root / lib / utils / io.py @ 7b0bf9cd
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#
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#
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# Copyright (C) 2006, 2007, 2010, 2011 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Utility functions for I/O.
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"""
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import os |
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import logging |
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import shutil |
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import tempfile |
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import errno |
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import time |
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from ganeti import errors |
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from ganeti import constants |
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from ganeti.utils import filelock |
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#: Path generating random UUID
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_RANDOM_UUID_FILE = "/proc/sys/kernel/random/uuid"
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def ReadFile(file_name, size=-1): |
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"""Reads a file.
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@type size: int
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@param size: Read at most size bytes (if negative, entire file)
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@rtype: str
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@return: the (possibly partial) content of the file
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"""
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f = open(file_name, "r") |
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try:
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return f.read(size)
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finally:
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f.close() |
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def WriteFile(file_name, fn=None, data=None, |
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mode=None, uid=-1, gid=-1, |
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atime=None, mtime=None, close=True, |
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dry_run=False, backup=False, |
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prewrite=None, postwrite=None): |
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"""(Over)write a file atomically.
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The file_name and either fn (a function taking one argument, the
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file descriptor, and which should write the data to it) or data (the
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contents of the file) must be passed. The other arguments are
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optional and allow setting the file mode, owner and group, and the
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mtime/atime of the file.
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If the function doesn't raise an exception, it has succeeded and the
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target file has the new contents. If the function has raised an
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exception, an existing target file should be unmodified and the
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temporary file should be removed.
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@type file_name: str
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@param file_name: the target filename
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@type fn: callable
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@param fn: content writing function, called with
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file descriptor as parameter
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@type data: str
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@param data: contents of the file
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@type mode: int
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@param mode: file mode
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@type uid: int
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@param uid: the owner of the file
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@type gid: int
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@param gid: the group of the file
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@type atime: int
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@param atime: a custom access time to be set on the file
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@type mtime: int
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@param mtime: a custom modification time to be set on the file
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@type close: boolean
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@param close: whether to close file after writing it
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@type prewrite: callable
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@param prewrite: function to be called before writing content
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@type postwrite: callable
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@param postwrite: function to be called after writing content
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@rtype: None or int
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@return: None if the 'close' parameter evaluates to True,
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otherwise the file descriptor
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@raise errors.ProgrammerError: if any of the arguments are not valid
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"""
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if not os.path.isabs(file_name): |
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raise errors.ProgrammerError("Path passed to WriteFile is not" |
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" absolute: '%s'" % file_name)
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if [fn, data].count(None) != 1: |
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raise errors.ProgrammerError("fn or data required") |
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if [atime, mtime].count(None) == 1: |
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raise errors.ProgrammerError("Both atime and mtime must be either" |
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" set or None")
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if backup and not dry_run and os.path.isfile(file_name): |
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CreateBackup(file_name) |
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dir_name, base_name = os.path.split(file_name) |
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fd, new_name = tempfile.mkstemp('.new', base_name, dir_name)
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do_remove = True
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# here we need to make sure we remove the temp file, if any error
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# leaves it in place
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try:
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if uid != -1 or gid != -1: |
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os.chown(new_name, uid, gid) |
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if mode:
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os.chmod(new_name, mode) |
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if callable(prewrite): |
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prewrite(fd) |
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if data is not None: |
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os.write(fd, data) |
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else:
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fn(fd) |
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if callable(postwrite): |
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postwrite(fd) |
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os.fsync(fd) |
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if atime is not None and mtime is not None: |
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os.utime(new_name, (atime, mtime)) |
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if not dry_run: |
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os.rename(new_name, file_name) |
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do_remove = False
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finally:
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if close:
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os.close(fd) |
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result = None
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else:
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result = fd |
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if do_remove:
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RemoveFile(new_name) |
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return result
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def GetFileID(path=None, fd=None): |
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"""Returns the file 'id', i.e. the dev/inode and mtime information.
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Either the path to the file or the fd must be given.
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@param path: the file path
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@param fd: a file descriptor
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@return: a tuple of (device number, inode number, mtime)
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"""
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if [path, fd].count(None) != 1: |
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raise errors.ProgrammerError("One and only one of fd/path must be given") |
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if fd is None: |
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st = os.stat(path) |
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else:
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st = os.fstat(fd) |
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return (st.st_dev, st.st_ino, st.st_mtime)
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def VerifyFileID(fi_disk, fi_ours): |
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"""Verifies that two file IDs are matching.
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Differences in the inode/device are not accepted, but and older
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timestamp for fi_disk is accepted.
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@param fi_disk: tuple (dev, inode, mtime) representing the actual
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file data
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@param fi_ours: tuple (dev, inode, mtime) representing the last
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written file data
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@rtype: boolean
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"""
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(d1, i1, m1) = fi_disk |
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(d2, i2, m2) = fi_ours |
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return (d1, i1) == (d2, i2) and m1 <= m2 |
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def SafeWriteFile(file_name, file_id, **kwargs): |
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"""Wraper over L{WriteFile} that locks the target file.
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By keeping the target file locked during WriteFile, we ensure that
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cooperating writers will safely serialise access to the file.
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@type file_name: str
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@param file_name: the target filename
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@type file_id: tuple
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@param file_id: a result from L{GetFileID}
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"""
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fd = os.open(file_name, os.O_RDONLY | os.O_CREAT) |
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try:
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filelock.LockFile(fd) |
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if file_id is not None: |
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disk_id = GetFileID(fd=fd) |
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if not VerifyFileID(disk_id, file_id): |
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raise errors.LockError("Cannot overwrite file %s, it has been modified" |
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" since last written" % file_name)
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return WriteFile(file_name, **kwargs)
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finally:
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os.close(fd) |
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def ReadOneLineFile(file_name, strict=False): |
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"""Return the first non-empty line from a file.
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@type strict: boolean
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@param strict: if True, abort if the file has more than one
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non-empty line
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"""
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file_lines = ReadFile(file_name).splitlines() |
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full_lines = filter(bool, file_lines) |
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if not file_lines or not full_lines: |
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raise errors.GenericError("No data in one-liner file %s" % file_name) |
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elif strict and len(full_lines) > 1: |
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raise errors.GenericError("Too many lines in one-liner file %s" % |
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file_name) |
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return full_lines[0] |
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def RemoveFile(filename): |
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"""Remove a file ignoring some errors.
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Remove a file, ignoring non-existing ones or directories. Other
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errors are passed.
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@type filename: str
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@param filename: the file to be removed
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"""
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try:
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os.unlink(filename) |
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except OSError, err: |
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if err.errno not in (errno.ENOENT, errno.EISDIR): |
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raise
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def RemoveDir(dirname): |
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"""Remove an empty directory.
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Remove a directory, ignoring non-existing ones.
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Other errors are passed. This includes the case,
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where the directory is not empty, so it can't be removed.
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@type dirname: str
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@param dirname: the empty directory to be removed
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"""
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try:
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os.rmdir(dirname) |
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except OSError, err: |
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if err.errno != errno.ENOENT:
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raise
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def RenameFile(old, new, mkdir=False, mkdir_mode=0750): |
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"""Renames a file.
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@type old: string
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@param old: Original path
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@type new: string
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@param new: New path
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@type mkdir: bool
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@param mkdir: Whether to create target directory if it doesn't exist
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@type mkdir_mode: int
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@param mkdir_mode: Mode for newly created directories
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"""
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try:
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return os.rename(old, new)
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except OSError, err: |
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# In at least one use case of this function, the job queue, directory
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# creation is very rare. Checking for the directory before renaming is not
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# as efficient.
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if mkdir and err.errno == errno.ENOENT: |
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# Create directory and try again
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Makedirs(os.path.dirname(new), mode=mkdir_mode) |
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return os.rename(old, new)
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raise
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def Makedirs(path, mode=0750): |
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"""Super-mkdir; create a leaf directory and all intermediate ones.
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This is a wrapper around C{os.makedirs} adding error handling not implemented
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before Python 2.5.
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"""
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try:
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os.makedirs(path, mode) |
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except OSError, err: |
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# Ignore EEXIST. This is only handled in os.makedirs as included in
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# Python 2.5 and above.
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if err.errno != errno.EEXIST or not os.path.exists(path): |
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raise
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def TimestampForFilename(): |
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"""Returns the current time formatted for filenames.
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The format doesn't contain colons as some shells and applications treat them
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as separators. Uses the local timezone.
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"""
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return time.strftime("%Y-%m-%d_%H_%M_%S") |
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def CreateBackup(file_name): |
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"""Creates a backup of a file.
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@type file_name: str
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@param file_name: file to be backed up
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@rtype: str
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@return: the path to the newly created backup
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@raise errors.ProgrammerError: for invalid file names
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"""
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if not os.path.isfile(file_name): |
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raise errors.ProgrammerError("Can't make a backup of a non-file '%s'" % |
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file_name) |
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prefix = ("%s.backup-%s." %
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(os.path.basename(file_name), TimestampForFilename())) |
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dir_name = os.path.dirname(file_name) |
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fsrc = open(file_name, 'rb') |
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try:
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(fd, backup_name) = tempfile.mkstemp(prefix=prefix, dir=dir_name) |
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fdst = os.fdopen(fd, 'wb')
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try:
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logging.debug("Backing up %s at %s", file_name, backup_name)
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shutil.copyfileobj(fsrc, fdst) |
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finally:
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fdst.close() |
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finally:
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fsrc.close() |
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return backup_name
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def ListVisibleFiles(path): |
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"""Returns a list of visible files in a directory.
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@type path: str
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@param path: the directory to enumerate
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@rtype: list
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@return: the list of all files not starting with a dot
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@raise ProgrammerError: if L{path} is not an absolue and normalized path
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"""
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if not IsNormAbsPath(path): |
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raise errors.ProgrammerError("Path passed to ListVisibleFiles is not" |
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" absolute/normalized: '%s'" % path)
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files = [i for i in os.listdir(path) if not i.startswith(".")] |
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return files
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def EnsureDirs(dirs): |
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"""Make required directories, if they don't exist.
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@param dirs: list of tuples (dir_name, dir_mode)
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@type dirs: list of (string, integer)
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"""
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for dir_name, dir_mode in dirs: |
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try:
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os.mkdir(dir_name, dir_mode) |
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except EnvironmentError, err: |
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if err.errno != errno.EEXIST:
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raise errors.GenericError("Cannot create needed directory" |
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" '%s': %s" % (dir_name, err))
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try:
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os.chmod(dir_name, dir_mode) |
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except EnvironmentError, err: |
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raise errors.GenericError("Cannot change directory permissions on" |
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" '%s': %s" % (dir_name, err))
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if not os.path.isdir(dir_name): |
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raise errors.GenericError("%s is not a directory" % dir_name) |
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def FindFile(name, search_path, test=os.path.exists): |
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"""Look for a filesystem object in a given path.
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This is an abstract method to search for filesystem object (files,
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dirs) under a given search path.
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@type name: str
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@param name: the name to look for
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@type search_path: str
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@param search_path: location to start at
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@type test: callable
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@param test: a function taking one argument that should return True
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if the a given object is valid; the default value is
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os.path.exists, causing only existing files to be returned
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@rtype: str or None
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@return: full path to the object if found, None otherwise
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"""
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# validate the filename mask
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if constants.EXT_PLUGIN_MASK.match(name) is None: |
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logging.critical("Invalid value passed for external script name: '%s'",
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name) |
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return None |
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for dir_name in search_path: |
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# FIXME: investigate switch to PathJoin
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item_name = os.path.sep.join([dir_name, name]) |
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# check the user test and that we're indeed resolving to the given
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# basename
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if test(item_name) and os.path.basename(item_name) == name: |
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return item_name
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return None |
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def IsNormAbsPath(path): |
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"""Check whether a path is absolute and also normalized
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This avoids things like /dir/../../other/path to be valid.
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"""
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return os.path.normpath(path) == path and os.path.isabs(path) |
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def PathJoin(*args): |
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"""Safe-join a list of path components.
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Requirements:
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- the first argument must be an absolute path
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- no component in the path must have backtracking (e.g. /../),
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since we check for normalization at the end
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@param args: the path components to be joined
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@raise ValueError: for invalid paths
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"""
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# ensure we're having at least one path passed in
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assert args
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# ensure the first component is an absolute and normalized path name
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root = args[0]
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if not IsNormAbsPath(root): |
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raise ValueError("Invalid parameter to PathJoin: '%s'" % str(args[0])) |
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result = os.path.join(*args) |
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# ensure that the whole path is normalized
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if not IsNormAbsPath(result): |
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raise ValueError("Invalid parameters to PathJoin: '%s'" % str(args)) |
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# check that we're still under the original prefix
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prefix = os.path.commonprefix([root, result]) |
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if prefix != root:
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raise ValueError("Error: path joining resulted in different prefix" |
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" (%s != %s)" % (prefix, root))
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return result
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def TailFile(fname, lines=20): |
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"""Return the last lines from a file.
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@note: this function will only read and parse the last 4KB of
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the file; if the lines are very long, it could be that less
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than the requested number of lines are returned
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@param fname: the file name
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@type lines: int
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@param lines: the (maximum) number of lines to return
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"""
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fd = open(fname, "r") |
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try:
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fd.seek(0, 2) |
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pos = fd.tell() |
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pos = max(0, pos-4096) |
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fd.seek(pos, 0)
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raw_data = fd.read() |
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finally:
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fd.close() |
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rows = raw_data.splitlines() |
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return rows[-lines:]
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def BytesToMebibyte(value): |
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"""Converts bytes to mebibytes.
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@type value: int
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@param value: Value in bytes
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@rtype: int
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@return: Value in mebibytes
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"""
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return int(round(value / (1024.0 * 1024.0), 0)) |
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def CalculateDirectorySize(path): |
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"""Calculates the size of a directory recursively.
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|
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@type path: string
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@param path: Path to directory
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@rtype: int
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@return: Size in mebibytes
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|
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"""
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size = 0
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|
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for (curpath, _, files) in os.walk(path): |
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for filename in files: |
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st = os.lstat(PathJoin(curpath, filename)) |
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size += st.st_size |
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|
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return BytesToMebibyte(size)
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|
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|
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def GetFilesystemStats(path): |
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"""Returns the total and free space on a filesystem.
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|
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@type path: string
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@param path: Path on filesystem to be examined
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@rtype: int
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537 |
@return: tuple of (Total space, Free space) in mebibytes
|
538 |
|
539 |
"""
|
540 |
st = os.statvfs(path) |
541 |
|
542 |
fsize = BytesToMebibyte(st.f_bavail * st.f_frsize) |
543 |
tsize = BytesToMebibyte(st.f_blocks * st.f_frsize) |
544 |
return (tsize, fsize)
|
545 |
|
546 |
|
547 |
def ReadPidFile(pidfile): |
548 |
"""Read a pid from a file.
|
549 |
|
550 |
@type pidfile: string
|
551 |
@param pidfile: path to the file containing the pid
|
552 |
@rtype: int
|
553 |
@return: The process id, if the file exists and contains a valid PID,
|
554 |
otherwise 0
|
555 |
|
556 |
"""
|
557 |
try:
|
558 |
raw_data = ReadOneLineFile(pidfile) |
559 |
except EnvironmentError, err: |
560 |
if err.errno != errno.ENOENT:
|
561 |
logging.exception("Can't read pid file")
|
562 |
return 0 |
563 |
|
564 |
try:
|
565 |
pid = int(raw_data)
|
566 |
except (TypeError, ValueError), err: |
567 |
logging.info("Can't parse pid file contents", exc_info=True) |
568 |
return 0 |
569 |
|
570 |
return pid
|
571 |
|
572 |
|
573 |
def ReadLockedPidFile(path): |
574 |
"""Reads a locked PID file.
|
575 |
|
576 |
This can be used together with L{utils.process.StartDaemon}.
|
577 |
|
578 |
@type path: string
|
579 |
@param path: Path to PID file
|
580 |
@return: PID as integer or, if file was unlocked or couldn't be opened, None
|
581 |
|
582 |
"""
|
583 |
try:
|
584 |
fd = os.open(path, os.O_RDONLY) |
585 |
except EnvironmentError, err: |
586 |
if err.errno == errno.ENOENT:
|
587 |
# PID file doesn't exist
|
588 |
return None |
589 |
raise
|
590 |
|
591 |
try:
|
592 |
try:
|
593 |
# Try to acquire lock
|
594 |
filelock.LockFile(fd) |
595 |
except errors.LockError:
|
596 |
# Couldn't lock, daemon is running
|
597 |
return int(os.read(fd, 100)) |
598 |
finally:
|
599 |
os.close(fd) |
600 |
|
601 |
return None |
602 |
|
603 |
|
604 |
def AddAuthorizedKey(file_obj, key): |
605 |
"""Adds an SSH public key to an authorized_keys file.
|
606 |
|
607 |
@type file_obj: str or file handle
|
608 |
@param file_obj: path to authorized_keys file
|
609 |
@type key: str
|
610 |
@param key: string containing key
|
611 |
|
612 |
"""
|
613 |
key_fields = key.split() |
614 |
|
615 |
if isinstance(file_obj, basestring): |
616 |
f = open(file_obj, 'a+') |
617 |
else:
|
618 |
f = file_obj |
619 |
|
620 |
try:
|
621 |
nl = True
|
622 |
for line in f: |
623 |
# Ignore whitespace changes
|
624 |
if line.split() == key_fields:
|
625 |
break
|
626 |
nl = line.endswith('\n')
|
627 |
else:
|
628 |
if not nl: |
629 |
f.write("\n")
|
630 |
f.write(key.rstrip('\r\n'))
|
631 |
f.write("\n")
|
632 |
f.flush() |
633 |
finally:
|
634 |
f.close() |
635 |
|
636 |
|
637 |
def RemoveAuthorizedKey(file_name, key): |
638 |
"""Removes an SSH public key from an authorized_keys file.
|
639 |
|
640 |
@type file_name: str
|
641 |
@param file_name: path to authorized_keys file
|
642 |
@type key: str
|
643 |
@param key: string containing key
|
644 |
|
645 |
"""
|
646 |
key_fields = key.split() |
647 |
|
648 |
fd, tmpname = tempfile.mkstemp(dir=os.path.dirname(file_name)) |
649 |
try:
|
650 |
out = os.fdopen(fd, 'w')
|
651 |
try:
|
652 |
f = open(file_name, 'r') |
653 |
try:
|
654 |
for line in f: |
655 |
# Ignore whitespace changes while comparing lines
|
656 |
if line.split() != key_fields:
|
657 |
out.write(line) |
658 |
|
659 |
out.flush() |
660 |
os.rename(tmpname, file_name) |
661 |
finally:
|
662 |
f.close() |
663 |
finally:
|
664 |
out.close() |
665 |
except:
|
666 |
RemoveFile(tmpname) |
667 |
raise
|
668 |
|
669 |
|
670 |
def DaemonPidFileName(name): |
671 |
"""Compute a ganeti pid file absolute path
|
672 |
|
673 |
@type name: str
|
674 |
@param name: the daemon name
|
675 |
@rtype: str
|
676 |
@return: the full path to the pidfile corresponding to the given
|
677 |
daemon name
|
678 |
|
679 |
"""
|
680 |
return PathJoin(constants.RUN_GANETI_DIR, "%s.pid" % name) |
681 |
|
682 |
|
683 |
def WritePidFile(pidfile): |
684 |
"""Write the current process pidfile.
|
685 |
|
686 |
@type pidfile: string
|
687 |
@param pidfile: the path to the file to be written
|
688 |
@raise errors.LockError: if the pid file already exists and
|
689 |
points to a live process
|
690 |
@rtype: int
|
691 |
@return: the file descriptor of the lock file; do not close this unless
|
692 |
you want to unlock the pid file
|
693 |
|
694 |
"""
|
695 |
# We don't rename nor truncate the file to not drop locks under
|
696 |
# existing processes
|
697 |
fd_pidfile = os.open(pidfile, os.O_WRONLY | os.O_CREAT, 0600)
|
698 |
|
699 |
# Lock the PID file (and fail if not possible to do so). Any code
|
700 |
# wanting to send a signal to the daemon should try to lock the PID
|
701 |
# file before reading it. If acquiring the lock succeeds, the daemon is
|
702 |
# no longer running and the signal should not be sent.
|
703 |
filelock.LockFile(fd_pidfile) |
704 |
|
705 |
os.write(fd_pidfile, "%d\n" % os.getpid())
|
706 |
|
707 |
return fd_pidfile
|
708 |
|
709 |
|
710 |
def ReadWatcherPauseFile(filename, now=None, remove_after=3600): |
711 |
"""Reads the watcher pause file.
|
712 |
|
713 |
@type filename: string
|
714 |
@param filename: Path to watcher pause file
|
715 |
@type now: None, float or int
|
716 |
@param now: Current time as Unix timestamp
|
717 |
@type remove_after: int
|
718 |
@param remove_after: Remove watcher pause file after specified amount of
|
719 |
seconds past the pause end time
|
720 |
|
721 |
"""
|
722 |
if now is None: |
723 |
now = time.time() |
724 |
|
725 |
try:
|
726 |
value = ReadFile(filename) |
727 |
except IOError, err: |
728 |
if err.errno != errno.ENOENT:
|
729 |
raise
|
730 |
value = None
|
731 |
|
732 |
if value is not None: |
733 |
try:
|
734 |
value = int(value)
|
735 |
except ValueError: |
736 |
logging.warning(("Watcher pause file (%s) contains invalid value,"
|
737 |
" removing it"), filename)
|
738 |
RemoveFile(filename) |
739 |
value = None
|
740 |
|
741 |
if value is not None: |
742 |
# Remove file if it's outdated
|
743 |
if now > (value + remove_after):
|
744 |
RemoveFile(filename) |
745 |
value = None
|
746 |
|
747 |
elif now > value:
|
748 |
value = None
|
749 |
|
750 |
return value
|
751 |
|
752 |
|
753 |
def NewUUID(): |
754 |
"""Returns a random UUID.
|
755 |
|
756 |
@note: This is a Linux-specific method as it uses the /proc
|
757 |
filesystem.
|
758 |
@rtype: str
|
759 |
|
760 |
"""
|
761 |
return ReadFile(_RANDOM_UUID_FILE, size=128).rstrip("\n") |