|
'wait', 'wait_for', 'as_completed', 'sleep', 'async',
|
|
'gather', 'shield',
|
|
]
|
|
|
|
import collections
|
|
import concurrent.futures
|
|
import functools
|
|
import inspect
|
|
import linecache
|
|
import traceback
|
|
import weakref
|
|
|
|
from . import events
|
|
from . import futures
|
|
from .log import logger
|
|
|
|
# If you set _DEBUG to true, @coroutine will wrap the resulting
|
|
# generator objects in a CoroWrapper instance (defined below). That
|
|
# instance will log a message when the generator is never iterated
|
|
# over, which may happen when you forget to use "yield from" with a
|
|
# coroutine call. Note that the value of the _DEBUG flag is taken
|
|
# when the decorator is used, so to be of any use it must be set
|
|
# before you define your coroutines. A downside of using this feature
|
|
# is that tracebacks show entries for the CoroWrapper.__next__ method
|
|
# when _DEBUG is true.
|
|
_DEBUG = False
|
|
|
|
|
|
class CoroWrapper:
|
|
# Wrapper for coroutine in _DEBUG mode.
|
|
|
|
__slots__ = ['gen', 'func', '__name__', '__doc__']
|
|
|
|
def __init__(self, gen, func):
|
|
assert inspect.isgenerator(gen), gen
|
|
self.gen = gen
|
|
self.func = func
|
|
|
|
def __iter__(self):
|
|
return self
|
|
|
|
def __next__(self):
|
|
return next(self.gen)
|
|
|
|
def send(self, value):
|
|
return self.gen.send(value)
|
|
|
|
def throw(self, exc):
|
|
return self.gen.throw(exc)
|
|
|
|
def close(self):
|
|
return self.gen.close()
|
|
|
|
def __del__(self):
|
|
frame = self.gen.gi_frame
|
|
if frame is not None and frame.f_lasti == -1:
|
|
func = self.func
|
|
code = func.__code__
|
|
filename = code.co_filename
|
|
lineno = code.co_firstlineno
|
|
logger.error(
|
|
'Coroutine %r defined at %s:%s was never yielded from',
|
|
func.__name__, filename, lineno)
|
|
|
|
|
|
def coroutine(func):
|
|
"""Decorator to mark coroutines.
|
|
|
|
If the coroutine is not yielded from before it is destroyed,
|
|
an error message is logged.
|
|
"""
|
|
if inspect.isgeneratorfunction(func):
|
|
coro = func
|
|
else:
|
|
@functools.wraps(func)
|
|
def coro(*args, **kw):
|
|
res = func(*args, **kw)
|
|
if isinstance(res, futures.Future) or inspect.isgenerator(res):
|
|
res = yield from res
|
|
return res
|
|
|
|
if not _DEBUG:
|
|
wrapper = coro
|
|
else:
|
|
@functools.wraps(func)
|
|
def wrapper(*args, **kwds):
|
|
w = CoroWrapper(coro(*args, **kwds), func)
|
|
w.__name__ = coro.__name__
|
|
w.__doc__ = coro.__doc__
|
|
return w
|
|
|
|
wrapper._is_coroutine = True # For iscoroutinefunction().
|
|
return wrapper
|
|
|
|
|
|
def iscoroutinefunction(func):
|
|
"""Return True if func is a decorated coroutine function."""
|
|
return getattr(func, '_is_coroutine', False)
|
|
|
|
|
|
def iscoroutine(obj):
|
|
"""Return True if obj is a coroutine object."""
|
|
return isinstance(obj, CoroWrapper) or inspect.isgenerator(obj)
|
|
|
|
|
|
class Task(futures.Future):
|
|
"""A coroutine wrapped in a Future."""
|
|
|
|
# An important invariant maintained while a Task not done:
|
|
#
|
|
# - Either _fut_waiter is None, and _step() is scheduled;
|
|
# - or _fut_waiter is some Future, and _step() is *not* scheduled.
|
|
#
|
|
# The only transition from the latter to the former is through
|
|
# _wakeup(). When _fut_waiter is not None, one of its callbacks
|
|
# must be _wakeup().
|
|
|
|
# Weak set containing all tasks alive.
|
|
_all_tasks = weakref.WeakSet()
|
|
|
|
# Dictionary containing tasks that are currently active in
|
|
# all running event loops. {EventLoop: Task}
|
|
_current_tasks = {}
|
|
|
|
@classmethod
|
|
def current_task(cls, loop=None):
|
|
"""Return the currently running task in an event loop or None.
|
|
|
|
By default the current task for the current event loop is returned.
|
|
|
|
None is returned when called not in the context of a Task.
|
|
"""
|
|
if loop is None:
|
|
loop = events.get_event_loop()
|
|
return cls._current_tasks.get(loop)
|
|
|
|
@classmethod
|
|
def all_tasks(cls, loop=None):
|
|
"""Return a set of all tasks for an event loop.
|
|
|
|
By default all tasks for the current event loop are returned.
|
|
"""
|
|
if loop is None:
|
|
loop = events.get_event_loop()
|
|
return {t for t in cls._all_tasks if t._loop is loop}
|
|
|
|
def __init__(self, coro, *, loop=None):
|
|
assert iscoroutine(coro), repr(coro) # Not a coroutine function!
|
|
super().__init__(loop=loop)
|
|
self._coro = iter(coro) # Use the iterator just in case.
|
|
self._fut_waiter = None
|
|
self._must_cancel = False
|
|
self._loop.call_soon(self._step)
|
|
self.__class__._all_tasks.add(self)
|
|
|
|
def __repr__(self):
|
|
res = super().__repr__()
|
|
if (self._must_cancel and
|
|
self._state == futures._PENDING and
|
|
'<PENDING' in res):
|
|
res = res.replace('<PENDING', '<CANCELLING', 1)
|
|
i = res.find('<')
|
|
if i < 0:
|
|
i = len(res)
|
|
res = res[:i] + '(<{}>)'.format(self._coro.__name__) + res[i:]
|
|
return res
|
|
|
|
def get_stack(self, *, limit=None):
|
|
"""Return the list of stack frames for this task's coroutine.
|
|
|
|
If the coroutine is active, this returns the stack where it is
|
|
suspended. If the coroutine has completed successfully or was
|
|
cancelled, this returns an empty list. If the coroutine was
|
|
terminated by an exception, this returns the list of traceback
|
|
frames.
|
|
|
|
The frames are always ordered from oldest to newest.
|
|
|
|
The optional limit gives the maximum nummber of frames to
|
|
return; by default all available frames are returned. Its
|
|
meaning differs depending on whether a stack or a traceback is
|
|
returned: the newest frames of a stack are returned, but the
|
|
oldest frames of a traceback are returned. (This matches the
|
|
behavior of the traceback module.)
|
|
|
|
For reasons beyond our control, only one stack frame is
|
|
returned for a suspended coroutine.
|
|
"""
|
|
frames = []
|
|
f = self._coro.gi_frame
|
|
if f is not None:
|
|
while f is not None:
|
|
if limit is not None:
|
|
if limit <= 0:
|
|
break
|
|
limit -= 1
|
|
frames.append(f)
|
|
f = f.f_back
|
|
frames.reverse()
|
|
elif self._exception is not None:
|
|
tb = self._exception.__traceback__
|
|
while tb is not None:
|
|
if limit is not None:
|
|
if limit <= 0:
|
|
break
|
|
limit -= 1
|
|
frames.append(tb.tb_frame)
|
|
tb = tb.tb_next
|
|
return frames
|
|
|
|
def print_stack(self, *, limit=None, file=None):
|
|
"""Print the stack or traceback for this task's coroutine.
|
|
|
|
This produces output similar to that of the traceback module,
|
|
for the frames retrieved by get_stack(). The limit argument
|
|
is passed to get_stack(). The file argument is an I/O stream
|
|
to which the output goes; by default it goes to sys.stderr.
|
|
"""
|
|
extracted_list = []
|
|
checked = set()
|
|
for f in self.get_stack(limit=limit):
|
|
lineno = f.f_lineno
|
|
co = f.f_code
|
|
filename = co.co_filename
|
|
name = co.co_name
|
|
if filename not in checked:
|
|
checked.add(filename)
|
|
linecache.checkcache(filename)
|
|
line = linecache.getline(filename, lineno, f.f_globals)
|
|
extracted_list.append((filename, lineno, name, line))
|
|
exc = self._exception
|
|
if not extracted_list:
|
|
print('No stack for %r' % self, file=file)
|
|
elif exc is not None:
|
|
print('Traceback for %r (most recent call last):' % self,
|
|
file=file)
|
|
else:
|
|
print('Stack for %r (most recent call last):' % self,
|
|
file=file)
|
|
traceback.print_list(extracted_list, file=file)
|
|
if exc is not None:
|
|
for line in traceback.format_exception_only(exc.__class__, exc):
|
|
print(line, file=file, end='')
|
|
|
|
def cancel(self):
|
|
if self.done():
|
|
return False
|
|
if self._fut_waiter is not None:
|
|
if self._fut_waiter.cancel():
|
|
# Leave self._fut_waiter; it may be a Task that
|
|
# catches and ignores the cancellation so we may have
|
|
# to cancel it again later.
|
|
return True
|
|
# It must be the case that self._step is already scheduled.
|
|
self._must_cancel = True
|
|
return True
|
|
|
|
def _step(self, value=None, exc=None):
|
|
assert not self.done(), \
|
|
'_step(): already done: {!r}, {!r}, {!r}'.format(self, value, exc)
|
|
if self._must_cancel:
|
|
if not isinstance(exc, futures.CancelledError):
|
|
exc = futures.CancelledError()
|
|
self._must_cancel = False
|
|
coro = self._coro
|
|
self._fut_waiter = None
|
|
|
|
self.__class__._current_tasks[self._loop] = self
|
|
# Call either coro.throw(exc) or coro.send(value).
|
|
try:
|
|
if exc is not None:
|
|
result = coro.throw(exc)
|
|
elif value is not None:
|
|
result = coro.send(value)
|
|
else:
|
|
result = next(coro)
|
|
except StopIteration as exc:
|
|
self.set_result(exc.value)
|
|
except futures.CancelledError as exc:
|
|
super().cancel() # I.e., Future.cancel(self).
|
|
except Exception as exc:
|
|
self.set_exception(exc)
|
|
except BaseException as exc:
|
|
self.set_exception(exc)
|
|
raise
|
|
else:
|
|
if isinstance(result, futures.Future):
|
|
# Yielded Future must come from Future.__iter__().
|
|
if result._blocking:
|
|
result._blocking = False
|
|
result.add_done_callback(self._wakeup)
|
|
self._fut_waiter = result
|
|
if self._must_cancel:
|
|
if self._fut_waiter.cancel():
|
|
self._must_cancel = False
|
|
else:
|
|
self._loop.call_soon(
|
|
self._step, None,
|
|
RuntimeError(
|
|
'yield was used instead of yield from '
|
|
'in task {!r} with {!r}'.format(self, result)))
|
|
elif result is None:
|
|
# Bare yield relinquishes control for one event loop iteration.
|
|
self._loop.call_soon(self._step)
|
|
elif inspect.isgenerator(result):
|
|
# Yielding a generator is just wrong.
|
|
self._loop.call_soon(
|
|
self._step, None,
|
|
RuntimeError(
|
|
'yield was used instead of yield from for '
|
|
'generator in task {!r} with {}'.format(
|
|
self, result)))
|
|
else:
|
|
# Yielding something else is an error.
|
|
self._loop.call_soon(
|
|
self._step, None,
|
|
RuntimeError(
|
|
'Task got bad yield: {!r}'.format(result)))
|
|
finally:
|
|
self.__class__._current_tasks.pop(self._loop)
|
|
self = None
|
|
|
|
def _wakeup(self, future):
|
|
try:
|
|
value = future.result()
|
|
except Exception as exc:
|
|
# This may also be a cancellation.
|
|
self._step(None, exc)
|
|
else:
|
|
self._step(value, None)
|
|
self = None # Needed to break cycles when an exception occurs.
|
|
|
|
|
|
# wait() and as_completed() similar to those in PEP 3148.
|
|
|
|
FIRST_COMPLETED = concurrent.futures.FIRST_COMPLETED
|
|
FIRST_EXCEPTION = concurrent.futures.FIRST_EXCEPTION
|
|
ALL_COMPLETED = concurrent.futures.ALL_COMPLETED
|
|
|
|
|
|
@coroutine
|
|
def wait(fs, *, loop=None, timeout=None, return_when=ALL_COMPLETED):
|
|
"""Wait for the Futures and coroutines given by fs to complete.
|
|
|
|
Coroutines will be wrapped in Tasks.
|
|
|
|
Returns two sets of Future: (done, pending).
|
|
|
|
Usage:
|
|
|
|
done, pending = yield from asyncio.wait(fs)
|
|
|
|
Note: This does not raise TimeoutError! Futures that aren't done
|
|
when the timeout occurs are returned in the second set.
|
|
"""
|
|
if not fs:
|
|
raise ValueError('Set of coroutines/Futures is empty.')
|
|
|
|
if loop is None:
|
|
loop = events.get_event_loop()
|
|
|
|
fs = set(async(f, loop=loop) for f in fs)
|
|
|
|
if return_when not in (FIRST_COMPLETED, FIRST_EXCEPTION, ALL_COMPLETED):
|
|
raise ValueError('Invalid return_when value: {}'.format(return_when))
|
|
return (yield from _wait(fs, timeout, return_when, loop))
|
|
|
|
|
|
def _release_waiter(waiter, value=True, *args):
|
|
if not waiter.done():
|
|
waiter.set_result(value)
|
|
|
|
|
|
@coroutine
|
|
def wait_for(fut, timeout, *, loop=None):
|
|
"""Wait for the single Future or coroutine to complete, with timeout.
|
|
|
|
Coroutine will be wrapped in Task.
|
|
|
|
Returns result of the Future or coroutine. When a timeout occurs,
|
|
it cancels the task and raises TimeoutError. To avoid the task
|
|
cancellation, wrap it in shield().
|
|
|
|
Usage:
|
|
|
|
result = yield from asyncio.wait_for(fut, 10.0)
|
|
|
|
"""
|
|
if loop is None:
|
|
loop = events.get_event_loop()
|
|
|
|
waiter = futures.Future(loop=loop)
|
|
timeout_handle = loop.call_later(timeout, _release_waiter, waiter, False)
|
|
cb = functools.partial(_release_waiter, waiter, True)
|
|
|
|
fut = async(fut, loop=loop)
|
|
fut.add_done_callback(cb)
|
|
|
|
try:
|
|
if (yield from waiter):
|
|
return fut.result()
|
|
else:
|
|
fut.remove_done_callback(cb)
|
|
fut.cancel()
|
|
raise futures.TimeoutError()
|
|
finally:
|
|
timeout_handle.cancel()
|
|
|
|
|
|
@coroutine
|
|
def _wait(fs, timeout, return_when, loop):
|
|
"""Internal helper for wait() and _wait_for().
|
|
|
|
The fs argument must be a collection of Futures.
|
|
"""
|
|
assert fs, 'Set of Futures is empty.'
|
|
waiter = futures.Future(loop=loop)
|
|
timeout_handle = None
|
|
if timeout is not None:
|
|
timeout_handle = loop.call_later(timeout, _release_waiter, waiter)
|
|
counter = len(fs)
|
|
|
|
def _on_completion(f):
|
|
nonlocal counter
|
|
counter -= 1
|
|
if (counter <= 0 or
|
|
return_when == FIRST_COMPLETED or
|
|
return_when == FIRST_EXCEPTION and (not f.cancelled() and
|
|
f.exception() is not None)):
|
|
if timeout_handle is not None:
|
|
timeout_handle.cancel()
|
|
if not waiter.done():
|
|
waiter.set_result(False)
|
|
|
|
for f in fs:
|
|
f.add_done_callback(_on_completion)
|
|
|
|
try:
|
|
yield from waiter
|
|
finally:
|
|
if timeout_handle is not None:
|
|
timeout_handle.cancel()
|
|
|
|
done, pending = set(), set()
|
|
for f in fs:
|
|
f.remove_done_callback(_on_completion)
|
|
if f.done():
|
|
done.add(f)
|
|
else:
|
|
pending.add(f)
|
|
return done, pending
|
|
|
|
|
|
# This is *not* a @coroutine! It is just an iterator (yielding Futures).
|
|
def as_completed(fs, *, loop=None, timeout=None):
|
|
"""Return an iterator whose values, when waited for, are Futures.
|
|
|
|
This differs from PEP 3148; the proper way to use this is:
|
|
|
|
for f in as_completed(fs):
|
|
result = yield from f # The 'yield from' may raise.
|
|
# Use result.
|
|
|
|
Raises TimeoutError if the timeout occurs before all Futures are
|
|
done.
|
|
|
|
Note: The futures 'f' are not necessarily members of fs.
|
|
"""
|
|
loop = loop if loop is not None else events.get_event_loop()
|
|
deadline = None if timeout is None else loop.time() + timeout
|
|
todo = set(async(f, loop=loop) for f in fs)
|
|
completed = collections.deque()
|
|
|
|
@coroutine
|
|
def _wait_for_one():
|
|
while not completed:
|
|
timeout = None
|
|
if deadline is not None:
|
|
timeout = deadline - loop.time()
|
|
if timeout < 0:
|
|
raise futures.TimeoutError()
|
|
done, pending = yield from _wait(
|
|
todo, timeout, FIRST_COMPLETED, loop)
|
|
# Multiple callers might be waiting for the same events
|
|
# and getting the same outcome. Dedupe by updating todo.
|
|
for f in done:
|
|
if f in todo:
|
|
todo.remove(f)
|
|
completed.append(f)
|
|
f = completed.popleft()
|
|
return f.result() # May raise.
|
|
|
|
for _ in range(len(todo)):
|
|
yield _wait_for_one()
|
|
|
|
|
|
@coroutine
|
|
def sleep(delay, result=None, *, loop=None):
|
|
"""Coroutine that completes after a given time (in seconds)."""
|
|
future = futures.Future(loop=loop)
|
|
h = future._loop.call_later(delay, future.set_result, result)
|
|
try:
|
|
return (yield from future)
|
|
finally:
|
|
h.cancel()
|
|
|
|
|
|
def async(coro_or_future, *, loop=None):
|
|
"""Wrap a coroutine in a future.
|
|
|
|
If the argument is a Future, it is returned directly.
|
|
"""
|
|
if isinstance(coro_or_future, futures.Future):
|
|
if loop is not None and loop is not coro_or_future._loop:
|
|
raise ValueError('loop argument must agree with Future')
|
|
return coro_or_future
|
|
elif iscoroutine(coro_or_future):
|
|
return Task(coro_or_future, loop=loop)
|
|
else:
|
|
raise TypeError('A Future or coroutine is required')
|
|
|
|
|
|
class _GatheringFuture(futures.Future):
|
|
"""Helper for gather().
|
|
|
|
This overrides cancel() to cancel all the children and act more
|
|
like Task.cancel(), which doesn't immediately mark itself as
|
|
cancelled.
|
|
"""
|
|
|
|
def __init__(self, children, *, loop=None):
|
|
super().__init__(loop=loop)
|
|
self._children = children
|
|
|
|
def cancel(self):
|
|
if self.done():
|
|
return False
|
|
for child in self._children:
|
|
child.cancel()
|
|
return True
|
|
|
|
|
|
def gather(*coros_or_futures, loop=None, return_exceptions=False):
|
|
"""Return a future aggregating results from the given coroutines
|
|
or futures.
|
|
|
|
All futures must share the same event loop. If all the tasks are
|
|
done successfully, the returned future's result is the list of
|
|
results (in the order of the original sequence, not necessarily
|
|
the order of results arrival). If *result_exception* is True,
|
|
exceptions in the tasks are treated the same as successful
|
|
results, and gathered in the result list; otherwise, the first
|
|
raised exception will be immediately propagated to the returned
|
|
future.
|
|
|
|
Cancellation: if the outer Future is cancelled, all children (that
|
|
have not completed yet) are also cancelled. If any child is
|
|
cancelled, this is treated as if it raised CancelledError --
|
|
the outer Future is *not* cancelled in this case. (This is to
|
|
prevent the cancellation of one child to cause other children to
|
|
be cancelled.)
|
|
"""
|
|
children = [async(fut, loop=loop) for fut in coros_or_futures]
|
|
n = len(children)
|
|
if n == 0:
|
|
outer = futures.Future(loop=loop)
|
|
outer.set_result([])
|
|
return outer
|
|
if loop is None:
|
|
loop = children[0]._loop
|
|
for fut in children:
|
|
if fut._loop is not loop:
|
|
raise ValueError("futures are tied to different event loops")
|
|
outer = _GatheringFuture(children, loop=loop)
|
|
nfinished = 0
|
|
results = [None] * n
|
|
|
|
def _done_callback(i, fut):
|
|
nonlocal nfinished
|
|
if outer._state != futures._PENDING:
|
|
if fut._exception is not None:
|
|
# Mark exception retrieved.
|
|
fut.exception()
|
|
return
|
|
if fut._state == futures._CANCELLED:
|
|
res = futures.CancelledError()
|
|
if not return_exceptions:
|
|
outer.set_exception(res)
|
|
return
|
|
elif fut._exception is not None:
|
|
res = fut.exception() # Mark exception retrieved.
|
|
if not return_exceptions:
|
|
outer.set_exception(res)
|
|
return
|
|
else:
|
|
res = fut._result
|
|
results[i] = res
|
|
nfinished += 1
|
|
if nfinished == n:
|
|
outer.set_result(results)
|
|
|
|
for i, fut in enumerate(children):
|
|
fut.add_done_callback(functools.partial(_done_callback, i))
|
|
return outer
|
|
|
|
|
|
def shield(arg, *, loop=None):
|
|
"""Wait for a future, shielding it from cancellation.
|
|
|
|
The statement
|
|
|
|
res = yield from shield(something())
|
|
|
|
is exactly equivalent to the statement
|
|
|
|
res = yield from something()
|
|
|
|
*except* that if the coroutine containing it is cancelled, the
|
|
task running in something() is not cancelled. From the POV of
|
|
something(), the cancellation did not happen. But its caller is
|
|
still cancelled, so the yield-from expression still raises
|
|
CancelledError. Note: If something() is cancelled by other means
|
|
this will still cancel shield().
|
|
|
|
If you want to completely ignore cancellation (not recommended)
|
|
you can combine shield() with a try/except clause, as follows:
|
|
|
|
try:
|
|
res = yield from shield(something())
|
|
except CancelledError:
|
|
res = None
|
|
"""
|
|
inner = async(arg, loop=loop)
|
|
if inner.done():
|
|
# Shortcut.
|
|
return inner
|
|
loop = inner._loop
|
|
outer = futures.Future(loop=loop)
|
|
|
|
def _done_callback(inner):
|
|
if outer.cancelled():
|
|
# Mark inner's result as retrieved.
|
|
inner.cancelled() or inner.exception()
|
|
return
|
|
if inner.cancelled():
|
|
outer.cancel()
|
|
else:
|
|
exc = inner.exception()
|
|
if exc is not None:
|
|
outer.set_exception(exc)
|
|
else:
|
|
outer.set_result(inner.result())
|
|
|
|
inner.add_done_callback(_done_callback)
|
|
return outer
|