Package ganeti :: Package utils :: Module io

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Module io

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Utility functions for I/O.

Functions

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str

ReadFile(file_name, size=-1, preread=None)
Reads a file.

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None or int

WriteFile(file_name, fn=None, data=None, mode=None, uid=-1, gid=-1, atime=None, mtime=None, close=True, dry_run=False, backup=False, prewrite=None, postwrite=None)
(Over)write a file atomically.

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GetFileID(path=None, fd=None)
Returns the file 'id', i.e.

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boolean

VerifyFileID(fi_disk, fi_ours)
Verifies that two file IDs are matching.

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SafeWriteFile(file_name, file_id, **kwargs)
Wraper over WriteFile that locks the target file.

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ReadOneLineFile(file_name, strict=False)
Return the first non-empty line from a file.

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RemoveFile(filename)
Remove a file ignoring some errors.

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RemoveDir(dirname)
Remove an empty directory.

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RenameFile(old, new, mkdir=False, mkdir_mode=0750, dir_uid=None, dir_gid=None)
Renames a file.

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Makedirs(path, mode=0750)
Super-mkdir; create a leaf directory and all intermediate ones.

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TimestampForFilename()
Returns the current time formatted for filenames.

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str

CreateBackup(file_name)
Creates a backup of a file.

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list

ListVisibleFiles(path)
Returns a list of visible files in a directory.

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EnsureDirs(dirs)
Make required directories, if they don't exist.

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str or None

FindFile(name, search_path, test=os.path.exists)
Look for a filesystem object in a given path.

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IsNormAbsPath(path)
Check whether a path is absolute and also normalized

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PathJoin(*args)
Safe-join a list of path components.

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TailFile(fname, lines=20)
Return the last lines from a file.

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int

BytesToMebibyte(value)
Converts bytes to mebibytes.

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int

CalculateDirectorySize(path)
Calculates the size of a directory recursively.

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int

GetFilesystemStats(path)
Returns the total and free space on a filesystem.

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int

ReadPidFile(pidfile)
Read a pid from a file.

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ReadLockedPidFile(path)
Reads a locked PID file.

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AddAuthorizedKey(file_obj, key)
Adds an SSH public key to an authorized_keys file.

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RemoveAuthorizedKey(file_name, key)
Removes an SSH public key from an authorized_keys file.

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str

DaemonPidFileName(name)
Compute a ganeti pid file absolute path

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int

WritePidFile(pidfile)
Write the current process pidfile.

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ReadWatcherPauseFile(filename, now=None, remove_after=3600)
Reads the watcher pause file.

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str

NewUUID()
Returns a random UUID.

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Variables

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_RANDOM_UUID_FILE = "/proc/sys/kernel/random/uuid"
Path generating random UUID

Imports: os, logging, shutil, tempfile, errno, time, errors, constants, filelock

Function Details

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ReadFile(file_name, size=-1, preread=None)

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Reads a file.

Parameters:

size (int) - Read at most size bytes (if negative, entire file)
preread (callable receiving file handle as single parameter) - Function called before file is read

Returns: str

the (possibly partial) content of the file

WriteFile(file_name, fn=None, data=None, mode=None, uid=-1, gid=-1, atime=None, mtime=None, close=True, dry_run=False, backup=False, prewrite=None, postwrite=None)

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(Over)write a file atomically.

The file_name and either fn (a function taking one argument, the file descriptor, and which should write the data to it) or data (the contents of the file) must be passed. The other arguments are optional and allow setting the file mode, owner and group, and the mtime/atime of the file.

If the function doesn't raise an exception, it has succeeded and the target file has the new contents. If the function has raised an exception, an existing target file should be unmodified and the temporary file should be removed.

Parameters:

file_name (str) - the target filename
fn (callable) - content writing function, called with file descriptor as parameter
data (str) - contents of the file
mode (int) - file mode
uid (int) - the owner of the file
gid (int) - the group of the file
atime (int) - a custom access time to be set on the file
mtime (int) - a custom modification time to be set on the file
close (boolean) - whether to close file after writing it
prewrite (callable) - function to be called before writing content
postwrite (callable) - function to be called after writing content

Returns: None or int

None if the 'close' parameter evaluates to True, otherwise the file descriptor

Raises:

errors.ProgrammerError - if any of the arguments are not valid

GetFileID(path=None, fd=None)

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Returns the file 'id', i.e. the dev/inode and mtime information.

Either the path to the file or the fd must be given.

Parameters:

path - the file path
fd - a file descriptor

Returns:

a tuple of (device number, inode number, mtime)

VerifyFileID(fi_disk, fi_ours)

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Verifies that two file IDs are matching.

Differences in the inode/device are not accepted, but and older timestamp for fi_disk is accepted.

Parameters:

fi_disk - tuple (dev, inode, mtime) representing the actual file data
fi_ours - tuple (dev, inode, mtime) representing the last written file data

Returns: boolean

SafeWriteFile(file_name, file_id, **kwargs)

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Wraper over WriteFile that locks the target file.

By keeping the target file locked during WriteFile, we ensure that cooperating writers will safely serialise access to the file.

Parameters:

file_name (str) - the target filename
file_id (tuple) - a result from GetFileID

ReadOneLineFile(file_name, strict=False)

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Return the first non-empty line from a file.

Parameters:

strict (boolean) - if True, abort if the file has more than one non-empty line

RemoveFile(filename)

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Remove a file ignoring some errors.

Remove a file, ignoring non-existing ones or directories. Other errors are passed.

Parameters:

filename (str) - the file to be removed

RemoveDir(dirname)

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Remove an empty directory.

Remove a directory, ignoring non-existing ones. Other errors are passed. This includes the case, where the directory is not empty, so it can't be removed.

Parameters:

dirname (str) - the empty directory to be removed

RenameFile(old, new, mkdir=False, mkdir_mode=0750, dir_uid=None, dir_gid=None)

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Renames a file.

Parameters:

old (string) - Original path
new (string) - New path
mkdir (bool) - Whether to create target directory if it doesn't exist
mkdir_mode (int) - Mode for newly created directories
dir_uid (int) - The uid for the (if fresh created) dir
dir_gid (int) - The gid for the (if fresh created) dir

Makedirs(path, mode=0750)

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Super-mkdir; create a leaf directory and all intermediate ones.

This is a wrapper around os.makedirs adding error handling not implemented before Python 2.5.

TimestampForFilename()

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Returns the current time formatted for filenames.

The format doesn't contain colons as some shells and applications treat them as separators. Uses the local timezone.

CreateBackup(file_name)

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Creates a backup of a file.

Parameters:

file_name (str) - file to be backed up

Returns: str

the path to the newly created backup

Raises:

errors.ProgrammerError - for invalid file names

ListVisibleFiles(path)

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Returns a list of visible files in a directory.

Parameters:

path (str) - the directory to enumerate

Returns: list

the list of all files not starting with a dot

Raises:

ProgrammerError - if path is not an absolue and normalized path

EnsureDirs(dirs)

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Make required directories, if they don't exist.

Parameters:

dirs (list of (string, integer)) - list of tuples (dir_name, dir_mode)

FindFile(name, search_path, test=os.path.exists)

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Look for a filesystem object in a given path.

This is an abstract method to search for filesystem object (files, dirs) under a given search path.

Parameters:

name (str) - the name to look for
search_path (str) - location to start at
test (callable) - a function taking one argument that should return True if the a given object is valid; the default value is os.path.exists, causing only existing files to be returned

Returns: str or None

full path to the object if found, None otherwise

IsNormAbsPath(path)

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Check whether a path is absolute and also normalized

This avoids things like /dir/../../other/path to be valid.

PathJoin(*args)

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Safe-join a list of path components.

Requirements:

the first argument must be an absolute path
no component in the path must have backtracking (e.g. /../), since we check for normalization at the end

Parameters:

args - the path components to be joined

Raises:

ValueError - for invalid paths

TailFile(fname, lines=20)

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Return the last lines from a file.

Parameters:

fname - the file name
lines (int) - the (maximum) number of lines to return

Note: this function will only read and parse the last 4KB of the file; if the lines are very long, it could be that less than the requested number of lines are returned

BytesToMebibyte(value)

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Converts bytes to mebibytes.

Parameters:

value (int) - Value in bytes

Returns: int

Value in mebibytes

CalculateDirectorySize(path)

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Calculates the size of a directory recursively.

Parameters:

path (string) - Path to directory

Returns: int

Size in mebibytes

GetFilesystemStats(path)

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Returns the total and free space on a filesystem.

Parameters:

path (string) - Path on filesystem to be examined

Returns: int

tuple of (Total space, Free space) in mebibytes

ReadPidFile(pidfile)

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Read a pid from a file.

Parameters:

pidfile (string) - path to the file containing the pid

Returns: int

The process id, if the file exists and contains a valid PID, otherwise 0

ReadLockedPidFile(path)

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Reads a locked PID file.

This can be used together with utils.process.StartDaemon.

Parameters:

path (string) - Path to PID file

Returns:

PID as integer or, if file was unlocked or couldn't be opened, None

AddAuthorizedKey(file_obj, key)

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Adds an SSH public key to an authorized_keys file.

Parameters:

file_obj (str or file handle) - path to authorized_keys file
key (str) - string containing key

RemoveAuthorizedKey(file_name, key)

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Removes an SSH public key from an authorized_keys file.

Parameters:

file_name (str) - path to authorized_keys file
key (str) - string containing key

DaemonPidFileName(name)

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Compute a ganeti pid file absolute path

Parameters:

name (str) - the daemon name

Returns: str

the full path to the pidfile corresponding to the given daemon name

WritePidFile(pidfile)

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Write the current process pidfile.

Parameters:

pidfile (string) - the path to the file to be written

Returns: int

the file descriptor of the lock file; do not close this unless you want to unlock the pid file

Raises:

errors.LockError - if the pid file already exists and points to a live process

ReadWatcherPauseFile(filename, now=None, remove_after=3600)

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Reads the watcher pause file.

Parameters:

filename (string) - Path to watcher pause file
now (None, float or int) - Current time as Unix timestamp
remove_after (int) - Remove watcher pause file after specified amount of seconds past the pause end time

NewUUID()

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Returns a random UUID.

Returns: str

Note: This is a Linux-specific method as it uses the /proc filesystem.