116 lines
3.7 KiB
Python
116 lines
3.7 KiB
Python
# SPDX-License-Identifier: Apache-2.0
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# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
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"""Stable POSIX advisory locks used by the filesystem store."""
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from __future__ import annotations
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import errno
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import fcntl
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import os
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import time
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from pathlib import Path
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class FileLockTimeoutError(TimeoutError):
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pass
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class FileLock:
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"""One held flock whose inode is stable outside artifact directories."""
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def __init__(self, path: Path, *, exclusive: bool, deadline: float | None, nonblocking: bool = False) -> None:
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path.parent.mkdir(parents=True, exist_ok=True)
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self.path = path
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self._fd = os.open(path, os.O_CREAT | os.O_RDWR | os.O_CLOEXEC | os.O_NOFOLLOW, 0o600)
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self._creator_pid = os.getpid()
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self._closed = False
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operation = fcntl.LOCK_EX if exclusive else fcntl.LOCK_SH
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if nonblocking:
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operation |= fcntl.LOCK_NB
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try:
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if nonblocking:
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self._acquire_once(operation)
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elif deadline is None:
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self._acquire_blocking(operation)
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else:
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self._acquire_until(operation | fcntl.LOCK_NB, deadline)
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except BaseException:
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os.close(self._fd)
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self._closed = True
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raise
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def _acquire_once(self, operation: int) -> None:
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try:
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fcntl.flock(self._fd, operation)
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except OSError as exc:
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if exc.errno in (errno.EACCES, errno.EAGAIN):
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raise FileLockTimeoutError(f"lock is active: {self.path}") from exc
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raise
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def _acquire_blocking(self, operation: int) -> None:
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while True:
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try:
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fcntl.flock(self._fd, operation)
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return
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except OSError as exc:
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if exc.errno != errno.EINTR:
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raise
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def _acquire_until(self, operation: int, deadline: float) -> None:
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while True:
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try:
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fcntl.flock(self._fd, operation)
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return
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except OSError as exc:
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if exc.errno == errno.EINTR:
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continue
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if exc.errno not in (errno.EACCES, errno.EAGAIN):
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raise
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remaining = deadline - time.monotonic()
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if remaining <= 0:
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raise FileLockTimeoutError(f"timed out waiting for {self.path}") from exc
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time.sleep(min(0.05, remaining))
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def close(self) -> None:
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if self._closed:
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return
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self._closed = True
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if os.getpid() != self._creator_pid:
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# flock state belongs to the inherited open-file description. A
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# child must only drop its descriptor reference; LOCK_UN would
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# release the creator process's active lock as well.
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os.close(self._fd)
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return
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try:
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fcntl.flock(self._fd, fcntl.LOCK_UN)
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finally:
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os.close(self._fd)
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def __enter__(self) -> FileLock:
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return self
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def __exit__(self, exc_type: object, exc: object, _traceback: object) -> None:
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self.close()
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def lock_is_active(path: Path) -> bool:
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"""Return a point-in-time contention snapshot without creating a lock file."""
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try:
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fd = os.open(path, os.O_RDWR | os.O_CLOEXEC | os.O_NOFOLLOW)
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except FileNotFoundError:
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return False
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try:
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try:
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fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
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except OSError as exc:
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if exc.errno in (errno.EACCES, errno.EAGAIN):
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return True
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raise
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fcntl.flock(fd, fcntl.LOCK_UN)
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return False
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finally:
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os.close(fd)
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__all__ = ["FileLock", "FileLockTimeoutError", "lock_is_active"]
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