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from __future__ import annotations
from collections import deque
from dataclasses import dataclass
from types import TracebackType
from warnings import warn
from ..lowlevel import cancel_shielded_checkpoint, checkpoint, checkpoint_if_cancelled
from ._compat import DeprecatedAwaitable
from ._eventloop import get_asynclib
from ._exceptions import BusyResourceError, WouldBlock
from ._tasks import CancelScope
from ._testing import TaskInfo, get_current_task
@dataclass(frozen=True)
class EventStatistics:
"""
:ivar int tasks_waiting: number of tasks waiting on :meth:`~.Event.wait`
"""
tasks_waiting: int
@dataclass(frozen=True)
class CapacityLimiterStatistics:
"""
:ivar int borrowed_tokens: number of tokens currently borrowed by tasks
:ivar float total_tokens: total number of available tokens
:ivar tuple borrowers: tasks or other objects currently holding tokens borrowed from this
limiter
:ivar int tasks_waiting: number of tasks waiting on :meth:`~.CapacityLimiter.acquire` or
:meth:`~.CapacityLimiter.acquire_on_behalf_of`
"""
borrowed_tokens: int
total_tokens: float
borrowers: tuple[object, ...]
tasks_waiting: int
@dataclass(frozen=True)
class LockStatistics:
"""
:ivar bool locked: flag indicating if this lock is locked or not
:ivar ~anyio.TaskInfo owner: task currently holding the lock (or ``None`` if the lock is not
held by any task)
:ivar int tasks_waiting: number of tasks waiting on :meth:`~.Lock.acquire`
"""
locked: bool
owner: TaskInfo | None
tasks_waiting: int
@dataclass(frozen=True)
class ConditionStatistics:
"""
:ivar int tasks_waiting: number of tasks blocked on :meth:`~.Condition.wait`
:ivar ~anyio.LockStatistics lock_statistics: statistics of the underlying :class:`~.Lock`
"""
tasks_waiting: int
lock_statistics: LockStatistics
@dataclass(frozen=True)
class SemaphoreStatistics:
"""
:ivar int tasks_waiting: number of tasks waiting on :meth:`~.Semaphore.acquire`
"""
tasks_waiting: int
class Event:
def __new__(cls) -> Event:
return get_asynclib().Event()
def set(self) -> DeprecatedAwaitable:
"""Set the flag, notifying all listeners."""
raise NotImplementedError
def is_set(self) -> bool:
"""Return ``True`` if the flag is set, ``False`` if not."""
raise NotImplementedError
async def wait(self) -> None:
"""
Wait until the flag has been set.
If the flag has already been set when this method is called, it returns immediately.
"""
raise NotImplementedError
def statistics(self) -> EventStatistics:
"""Return statistics about the current state of this event."""
raise NotImplementedError
class Lock:
_owner_task: TaskInfo | None = None
def __init__(self) -> None:
self._waiters: deque[tuple[TaskInfo, Event]] = deque()
async def __aenter__(self) -> None:
await self.acquire()
async def __aexit__(
self,
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> None:
self.release()
async def acquire(self) -> None:
"""Acquire the lock."""
await checkpoint_if_cancelled()
try:
self.acquire_nowait()
except WouldBlock:
task = get_current_task()
event = Event()
token = task, event
self._waiters.append(token)
try:
await event.wait()
except BaseException:
if not event.is_set():
self._waiters.remove(token)
elif self._owner_task == task:
self.release()
raise
assert self._owner_task == task
else:
try:
await cancel_shielded_checkpoint()
except BaseException:
self.release()
raise
def acquire_nowait(self) -> None:
"""
Acquire the lock, without blocking.
:raises ~WouldBlock: if the operation would block
"""
task = get_current_task()
if self._owner_task == task:
raise RuntimeError("Attempted to acquire an already held Lock")
if self._owner_task is not None:
raise WouldBlock
self._owner_task = task
def release(self) -> DeprecatedAwaitable:
"""Release the lock."""
if self._owner_task != get_current_task():
raise RuntimeError("The current task is not holding this lock")
if self._waiters:
self._owner_task, event = self._waiters.popleft()
event.set()
else:
del self._owner_task
return DeprecatedAwaitable(self.release)
def locked(self) -> bool:
"""Return True if the lock is currently held."""
return self._owner_task is not None
def statistics(self) -> LockStatistics:
"""
Return statistics about the current state of this lock.
.. versionadded:: 3.0
"""
return LockStatistics(self.locked(), self._owner_task, len(self._waiters))
class Condition:
_owner_task: TaskInfo | None = None
def __init__(self, lock: Lock | None = None):
self._lock = lock or Lock()
self._waiters: deque[Event] = deque()
async def __aenter__(self) -> None:
await self.acquire()
async def __aexit__(
self,
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> None:
self.release()
def _check_acquired(self) -> None:
if self._owner_task != get_current_task():
raise RuntimeError("The current task is not holding the underlying lock")
async def acquire(self) -> None:
"""Acquire the underlying lock."""
await self._lock.acquire()
self._owner_task = get_current_task()
def acquire_nowait(self) -> None:
"""
Acquire the underlying lock, without blocking.
:raises ~WouldBlock: if the operation would block
"""
self._lock.acquire_nowait()
self._owner_task = get_current_task()
def release(self) -> DeprecatedAwaitable:
"""Release the underlying lock."""
self._lock.release()
return DeprecatedAwaitable(self.release)
def locked(self) -> bool:
"""Return True if the lock is set."""
return self._lock.locked()
def notify(self, n: int = 1) -> None:
"""Notify exactly n listeners."""
self._check_acquired()
for _ in range(n):
try:
event = self._waiters.popleft()
except IndexError:
break
event.set()
def notify_all(self) -> None:
"""Notify all the listeners."""
self._check_acquired()
for event in self._waiters:
event.set()
self._waiters.clear()
async def wait(self) -> None:
"""Wait for a notification."""
await checkpoint()
event = Event()
self._waiters.append(event)
self.release()
try:
await event.wait()
except BaseException:
if not event.is_set():
self._waiters.remove(event)
raise
finally:
with CancelScope(shield=True):
await self.acquire()
def statistics(self) -> ConditionStatistics:
"""
Return statistics about the current state of this condition.
.. versionadded:: 3.0
"""
return ConditionStatistics(len(self._waiters), self._lock.statistics())
class Semaphore:
def __init__(self, initial_value: int, *, max_value: int | None = None):
if not isinstance(initial_value, int):
raise TypeError("initial_value must be an integer")
if initial_value < 0:
raise ValueError("initial_value must be >= 0")
if max_value is not None:
if not isinstance(max_value, int):
raise TypeError("max_value must be an integer or None")
if max_value < initial_value:
raise ValueError(
"max_value must be equal to or higher than initial_value"
)
self._value = initial_value
self._max_value = max_value
self._waiters: deque[Event] = deque()
async def __aenter__(self) -> Semaphore:
await self.acquire()
return self
async def __aexit__(
self,
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> None:
self.release()
async def acquire(self) -> None:
"""Decrement the semaphore value, blocking if necessary."""
await checkpoint_if_cancelled()
try:
self.acquire_nowait()
except WouldBlock:
event = Event()
self._waiters.append(event)
try:
await event.wait()
except BaseException:
if not event.is_set():
self._waiters.remove(event)
else:
self.release()
raise
else:
try:
await cancel_shielded_checkpoint()
except BaseException:
self.release()
raise
def acquire_nowait(self) -> None:
"""
Acquire the underlying lock, without blocking.
:raises ~WouldBlock: if the operation would block
"""
if self._value == 0:
raise WouldBlock
self._value -= 1
def release(self) -> DeprecatedAwaitable:
"""Increment the semaphore value."""
if self._max_value is not None and self._value == self._max_value:
raise ValueError("semaphore released too many times")
if self._waiters:
self._waiters.popleft().set()
else:
self._value += 1
return DeprecatedAwaitable(self.release)
@property
def value(self) -> int:
"""The current value of the semaphore."""
return self._value
@property
def max_value(self) -> int | None:
"""The maximum value of the semaphore."""
return self._max_value
def statistics(self) -> SemaphoreStatistics:
"""
Return statistics about the current state of this semaphore.
.. versionadded:: 3.0
"""
return SemaphoreStatistics(len(self._waiters))
class CapacityLimiter:
def __new__(cls, total_tokens: float) -> CapacityLimiter:
return get_asynclib().CapacityLimiter(total_tokens)
async def __aenter__(self) -> None:
raise NotImplementedError
async def __aexit__(
self,
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> bool | None:
raise NotImplementedError
@property
def total_tokens(self) -> float:
"""
The total number of tokens available for borrowing.
This is a read-write property. If the total number of tokens is increased, the
proportionate number of tasks waiting on this limiter will be granted their tokens.
.. versionchanged:: 3.0
The property is now writable.
"""
raise NotImplementedError
@total_tokens.setter
def total_tokens(self, value: float) -> None:
raise NotImplementedError
async def set_total_tokens(self, value: float) -> None:
warn(
"CapacityLimiter.set_total_tokens has been deprecated. Set the value of the"
'"total_tokens" attribute directly.',
DeprecationWarning,
)
self.total_tokens = value
@property
def borrowed_tokens(self) -> int:
"""The number of tokens that have currently been borrowed."""
raise NotImplementedError
@property
def available_tokens(self) -> float:
"""The number of tokens currently available to be borrowed"""
raise NotImplementedError
def acquire_nowait(self) -> DeprecatedAwaitable:
"""
Acquire a token for the current task without waiting for one to become available.
:raises ~anyio.WouldBlock: if there are no tokens available for borrowing
"""
raise NotImplementedError
def acquire_on_behalf_of_nowait(self, borrower: object) -> DeprecatedAwaitable:
"""
Acquire a token without waiting for one to become available.
:param borrower: the entity borrowing a token
:raises ~anyio.WouldBlock: if there are no tokens available for borrowing
"""
raise NotImplementedError
async def acquire(self) -> None:
"""
Acquire a token for the current task, waiting if necessary for one to become available.
"""
raise NotImplementedError
async def acquire_on_behalf_of(self, borrower: object) -> None:
"""
Acquire a token, waiting if necessary for one to become available.
:param borrower: the entity borrowing a token
"""
raise NotImplementedError
def release(self) -> None:
"""
Release the token held by the current task.
:raises RuntimeError: if the current task has not borrowed a token from this limiter.
"""
raise NotImplementedError
def release_on_behalf_of(self, borrower: object) -> None:
"""
Release the token held by the given borrower.
:raises RuntimeError: if the borrower has not borrowed a token from this limiter.
"""
raise NotImplementedError
def statistics(self) -> CapacityLimiterStatistics:
"""
Return statistics about the current state of this limiter.
.. versionadded:: 3.0
"""
raise NotImplementedError
def create_lock() -> Lock:
"""
Create an asynchronous lock.
:return: a lock object
.. deprecated:: 3.0
Use :class:`~Lock` directly.
"""
warn("create_lock() is deprecated -- use Lock() directly", DeprecationWarning)
return Lock()
def create_condition(lock: Lock | None = None) -> Condition:
"""
Create an asynchronous condition.
:param lock: the lock to base the condition object on
:return: a condition object
.. deprecated:: 3.0
Use :class:`~Condition` directly.
"""
warn(
"create_condition() is deprecated -- use Condition() directly",
DeprecationWarning,
)
return Condition(lock=lock)
def create_event() -> Event:
"""
Create an asynchronous event object.
:return: an event object
.. deprecated:: 3.0
Use :class:`~Event` directly.
"""
warn("create_event() is deprecated -- use Event() directly", DeprecationWarning)
return get_asynclib().Event()
def create_semaphore(value: int, *, max_value: int | None = None) -> Semaphore:
"""
Create an asynchronous semaphore.
:param value: the semaphore's initial value
:param max_value: if set, makes this a "bounded" semaphore that raises :exc:`ValueError` if the
semaphore's value would exceed this number
:return: a semaphore object
.. deprecated:: 3.0
Use :class:`~Semaphore` directly.
"""
warn(
"create_semaphore() is deprecated -- use Semaphore() directly",
DeprecationWarning,
)
return Semaphore(value, max_value=max_value)
def create_capacity_limiter(total_tokens: float) -> CapacityLimiter:
"""
Create a capacity limiter.
:param total_tokens: the total number of tokens available for borrowing (can be an integer or
:data:`math.inf`)
:return: a capacity limiter object
.. deprecated:: 3.0
Use :class:`~CapacityLimiter` directly.
"""
warn(
"create_capacity_limiter() is deprecated -- use CapacityLimiter() directly",
DeprecationWarning,
)
return get_asynclib().CapacityLimiter(total_tokens)
class ResourceGuard:
__slots__ = "action", "_guarded"
def __init__(self, action: str):
self.action = action
self._guarded = False
def __enter__(self) -> None:
if self._guarded:
raise BusyResourceError(self.action)
self._guarded = True
def __exit__(
self,
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> bool | None:
self._guarded = False
return None
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