Synnefo » snf-ganeti » ganeti-local

#

#

# Copyright (C) 2006, 2007, 2010, 2011, 2012 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.

"""Utility functions wrapping other functions.

"""

import sys

import time

import socket

import errno

import tempfile

import fcntl

import os

import select

import logging

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 CloseFdNoError(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:

        CloseFdNoError(fd, retries - 1)

    # else either it's closed already or we're out of retries, so we

    # ignore this and go on

def SetCloseOnExecFlag(fd, enable):

  """Sets or unsets the close-on-exec flag on a file descriptor.

  @type fd: int

  @param fd: File descriptor

  @type enable: bool

  @param enable: Whether to set or unset it.

  """

  flags = fcntl.fcntl(fd, fcntl.F_GETFD)

  if enable:

    flags |= fcntl.FD_CLOEXEC

  else:

    flags &= ~fcntl.FD_CLOEXEC

  fcntl.fcntl(fd, fcntl.F_SETFD, flags)

def SetNonblockFlag(fd, enable):

  """Sets or unsets the O_NONBLOCK flag on on a file descriptor.

  @type fd: int

  @param fd: File descriptor

  @type enable: bool

  @param enable: Whether to set or unset it

  """

  flags = fcntl.fcntl(fd, fcntl.F_GETFL)

  if enable:

    flags |= os.O_NONBLOCK

  else:

    flags &= ~os.O_NONBLOCK

  fcntl.fcntl(fd, fcntl.F_SETFL, flags)

def RetryOnSignal(fn, *args, **kwargs):

  """Calls a function again if it failed due to EINTR.

  """

  while True:

    try:

      return fn(*args, **kwargs)

    except EnvironmentError, err:

      if err.errno != errno.EINTR:

        raise

    except (socket.error, select.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 not (err.args and err.args[0] == errno.EINTR):

        raise

def IgnoreProcessNotFound(fn, *args, **kwargs):

  """Ignores ESRCH when calling a process-related function.

  ESRCH is raised when a process is not found.

  @rtype: bool

  @return: Whether process was found

  """

  try:

    fn(*args, **kwargs)

  except EnvironmentError, err:

    # Ignore ESRCH

    if err.errno == errno.ESRCH:

      return False

    raise

  return True

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 GetClosedTempfile(*args, **kwargs):

  """Creates a temporary file and returns its path.

  """

  (fd, path) = tempfile.mkstemp(*args, **kwargs)

  CloseFdNoError(fd)

  return path

def IsExecutable(filename):

  """Checks whether a file exists and is executable.

  @type filename: string

  @param filename: Filename

  @rtype: bool

  """

  return os.path.isfile(filename) and os.access(filename, os.X_OK)

def ResetTempfileModule(_time=time.time):

  """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=W0212

  if ((sys.hexversion >= 0x020703F0 and sys.hexversion < 0x03000000) or

      sys.hexversion >= 0x030203F0):

    # Python 2.7 automatically resets the RNG on pid changes (i.e. forking)

    return

  try:

    lock = tempfile._once_lock

    lock.acquire()

    try:

      # Re-seed random name generator

      if tempfile._name_sequence:

        tempfile._name_sequence.rng.seed(hash(_time()) ^ os.getpid())

    finally:

      lock.release()

  except AttributeError:

    logging.critical("The tempfile module misses at least one of the"

                     " '_once_lock' and '_name_sequence' attributes")