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import math
from collections import deque
from collections.abc import Callable
from dataclasses import dataclass
from types import TracebackType
from typing import TypeVar
from ..lowlevel import checkpoint_if_cancelled
from ._eventloop import get_async_backend
from ._exceptions import BusyResourceError, NoEventLoopError
from ._tasks import CancelScope
from ._testing import TaskInfo, get_current_task
T = TypeVar("T")
@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:
try:
return get_async_backend().create_event()
except NoEventLoopError:
return EventAdapter()
def set(self) -> None:
"""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 EventAdapter(Event):
_internal_event: Event | None = None
_is_set: bool = False
def __new__(cls) -> EventAdapter:
return object.__new__(cls)
@property
def _event(self) -> Event:
if self._internal_event is None:
self._internal_event = get_async_backend().create_event()
if self._is_set:
self._internal_event.set()
return self._internal_event
def set(self) -> None:
if self._internal_event is None:
self._is_set = True
else:
self._event.set()
def is_set(self) -> bool:
if self._internal_event is None:
return self._is_set
return self._internal_event.is_set()
async def wait(self) -> None:
await self._event.wait()
def statistics(self) -> EventStatistics:
if self._internal_event is None:
return EventStatistics(tasks_waiting=0)
return self._internal_event.statistics()
class Lock:
def __new__(cls, *, fast_acquire: bool = False) -> Lock:
try:
return get_async_backend().create_lock(fast_acquire=fast_acquire)
except NoEventLoopError:
return LockAdapter(fast_acquire=fast_acquire)
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."""
raise NotImplementedError
def acquire_nowait(self) -> None:
"""
Acquire the lock, without blocking.
:raises ~anyio.WouldBlock: if the operation would block
"""
raise NotImplementedError
def release(self) -> None:
"""Release the lock."""
raise NotImplementedError
def locked(self) -> bool:
"""Return True if the lock is currently held."""
raise NotImplementedError
def statistics(self) -> LockStatistics:
"""
Return statistics about the current state of this lock.
.. versionadded:: 3.0
"""
raise NotImplementedError
class LockAdapter(Lock):
_internal_lock: Lock | None = None
def __new__(cls, *, fast_acquire: bool = False) -> LockAdapter:
return object.__new__(cls)
def __init__(self, *, fast_acquire: bool = False):
self._fast_acquire = fast_acquire
@property
def _lock(self) -> Lock:
if self._internal_lock is None:
self._internal_lock = get_async_backend().create_lock(
fast_acquire=self._fast_acquire
)
return self._internal_lock
async def __aenter__(self) -> None:
await self._lock.acquire()
async def __aexit__(
self,
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> None:
if self._internal_lock is not None:
self._internal_lock.release()
async def acquire(self) -> None:
"""Acquire the lock."""
await self._lock.acquire()
def acquire_nowait(self) -> None:
"""
Acquire the lock, without blocking.
:raises ~anyio.WouldBlock: if the operation would block
"""
self._lock.acquire_nowait()
def release(self) -> None:
"""Release the lock."""
self._lock.release()
def locked(self) -> bool:
"""Return True if the lock is currently held."""
return self._lock.locked()
def statistics(self) -> LockStatistics:
"""
Return statistics about the current state of this lock.
.. versionadded:: 3.0
"""
if self._internal_lock is None:
return LockStatistics(False, None, 0)
return self._internal_lock.statistics()
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 ~anyio.WouldBlock: if the operation would block
"""
self._lock.acquire_nowait()
self._owner_task = get_current_task()
def release(self) -> None:
"""Release the underlying lock."""
self._lock.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_if_cancelled()
self._check_acquired()
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()
async def wait_for(self, predicate: Callable[[], T]) -> T:
"""
Wait until a predicate becomes true.
:param predicate: a callable that returns a truthy value when the condition is
met
:return: the result of the predicate
.. versionadded:: 4.11.0
"""
while not (result := predicate()):
await self.wait()
return result
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 __new__(
cls,
initial_value: int,
*,
max_value: int | None = None,
fast_acquire: bool = False,
) -> Semaphore:
try:
return get_async_backend().create_semaphore(
initial_value, max_value=max_value, fast_acquire=fast_acquire
)
except NoEventLoopError:
return SemaphoreAdapter(initial_value, max_value=max_value)
def __init__(
self,
initial_value: int,
*,
max_value: int | None = None,
fast_acquire: bool = False,
):
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._fast_acquire = fast_acquire
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."""
raise NotImplementedError
def acquire_nowait(self) -> None:
"""
Acquire the underlying lock, without blocking.
:raises ~anyio.WouldBlock: if the operation would block
"""
raise NotImplementedError
def release(self) -> None:
"""Increment the semaphore value."""
raise NotImplementedError
@property
def value(self) -> int:
"""The current value of the semaphore."""
raise NotImplementedError
@property
def max_value(self) -> int | None:
"""The maximum value of the semaphore."""
raise NotImplementedError
def statistics(self) -> SemaphoreStatistics:
"""
Return statistics about the current state of this semaphore.
.. versionadded:: 3.0
"""
raise NotImplementedError
class SemaphoreAdapter(Semaphore):
_internal_semaphore: Semaphore | None = None
def __new__(
cls,
initial_value: int,
*,
max_value: int | None = None,
fast_acquire: bool = False,
) -> SemaphoreAdapter:
return object.__new__(cls)
def __init__(
self,
initial_value: int,
*,
max_value: int | None = None,
fast_acquire: bool = False,
) -> None:
super().__init__(initial_value, max_value=max_value, fast_acquire=fast_acquire)
self._initial_value = initial_value
self._max_value = max_value
@property
def _semaphore(self) -> Semaphore:
if self._internal_semaphore is None:
self._internal_semaphore = get_async_backend().create_semaphore(
self._initial_value, max_value=self._max_value
)
return self._internal_semaphore
async def acquire(self) -> None:
await self._semaphore.acquire()
def acquire_nowait(self) -> None:
self._semaphore.acquire_nowait()
def release(self) -> None:
self._semaphore.release()
@property
def value(self) -> int:
if self._internal_semaphore is None:
return self._initial_value
return self._semaphore.value
@property
def max_value(self) -> int | None:
return self._max_value
def statistics(self) -> SemaphoreStatistics:
if self._internal_semaphore is None:
return SemaphoreStatistics(tasks_waiting=0)
return self._semaphore.statistics()
class CapacityLimiter:
def __new__(cls, total_tokens: float) -> CapacityLimiter:
try:
return get_async_backend().create_capacity_limiter(total_tokens)
except NoEventLoopError:
return CapacityLimiterAdapter(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,
) -> 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.
.. versionchanged:: 4.12
The value can now be set to 0.
"""
raise NotImplementedError
@total_tokens.setter
def total_tokens(self, value: float) -> None:
raise NotImplementedError
@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) -> None:
"""
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) -> None:
"""
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
class CapacityLimiterAdapter(CapacityLimiter):
_internal_limiter: CapacityLimiter | None = None
def __new__(cls, total_tokens: float) -> CapacityLimiterAdapter:
return object.__new__(cls)
def __init__(self, total_tokens: float) -> None:
self.total_tokens = total_tokens
@property
def _limiter(self) -> CapacityLimiter:
if self._internal_limiter is None:
self._internal_limiter = get_async_backend().create_capacity_limiter(
self._total_tokens
)
return self._internal_limiter
async def __aenter__(self) -> None:
await self._limiter.__aenter__()
async def __aexit__(
self,
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> None:
return await self._limiter.__aexit__(exc_type, exc_val, exc_tb)
@property
def total_tokens(self) -> float:
if self._internal_limiter is None:
return self._total_tokens
return self._internal_limiter.total_tokens
@total_tokens.setter
def total_tokens(self, value: float) -> None:
if not isinstance(value, int) and value is not math.inf:
raise TypeError("total_tokens must be an int or math.inf")
elif value < 1:
raise ValueError("total_tokens must be >= 1")
if self._internal_limiter is None:
self._total_tokens = value
return
self._limiter.total_tokens = value
@property
def borrowed_tokens(self) -> int:
if self._internal_limiter is None:
return 0
return self._internal_limiter.borrowed_tokens
@property
def available_tokens(self) -> float:
if self._internal_limiter is None:
return self._total_tokens
return self._internal_limiter.available_tokens
def acquire_nowait(self) -> None:
self._limiter.acquire_nowait()
def acquire_on_behalf_of_nowait(self, borrower: object) -> None:
self._limiter.acquire_on_behalf_of_nowait(borrower)
async def acquire(self) -> None:
await self._limiter.acquire()
async def acquire_on_behalf_of(self, borrower: object) -> None:
await self._limiter.acquire_on_behalf_of(borrower)
def release(self) -> None:
self._limiter.release()
def release_on_behalf_of(self, borrower: object) -> None:
self._limiter.release_on_behalf_of(borrower)
def statistics(self) -> CapacityLimiterStatistics:
if self._internal_limiter is None:
return CapacityLimiterStatistics(
borrowed_tokens=0,
total_tokens=self.total_tokens,
borrowers=(),
tasks_waiting=0,
)
return self._internal_limiter.statistics()
class ResourceGuard:
"""
A context manager for ensuring that a resource is only used by a single task at a
time.
Entering this context manager while the previous has not exited it yet will trigger
:exc:`BusyResourceError`.
:param action: the action to guard against (visible in the :exc:`BusyResourceError`
when triggered, e.g. "Another task is already {action} this resource")
.. versionadded:: 4.1
"""
__slots__ = "action", "_guarded"
def __init__(self, action: str = "using"):
self.action: str = 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,
) -> None:
self._guarded = False
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