54 lines
2.2 KiB
Python
54 lines
2.2 KiB
Python
"""Supervised daemon thread for the in-process cron ticker.
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The gateway (and the Desktop backend) run ``InProcessCronScheduler.start`` on a bare daemon thread.
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Every guard inside ``start`` keeps the loop alive on a per-tick failure, but nothing outside it could
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notice a thread that had already ended — the gateway kept serving while ``ticker_heartbeat`` froze and
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no job fired again until a restart (#111010). The supervisor is the missing outer layer: the
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housekeeping loop asks it once a cycle to respawn a ticker that died while shutdown was not requested.
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"""
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from __future__ import annotations
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import logging
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import threading
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from typing import Any, Callable, Mapping
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logger = logging.getLogger(__name__)
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class SupervisedTickerThread:
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"""``threading.Thread``-shaped handle whose ``restart_if_dead`` respawns a dead ticker."""
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def __init__(self, target: Callable[..., Any], *, args: tuple = (), kwargs: Mapping[str, Any] | None = None,
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stop_event: threading.Event, name: str = "cron-scheduler") -> None:
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self._target, self._args, self._kwargs = target, args, dict(kwargs or {})
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self._stop_event, self._name = stop_event, name
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self._thread = self._spawn()
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self.restarts = 0
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def _spawn(self) -> threading.Thread:
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return threading.Thread(target=self._target, args=self._args, kwargs=self._kwargs, daemon=True, name=self._name)
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def start(self) -> None:
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self._thread.start()
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def is_alive(self) -> bool:
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return self._thread.is_alive()
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def join(self, timeout: float | None = None) -> None:
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self._thread.join(timeout)
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def restart_if_dead(self) -> bool:
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"""Respawn the ticker when it ended without ``stop_event``; True when a restart happened."""
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if self._stop_event.is_set() or self._thread.is_alive():
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return False
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self.restarts += 1
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logger.error(
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"Cron ticker thread %r died without a stop request; restarting (restart #%d). Scheduled jobs "
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"did not fire while it was down — check errors.log for the escaping exception.",
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self._name, self.restarts,
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)
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self._thread = self._spawn()
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self._thread.start()
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return True
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