Synnefo » snf-ganeti

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 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 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