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