Source Code for Module ganeti.utils.wrapper

  1  # 
  2  # 
  3   
  4  # Copyright (C) 2006, 2007, 2010, 2011, 2012 Google Inc. 
  5  # 
  6  # This program is free software; you can redistribute it and/or modify 
  7  # it under the terms of the GNU General Public License as published by 
  8  # the Free Software Foundation; either version 2 of the License, or 
  9  # (at your option) any later version. 
 10  # 
 11  # This program is distributed in the hope that it will be useful, but 
 12  # WITHOUT ANY WARRANTY; without even the implied warranty of 
 13  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU 
 14  # General Public License for more details. 
 15  # 
 16  # You should have received a copy of the GNU General Public License 
 17  # along with this program; if not, write to the Free Software 
 18  # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 
 19  # 02110-1301, USA. 
 20   
 21  """Utility functions wrapping other functions. 
 22   
 23  """ 
 24   
 25  import sys 
 26  import time 
 27  import socket 
 28  import errno 
 29  import tempfile 
 30  import fcntl 
 31  import os 
 32  import select 
 33  import logging 
 34   
 35   
 36 -def TestDelay(duration): 
 37    """Sleep for a fixed amount of time. 
 38   
 39    @type duration: float 
 40    @param duration: the sleep duration 
 41    @rtype: boolean 
 42    @return: False for negative value, True otherwise 
 43   
 44    """ 
 45    if duration < 0: 
 46      return False, "Invalid sleep duration" 
 47    time.sleep(duration) 
 48    return True, None 
 49   
 50   
 51 -def CloseFdNoError(fd, retries=5): 
 52    """Close a file descriptor ignoring errors. 
 53   
 54    @type fd: int 
 55    @param fd: the file descriptor 
 56    @type retries: int 
 57    @param retries: how many retries to make, in case we get any 
 58        other error than EBADF 
 59   
 60    """ 
 61    try: 
 62      os.close(fd) 
 63    except OSError, err: 
 64      if err.errno != errno.EBADF: 
 65        if retries > 0: 
 66          CloseFdNoError(fd, retries - 1) 
 67      # else either it's closed already or we're out of retries, so we 
 68      # ignore this and go on 
 69   
 70   
 71 -def SetCloseOnExecFlag(fd, enable): 
 72    """Sets or unsets the close-on-exec flag on a file descriptor. 
 73   
 74    @type fd: int 
 75    @param fd: File descriptor 
 76    @type enable: bool 
 77    @param enable: Whether to set or unset it. 
 78   
 79    """ 
 80    flags = fcntl.fcntl(fd, fcntl.F_GETFD) 
 81   
 82    if enable: 
 83      flags |= fcntl.FD_CLOEXEC 
 84    else: 
 85      flags &= ~fcntl.FD_CLOEXEC 
 86   
 87    fcntl.fcntl(fd, fcntl.F_SETFD, flags) 
 88   
 89   
 90 -def SetNonblockFlag(fd, enable): 
 91    """Sets or unsets the O_NONBLOCK flag on on a file descriptor. 
 92   
 93    @type fd: int 
 94    @param fd: File descriptor 
 95    @type enable: bool 
 96    @param enable: Whether to set or unset it 
 97   
 98    """ 
 99    flags = fcntl.fcntl(fd, fcntl.F_GETFL) 
100   
101    if enable: 
102      flags |= os.O_NONBLOCK 
103    else: 
104      flags &= ~os.O_NONBLOCK 
105   
106    fcntl.fcntl(fd, fcntl.F_SETFL, flags) 
107   
108   
109 -def RetryOnSignal(fn, *args, **kwargs): 
110    """Calls a function again if it failed due to EINTR. 
111   
112    """ 
113    while True: 
114      try: 
115        return fn(*args, **kwargs) 
116      except EnvironmentError, err: 
117        if err.errno != errno.EINTR: 
118          raise 
119      except (socket.error, select.error), err: 
120        # In python 2.6 and above select.error is an IOError, so it's handled 
121        # above, in 2.5 and below it's not, and it's handled here. 
122        if not (err.args and err.args[0] == errno.EINTR): 
123          raise 
124   
125   
126 -def IgnoreProcessNotFound(fn, *args, **kwargs): 
127    """Ignores ESRCH when calling a process-related function. 
128   
129    ESRCH is raised when a process is not found. 
130   
131    @rtype: bool 
132    @return: Whether process was found 
133   
134    """ 
135    try: 
136      fn(*args, **kwargs) 
137    except EnvironmentError, err: 
138      # Ignore ESRCH 
139      if err.errno == errno.ESRCH: 
140        return False 
141      raise 
142   
143    return True 
144   
145   
146 -def IgnoreSignals(fn, *args, **kwargs): 
147    """Tries to call a function ignoring failures due to EINTR. 
148   
149    """ 
150    try: 
151      return fn(*args, **kwargs) 
152    except EnvironmentError, err: 
153      if err.errno == errno.EINTR: 
154        return None 
155      else: 
156        raise 
157    except (select.error, socket.error), err: 
158      # In python 2.6 and above select.error is an IOError, so it's handled 
159      # above, in 2.5 and below it's not, and it's handled here. 
160      if err.args and err.args[0] == errno.EINTR: 
161        return None 
162      else: 
163        raise 
164   
165   
166 -def GetClosedTempfile(*args, **kwargs): 
167    """Creates a temporary file and returns its path. 
168   
169    """ 
170    (fd, path) = tempfile.mkstemp(*args, **kwargs) 
171    CloseFdNoError(fd) 
172    return path 
173   
174   
175 -def IsExecutable(filename): 
176    """Checks whether a file exists and is executable. 
177   
178    @type filename: string 
179    @param filename: Filename 
180    @rtype: bool 
181   
182    """ 
183    return os.path.isfile(filename) and os.access(filename, os.X_OK) 
184   
185   
186 -def ResetTempfileModule(_time=time.time): 
187    """Resets the random name generator of the tempfile module. 
188   
189    This function should be called after C{os.fork} in the child process to 
190    ensure it creates a newly seeded random generator. Otherwise it would 
191    generate the same random parts as the parent process. If several processes 
192    race for the creation of a temporary file, this could lead to one not getting 
193    a temporary name. 
194   
195    """ 
196    # pylint: disable=W0212 
197    if ((sys.hexversion >= 0x020703F0 and sys.hexversion < 0x03000000) or 
198        sys.hexversion >= 0x030203F0): 
199      # Python 2.7 automatically resets the RNG on pid changes (i.e. forking) 
200      return 
201   
202    try: 
203      lock = tempfile._once_lock 
204      lock.acquire() 
205      try: 
206        # Re-seed random name generator 
207        if tempfile._name_sequence: 
208          tempfile._name_sequence.rng.seed(hash(_time()) ^ os.getpid()) 
209      finally: 
210        lock.release() 
211    except AttributeError: 
212      logging.critical("The tempfile module misses at least one of the" 
213                       " '_once_lock' and '_name_sequence' attributes") 
214