greatmengqi
3e17417122
Lightweight actor library built on asyncio primitives (~800 lines): - Actor base class with lifecycle hooks (on_started/on_stopped/on_restart) - ActorRef with tell (fire-and-forget) and ask (request-response) - Supervision: OneForOne/AllForOne strategies with restart limits - Middleware pipeline for cross-cutting concerns - Pluggable Mailbox interface (MemoryMailbox default, RedisMailbox optional) - ReplyRegistry + ReplyChannel: ask() works across any mailbox backend - System-level thread pool for blocking I/O (run_in_executor) - Dead letter handling, poison message quarantine, parallel shutdown - 22 tests + benchmark suite
76 lines
2.5 KiB
Python
76 lines
2.5 KiB
Python
"""Supervision strategies — Erlang/Akka-inspired fault tolerance."""
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from __future__ import annotations
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import enum
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import time
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from collections import deque
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from collections.abc import Callable
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from typing import Any
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class Directive(enum.Enum):
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"""What a supervisor should do when a child fails."""
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resume = "resume" # ignore error, keep processing
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restart = "restart" # discard state, create fresh instance
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stop = "stop" # terminate the child permanently
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escalate = "escalate" # propagate to grandparent
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class SupervisorStrategy:
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"""Base class for supervision strategies.
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Args:
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max_restarts: Maximum restarts allowed within *within_seconds*.
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Exceeding this limit stops the child permanently.
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within_seconds: Time window for restart counting.
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decider: Maps exception → Directive. Default: always restart.
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"""
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def __init__(
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self,
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*,
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max_restarts: int = 3,
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within_seconds: float = 60.0,
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decider: Callable[[Exception], Directive] | None = None,
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) -> None:
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self.max_restarts = max_restarts
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self.within_seconds = within_seconds
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self.decider = decider or (lambda _: Directive.restart)
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self._restart_timestamps: dict[str, deque[float]] = {}
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def decide(self, error: Exception) -> Directive:
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return self.decider(error)
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def record_restart(self, child_name: str) -> bool:
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"""Record a restart and return True if within limits."""
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now = time.monotonic()
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if child_name not in self._restart_timestamps:
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self._restart_timestamps[child_name] = deque()
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ts = self._restart_timestamps[child_name]
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# Purge old entries outside the window
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cutoff = now - self.within_seconds
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while ts and ts[0] < cutoff:
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ts.popleft()
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ts.append(now)
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return len(ts) <= self.max_restarts
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def apply_to_children(self, failed_child: str, all_children: list[str]) -> list[str]:
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"""Return which children should be affected by the directive."""
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raise NotImplementedError
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class OneForOneStrategy(SupervisorStrategy):
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"""Only the failed child is affected."""
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def apply_to_children(self, failed_child: str, all_children: list[str]) -> list[str]:
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return [failed_child]
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class AllForOneStrategy(SupervisorStrategy):
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"""All children are affected when any one fails."""
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def apply_to_children(self, failed_child: str, all_children: list[str]) -> list[str]:
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return list(all_children)
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