221 lines
7.5 KiB
Python
221 lines
7.5 KiB
Python
"""Background subtitle translation so long videos do not block HTTP."""
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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 dataclasses import dataclass
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from .ai_tutor import AITutor, AITutorError
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from .models import SentenceBoundaryDocument, SubtitleTranslationItem, SubtitleTranslationResponse
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from .repository import VideoRepository
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logger = logging.getLogger(__name__)
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@dataclass
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class _Job:
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video_hash: str
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done: threading.Event
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lock: threading.Lock
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running: bool = True
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cancelled: bool = False
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error: str | None = None
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thread: threading.Thread | None = None
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class SubtitleTranslationService:
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def __init__(
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self,
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repository: VideoRepository,
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ai_tutor: AITutor,
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*,
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post_wait_seconds: float = 8.0,
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) -> None:
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self.repository = repository
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self._ai_tutor = ai_tutor
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self.post_wait_seconds = post_wait_seconds
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self._lock = threading.Lock()
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self._jobs: dict[str, _Job] = {}
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@property
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def ai_tutor(self) -> AITutor:
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value = self._ai_tutor
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return value() if callable(value) else value
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@ai_tutor.setter
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def ai_tutor(self, value) -> None:
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self._ai_tutor = value
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def snapshot(self, document: SentenceBoundaryDocument) -> SubtitleTranslationResponse:
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translations = [
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SubtitleTranslationItem(index=sentence.index, zh_text=sentence.zh_text)
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for sentence in document.sentences
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if sentence.zh_text and sentence.zh_text.strip()
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]
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needed = [
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sentence
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for sentence in document.sentences
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if (sentence.text or "").strip()
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]
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complete = bool(needed) and all((sentence.zh_text or "").strip() for sentence in needed)
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job = self._jobs.get(document.video_hash)
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running = False
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error: str | None = None
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if job is not None:
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with job.lock:
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running = job.running
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error = job.error
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if complete:
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status = "ready"
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error = None
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elif running:
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status = "running"
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elif error:
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status = "error"
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else:
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status = "idle"
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return SubtitleTranslationResponse(
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video_hash=document.video_hash,
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translations=translations,
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complete=complete,
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status=status,
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error=error,
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)
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def current(self, video_hash: str) -> SubtitleTranslationResponse | None:
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document = self.repository.get_document(video_hash)
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if document is None:
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return None
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return self.snapshot(document)
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def invalidate(self, video_hash: str) -> None:
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"""Stop an in-flight job so stale translations cannot be written back."""
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with self._lock:
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job = self._jobs.pop(video_hash, None)
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if job is None:
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return
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with job.lock:
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job.cancelled = True
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def refresh(self, video_hash: str) -> None:
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"""Drop saved Chinese subtitles and translate the current sentences again."""
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self.invalidate(video_hash)
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self.repository.clear_sentence_translations(video_hash)
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if not getattr(self.ai_tutor, "available", False):
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return
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try:
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self._start_if_needed(video_hash)
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except (KeyError, ValueError, AITutorError):
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logger.exception("Could not restart subtitle translation: video=%s", video_hash)
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def ensure(self, video_hash: str) -> SubtitleTranslationResponse:
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if not getattr(self.ai_tutor, "available", False):
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raise AITutorError("AI translation is not configured.")
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document = self.repository.get_document(video_hash)
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if document is None:
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raise KeyError(video_hash)
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current = self.snapshot(document)
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if current.complete:
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return current
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payload = [
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(sentence.index, sentence.text or "")
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for sentence in document.sentences
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if (sentence.text or "").strip()
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]
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if not payload:
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raise ValueError("No sentence text is available to translate.")
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job = self._start_if_needed(video_hash)
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wait_seconds = max(0.0, float(self.post_wait_seconds))
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if wait_seconds > 0:
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job.done.wait(timeout=wait_seconds)
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latest = self.current(video_hash)
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if latest is None:
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raise KeyError(video_hash)
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return latest
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def _start_if_needed(self, video_hash: str) -> _Job:
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with self._lock:
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existing = self._jobs.get(video_hash)
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if existing is not None:
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with existing.lock:
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still_running = (
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not existing.cancelled
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and (
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existing.running
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or (
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existing.thread is not None
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and existing.thread.is_alive()
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)
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)
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)
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if still_running:
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return existing
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job = _Job(
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video_hash=video_hash,
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done=threading.Event(),
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lock=threading.Lock(),
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)
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thread = threading.Thread(
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target=self._run_job,
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args=(job,),
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name=f"subtitle-translate-{video_hash[:8]}",
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daemon=True,
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)
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job.thread = thread
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self._jobs[video_hash] = job
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thread.start()
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return job
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def _persist(self, job: _Job, translations: dict[int, str]) -> None:
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with job.lock:
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if job.cancelled:
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return
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self.repository.save_sentence_translations(job.video_hash, translations)
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def _run_job(self, job: _Job) -> None:
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try:
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with job.lock:
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if job.cancelled:
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return
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document = self.repository.get_document(job.video_hash)
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if document is None:
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raise AITutorError("Course is not available.")
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payload = [
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(sentence.index, sentence.text or "")
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for sentence in document.sentences
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if (sentence.text or "").strip()
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]
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if not payload:
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return
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existing = {
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sentence.index: sentence.zh_text
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for sentence in document.sentences
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if sentence.zh_text and sentence.zh_text.strip()
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}
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video = self.repository.get_video(job.video_hash)
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translated = self.ai_tutor.translate_sentences(
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payload,
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course_title=(video["title"] if video is not None else "") or "",
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existing=existing,
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persist=lambda part: self._persist(job, part),
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)
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if translated:
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self._persist(job, translated)
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with job.lock:
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if not job.cancelled:
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job.error = None
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except Exception as exc: # noqa: BLE001 - surface job failure to clients
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with job.lock:
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cancelled = job.cancelled
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if cancelled:
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return
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logger.exception("Subtitle translation job failed: video=%s", job.video_hash)
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with job.lock:
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job.error = str(exc)
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finally:
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with job.lock:
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job.running = False
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job.done.set()
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