68 lines
2.0 KiB
Python
68 lines
2.0 KiB
Python
"""Crash-safe interprocess locking scoped by workspace and job type."""
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from __future__ import annotations
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import fcntl
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import hashlib
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import os
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import re
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from pathlib import Path
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from types import TracebackType
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class JobAlreadyRunningError(RuntimeError):
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pass
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_JOB_KEY = re.compile(r"^[a-z][a-z0-9_-]{0,63}$")
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def _lock_name(workspace_id: str, job_type: str) -> str:
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if not _JOB_KEY.fullmatch(workspace_id) or not _JOB_KEY.fullmatch(job_type):
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raise ValueError("lock identifiers must be lowercase filesystem-safe keys")
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workspace_key = hashlib.sha256(workspace_id.encode("utf-8")).hexdigest()[:16]
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return f"{workspace_key}-{job_type}.lock"
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class WorkspaceJobLock:
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"""Advisory kernel lock; the inode remains stable and is never deleted by PID."""
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def __init__(self, workspace_root: Path, workspace_id: str, job_type: str) -> None:
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self.path = workspace_root / ".tht-jobs" / ".locks" / _lock_name(
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workspace_id, job_type
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)
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self._fd: int | None = None
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def acquire(self) -> "WorkspaceJobLock":
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if self._fd is not None:
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raise RuntimeError("job lock is already held by this object")
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self.path.parent.mkdir(parents=True, exist_ok=True)
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fd = os.open(self.path, os.O_RDWR | os.O_CREAT, 0o600)
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try:
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fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
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except BlockingIOError as error:
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os.close(fd)
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raise JobAlreadyRunningError("this workspace job is already running") from error
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self._fd = fd
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return self
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def release(self) -> None:
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if self._fd is None:
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return
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fd, self._fd = self._fd, None
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try:
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fcntl.flock(fd, fcntl.LOCK_UN)
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finally:
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os.close(fd)
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def __enter__(self) -> "WorkspaceJobLock":
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return self.acquire()
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def __exit__(
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self,
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exc_type: type[BaseException] | None,
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exc: BaseException | None,
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traceback: TracebackType | None,
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) -> None:
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self.release()
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