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from __future__ import annotations
import os
import platform
from contextlib import AsyncExitStack
from datetime import datetime, timedelta, timezone
from logging import Logger, getLogger
from typing import Any, Callable, Iterable, Mapping, Optional, Type
from uuid import uuid4
import anyio
from anyio import TASK_STATUS_IGNORED, create_task_group, get_cancelled_exc_class, move_on_after
from anyio.abc import TaskGroup
from ..abc import AsyncDataStore, DataStore, EventSource, Job, Schedule, Trigger
from ..datastores.async_.sync_adapter import AsyncDataStoreAdapter
from ..datastores.sync.memory import MemoryDataStore
from ..enums import CoalescePolicy, ConflictPolicy, RunState
from ..events import (
AsyncEventHub, Event, ScheduleAdded, SchedulerStarted, SchedulerStopped, ScheduleUpdated,
SubscriptionToken)
from ..marshalling import callable_to_ref
from ..structures import Task
from ..workers.async_ import AsyncWorker
class AsyncScheduler(EventSource):
"""An asynchronous (AnyIO based) scheduler implementation."""
data_store: AsyncDataStore
_state: RunState = RunState.stopped
_wakeup_event: anyio.Event
_worker: Optional[AsyncWorker] = None
_task_group: Optional[TaskGroup] = None
def __init__(self, data_store: DataStore | AsyncDataStore | None = None, *,
identity: Optional[str] = None, logger: Optional[Logger] = None,
start_worker: bool = True):
self.identity = identity or f'{platform.node()}-{os.getpid()}-{id(self)}'
self.logger = logger or getLogger(__name__)
self.start_worker = start_worker
self._exit_stack = AsyncExitStack()
self._events = AsyncEventHub()
data_store = data_store or MemoryDataStore()
if isinstance(data_store, DataStore):
self.data_store = AsyncDataStoreAdapter(data_store)
else:
self.data_store = data_store
@property
def worker(self) -> Optional[AsyncWorker]:
return self._worker
async def __aenter__(self):
self._state = RunState.starting
self._wakeup_event = anyio.Event()
await self._exit_stack.__aenter__()
await self._exit_stack.enter_async_context(self._events)
# Initialize the data store
await self._exit_stack.enter_async_context(self.data_store)
relay_token = self._events.relay_events_from(self.data_store)
self._exit_stack.callback(self.data_store.unsubscribe, relay_token)
# Wake up the scheduler if the data store emits a significant schedule event
wakeup_token = self.data_store.subscribe(
lambda event: self._wakeup_event.set(), {ScheduleAdded, ScheduleUpdated})
self._exit_stack.callback(self.data_store.unsubscribe, wakeup_token)
# Start the built-in worker, if configured to do so
if self.start_worker:
self._worker = AsyncWorker(self.data_store)
await self._exit_stack.enter_async_context(self._worker)
# Start the worker and return when it has signalled readiness or raised an exception
self._task_group = create_task_group()
await self._exit_stack.enter_async_context(self._task_group)
await self._task_group.start(self.run)
return self
async def __aexit__(self, exc_type, exc_val, exc_tb):
self._state = RunState.stopping
self._wakeup_event.set()
await self._exit_stack.__aexit__(exc_type, exc_val, exc_tb)
del self._task_group
del self._wakeup_event
def subscribe(self, callback: Callable[[Event], Any],
event_types: Optional[Iterable[Type[Event]]] = None) -> SubscriptionToken:
return self._events.subscribe(callback, event_types)
def unsubscribe(self, token: SubscriptionToken) -> None:
self._events.unsubscribe(token)
async def add_schedule(
self, func_or_task_id: str | Callable, trigger: Trigger, *, id: Optional[str] = None,
args: Optional[Iterable] = None, kwargs: Optional[Mapping[str, Any]] = None,
coalesce: CoalescePolicy = CoalescePolicy.latest,
misfire_grace_time: float | timedelta | None = None, tags: Optional[Iterable[str]] = None,
conflict_policy: ConflictPolicy = ConflictPolicy.do_nothing
) -> str:
id = id or str(uuid4())
args = tuple(args or ())
kwargs = dict(kwargs or {})
tags = frozenset(tags or ())
if isinstance(misfire_grace_time, (int, float)):
misfire_grace_time = timedelta(seconds=misfire_grace_time)
if callable(func_or_task_id):
task = Task(id=callable_to_ref(func_or_task_id), func=func_or_task_id)
await self.data_store.add_task(task)
else:
task = await self.data_store.get_task(func_or_task_id)
schedule = Schedule(id=id, task_id=task.id, trigger=trigger, args=args, kwargs=kwargs,
coalesce=coalesce, misfire_grace_time=misfire_grace_time, tags=tags)
schedule.next_fire_time = trigger.next()
await self.data_store.add_schedule(schedule, conflict_policy)
self.logger.info('Added new schedule (task=%r, trigger=%r); next run time at %s', task,
trigger, schedule.next_fire_time)
return schedule.id
async def remove_schedule(self, schedule_id: str) -> None:
await self.data_store.remove_schedules({schedule_id})
async def run(self, *, task_status=TASK_STATUS_IGNORED) -> None:
if self._state is not RunState.starting:
raise RuntimeError(f'This function cannot be called while the scheduler is in the '
f'{self._state} state')
# Signal that the scheduler has started
self._state = RunState.started
task_status.started()
self._events.publish(SchedulerStarted())
try:
while self._state is RunState.started:
schedules = await self.data_store.acquire_schedules(self.identity, 100)
now = datetime.now(timezone.utc)
for schedule in schedules:
# Calculate a next fire time for the schedule, if possible
fire_times = [schedule.next_fire_time]
calculate_next = schedule.trigger.next
while True:
try:
fire_time = calculate_next()
except Exception:
self.logger.exception(
'Error computing next fire time for schedule %r of task %r – '
'removing schedule', schedule.id, schedule.task_id)
break
# Stop if the calculated fire time is in the future
if fire_time is None or fire_time > now:
schedule.next_fire_time = fire_time
break
# Only keep all the fire times if coalesce policy = "all"
if schedule.coalesce is CoalescePolicy.all:
fire_times.append(fire_time)
elif schedule.coalesce is CoalescePolicy.latest:
fire_times[0] = fire_time
# Add one or more jobs to the job queue
for fire_time in fire_times:
schedule.last_fire_time = fire_time
job = Job(task_id=schedule.task_id, args=schedule.args,
kwargs=schedule.kwargs, schedule_id=schedule.id,
scheduled_fire_time=fire_time,
start_deadline=schedule.next_deadline, tags=schedule.tags)
await self.data_store.add_job(job)
# Update the schedules (and release the scheduler's claim on them)
await self.data_store.release_schedules(self.identity, schedules)
# If we received fewer schedules than the maximum amount, sleep until the next
# schedule is due or the scheduler is explicitly woken up
wait_time = None
if len(schedules) < 100:
next_fire_time = await self.data_store.get_next_schedule_run_time()
if next_fire_time:
wait_time = (datetime.now(timezone.utc) - next_fire_time).total_seconds()
with move_on_after(wait_time):
await self._wakeup_event.wait()
self._wakeup_event = anyio.Event()
except get_cancelled_exc_class():
pass
except BaseException as exc:
self._state = RunState.stopped
self._events.publish(SchedulerStopped(exception=exc))
raise
self._state = RunState.stopped
self._events.publish(SchedulerStopped())
# async def stop(self, force: bool = False) -> None:
# self._running = False
# if self._worker:
# await self._worker.stop(force)
#
# if self._acquire_cancel_scope:
# self._acquire_cancel_scope.cancel()
# if force and self._task_group:
# self._task_group.cancel_scope.cancel()
#
# async def wait_until_stopped(self) -> None:
# if self._stop_event:
# await self._stop_event.wait()
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