Supervision

casty.SupervisionStrategy

Bases: Protocol

Protocol for deciding how to handle actor failures.

Implementations receive the exception raised by a child actor and return a Directive indicating the recovery action.

Examples:

>>> class AlwaysRestart:
...     def decide(self, exception, *, child_id="", **kw):
...         return Directive.restart

decide(exception, *, child_id=..., **kwargs)

casty.OneForOneStrategy

Bases: SupervisionStrategy

Supervision strategy that handles each child failure independently.

Restarts a failing child up to max_restarts times within a sliding time window. If the limit is exceeded the child is stopped.

Parameters:

Name	Type	Description	Default
max_restarts	int	Maximum number of restarts allowed within the time window.	3
within	float	Length of the sliding time window in seconds.	60.0
decider	Callable[[Exception], Directive] | None	Optional function to override the directive for specific exceptions. If it returns Directive.restart, the rate-limit logic still applies.	None

Examples:

>>> from casty import OneForOneStrategy, Directive
>>> strategy = OneForOneStrategy(max_restarts=5, within=30.0)

__init__(max_restarts=3, within=60.0, decider=None)

decide(exception, *, child_id='__default__', **kwargs)

Decide the recovery action for a failed child actor.

Parameters:

Name	Type	Description	Default
exception	Exception	The exception that caused the child to fail.	required
child_id	str	Identifier for the child actor, used to track per-child restart frequency.	'__default__'

Returns:

Type	Description
Directive	The action to take: restart, stop, or escalate.

Examples:

>>> strategy = OneForOneStrategy(max_restarts=1, within=60.0)
>>> strategy.decide(ValueError("bad"), child_id="a")
<Directive.restart: 1>

casty.Directive

Bases: Enum

Action to take when a supervised actor fails.

Examples:

>>> from casty import Directive
>>> Directive.restart
<Directive.restart: 1>

restart = auto() class-attribute instance-attribute

stop = auto() class-attribute instance-attribute

escalate = auto() class-attribute instance-attribute