mirror of
https://github.com/GNS3/gns3-server.git
synced 2026-10-03 17:20:16 +03:00
100 lines
3.0 KiB
Python
100 lines
3.0 KiB
Python
"""Filesystem primitives shared by image writers and inventory reconciliation."""
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import asyncio
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import hashlib
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import os
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import stat
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from gns3server.config import Config
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def normalized_path(path):
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return os.path.normcase(os.path.abspath(os.path.expanduser(path)))
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def contained_path(path, root):
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try:
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return os.path.commonpath((normalized_path(path), normalized_path(root))) == normalized_path(root)
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except ValueError:
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return False
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def fingerprint(path):
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info = os.stat(path, follow_symlinks=True)
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if not stat.S_ISREG(info.st_mode):
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raise OSError(f"Not a regular image file: {path}")
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return stat_fingerprint(info)
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def stat_fingerprint(info):
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# Store as text: inode/device numbers need not fit a signed SQL BIGINT.
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return ":".join(
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str(value) for value in (info.st_dev, info.st_ino, info.st_size, info.st_mtime_ns, info.st_ctime_ns)
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)
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class ImageLockBusy(Exception):
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pass
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class ImageLock:
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"""Advisory lock shared by controller processes using the same config directory.
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Lock files are deliberately retained: unlinking them permits two processes to
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lock different inodes for the same name. OS locks are released on process exit.
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"""
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def __init__(self, key, wait=True):
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self.key = key
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self.wait = wait
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self._file = None
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async def __aenter__(self):
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directory = os.path.join(Config.instance().config_dir, ".image-locks")
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os.makedirs(directory, exist_ok=True)
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path = os.path.join(directory, hashlib.sha256(self.key.encode()).hexdigest() + ".lock")
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self._file = open(path, "a+b")
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if os.name == "nt" and os.fstat(self._file.fileno()).st_size == 0:
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self._file.write(b"\0")
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self._file.flush()
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try:
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while True:
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try:
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if os.name == "nt":
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import msvcrt
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self._file.seek(0)
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msvcrt.locking(self._file.fileno(), msvcrt.LK_NBLCK, 1)
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else:
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import fcntl
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fcntl.flock(self._file, fcntl.LOCK_EX | fcntl.LOCK_NB)
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return self
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except (BlockingIOError, PermissionError):
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if not self.wait:
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raise ImageLockBusy(self.key)
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await asyncio.sleep(0.05)
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except BaseException:
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self._file.close()
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self._file = None
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raise
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async def __aexit__(self, *args):
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if self._file is not None:
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self._file.close()
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self._file = None
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def image_lock(path):
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return ImageLock("image:" + normalized_path(os.path.realpath(path)))
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def publish_image(temporary, destination):
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"""Atomically publish a complete file without replacing an existing image.
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Both paths must be on the same filesystem. Hard linking provides the atomic
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no-overwrite operation that os.replace()/shutil.move() cannot provide.
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"""
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os.link(temporary, destination)
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os.unlink(temporary)
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