/lib/utils.py - snf-ganeti - Greek Research and Technology Network's projects

| Branch: | Tag: | Revision:

root / lib / utils.py @ 4c32a8bd

History | View | Annotate | Download (85.2 kB)

+      #
+      #
       # Copyright (C) 2006, 2007 Google Inc.
+      #
       # This program is free software; you can redistribute it and/or modify
       # it under the terms of the GNU General Public License as published by
       # the Free Software Foundation; either version 2 of the License, or
       # (at your option) any later version.
+      #
       # This program is distributed in the hope that it will be useful, but
       # WITHOUT ANY WARRANTY; without even the implied warranty of
       # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
       # General Public License for more details.
+      #
       # You should have received a copy of the GNU General Public License
       # along with this program; if not, write to the Free Software
       # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
       # 02110-1301, USA.
       """Ganeti utility module.
       This module holds functions that can be used in both daemons (all) and
       the command line scripts.
       """
       import os
       import time
       import subprocess
       import re
       import socket
       import tempfile
       import shutil
       import errno
       import pwd
       import itertools
       import select
       import fcntl
       import resource
       import logging
       import logging.handlers
       import signal
       import datetime
       import calendar
       import collections
       import struct
       import IN
       from cStringIO import StringIO
       try:
         from hashlib import sha1
       except ImportError:
         import sha
         sha1 = sha.new
       try:
         import ctypes
       except ImportError:
         ctypes = None
       from ganeti import errors
       from ganeti import constants
       _locksheld = []
       _re_shell_unquoted = re.compile('^[-.,=:/_+@A-Za-z0-9]+$')
       debug_locks = False
       #: when set to True, L{RunCmd} is disabled
       no_fork = False
       _RANDOM_UUID_FILE = "/proc/sys/kernel/random/uuid"
       # Structure definition for getsockopt(SOL_SOCKET, SO_PEERCRED, ...):
       # struct ucred { pid_t pid; uid_t uid; gid_t gid; };
+      #
       # The GNU C Library defines gid_t and uid_t to be "unsigned int" and
       # pid_t to "int".
+      #
       # IEEE Std 1003.1-2008:
       # "nlink_t, uid_t, gid_t, and id_t shall be integer types"
       # "blksize_t, pid_t, and ssize_t shall be signed integer types"
       _STRUCT_UCRED = "iII"
       _STRUCT_UCRED_SIZE = struct.calcsize(_STRUCT_UCRED)
       # Flags for mlockall() (from bits/mman.h)
       _MCL_CURRENT = 1
       _MCL_FUTURE = 2
       class RunResult(object):
         """Holds the result of running external programs.
         @type exit_code: int
         @ivar exit_code: the exit code of the program, or None (if the program
             didn't exit())
         @type signal: int or None
         @ivar signal: the signal that caused the program to finish, or None
             (if the program wasn't terminated by a signal)
         @type stdout: str
         @ivar stdout: the standard output of the program
         @type stderr: str
         @ivar stderr: the standard error of the program
         @type failed: boolean
         @ivar failed: True in case the program was
             terminated by a signal or exited with a non-zero exit code
         @ivar fail_reason: a string detailing the termination reason
         """
         __slots__ = ["exit_code", "signal", "stdout", "stderr",
                      "failed", "fail_reason", "cmd"]
         def __init__(self, exit_code, signal_, stdout, stderr, cmd):
           self.cmd = cmd
           self.exit_code = exit_code
           self.signal = signal_
           self.stdout = stdout
           self.stderr = stderr
           self.failed = (signal_ is not None or exit_code != 0)
           if self.signal is not None:
             self.fail_reason = "terminated by signal %s" % self.signal
           elif self.exit_code is not None:
             self.fail_reason = "exited with exit code %s" % self.exit_code
           else:
             self.fail_reason = "unable to determine termination reason"
           if self.failed:
             logging.debug("Command '%s' failed (%s); output: %s",
                           self.cmd, self.fail_reason, self.output)
         def _GetOutput(self):
           """Returns the combined stdout and stderr for easier usage.
           """
           return self.stdout + self.stderr
         output = property(_GetOutput, None, None, "Return full output")
       def RunCmd(cmd, env=None, output=None, cwd='/', reset_env=False):
         """Execute a (shell) command.
         The command should not read from its standard input, as it will be
         closed.
         @type cmd: string or list
         @param cmd: Command to run
         @type env: dict
         @param env: Additional environment
         @type output: str
         @param output: if desired, the output of the command can be
             saved in a file instead of the RunResult instance; this
             parameter denotes the file name (if not None)
         @type cwd: string
         @param cwd: if specified, will be used as the working
             directory for the command; the default will be /
         @type reset_env: boolean
         @param reset_env: whether to reset or keep the default os environment
         @rtype: L{RunResult}
         @return: RunResult instance
         @raise errors.ProgrammerError: if we call this when forks are disabled
         """
         if no_fork:
           raise errors.ProgrammerError("utils.RunCmd() called with fork() disabled")
         if isinstance(cmd, list):
           cmd = [str(val) for val in cmd]
           strcmd = " ".join(cmd)
           shell = False
         else:
           strcmd = cmd
           shell = True
         logging.debug("RunCmd '%s'", strcmd)
         if not reset_env:
           cmd_env = os.environ.copy()
           cmd_env["LC_ALL"] = "C"
         else:
           cmd_env = {}
         if env is not None:
           cmd_env.update(env)
         try:
           if output is None:
             out, err, status = _RunCmdPipe(cmd, cmd_env, shell, cwd)
           else:
             status = _RunCmdFile(cmd, cmd_env, shell, output, cwd)
             out = err = ""
         except OSError, err:
           if err.errno == errno.ENOENT:
             raise errors.OpExecError("Can't execute '%s': not found (%s)" %
                                      (strcmd, err))
           else:
             raise
         if status >= 0:
           exitcode = status
           signal_ = None
         else:
           exitcode = None
           signal_ = -status
         return RunResult(exitcode, signal_, out, err, strcmd)
       def _RunCmdPipe(cmd, env, via_shell, cwd):
         """Run a command and return its output.
         @type  cmd: string or list
         @param cmd: Command to run
         @type env: dict
         @param env: The environment to use
         @type via_shell: bool
         @param via_shell: if we should run via the shell
         @type cwd: string
         @param cwd: the working directory for the program
         @rtype: tuple
         @return: (out, err, status)
         """
         poller = select.poll()
         child = subprocess.Popen(cmd, shell=via_shell,
                                  stderr=subprocess.PIPE,
                                  stdout=subprocess.PIPE,
                                  stdin=subprocess.PIPE,
                                  close_fds=True, env=env,
                                  cwd=cwd)
         child.stdin.close()
         poller.register(child.stdout, select.POLLIN)
         poller.register(child.stderr, select.POLLIN)
         out = StringIO()
         err = StringIO()
         fdmap = {
           child.stdout.fileno(): (out, child.stdout),
           child.stderr.fileno(): (err, child.stderr),
+          }
         for fd in fdmap:
           status = fcntl.fcntl(fd, fcntl.F_GETFL)
           fcntl.fcntl(fd, fcntl.F_SETFL, status | os.O_NONBLOCK)
         while fdmap:
           try:
             pollresult = poller.poll()
           except EnvironmentError, eerr:
             if eerr.errno == errno.EINTR:
               continue
             raise
           except select.error, serr:
             if serr[0] == errno.EINTR:
               continue
             raise
           for fd, event in pollresult:
             if event & select.POLLIN or event & select.POLLPRI:
               data = fdmap[fd][1].read()
               # no data from read signifies EOF (the same as POLLHUP)
               if not data:
                 poller.unregister(fd)
                 del fdmap[fd]
                 continue
               fdmap[fd][0].write(data)
             if (event & select.POLLNVAL or event & select.POLLHUP or
                 event & select.POLLERR):
               poller.unregister(fd)
               del fdmap[fd]
         out = out.getvalue()
         err = err.getvalue()
         status = child.wait()
         return out, err, status
       def _RunCmdFile(cmd, env, via_shell, output, cwd):
         """Run a command and save its output to a file.
         @type  cmd: string or list
         @param cmd: Command to run
         @type env: dict
         @param env: The environment to use
         @type via_shell: bool
         @param via_shell: if we should run via the shell
         @type output: str
         @param output: the filename in which to save the output
         @type cwd: string
         @param cwd: the working directory for the program
         @rtype: int
         @return: the exit status
         """
         fh = open(output, "a")
         try:
           child = subprocess.Popen(cmd, shell=via_shell,
                                    stderr=subprocess.STDOUT,
                                    stdout=fh,
                                    stdin=subprocess.PIPE,
                                    close_fds=True, env=env,
                                    cwd=cwd)
           child.stdin.close()
           status = child.wait()
         finally:
           fh.close()
         return status
       def RunParts(dir_name, env=None, reset_env=False):
         """Run Scripts or programs in a directory
         @type dir_name: string
         @param dir_name: absolute path to a directory
         @type env: dict
         @param env: The environment to use
         @type reset_env: boolean
         @param reset_env: whether to reset or keep the default os environment
         @rtype: list of tuples
         @return: list of (name, (one of RUNDIR_STATUS), RunResult)
         """
         rr = []
         try:
           dir_contents = ListVisibleFiles(dir_name)
         except OSError, err:
           logging.warning("RunParts: skipping %s (cannot list: %s)", dir_name, err)
           return rr
         for relname in sorted(dir_contents):
           fname = PathJoin(dir_name, relname)
           if not (os.path.isfile(fname) and os.access(fname, os.X_OK) and
                   constants.EXT_PLUGIN_MASK.match(relname) is not None):
             rr.append((relname, constants.RUNPARTS_SKIP, None))
           else:
             try:
               result = RunCmd([fname], env=env, reset_env=reset_env)
             except Exception, err: # pylint: disable-msg=W0703
               rr.append((relname, constants.RUNPARTS_ERR, str(err)))
             else:
               rr.append((relname, constants.RUNPARTS_RUN, result))
         return rr
       def GetSocketCredentials(sock):
         """Returns the credentials of the foreign process connected to a socket.
         @param sock: Unix socket
         @rtype: tuple; (number, number, number)
         @return: The PID, UID and GID of the connected foreign process.
         """
         peercred = sock.getsockopt(socket.SOL_SOCKET, IN.SO_PEERCRED,
                                    _STRUCT_UCRED_SIZE)
         return struct.unpack(_STRUCT_UCRED, peercred)
       def RemoveFile(filename):
         """Remove a file ignoring some errors.
         Remove a file, ignoring non-existing ones or directories. Other
         errors are passed.
         @type filename: str
         @param filename: the file to be removed
         """
         try:
           os.unlink(filename)
         except OSError, err:
           if err.errno not in (errno.ENOENT, errno.EISDIR):
             raise
       def RemoveDir(dirname):
         """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.
         @type dirname: str
         @param dirname: the empty directory to be removed
         """
         try:
           os.rmdir(dirname)
         except OSError, err:
           if err.errno != errno.ENOENT:
             raise
       def RenameFile(old, new, mkdir=False, mkdir_mode=0750):
         """Renames a file.
         @type old: string
         @param old: Original path
         @type new: string
         @param new: New path
         @type mkdir: bool
         @param mkdir: Whether to create target directory if it doesn't exist
         @type mkdir_mode: int
         @param mkdir_mode: Mode for newly created directories
         """
         try:
           return os.rename(old, new)
         except OSError, err:
           # In at least one use case of this function, the job queue, directory
           # creation is very rare. Checking for the directory before renaming is not
           # as efficient.
           if mkdir and err.errno == errno.ENOENT:
             # Create directory and try again
             Makedirs(os.path.dirname(new), mode=mkdir_mode)
             return os.rename(old, new)
           raise
       def Makedirs(path, mode=0750):
         """Super-mkdir; create a leaf directory and all intermediate ones.
         This is a wrapper around C{os.makedirs} adding error handling not implemented
         before Python 2.5.
         """
         try:
           os.makedirs(path, mode)
         except OSError, err:
           # Ignore EEXIST. This is only handled in os.makedirs as included in
           # Python 2.5 and above.
           if err.errno != errno.EEXIST or not os.path.exists(path):
             raise
       def ResetTempfileModule():
         """Resets the random name generator of the tempfile module.
         This function should be called after C{os.fork} in the child process to
         ensure it creates a newly seeded random generator. Otherwise it would
         generate the same random parts as the parent process. If several processes
         race for the creation of a temporary file, this could lead to one not getting
         a temporary name.
         """
         # pylint: disable-msg=W0212
         if hasattr(tempfile, "_once_lock") and hasattr(tempfile, "_name_sequence"):
           tempfile._once_lock.acquire()
           try:
             # Reset random name generator
             tempfile._name_sequence = None
           finally:
             tempfile._once_lock.release()
         else:
           logging.critical("The tempfile module misses at least one of the"
                            " '_once_lock' and '_name_sequence' attributes")
       def _FingerprintFile(filename):
         """Compute the fingerprint of a file.
         If the file does not exist, a None will be returned
         instead.
         @type filename: str
         @param filename: the filename to checksum
         @rtype: str
         @return: the hex digest of the sha checksum of the contents
             of the file
         """
         if not (os.path.exists(filename) and os.path.isfile(filename)):
           return None
         f = open(filename)
         fp = sha1()
         while True:
           data = f.read(4096)
           if not data:
             break
           fp.update(data)
         return fp.hexdigest()
       def FingerprintFiles(files):
         """Compute fingerprints for a list of files.
         @type files: list
         @param files: the list of filename to fingerprint
         @rtype: dict
         @return: a dictionary filename: fingerprint, holding only
             existing files
         """
         ret = {}
         for filename in files:
           cksum = _FingerprintFile(filename)
           if cksum:
             ret[filename] = cksum
         return ret
       def ForceDictType(target, key_types, allowed_values=None):
         """Force the values of a dict to have certain types.
         @type target: dict
         @param target: the dict to update
         @type key_types: dict
         @param key_types: dict mapping target dict keys to types
                           in constants.ENFORCEABLE_TYPES
         @type allowed_values: list
         @keyword allowed_values: list of specially allowed values
         """
         if allowed_values is None:
           allowed_values = []
         if not isinstance(target, dict):
           msg = "Expected dictionary, got '%s'" % target
           raise errors.TypeEnforcementError(msg)
         for key in target:
           if key not in key_types:
             msg = "Unknown key '%s'" % key
             raise errors.TypeEnforcementError(msg)
           if target[key] in allowed_values:
             continue
           ktype = key_types[key]
           if ktype not in constants.ENFORCEABLE_TYPES:
             msg = "'%s' has non-enforceable type %s" % (key, ktype)
             raise errors.ProgrammerError(msg)
           if ktype == constants.VTYPE_STRING:
             if not isinstance(target[key], basestring):
               if isinstance(target[key], bool) and not target[key]:
                 target[key] = ''
               else:
                 msg = "'%s' (value %s) is not a valid string" % (key, target[key])
                 raise errors.TypeEnforcementError(msg)
           elif ktype == constants.VTYPE_BOOL:
             if isinstance(target[key], basestring) and target[key]:
               if target[key].lower() == constants.VALUE_FALSE:
                 target[key] = False
               elif target[key].lower() == constants.VALUE_TRUE:
                 target[key] = True
               else:
                 msg = "'%s' (value %s) is not a valid boolean" % (key, target[key])
                 raise errors.TypeEnforcementError(msg)
             elif target[key]:
               target[key] = True
             else:
               target[key] = False
           elif ktype == constants.VTYPE_SIZE:
             try:
               target[key] = ParseUnit(target[key])
             except errors.UnitParseError, err:
               msg = "'%s' (value %s) is not a valid size. error: %s" % \
                     (key, target[key], err)
               raise errors.TypeEnforcementError(msg)
           elif ktype == constants.VTYPE_INT:
             try:
               target[key] = int(target[key])
             except (ValueError, TypeError):
               msg = "'%s' (value %s) is not a valid integer" % (key, target[key])
               raise errors.TypeEnforcementError(msg)
       def IsProcessAlive(pid):
         """Check if a given pid exists on the system.
         @note: zombie status is not handled, so zombie processes
             will be returned as alive
         @type pid: int
         @param pid: the process ID to check
         @rtype: boolean
         @return: True if the process exists
         """
         def _TryStat(name):
           try:
             os.stat(name)
             return True
           except EnvironmentError, err:
             if err.errno in (errno.ENOENT, errno.ENOTDIR):
               return False
             elif err.errno == errno.EINVAL:
               raise RetryAgain(err)
             raise
         assert isinstance(pid, int), "pid must be an integer"
         if pid <= 0:
           return False
         proc_entry = "/proc/%d/status" % pid
         # /proc in a multiprocessor environment can have strange behaviors.
         # Retry the os.stat a few times until we get a good result.
         try:
           return Retry(_TryStat, (0.01, 1.5, 0.1), 0.5, args=[proc_entry])
         except RetryTimeout, err:
           err.RaiseInner()
       def ReadPidFile(pidfile):
         """Read a pid from a file.
         @type  pidfile: string
         @param pidfile: path to the file containing the pid
         @rtype: int
         @return: The process id, if the file exists and contains a valid PID,
                  otherwise 0
         """
         try:
           raw_data = ReadOneLineFile(pidfile)
         except EnvironmentError, err:
           if err.errno != errno.ENOENT:
             logging.exception("Can't read pid file")
           return 0
         try:
           pid = int(raw_data)
         except (TypeError, ValueError), err:
           logging.info("Can't parse pid file contents", exc_info=True)
           return 0
         return pid
       def MatchNameComponent(key, name_list, case_sensitive=True):
         """Try to match a name against a list.
         This function will try to match a name like test1 against a list
         like C{['test1.example.com', 'test2.example.com', ...]}. Against
         this list, I{'test1'} as well as I{'test1.example'} will match, but
         not I{'test1.ex'}. A multiple match will be considered as no match
         at all (e.g. I{'test1'} against C{['test1.example.com',
         'test1.example.org']}), except when the key fully matches an entry
         (e.g. I{'test1'} against C{['test1', 'test1.example.com']}).
         @type key: str
         @param key: the name to be searched
         @type name_list: list
         @param name_list: the list of strings against which to search the key
         @type case_sensitive: boolean
         @param case_sensitive: whether to provide a case-sensitive match
         @rtype: None or str
         @return: None if there is no match I{or} if there are multiple matches,
             otherwise the element from the list which matches
         """
         if key in name_list:
           return key
         re_flags = 0
         if not case_sensitive:
           re_flags |= re.IGNORECASE
           key = key.upper()
         mo = re.compile("^%s(\..*)?$" % re.escape(key), re_flags)
         names_filtered = []
         string_matches = []
         for name in name_list:
           if mo.match(name) is not None:
             names_filtered.append(name)
             if not case_sensitive and key == name.upper():
               string_matches.append(name)
         if len(string_matches) == 1:
           return string_matches[0]
         if len(names_filtered) == 1:
           return names_filtered[0]
         return None
       class HostInfo:
         """Class implementing resolver and hostname functionality
         """
         _VALID_NAME_RE = re.compile("^[a-z0-9._-]{1,255}$")
         def __init__(self, name=None):
           """Initialize the host name object.
           If the name argument is not passed, it will use this system's
           name.
           """
           if name is None:
             name = self.SysName()
           self.query = name
           self.name, self.aliases, self.ipaddrs = self.LookupHostname(name)
           self.ip = self.ipaddrs[0]
         def ShortName(self):
           """Returns the hostname without domain.
           """
           return self.name.split('.')[0]
         @staticmethod
         def SysName():
           """Return the current system's name.
           This is simply a wrapper over C{socket.gethostname()}.
           """
           return socket.gethostname()
         @staticmethod
         def LookupHostname(hostname):
           """Look up hostname
           @type hostname: str
           @param hostname: hostname to look up
           @rtype: tuple
           @return: a tuple (name, aliases, ipaddrs) as returned by
               C{socket.gethostbyname_ex}
           @raise errors.ResolverError: in case of errors in resolving
           """
           try:
             result = socket.gethostbyname_ex(hostname)
           except (socket.gaierror, socket.herror, socket.error), err:
             # hostname not found in DNS, or other socket exception in the
             # (code, description format)
             raise errors.ResolverError(hostname, err.args[0], err.args[1])
           return result
         @classmethod
         def NormalizeName(cls, hostname):
           """Validate and normalize the given hostname.
           @attention: the validation is a bit more relaxed than the standards
               require; most importantly, we allow underscores in names
           @raise errors.OpPrereqError: when the name is not valid
           """
           hostname = hostname.lower()
           if (not cls._VALID_NAME_RE.match(hostname) or
               # double-dots, meaning empty label
               ".." in hostname or
               # empty initial label
               hostname.startswith(".")):
             raise errors.OpPrereqError("Invalid hostname '%s'" % hostname,
                                        errors.ECODE_INVAL)
           if hostname.endswith("."):
             hostname = hostname.rstrip(".")
           return hostname
       def GetHostInfo(name=None):
         """Lookup host name and raise an OpPrereqError for failures"""
         try:
           return HostInfo(name)
         except errors.ResolverError, err:
           raise errors.OpPrereqError("The given name (%s) does not resolve: %s" %
                                      (err[0], err[2]), errors.ECODE_RESOLVER)
       def ListVolumeGroups():
         """List volume groups and their size
         @rtype: dict
         @return:
              Dictionary with keys volume name and values
              the size of the volume
         """
         command = "vgs --noheadings --units m --nosuffix -o name,size"
         result = RunCmd(command)
         retval = {}
         if result.failed:
           return retval
         for line in result.stdout.splitlines():
           try:
             name, size = line.split()
             size = int(float(size))
           except (IndexError, ValueError), err:
             logging.error("Invalid output from vgs (%s): %s", err, line)
             continue
           retval[name] = size
         return retval
       def BridgeExists(bridge):
         """Check whether the given bridge exists in the system
         @type bridge: str
         @param bridge: the bridge name to check
         @rtype: boolean
         @return: True if it does
         """
         return os.path.isdir("/sys/class/net/%s/bridge" % bridge)
       def NiceSort(name_list):
         """Sort a list of strings based on digit and non-digit groupings.
         Given a list of names C{['a1', 'a10', 'a11', 'a2']} this function
         will sort the list in the logical order C{['a1', 'a2', 'a10',
         'a11']}.
         The sort algorithm breaks each name in groups of either only-digits
         or no-digits. Only the first eight such groups are considered, and
         after that we just use what's left of the string.
         @type name_list: list
         @param name_list: the names to be sorted
         @rtype: list
         @return: a copy of the name list sorted with our algorithm
         """
         _SORTER_BASE = "(\D+|\d+)"
         _SORTER_FULL = "^%s%s?%s?%s?%s?%s?%s?%s?.*$" % (_SORTER_BASE, _SORTER_BASE,
                                                         _SORTER_BASE, _SORTER_BASE,
                                                         _SORTER_BASE, _SORTER_BASE,
                                                         _SORTER_BASE, _SORTER_BASE)
         _SORTER_RE = re.compile(_SORTER_FULL)
         _SORTER_NODIGIT = re.compile("^\D*$")
         def _TryInt(val):
           """Attempts to convert a variable to integer."""
           if val is None or _SORTER_NODIGIT.match(val):
             return val
           rval = int(val)
           return rval
         to_sort = [([_TryInt(grp) for grp in _SORTER_RE.match(name).groups()], name)
                    for name in name_list]
         to_sort.sort()
         return [tup[1] for tup in to_sort]
       def TryConvert(fn, val):
         """Try to convert a value ignoring errors.
         This function tries to apply function I{fn} to I{val}. If no
         C{ValueError} or C{TypeError} exceptions are raised, it will return
         the result, else it will return the original value. Any other
         exceptions are propagated to the caller.
         @type fn: callable
         @param fn: function to apply to the value
         @param val: the value to be converted
         @return: The converted value if the conversion was successful,
             otherwise the original value.
         """
         try:
           nv = fn(val)
         except (ValueError, TypeError):
           nv = val
         return nv
       def IsValidIP(ip):
         """Verifies the syntax of an IPv4 address.
         This function checks if the IPv4 address passes is valid or not based
         on syntax (not IP range, class calculations, etc.).
         @type ip: str
         @param ip: the address to be checked
         @rtype: a regular expression match object
         @return: a regular expression match object, or None if the
             address is not valid
         """
         unit = "(0|[1-9]\d{0,2})"
         #TODO: convert and return only boolean
         return re.match("^%s\.%s\.%s\.%s$" % (unit, unit, unit, unit), ip)
       def IsValidShellParam(word):
         """Verifies is the given word is safe from the shell's p.o.v.
         This means that we can pass this to a command via the shell and be
         sure that it doesn't alter the command line and is passed as such to
         the actual command.
         Note that we are overly restrictive here, in order to be on the safe
         side.
         @type word: str
         @param word: the word to check
         @rtype: boolean
         @return: True if the word is 'safe'
         """
         return bool(re.match("^[-a-zA-Z0-9._+/:%@]+$", word))
       def BuildShellCmd(template, *args):
         """Build a safe shell command line from the given arguments.
         This function will check all arguments in the args list so that they
         are valid shell parameters (i.e. they don't contain shell
         metacharacters). If everything is ok, it will return the result of
         template % args.
         @type template: str
         @param template: the string holding the template for the
             string formatting
         @rtype: str
         @return: the expanded command line
         """
         for word in args:
           if not IsValidShellParam(word):
             raise errors.ProgrammerError("Shell argument '%s' contains"
                                          " invalid characters" % word)
         return template % args
       def FormatUnit(value, units):
         """Formats an incoming number of MiB with the appropriate unit.
         @type value: int
         @param value: integer representing the value in MiB (1048576)
         @type units: char
         @param units: the type of formatting we should do:
             - 'h' for automatic scaling
             - 'm' for MiBs
             - 'g' for GiBs
             - 't' for TiBs
         @rtype: str
         @return: the formatted value (with suffix)
         """
         if units not in ('m', 'g', 't', 'h'):
           raise errors.ProgrammerError("Invalid unit specified '%s'" % str(units))
         suffix = ''
         if units == 'm' or (units == 'h' and value < 1024):
           if units == 'h':
             suffix = 'M'
           return "%d%s" % (round(value, 0), suffix)
         elif units == 'g' or (units == 'h' and value < (1024 * 1024)):
           if units == 'h':
             suffix = 'G'
           return "%0.1f%s" % (round(float(value) / 1024, 1), suffix)
         else:
           if units == 'h':
             suffix = 'T'
           return "%0.1f%s" % (round(float(value) / 1024 / 1024, 1), suffix)
       def ParseUnit(input_string):
         """Tries to extract number and scale from the given string.
         Input must be in the format C{NUMBER+ [DOT NUMBER+] SPACE*
         [UNIT]}. If no unit is specified, it defaults to MiB. Return value
         is always an int in MiB.
         """
         m = re.match('^([.\d]+)\s*([a-zA-Z]+)?$', str(input_string))
         if not m:
           raise errors.UnitParseError("Invalid format")
         value = float(m.groups()[0])
         unit = m.groups()[1]
         if unit:
           lcunit = unit.lower()
         else:
           lcunit = 'm'
         if lcunit in ('m', 'mb', 'mib'):
           # Value already in MiB
           pass
         elif lcunit in ('g', 'gb', 'gib'):
           value *= 1024
         elif lcunit in ('t', 'tb', 'tib'):
           value *= 1024 * 1024
         else:
           raise errors.UnitParseError("Unknown unit: %s" % unit)
         # Make sure we round up
         if int(value) < value:
           value += 1
         # Round up to the next multiple of 4
         value = int(value)
         if value % 4:
           value += 4 - value % 4
         return value
       def AddAuthorizedKey(file_name, key):
         """Adds an SSH public key to an authorized_keys file.
         @type file_name: str
         @param file_name: path to authorized_keys file
         @type key: str
         @param key: string containing key
         """
         key_fields = key.split()
         f = open(file_name, 'a+')
         try:
           nl = True
           for line in f:
             # Ignore whitespace changes
             if line.split() == key_fields:
               break
             nl = line.endswith('\n')
           else:
             if not nl:
               f.write("\n")
             f.write(key.rstrip('\r\n'))
             f.write("\n")
             f.flush()
         finally:
           f.close()
       def RemoveAuthorizedKey(file_name, key):
         """Removes an SSH public key from an authorized_keys file.
         @type file_name: str
         @param file_name: path to authorized_keys file
         @type key: str
         @param key: string containing key
         """
         key_fields = key.split()
         fd, tmpname = tempfile.mkstemp(dir=os.path.dirname(file_name))
         try:
           out = os.fdopen(fd, 'w')
           try:
             f = open(file_name, 'r')
             try:
               for line in f:
                 # Ignore whitespace changes while comparing lines
                 if line.split() != key_fields:
                   out.write(line)
               out.flush()
               os.rename(tmpname, file_name)
             finally:
               f.close()
           finally:
             out.close()
         except:
           RemoveFile(tmpname)
           raise
       def SetEtcHostsEntry(file_name, ip, hostname, aliases):
         """Sets the name of an IP address and hostname in /etc/hosts.
         @type file_name: str
         @param file_name: path to the file to modify (usually C{/etc/hosts})
         @type ip: str
         @param ip: the IP address
         @type hostname: str
         @param hostname: the hostname to be added
         @type aliases: list
         @param aliases: the list of aliases to add for the hostname
         """
         # FIXME: use WriteFile + fn rather than duplicating its efforts
         # Ensure aliases are unique
         aliases = UniqueSequence([hostname] + aliases)[1:]
         fd, tmpname = tempfile.mkstemp(dir=os.path.dirname(file_name))
         try:
           out = os.fdopen(fd, 'w')
           try:
             f = open(file_name, 'r')
             try:
               for line in f:
                 fields = line.split()
                 if fields and not fields[0].startswith('#') and ip == fields[0]:
                   continue
                 out.write(line)
               out.write("%s\t%s" % (ip, hostname))
               if aliases:
                 out.write(" %s" % ' '.join(aliases))
               out.write('\n')
               out.flush()
               os.fsync(out)
               os.chmod(tmpname, 0644)
               os.rename(tmpname, file_name)
             finally:
               f.close()
           finally:
             out.close()
         except:
           RemoveFile(tmpname)
           raise
       def AddHostToEtcHosts(hostname):
         """Wrapper around SetEtcHostsEntry.
         @type hostname: str
         @param hostname: a hostname that will be resolved and added to
             L{constants.ETC_HOSTS}
         """
         hi = HostInfo(name=hostname)
         SetEtcHostsEntry(constants.ETC_HOSTS, hi.ip, hi.name, [hi.ShortName()])
       def RemoveEtcHostsEntry(file_name, hostname):
         """Removes a hostname from /etc/hosts.
         IP addresses without names are removed from the file.
         @type file_name: str
         @param file_name: path to the file to modify (usually C{/etc/hosts})
         @type hostname: str
         @param hostname: the hostname to be removed
         """
         # FIXME: use WriteFile + fn rather than duplicating its efforts
         fd, tmpname = tempfile.mkstemp(dir=os.path.dirname(file_name))
         try:
           out = os.fdopen(fd, 'w')
           try:
             f = open(file_name, 'r')
             try:
               for line in f:
                 fields = line.split()
                 if len(fields) > 1 and not fields[0].startswith('#'):
                   names = fields[1:]
                   if hostname in names:
                     while hostname in names:
                       names.remove(hostname)
                     if names:
                       out.write("%s %s\n" % (fields[0], ' '.join(names)))
                     continue
                 out.write(line)
               out.flush()
               os.fsync(out)
               os.chmod(tmpname, 0644)
               os.rename(tmpname, file_name)
             finally:
               f.close()
           finally:
             out.close()
         except:
           RemoveFile(tmpname)
           raise
       def RemoveHostFromEtcHosts(hostname):
         """Wrapper around RemoveEtcHostsEntry.
         @type hostname: str
         @param hostname: hostname that will be resolved and its
             full and shot name will be removed from
             L{constants.ETC_HOSTS}
         """
         hi = HostInfo(name=hostname)
         RemoveEtcHostsEntry(constants.ETC_HOSTS, hi.name)
         RemoveEtcHostsEntry(constants.ETC_HOSTS, hi.ShortName())
       def TimestampForFilename():
         """Returns the current time formatted for filenames.
         The format doesn't contain colons as some shells and applications them as
         separators.
         """
         return time.strftime("%Y-%m-%d_%H_%M_%S")
       def CreateBackup(file_name):
         """Creates a backup of a file.
         @type file_name: str
         @param file_name: file to be backed up
         @rtype: str
         @return: the path to the newly created backup
         @raise errors.ProgrammerError: for invalid file names
         """
         if not os.path.isfile(file_name):
           raise errors.ProgrammerError("Can't make a backup of a non-file '%s'" %
                                       file_name)
         prefix = ("%s.backup-%s." %
                   (os.path.basename(file_name), TimestampForFilename()))
         dir_name = os.path.dirname(file_name)
         fsrc = open(file_name, 'rb')
         try:
           (fd, backup_name) = tempfile.mkstemp(prefix=prefix, dir=dir_name)
           fdst = os.fdopen(fd, 'wb')
           try:
             logging.debug("Backing up %s at %s", file_name, backup_name)
             shutil.copyfileobj(fsrc, fdst)
           finally:
             fdst.close()
         finally:
           fsrc.close()
         return backup_name
       def ShellQuote(value):
         """Quotes shell argument according to POSIX.
         @type value: str
         @param value: the argument to be quoted
         @rtype: str
         @return: the quoted value
         """
         if _re_shell_unquoted.match(value):
           return value
         else:
           return "'%s'" % value.replace("'", "'\\''")
       def ShellQuoteArgs(args):
         """Quotes a list of shell arguments.
         @type args: list
         @param args: list of arguments to be quoted
         @rtype: str
         @return: the quoted arguments concatenated with spaces
         """
         return ' '.join([ShellQuote(i) for i in args])
       def TcpPing(target, port, timeout=10, live_port_needed=False, source=None):
         """Simple ping implementation using TCP connect(2).
         Check if the given IP is reachable by doing attempting a TCP connect
         to it.
         @type target: str
         @param target: the IP or hostname to ping
         @type port: int
         @param port: the port to connect to
         @type timeout: int
         @param timeout: the timeout on the connection attempt
         @type live_port_needed: boolean
         @param live_port_needed: whether a closed port will cause the
             function to return failure, as if there was a timeout
         @type source: str or None
         @param source: if specified, will cause the connect to be made
             from this specific source address; failures to bind other
             than C{EADDRNOTAVAIL} will be ignored
         """
         sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
         success = False
         if source is not None:
           try:
             sock.bind((source, 0))
           except socket.error, (errcode, _):
             if errcode == errno.EADDRNOTAVAIL:
               success = False
         sock.settimeout(timeout)
         try:
           sock.connect((target, port))
           sock.close()
           success = True
         except socket.timeout:
           success = False
         except socket.error, (errcode, _):
           success = (not live_port_needed) and (errcode == errno.ECONNREFUSED)
         return success
       def OwnIpAddress(address):
         """Check if the current host has the the given IP address.
         Currently this is done by TCP-pinging the address from the loopback
         address.
         @type address: string
         @param address: the address to check
         @rtype: bool
         @return: True if we own the address
         """
         return TcpPing(address, constants.DEFAULT_NODED_PORT,
                        source=constants.LOCALHOST_IP_ADDRESS)
       def ListVisibleFiles(path):
         """Returns a list of visible files in a directory.
         @type path: str
         @param path: the directory to enumerate
         @rtype: list
         @return: the list of all files not starting with a dot
         @raise ProgrammerError: if L{path} is not an absolue and normalized path
         """
         if not IsNormAbsPath(path):
           raise errors.ProgrammerError("Path passed to ListVisibleFiles is not"
                                        " absolute/normalized: '%s'" % path)
         files = [i for i in os.listdir(path) if not i.startswith(".")]
         files.sort()
         return files
       def GetHomeDir(user, default=None):
         """Try to get the homedir of the given user.
         The user can be passed either as a string (denoting the name) or as
         an integer (denoting the user id). If the user is not found, the
         'default' argument is returned, which defaults to None.
         """
         try:
           if isinstance(user, basestring):
             result = pwd.getpwnam(user)
           elif isinstance(user, (int, long)):
             result = pwd.getpwuid(user)
           else:
             raise errors.ProgrammerError("Invalid type passed to GetHomeDir (%s)" %
                                          type(user))
         except KeyError:
           return default
         return result.pw_dir
       def NewUUID():
         """Returns a random UUID.
         @note: This is a Linux-specific method as it uses the /proc
             filesystem.
         @rtype: str
         """
         return ReadFile(_RANDOM_UUID_FILE, size=128).rstrip("\n")
       def GenerateSecret(numbytes=20):
         """Generates a random secret.
         This will generate a pseudo-random secret returning an hex string
         (so that it can be used where an ASCII string is needed).
         @param numbytes: the number of bytes which will be represented by the returned
             string (defaulting to 20, the length of a SHA1 hash)
         @rtype: str
         @return: an hex representation of the pseudo-random sequence
         """
         return os.urandom(numbytes).encode('hex')
       def EnsureDirs(dirs):
         """Make required directories, if they don't exist.
         @param dirs: list of tuples (dir_name, dir_mode)
         @type dirs: list of (string, integer)
         """
         for dir_name, dir_mode in dirs:
           try:
             os.mkdir(dir_name, dir_mode)
           except EnvironmentError, err:
             if err.errno != errno.EEXIST:
               raise errors.GenericError("Cannot create needed directory"
                                         " '%s': %s" % (dir_name, err))
           try:
             os.chmod(dir_name, dir_mode)
           except EnvironmentError, err:
             raise errors.GenericError("Cannot change directory permissions on"
                                       " '%s': %s" % (dir_name, err))
           if not os.path.isdir(dir_name):
             raise errors.GenericError("%s is not a directory" % dir_name)
       def ReadFile(file_name, size=-1):
         """Reads a file.
         @type size: int
         @param size: Read at most size bytes (if negative, entire file)
         @rtype: str
         @return: the (possibly partial) content of the file
         """
         f = open(file_name, "r")
         try:
           return f.read(size)
         finally:
           f.close()
       def 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.
         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.
         @type file_name: str
         @param file_name: the target filename
         @type fn: callable
         @param fn: content writing function, called with
             file descriptor as parameter
         @type data: str
         @param data: contents of the file
         @type mode: int
         @param mode: file mode
         @type uid: int
         @param uid: the owner of the file
         @type gid: int
         @param gid: the group of the file
         @type atime: int
         @param atime: a custom access time to be set on the file
         @type mtime: int
         @param mtime: a custom modification time to be set on the file
         @type close: boolean
         @param close: whether to close file after writing it
         @type prewrite: callable
         @param prewrite: function to be called before writing content
         @type postwrite: callable
         @param postwrite: function to be called after writing content
         @rtype: None or int
         @return: None if the 'close' parameter evaluates to True,
             otherwise the file descriptor
         @raise errors.ProgrammerError: if any of the arguments are not valid
         """
         if not os.path.isabs(file_name):
           raise errors.ProgrammerError("Path passed to WriteFile is not"
                                        " absolute: '%s'" % file_name)
         if [fn, data].count(None) != 1:
           raise errors.ProgrammerError("fn or data required")
         if [atime, mtime].count(None) == 1:
           raise errors.ProgrammerError("Both atime and mtime must be either"
                                        " set or None")
         if backup and not dry_run and os.path.isfile(file_name):
           CreateBackup(file_name)
         dir_name, base_name = os.path.split(file_name)
         fd, new_name = tempfile.mkstemp('.new', base_name, dir_name)
         do_remove = True
         # here we need to make sure we remove the temp file, if any error
         # leaves it in place
         try:
           if uid != -1 or gid != -1:
             os.chown(new_name, uid, gid)
           if mode:
             os.chmod(new_name, mode)
           if callable(prewrite):
             prewrite(fd)
           if data is not None:
             os.write(fd, data)
           else:
             fn(fd)
           if callable(postwrite):
             postwrite(fd)
           os.fsync(fd)
           if atime is not None and mtime is not None:
             os.utime(new_name, (atime, mtime))
           if not dry_run:
             os.rename(new_name, file_name)
             do_remove = False
         finally:
           if close:
             os.close(fd)
             result = None
           else:
             result = fd
           if do_remove:
             RemoveFile(new_name)
         return result
       def ReadOneLineFile(file_name, strict=False):
         """Return the first non-empty line from a file.
         @type strict: boolean
         @param strict: if True, abort if the file has more than one
             non-empty line
         """
         file_lines = ReadFile(file_name).splitlines()
         full_lines = filter(bool, file_lines)
         if not file_lines or not full_lines:
           raise errors.GenericError("No data in one-liner file %s" % file_name)
         elif strict and len(full_lines) > 1:
           raise errors.GenericError("Too many lines in one-liner file %s" %
                                     file_name)
         return full_lines[0]
       def FirstFree(seq, base=0):
         """Returns the first non-existing integer from seq.
         The seq argument should be a sorted list of positive integers. The
         first time the index of an element is smaller than the element
         value, the index will be returned.
         The base argument is used to start at a different offset,
         i.e. C{[3, 4, 6]} with I{offset=3} will return 5.
         Example: C{[0, 1, 3]} will return I{2}.
         @type seq: sequence
         @param seq: the sequence to be analyzed.
         @type base: int
         @param base: use this value as the base index of the sequence
         @rtype: int
         @return: the first non-used index in the sequence
         """
         for idx, elem in enumerate(seq):
           assert elem >= base, "Passed element is higher than base offset"
           if elem > idx + base:
             # idx is not used
             return idx + base
         return None
       def SingleWaitForFdCondition(fdobj, event, timeout):
         """Waits for a condition to occur on the socket.
         Immediately returns at the first interruption.
         @type fdobj: integer or object supporting a fileno() method
         @param fdobj: entity to wait for events on
         @type event: integer
         @param event: ORed condition (see select module)
         @type timeout: float or None
         @param timeout: Timeout in seconds
         @rtype: int or None
         @return: None for timeout, otherwise occured conditions
         """
         check = (event | select.POLLPRI |
                  select.POLLNVAL | select.POLLHUP | select.POLLERR)
         if timeout is not None:
           # Poller object expects milliseconds
           timeout *= 1000
         poller = select.poll()
         poller.register(fdobj, event)
         try:
           # TODO: If the main thread receives a signal and we have no timeout, we
           # could wait forever. This should check a global "quit" flag or something
           # every so often.
           io_events = poller.poll(timeout)
         except select.error, err:
           if err[0] != errno.EINTR:
             raise
           io_events = []
         if io_events and io_events[0][1] & check:
           return io_events[0][1]
         else:
           return None
       class FdConditionWaiterHelper(object):
         """Retry helper for WaitForFdCondition.
         This class contains the retried and wait functions that make sure
         WaitForFdCondition can continue waiting until the timeout is actually
         expired.
         """
         def __init__(self, timeout):
           self.timeout = timeout
         def Poll(self, fdobj, event):
           result = SingleWaitForFdCondition(fdobj, event, self.timeout)
           if result is None:
             raise RetryAgain()
           else:
             return result
         def UpdateTimeout(self, timeout):
           self.timeout = timeout
       def WaitForFdCondition(fdobj, event, timeout):
         """Waits for a condition to occur on the socket.
         Retries until the timeout is expired, even if interrupted.
         @type fdobj: integer or object supporting a fileno() method
         @param fdobj: entity to wait for events on
         @type event: integer
         @param event: ORed condition (see select module)
         @type timeout: float or None
         @param timeout: Timeout in seconds
         @rtype: int or None
         @return: None for timeout, otherwise occured conditions
         """
         if timeout is not None:
           retrywaiter = FdConditionWaiterHelper(timeout)
           try:
             result = Retry(retrywaiter.Poll, RETRY_REMAINING_TIME, timeout,
                            args=(fdobj, event), wait_fn=retrywaiter.UpdateTimeout)
           except RetryTimeout:
             result = None
         else:
           result = None
           while result is None:
             result = SingleWaitForFdCondition(fdobj, event, timeout)
         return result
       def UniqueSequence(seq):
         """Returns a list with unique elements.
         Element order is preserved.
         @type seq: sequence
         @param seq: the sequence with the source elements
         @rtype: list
         @return: list of unique elements from seq
         """
         seen = set()
         return [i for i in seq if i not in seen and not seen.add(i)]
       def NormalizeAndValidateMac(mac):
         """Normalizes and check if a MAC address is valid.
         Checks whether the supplied MAC address is formally correct, only
         accepts colon separated format. Normalize it to all lower.
         @type mac: str
         @param mac: the MAC to be validated
         @rtype: str
         @return: returns the normalized and validated MAC.
         @raise errors.OpPrereqError: If the MAC isn't valid
         """
         mac_check = re.compile("^([0-9a-f]{2}(:|$)){6}$", re.I)
         if not mac_check.match(mac):
           raise errors.OpPrereqError("Invalid MAC address specified: %s" %
                                      mac, errors.ECODE_INVAL)
         return mac.lower()
       def TestDelay(duration):
         """Sleep for a fixed amount of time.
         @type duration: float
         @param duration: the sleep duration
         @rtype: boolean
         @return: False for negative value, True otherwise
         """
         if duration < 0:
           return False, "Invalid sleep duration"
         time.sleep(duration)
         return True, None
       def _CloseFDNoErr(fd, retries=5):
         """Close a file descriptor ignoring errors.
         @type fd: int
         @param fd: the file descriptor
         @type retries: int
         @param retries: how many retries to make, in case we get any
             other error than EBADF
         """
         try:
           os.close(fd)
         except OSError, err:
           if err.errno != errno.EBADF:
             if retries > 0:
               _CloseFDNoErr(fd, retries - 1)
           # else either it's closed already or we're out of retries, so we
           # ignore this and go on
       def CloseFDs(noclose_fds=None):
         """Close file descriptors.
         This closes all file descriptors above 2 (i.e. except
         stdin/out/err).
         @type noclose_fds: list or None
         @param noclose_fds: if given, it denotes a list of file descriptor
             that should not be closed
         """
         # Default maximum for the number of available file descriptors.
         if 'SC_OPEN_MAX' in os.sysconf_names:
           try:
             MAXFD = os.sysconf('SC_OPEN_MAX')
             if MAXFD < 0:
               MAXFD = 1024
           except OSError:
             MAXFD = 1024
         else:
           MAXFD = 1024
         maxfd = resource.getrlimit(resource.RLIMIT_NOFILE)[1]
         if (maxfd == resource.RLIM_INFINITY):
           maxfd = MAXFD
         # Iterate through and close all file descriptors (except the standard ones)
         for fd in range(3, maxfd):
           if noclose_fds and fd in noclose_fds:
             continue
           _CloseFDNoErr(fd)
       def Mlockall(_ctypes=ctypes):
         """Lock current process' virtual address space into RAM.
         This is equivalent to the C call mlockall(MCL_CURRENT|MCL_FUTURE),
         see mlock(2) for more details. This function requires ctypes module.
         @raises errors.NoCtypesError: if ctypes module is not found
         """
         if _ctypes is None:
           raise errors.NoCtypesError()
         libc = _ctypes.cdll.LoadLibrary("libc.so.6")
         if libc is None:
           logging.error("Cannot set memory lock, ctypes cannot load libc")
           return
         # Some older version of the ctypes module don't have built-in functionality
         # to access the errno global variable, where function error codes are stored.
         # By declaring this variable as a pointer to an integer we can then access
         # its value correctly, should the mlockall call fail, in order to see what
         # the actual error code was.
         # pylint: disable-msg=W0212
         libc.__errno_location.restype = _ctypes.POINTER(_ctypes.c_int)
         if libc.mlockall(_MCL_CURRENT | _MCL_FUTURE):
           # pylint: disable-msg=W0212
           logging.error("Cannot set memory lock: %s",
                         os.strerror(libc.__errno_location().contents.value))
           return
         logging.debug("Memory lock set")
       def Daemonize(logfile):
         """Daemonize the current process.
         This detaches the current process from the controlling terminal and
         runs it in the background as a daemon.
         @type logfile: str
         @param logfile: the logfile to which we should redirect stdout/stderr
         @rtype: int
         @return: the value zero
         """
         # pylint: disable-msg=W0212
         # yes, we really want os._exit
         UMASK = 077
         WORKDIR = "/"
         # this might fail
         pid = os.fork()
         if (pid == 0):  # The first child.
           os.setsid()
           # this might fail
           pid = os.fork() # Fork a second child.
           if (pid == 0):  # The second child.
             os.chdir(WORKDIR)
             os.umask(UMASK)
           else:
             # exit() or _exit()?  See below.
             os._exit(0) # Exit parent (the first child) of the second child.
         else:
           os._exit(0) # Exit parent of the first child.
         for fd in range(3):
           _CloseFDNoErr(fd)
         i = os.open("/dev/null", os.O_RDONLY) # stdin
         assert i == 0, "Can't close/reopen stdin"
         i = os.open(logfile, os.O_WRONLY|os.O_CREAT|os.O_APPEND, 0600) # stdout
         assert i == 1, "Can't close/reopen stdout"
         # Duplicate standard output to standard error.
         os.dup2(1, 2)
         return 0
       def DaemonPidFileName(name):
         """Compute a ganeti pid file absolute path
         @type name: str
         @param name: the daemon name
         @rtype: str
         @return: the full path to the pidfile corresponding to the given
             daemon name
         """
         return PathJoin(constants.RUN_GANETI_DIR, "%s.pid" % name)
       def EnsureDaemon(name):
         """Check for and start daemon if not alive.
         """
         result = RunCmd([constants.DAEMON_UTIL, "check-and-start", name])
         if result.failed:
           logging.error("Can't start daemon '%s', failure %s, output: %s",
                         name, result.fail_reason, result.output)
           return False
         return True
       def WritePidFile(name):
         """Write the current process pidfile.
         The file will be written to L{constants.RUN_GANETI_DIR}I{/name.pid}
         @type name: str
         @param name: the daemon name to use
         @raise errors.GenericError: if the pid file already exists and
             points to a live process
         """
         pid = os.getpid()
         pidfilename = DaemonPidFileName(name)
         if IsProcessAlive(ReadPidFile(pidfilename)):
           raise errors.GenericError("%s contains a live process" % pidfilename)
         WriteFile(pidfilename, data="%d\n" % pid)
       def RemovePidFile(name):
         """Remove the current process pidfile.
         Any errors are ignored.
         @type name: str
         @param name: the daemon name used to derive the pidfile name
         """
         pidfilename = DaemonPidFileName(name)
         # TODO: we could check here that the file contains our pid
         try:
           RemoveFile(pidfilename)
         except: # pylint: disable-msg=W0702
           pass
       def KillProcess(pid, signal_=signal.SIGTERM, timeout=30,
                       waitpid=False):
         """Kill a process given by its pid.
         @type pid: int
         @param pid: The PID to terminate.
         @type signal_: int
         @param signal_: The signal to send, by default SIGTERM
         @type timeout: int
         @param timeout: The timeout after which, if the process is still alive,
                         a SIGKILL will be sent. If not positive, no such checking
                         will be done
         @type waitpid: boolean
         @param waitpid: If true, we should waitpid on this process after
             sending signals, since it's our own child and otherwise it
             would remain as zombie
         """
         def _helper(pid, signal_, wait):
           """Simple helper to encapsulate the kill/waitpid sequence"""
           os.kill(pid, signal_)
           if wait:
             try:
               os.waitpid(pid, os.WNOHANG)
             except OSError:
               pass
         if pid <= 0:
           # kill with pid=0 == suicide
           raise errors.ProgrammerError("Invalid pid given '%s'" % pid)
         if not IsProcessAlive(pid):
           return
         _helper(pid, signal_, waitpid)
         if timeout <= 0:
           return
         def _CheckProcess():
           if not IsProcessAlive(pid):
             return
           try:
             (result_pid, _) = os.waitpid(pid, os.WNOHANG)
           except OSError:
             raise RetryAgain()
           if result_pid > 0:
             return
           raise RetryAgain()
         try:
           # Wait up to $timeout seconds
           Retry(_CheckProcess, (0.01, 1.5, 0.1), timeout)
         except RetryTimeout:
           pass
         if IsProcessAlive(pid):
           # Kill process if it's still alive
           _helper(pid, signal.SIGKILL, waitpid)
       def FindFile(name, search_path, test=os.path.exists):
         """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.
         @type name: str
         @param name: the name to look for
         @type search_path: str
         @param search_path: location to start at
         @type test: callable
         @param test: 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
         @rtype: str or None
         @return: full path to the object if found, None otherwise
         """
         # validate the filename mask
         if constants.EXT_PLUGIN_MASK.match(name) is None:
           logging.critical("Invalid value passed for external script name: '%s'",
                            name)
           return None
         for dir_name in search_path:
           # FIXME: investigate switch to PathJoin
           item_name = os.path.sep.join([dir_name, name])
           # check the user test and that we're indeed resolving to the given
           # basename
           if test(item_name) and os.path.basename(item_name) == name:
             return item_name
         return None
       def CheckVolumeGroupSize(vglist, vgname, minsize):
         """Checks if the volume group list is valid.
         The function will check if a given volume group is in the list of
         volume groups and has a minimum size.
         @type vglist: dict
         @param vglist: dictionary of volume group names and their size
         @type vgname: str
         @param vgname: the volume group we should check
         @type minsize: int
         @param minsize: the minimum size we accept
         @rtype: None or str
         @return: None for success, otherwise the error message
         """
         vgsize = vglist.get(vgname, None)
         if vgsize is None:
           return "volume group '%s' missing" % vgname
         elif vgsize < minsize:
           return ("volume group '%s' too small (%s MiB required, %d MiB found)" %
                   (vgname, minsize, vgsize))
         return None
       def SplitTime(value):
         """Splits time as floating point number into a tuple.
         @param value: Time in seconds
         @type value: int or float
         @return: Tuple containing (seconds, microseconds)
         """
         (seconds, microseconds) = divmod(int(value * 1000000), 1000000)
         assert 0 <= seconds, \
           "Seconds must be larger than or equal to 0, but are %s" % seconds
         assert 0 <= microseconds <= 999999, \
           "Microseconds must be 0-999999, but are %s" % microseconds
         return (int(seconds), int(microseconds))
       def MergeTime(timetuple):
         """Merges a tuple into time as a floating point number.
         @param timetuple: Time as tuple, (seconds, microseconds)
         @type timetuple: tuple
         @return: Time as a floating point number expressed in seconds
         """
         (seconds, microseconds) = timetuple
         assert 0 <= seconds, \
           "Seconds must be larger than or equal to 0, but are %s" % seconds
         assert 0 <= microseconds <= 999999, \
           "Microseconds must be 0-999999, but are %s" % microseconds
         return float(seconds) + (float(microseconds) * 0.000001)
       def GetDaemonPort(daemon_name):
         """Get the daemon port for this cluster.
         Note that this routine does not read a ganeti-specific file, but
         instead uses C{socket.getservbyname} to allow pre-customization of
         this parameter outside of Ganeti.
         @type daemon_name: string
         @param daemon_name: daemon name (in constants.DAEMONS_PORTS)
         @rtype: int
         """
         if daemon_name not in constants.DAEMONS_PORTS:
           raise errors.ProgrammerError("Unknown daemon: %s" % daemon_name)
         (proto, default_port) = constants.DAEMONS_PORTS[daemon_name]
         try:
           port = socket.getservbyname(daemon_name, proto)
         except socket.error:
           port = default_port
         return port
       class LogFileHandler(logging.FileHandler):
         """Log handler that doesn't fallback to stderr.
         When an error occurs while writing on the logfile, logging.FileHandler tries
         to log on stderr. This doesn't work in ganeti since stderr is redirected to
         the logfile. This class avoids failures reporting errors to /dev/console.
         """
         def __init__(self, filename, mode="a", encoding=None):
           """Open the specified file and use it as the stream for logging.
           Also open /dev/console to report errors while logging.
           """
           logging.FileHandler.__init__(self, filename, mode, encoding)
           self.console = open(constants.DEV_CONSOLE, "a")
         def handleError(self, record): # pylint: disable-msg=C0103
           """Handle errors which occur during an emit() call.
           Try to handle errors with FileHandler method, if it fails write to
           /dev/console.
           """
           try:
             logging.FileHandler.handleError(self, record)
           except Exception: # pylint: disable-msg=W0703
             try:
               self.console.write("Cannot log message:\n%s\n" % self.format(record))
             except Exception: # pylint: disable-msg=W0703
               # Log handler tried everything it could, now just give up
               pass
       def SetupLogging(logfile, debug=0, stderr_logging=False, program="",
                        multithreaded=False, syslog=constants.SYSLOG_USAGE,
                        console_logging=False):
         """Configures the logging module.
         @type logfile: str
         @param logfile: the filename to which we should log
         @type debug: integer
         @param debug: if greater than zero, enable debug messages, otherwise
             only those at C{INFO} and above level
         @type stderr_logging: boolean
         @param stderr_logging: whether we should also log to the standard error
         @type program: str
         @param program: the name under which we should log messages
         @type multithreaded: boolean
         @param multithreaded: if True, will add the thread name to the log file
         @type syslog: string
         @param syslog: one of 'no', 'yes', 'only':
             - if no, syslog is not used
             - if yes, syslog is used (in addition to file-logging)
             - if only, only syslog is used
         @type console_logging: boolean
         @param console_logging: if True, will use a FileHandler which falls back to
             the system console if logging fails
         @raise EnvironmentError: if we can't open the log file and
             syslog/stderr logging is disabled
         """
         fmt = "%(asctime)s: " + program + " pid=%(process)d"
         sft = program + "[%(process)d]:"
         if multithreaded:
           fmt += "/%(threadName)s"
           sft += " (%(threadName)s)"
         if debug:
           fmt += " %(module)s:%(lineno)s"
           # no debug info for syslog loggers
         fmt += " %(levelname)s %(message)s"
         # yes, we do want the textual level, as remote syslog will probably
         # lose the error level, and it's easier to grep for it
         sft += " %(levelname)s %(message)s"
         formatter = logging.Formatter(fmt)
         sys_fmt = logging.Formatter(sft)
         root_logger = logging.getLogger("")
         root_logger.setLevel(logging.NOTSET)
         # Remove all previously setup handlers
         for handler in root_logger.handlers:
           handler.close()
           root_logger.removeHandler(handler)
         if stderr_logging:
           stderr_handler = logging.StreamHandler()
           stderr_handler.setFormatter(formatter)
           if debug:
             stderr_handler.setLevel(logging.NOTSET)
           else:
             stderr_handler.setLevel(logging.CRITICAL)
           root_logger.addHandler(stderr_handler)
         if syslog in (constants.SYSLOG_YES, constants.SYSLOG_ONLY):
           facility = logging.handlers.SysLogHandler.LOG_DAEMON
           syslog_handler = logging.handlers.SysLogHandler(constants.SYSLOG_SOCKET,
                                                           facility)
           syslog_handler.setFormatter(sys_fmt)
           # Never enable debug over syslog
           syslog_handler.setLevel(logging.INFO)
           root_logger.addHandler(syslog_handler)
         if syslog != constants.SYSLOG_ONLY:
           # this can fail, if the logging directories are not setup or we have
           # a permisssion problem; in this case, it's best to log but ignore
           # the error if stderr_logging is True, and if false we re-raise the
           # exception since otherwise we could run but without any logs at all
           try:
             if console_logging:
               logfile_handler = LogFileHandler(logfile)
             else:
               logfile_handler = logging.FileHandler(logfile)
             logfile_handler.setFormatter(formatter)
             if debug:
               logfile_handler.setLevel(logging.DEBUG)
             else:
               logfile_handler.setLevel(logging.INFO)
             root_logger.addHandler(logfile_handler)
           except EnvironmentError:
             if stderr_logging or syslog == constants.SYSLOG_YES:
               logging.exception("Failed to enable logging to file '%s'", logfile)
             else:
               # we need to re-raise the exception
               raise
       def IsNormAbsPath(path):
         """Check whether a path is absolute and also normalized
         This avoids things like /dir/../../other/path to be valid.
         """
         return os.path.normpath(path) == path and os.path.isabs(path)
       def PathJoin(*args):
         """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
         @param args: the path components to be joined
         @raise ValueError: for invalid paths
         """
         # ensure we're having at least one path passed in
         assert args
         # ensure the first component is an absolute and normalized path name
         root = args[0]
         if not IsNormAbsPath(root):
           raise ValueError("Invalid parameter to PathJoin: '%s'" % str(args[0]))
         result = os.path.join(*args)
         # ensure that the whole path is normalized
         if not IsNormAbsPath(result):
           raise ValueError("Invalid parameters to PathJoin: '%s'" % str(args))
         # check that we're still under the original prefix
         prefix = os.path.commonprefix([root, result])
         if prefix != root:
           raise ValueError("Error: path joining resulted in different prefix"
                            " (%s != %s)" % (prefix, root))
         return result
       def TailFile(fname, lines=20):
         """Return the last lines from a file.
         @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
         @param fname: the file name
         @type lines: int
         @param lines: the (maximum) number of lines to return
         """
         fd = open(fname, "r")
         try:
           fd.seek(0, 2)
           pos = fd.tell()
           pos = max(0, pos-4096)
           fd.seek(pos, 0)
           raw_data = fd.read()
         finally:
           fd.close()
         rows = raw_data.splitlines()
         return rows[-lines:]
       def _ParseAsn1Generalizedtime(value):
         """Parses an ASN1 GENERALIZEDTIME timestamp as used by pyOpenSSL.
         @type value: string
         @param value: ASN1 GENERALIZEDTIME timestamp
         """
         m = re.match(r"^(\d+)([-+]\d\d)(\d\d)$", value)
         if m:
           # We have an offset
           asn1time = m.group(1)
           hours = int(m.group(2))
           minutes = int(m.group(3))
           utcoffset = (60 * hours) + minutes
         else:
           if not value.endswith("Z"):
             raise ValueError("Missing timezone")
           asn1time = value[:-1]
           utcoffset = 0
         parsed = time.strptime(asn1time, "%Y%m%d%H%M%S")
         tt = datetime.datetime(*(parsed[:7])) - datetime.timedelta(minutes=utcoffset)
         return calendar.timegm(tt.utctimetuple())
       def GetX509CertValidity(cert):
         """Returns the validity period of the certificate.
         @type cert: OpenSSL.crypto.X509
         @param cert: X509 certificate object
         """
         # The get_notBefore and get_notAfter functions are only supported in
         # pyOpenSSL 0.7 and above.
         try:
           get_notbefore_fn = cert.get_notBefore
         except AttributeError:
           not_before = None
         else:
           not_before_asn1 = get_notbefore_fn()
           if not_before_asn1 is None:
             not_before = None
           else:
             not_before = _ParseAsn1Generalizedtime(not_before_asn1)
         try:
           get_notafter_fn = cert.get_notAfter
         except AttributeError:
           not_after = None
         else:
           not_after_asn1 = get_notafter_fn()
           if not_after_asn1 is None:
             not_after = None
           else:
             not_after = _ParseAsn1Generalizedtime(not_after_asn1)
         return (not_before, not_after)
       def SafeEncode(text):
         """Return a 'safe' version of a source string.
         This function mangles the input string and returns a version that
         should be safe to display/encode as ASCII. To this end, we first
         convert it to ASCII using the 'backslashreplace' encoding which
         should get rid of any non-ASCII chars, and then we process it
         through a loop copied from the string repr sources in the python; we
         don't use string_escape anymore since that escape single quotes and
         backslashes too, and that is too much; and that escaping is not
         stable, i.e. string_escape(string_escape(x)) != string_escape(x).
         @type text: str or unicode
         @param text: input data
         @rtype: str
         @return: a safe version of text
         """
         if isinstance(text, unicode):
           # only if unicode; if str already, we handle it below
           text = text.encode('ascii', 'backslashreplace')
         resu = ""
         for char in text:
           c = ord(char)
           if char  == '\t':
             resu += r'\t'
           elif char == '\n':
             resu += r'\n'
           elif char == '\r':
             resu += r'\'r'
           elif c < 32 or c >= 127: # non-printable
             resu += "\\x%02x" % (c & 0xff)
           else:
             resu += char
         return resu
       def UnescapeAndSplit(text, sep=","):
         """Split and unescape a string based on a given separator.
         This function splits a string based on a separator where the
         separator itself can be escape in order to be an element of the
         elements. The escaping rules are (assuming coma being the
         separator):
           - a plain , separates the elements
           - a sequence \\\\, (double backslash plus comma) is handled as a
             backslash plus a separator comma
           - a sequence \, (backslash plus comma) is handled as a
             non-separator comma
         @type text: string
         @param text: the string to split
         @type sep: string
         @param text: the separator
         @rtype: string
         @return: a list of strings
         """
         # we split the list by sep (with no escaping at this stage)
         slist = text.split(sep)
         # next, we revisit the elements and if any of them ended with an odd
         # number of backslashes, then we join it with the next
         rlist = []
         while slist:
           e1 = slist.pop(0)
           if e1.endswith("\\"):
             num_b = len(e1) - len(e1.rstrip("\\"))
             if num_b % 2 == 1:
               e2 = slist.pop(0)
               # here the backslashes remain (all), and will be reduced in
               # the next step
               rlist.append(e1 + sep + e2)
               continue
           rlist.append(e1)
         # finally, replace backslash-something with something
         rlist = [re.sub(r"\\(.)", r"\1", v) for v in rlist]
         return rlist
       def CommaJoin(names):
         """Nicely join a set of identifiers.
         @param names: set, list or tuple
         @return: a string with the formatted results
         """
         return ", ".join([str(val) for val in names])
       def BytesToMebibyte(value):
         """Converts bytes to mebibytes.
         @type value: int
         @param value: Value in bytes
         @rtype: int
         @return: Value in mebibytes
         """
         return int(round(value / (1024.0 * 1024.0), 0))
       def CalculateDirectorySize(path):
         """Calculates the size of a directory recursively.
         @type path: string
         @param path: Path to directory
         @rtype: int
         @return: Size in mebibytes
         """
         size = 0
         for (curpath, _, files) in os.walk(path):
           for filename in files:
             st = os.lstat(PathJoin(curpath, filename))
             size += st.st_size
         return BytesToMebibyte(size)
       def GetFilesystemStats(path):
         """Returns the total and free space on a filesystem.
         @type path: string
         @param path: Path on filesystem to be examined
         @rtype: int
         @return: tuple of (Total space, Free space) in mebibytes
         """
         st = os.statvfs(path)
         fsize = BytesToMebibyte(st.f_bavail * st.f_frsize)
         tsize = BytesToMebibyte(st.f_blocks * st.f_frsize)
         return (tsize, fsize)
       def RunInSeparateProcess(fn, *args):
         """Runs a function in a separate process.
         Note: Only boolean return values are supported.
         @type fn: callable
         @param fn: Function to be called
         @rtype: bool
         @return: Function's result
         """
         pid = os.fork()
         if pid == 0:
           # Child process
           try:
             # In case the function uses temporary files
             ResetTempfileModule()
             # Call function
             result = int(bool(fn(*args)))
             assert result in (0, 1)
           except: # pylint: disable-msg=W0702
             logging.exception("Error while calling function in separate process")
             # 0 and 1 are reserved for the return value
             result = 33
           os._exit(result) # pylint: disable-msg=W0212
         # Parent process
         # Avoid zombies and check exit code
         (_, status) = os.waitpid(pid, 0)
         if os.WIFSIGNALED(status):
           exitcode = None
           signum = os.WTERMSIG(status)
         else:
           exitcode = os.WEXITSTATUS(status)
           signum = None
         if not (exitcode in (0, 1) and signum is None):
           raise errors.GenericError("Child program failed (code=%s, signal=%s)" %
                                     (exitcode, signum))
         return bool(exitcode)
       def IgnoreSignals(fn, *args, **kwargs):
         """Tries to call a function ignoring failures due to EINTR.
         """
         try:
           return fn(*args, **kwargs)
         except EnvironmentError, err:
           if err.errno == errno.EINTR:
             return None
           else:
             raise
         except (select.error, socket.error), err:
           # In python 2.6 and above select.error is an IOError, so it's handled
           # above, in 2.5 and below it's not, and it's handled here.
           if err.args and err.args[0] == errno.EINTR:
             return None
           else:
             raise
       def LockedMethod(fn):
         """Synchronized object access decorator.
         This decorator is intended to protect access to an object using the
         object's own lock which is hardcoded to '_lock'.
         """
         def _LockDebug(*args, **kwargs):
           if debug_locks:
             logging.debug(*args, **kwargs)
         def wrapper(self, *args, **kwargs):
           # pylint: disable-msg=W0212
           assert hasattr(self, '_lock')
           lock = self._lock
           _LockDebug("Waiting for %s", lock)
           lock.acquire()
           try:
             _LockDebug("Acquired %s", lock)
             result = fn(self, *args, **kwargs)
           finally:
             _LockDebug("Releasing %s", lock)
             lock.release()
             _LockDebug("Released %s", lock)
           return result
         return wrapper
       def LockFile(fd):
         """Locks a file using POSIX locks.
         @type fd: int
         @param fd: the file descriptor we need to lock
         """
         try:
           fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
         except IOError, err:
           if err.errno == errno.EAGAIN:
             raise errors.LockError("File already locked")
           raise
       def FormatTime(val):
         """Formats a time value.
         @type val: float or None
         @param val: the timestamp as returned by time.time()
         @return: a string value or N/A if we don't have a valid timestamp
         """
         if val is None or not isinstance(val, (int, float)):
           return "N/A"
         # these two codes works on Linux, but they are not guaranteed on all
         # platforms
         return time.strftime("%F %T", time.localtime(val))
       def ReadWatcherPauseFile(filename, now=None, remove_after=3600):
         """Reads the watcher pause file.
         @type filename: string
         @param filename: Path to watcher pause file
         @type now: None, float or int
         @param now: Current time as Unix timestamp
         @type remove_after: int
         @param remove_after: Remove watcher pause file after specified amount of
           seconds past the pause end time
         """
         if now is None:
           now = time.time()
         try:
           value = ReadFile(filename)
         except IOError, err:
           if err.errno != errno.ENOENT:
             raise
           value = None
         if value is not None:
           try:
             value = int(value)
           except ValueError:
             logging.warning(("Watcher pause file (%s) contains invalid value,"
                              " removing it"), filename)
             RemoveFile(filename)
             value = None
           if value is not None:
             # Remove file if it's outdated
             if now > (value + remove_after):
               RemoveFile(filename)
               value = None
             elif now > value:
               value = None
         return value
       class RetryTimeout(Exception):
         """Retry loop timed out.
         Any arguments which was passed by the retried function to RetryAgain will be
         preserved in RetryTimeout, if it is raised. If such argument was an exception
         the RaiseInner helper method will reraise it.
         """
         def RaiseInner(self):
           if self.args and isinstance(self.args[0], Exception):
             raise self.args[0]
           else:
             raise RetryTimeout(*self.args)
       class RetryAgain(Exception):
         """Retry again.
         Any arguments passed to RetryAgain will be preserved, if a timeout occurs, as
         arguments to RetryTimeout. If an exception is passed, the RaiseInner() method
         of the RetryTimeout() method can be used to reraise it.
         """
       class _RetryDelayCalculator(object):
         """Calculator for increasing delays.
         """
         __slots__ = [
           "_factor",
           "_limit",
           "_next",
           "_start",
+          ]
         def __init__(self, start, factor, limit):
           """Initializes this class.
           @type start: float
           @param start: Initial delay
           @type factor: float
           @param factor: Factor for delay increase
           @type limit: float or None
           @param limit: Upper limit for delay or None for no limit
           """
           assert start > 0.0
           assert factor >= 1.0
           assert limit is None or limit >= 0.0
           self._start = start
           self._factor = factor
           self._limit = limit
           self._next = start
         def __call__(self):
           """Returns current delay and calculates the next one.
           """
           current = self._next
           # Update for next run
           if self._limit is None or self._next < self._limit:
             self._next = min(self._limit, self._next * self._factor)
           return current
       #: Special delay to specify whole remaining timeout
       RETRY_REMAINING_TIME = object()
       def Retry(fn, delay, timeout, args=None, wait_fn=time.sleep,
                 _time_fn=time.time):
         """Call a function repeatedly until it succeeds.
         The function C{fn} is called repeatedly until it doesn't throw L{RetryAgain}
         anymore. Between calls a delay, specified by C{delay}, is inserted. After a
         total of C{timeout} seconds, this function throws L{RetryTimeout}.
         C{delay} can be one of the following:
           - callable returning the delay length as a float
           - Tuple of (start, factor, limit)
           - L{RETRY_REMAINING_TIME} to sleep until the timeout expires (this is
             useful when overriding L{wait_fn} to wait for an external event)
           - A static delay as a number (int or float)
         @type fn: callable
         @param fn: Function to be called
         @param delay: Either a callable (returning the delay), a tuple of (start,
                       factor, limit) (see L{_RetryDelayCalculator}),
                       L{RETRY_REMAINING_TIME} or a number (int or float)
         @type timeout: float
         @param timeout: Total timeout
         @type wait_fn: callable
         @param wait_fn: Waiting function
         @return: Return value of function
         """
         assert callable(fn)
         assert callable(wait_fn)
         assert callable(_time_fn)
         if args is None:
           args = []
         end_time = _time_fn() + timeout
         if callable(delay):
           # External function to calculate delay
           calc_delay = delay
         elif isinstance(delay, (tuple, list)):
           # Increasing delay with optional upper boundary
           (start, factor, limit) = delay
           calc_delay = _RetryDelayCalculator(start, factor, limit)
         elif delay is RETRY_REMAINING_TIME:
           # Always use the remaining time
           calc_delay = None
         else:
           # Static delay
           calc_delay = lambda: delay
         assert calc_delay is None or callable(calc_delay)
         while True:
           retry_args = []
           try:
             # pylint: disable-msg=W0142
             return fn(*args)
           except RetryAgain, err:
             retry_args = err.args
           except RetryTimeout:
             raise errors.ProgrammerError("Nested retry loop detected that didn't"
                                          " handle RetryTimeout")
           remaining_time = end_time - _time_fn()
           if remaining_time < 0.0:
             # pylint: disable-msg=W0142
             raise RetryTimeout(*retry_args)
           assert remaining_time >= 0.0
           if calc_delay is None:
             wait_fn(remaining_time)
           else:
             current_delay = calc_delay()
             if current_delay > 0.0:
               wait_fn(current_delay)
       class FileLock(object):
         """Utility class for file locks.
         """
         def __init__(self, fd, filename):
           """Constructor for FileLock.
           @type fd: file
           @param fd: File object
           @type filename: str
           @param filename: Path of the file opened at I{fd}
           """
           self.fd = fd
           self.filename = filename
         @classmethod
         def Open(cls, filename):
           """Creates and opens a file to be used as a file-based lock.
           @type filename: string
           @param filename: path to the file to be locked
           """
           # Using "os.open" is necessary to allow both opening existing file
           # read/write and creating if not existing. Vanilla "open" will truncate an
           # existing file -or- allow creating if not existing.
           return cls(os.fdopen(os.open(filename, os.O_RDWR | os.O_CREAT), "w+"),
                      filename)
         def __del__(self):
           self.Close()
         def Close(self):
           """Close the file and release the lock.
           """
           if hasattr(self, "fd") and self.fd:
             self.fd.close()
             self.fd = None
         def _flock(self, flag, blocking, timeout, errmsg):
           """Wrapper for fcntl.flock.
           @type flag: int
           @param flag: operation flag
           @type blocking: bool
           @param blocking: whether the operation should be done in blocking mode.
           @type timeout: None or float
           @param timeout: for how long the operation should be retried (implies
                           non-blocking mode).
           @type errmsg: string
           @param errmsg: error message in case operation fails.
           """
           assert self.fd, "Lock was closed"
           assert timeout is None or timeout >= 0, \
             "If specified, timeout must be positive"
           assert not (flag & fcntl.LOCK_NB), "LOCK_NB must not be set"
           # When a timeout is used, LOCK_NB must always be set
           if not (timeout is None and blocking):
             flag |= fcntl.LOCK_NB
           if timeout is None:
             self._Lock(self.fd, flag, timeout)
           else:
             try:
               Retry(self._Lock, (0.1, 1.2, 1.0), timeout,
                     args=(self.fd, flag, timeout))
             except RetryTimeout:
               raise errors.LockError(errmsg)
         @staticmethod
         def _Lock(fd, flag, timeout):
           try:
             fcntl.flock(fd, flag)
           except IOError, err:
             if timeout is not None and err.errno == errno.EAGAIN:
               raise RetryAgain()
             logging.exception("fcntl.flock failed")
             raise
         def Exclusive(self, blocking=False, timeout=None):
           """Locks the file in exclusive mode.
           @type blocking: boolean
           @param blocking: whether to block and wait until we
               can lock the file or return immediately
           @type timeout: int or None
           @param timeout: if not None, the duration to wait for the lock
               (in blocking mode)
           """
           self._flock(fcntl.LOCK_EX, blocking, timeout,
                       "Failed to lock %s in exclusive mode" % self.filename)
         def Shared(self, blocking=False, timeout=None):
           """Locks the file in shared mode.
           @type blocking: boolean
           @param blocking: whether to block and wait until we
               can lock the file or return immediately
           @type timeout: int or None
           @param timeout: if not None, the duration to wait for the lock
               (in blocking mode)
           """
           self._flock(fcntl.LOCK_SH, blocking, timeout,
                       "Failed to lock %s in shared mode" % self.filename)
         def Unlock(self, blocking=True, timeout=None):
           """Unlocks the file.
           According to C{flock(2)}, unlocking can also be a nonblocking
           operation::
             To make a non-blocking request, include LOCK_NB with any of the above
             operations.
           @type blocking: boolean
           @param blocking: whether to block and wait until we
               can lock the file or return immediately
           @type timeout: int or None
           @param timeout: if not None, the duration to wait for the lock
               (in blocking mode)
           """
           self._flock(fcntl.LOCK_UN, blocking, timeout,
                       "Failed to unlock %s" % self.filename)
       class LineSplitter:
         """Splits data chunks into lines separated by newline.
         Instances provide a file-like interface.
         """
         def __init__(self, line_fn, *args):
           """Initializes this class.
           @type line_fn: callable
           @param line_fn: Function called for each line, first parameter is line
           @param args: Extra arguments for L{line_fn}
           """
           assert callable(line_fn)
           if args:
             # Python 2.4 doesn't have functools.partial yet
             self._line_fn = \
               lambda line: line_fn(line, *args) # pylint: disable-msg=W0142
           else:
             self._line_fn = line_fn
           self._lines = collections.deque()
           self._buffer = ""
         def write(self, data):
           parts = (self._buffer + data).split("\n")
           self._buffer = parts.pop()
           self._lines.extend(parts)
         def flush(self):
           while self._lines:
             self._line_fn(self._lines.popleft().rstrip("\r\n"))
         def close(self):
           self.flush()
           if self._buffer:
             self._line_fn(self._buffer)
       def SignalHandled(signums):
         """Signal Handled decoration.
         This special decorator installs a signal handler and then calls the target
         function. The function must accept a 'signal_handlers' keyword argument,
         which will contain a dict indexed by signal number, with SignalHandler
         objects as values.
         The decorator can be safely stacked with iself, to handle multiple signals
         with different handlers.
         @type signums: list
         @param signums: signals to intercept
         """
         def wrap(fn):
           def sig_function(*args, **kwargs):
             assert 'signal_handlers' not in kwargs or \
                    kwargs['signal_handlers'] is None or \
                    isinstance(kwargs['signal_handlers'], dict), \
                    "Wrong signal_handlers parameter in original function call"
             if 'signal_handlers' in kwargs and kwargs['signal_handlers'] is not None:
               signal_handlers = kwargs['signal_handlers']
             else:
               signal_handlers = {}
               kwargs['signal_handlers'] = signal_handlers
             sighandler = SignalHandler(signums)
             try:
               for sig in signums:
                 signal_handlers[sig] = sighandler
               return fn(*args, **kwargs)
             finally:
               sighandler.Reset()
           return sig_function
         return wrap
       class SignalHandler(object):
         """Generic signal handler class.
         It automatically restores the original handler when deconstructed or
         when L{Reset} is called. You can either pass your own handler
         function in or query the L{called} attribute to detect whether the
         signal was sent.
         @type signum: list
         @ivar signum: the signals we handle
         @type called: boolean
         @ivar called: tracks whether any of the signals have been raised
         """
         def __init__(self, signum):
           """Constructs a new SignalHandler instance.
           @type signum: int or list of ints
           @param signum: Single signal number or set of signal numbers
           """
           self.signum = set(signum)
           self.called = False
           self._previous = {}
           try:
             for signum in self.signum:
               # Setup handler
               prev_handler = signal.signal(signum, self._HandleSignal)
               try:
                 self._previous[signum] = prev_handler
               except:
                 # Restore previous handler
                 signal.signal(signum, prev_handler)
                 raise
           except:
             # Reset all handlers
             self.Reset()
             # Here we have a race condition: a handler may have already been called,
             # but there's not much we can do about it at this point.
             raise
         def __del__(self):
           self.Reset()
         def Reset(self):
           """Restore previous handler.
           This will reset all the signals to their previous handlers.
           """
           for signum, prev_handler in self._previous.items():
             signal.signal(signum, prev_handler)
             # If successful, remove from dict
             del self._previous[signum]
         def Clear(self):
           """Unsets the L{called} flag.
           This function can be used in case a signal may arrive several times.
           """
           self.called = False
         # we don't care about arguments, but we leave them named for the future
         def _HandleSignal(self, signum, frame): # pylint: disable-msg=W0613
           """Actual signal handling function.
           """
           # This is not nice and not absolutely atomic, but it appears to be the only
           # solution in Python -- there are no atomic types.
           self.called = True
       class FieldSet(object):
         """A simple field set.
         Among the features are:
           - checking if a string is among a list of static string or regex objects
           - checking if a whole list of string matches
           - returning the matching groups from a regex match
         Internally, all fields are held as regular expression objects.
         """
         def __init__(self, *items):
           self.items = [re.compile("^%s$" % value) for value in items]
         def Extend(self, other_set):
           """Extend the field set with the items from another one"""
           self.items.extend(other_set.items)
         def Matches(self, field):
           """Checks if a field matches the current set
           @type field: str
           @param field: the string to match
           @return: either None or a regular expression match object
           """
           for m in itertools.ifilter(None, (val.match(field) for val in self.items)):
             return m
           return None
         def NonMatching(self, items):
           """Returns the list of fields not matching the current set
           @type items: list
           @param items: the list of fields to check
           @rtype: list
           @return: list of non-matching fields
           """
           return [val for val in items if not self.Matches(val)]

Synnefo » snf-ganeti

root / lib / utils.py @ 4c32a8bd