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from datetime import datetime
from typing import Callable, Optional, TypeVar, cast
from reactivex import abc, typing
from reactivex.abc.scheduler import SchedulerBase
from reactivex.disposable import Disposable, SingleAssignmentDisposable
from .periodicscheduler import PeriodicScheduler
_TState = TypeVar("_TState")
class CatchScheduler(PeriodicScheduler):
def __init__(
self, scheduler: abc.SchedulerBase, handler: Callable[[Exception], bool]
) -> None:
"""Wraps a scheduler, passed as constructor argument, adding exception
handling for scheduled actions. The handler should return True to
indicate it handled the exception successfully. Falsy return values will
be taken to indicate that the exception should be escalated (raised by
this scheduler).
Args:
scheduler: The scheduler to be wrapped.
handler: Callable to handle exceptions raised by wrapped scheduler.
"""
super().__init__()
self._scheduler: abc.SchedulerBase = scheduler
self._handler: Callable[[Exception], bool] = handler
self._recursive_original: Optional[abc.SchedulerBase] = None
self._recursive_wrapper: Optional["CatchScheduler"] = None
@property
def now(self) -> datetime:
"""Represents a notion of time for this scheduler. Tasks being
scheduled on a scheduler will adhere to the time denoted by this
property.
Returns:
The scheduler's current time, as a datetime instance.
"""
return self._scheduler.now
def schedule(
self, action: typing.ScheduledAction[_TState], state: Optional[_TState] = None
) -> abc.DisposableBase:
"""Schedules an action to be executed.
Args:
action: Action to be executed.
state: [Optional] state to be given to the action function.
Returns:
The disposable object used to cancel the scheduled action
(best effort).
"""
action = self._wrap(action)
return self._scheduler.schedule(action, state=state)
def schedule_relative(
self,
duetime: typing.RelativeTime,
action: typing.ScheduledAction[_TState],
state: Optional[_TState] = None,
) -> abc.DisposableBase:
"""Schedules an action to be executed after duetime.
Args:
duetime: Relative time after which to execute the action.
action: Action to be executed.
state: [Optional] state to be given to the action function.
Returns:
The disposable object used to cancel the scheduled action
(best effort).
"""
action = self._wrap(action)
return self._scheduler.schedule_relative(duetime, action, state=state)
def schedule_absolute(
self,
duetime: typing.AbsoluteTime,
action: typing.ScheduledAction[_TState],
state: Optional[_TState] = None,
) -> abc.DisposableBase:
"""Schedules an action to be executed at duetime.
Args:
duetime: Absolute time at which to execute the action.
action: Action to be executed.
state: [Optional] state to be given to the action function.
Returns:
The disposable object used to cancel the scheduled action
(best effort).
"""
action = self._wrap(action)
return self._scheduler.schedule_absolute(duetime, action, state=state)
def schedule_periodic(
self,
period: typing.RelativeTime,
action: typing.ScheduledPeriodicAction[_TState],
state: Optional[_TState] = None,
) -> abc.DisposableBase:
"""Schedules a periodic piece of work.
Args:
period: Period in seconds or timedelta for running the
work periodically.
action: Action to be executed.
state: [Optional] Initial state passed to the action upon
the first iteration.
Returns:
The disposable object used to cancel the scheduled
recurring action (best effort).
"""
schedule_periodic = getattr(self._scheduler, "schedule_periodic")
if not callable(schedule_periodic):
raise NotImplementedError
disp: SingleAssignmentDisposable = SingleAssignmentDisposable()
failed: bool = False
def periodic(state: Optional[_TState] = None) -> Optional[_TState]:
nonlocal failed
if failed:
return None
try:
return action(state)
except Exception as ex:
failed = True
if not self._handler(ex):
raise
disp.dispose()
return None
scheduler = cast(PeriodicScheduler, self._scheduler)
disp.disposable = scheduler.schedule_periodic(period, periodic, state=state)
return disp
def _clone(self, scheduler: abc.SchedulerBase) -> "CatchScheduler":
return CatchScheduler(scheduler, self._handler)
def _wrap(
self, action: typing.ScheduledAction[_TState]
) -> typing.ScheduledAction[_TState]:
parent = self
def wrapped_action(
self: abc.SchedulerBase, state: Optional[_TState]
) -> Optional[abc.DisposableBase]:
try:
return action(parent._get_recursive_wrapper(self), state)
except Exception as ex:
if not parent._handler(ex):
raise
return Disposable()
return wrapped_action
def _get_recursive_wrapper(self, scheduler: SchedulerBase) -> "CatchScheduler":
if self._recursive_wrapper is None or self._recursive_original != scheduler:
self._recursive_original = scheduler
wrapper = self._clone(scheduler)
wrapper._recursive_original = scheduler
wrapper._recursive_wrapper = wrapper
self._recursive_wrapper = wrapper
return self._recursive_wrapper
|
