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, in seconds 
 41    @rtype: (boolean, str) 
 42    @return: False for negative value, and an accompanying error message; 
 43        True otherwise (and msg is None) 
 44   
 45    """ 
 46    if duration < 0: 
 47      return False, "Invalid sleep duration" 
 48    time.sleep(duration) 
 49    return True, None 
 50   
 51   
 52 -def CloseFdNoError(fd, retries=5): 
 53    """Close a file descriptor ignoring errors. 
 54   
 55    @type fd: int 
 56    @param fd: the file descriptor 
 57    @type retries: int 
 58    @param retries: how many retries to make, in case we get any 
 59        other error than EBADF 
 60   
 61    """ 
 62    try: 
 63      os.close(fd) 
 64    except OSError, err: 
 65      if err.errno != errno.EBADF: 
 66        if retries > 0: 
 67          CloseFdNoError(fd, retries - 1) 
 68      # else either it's closed already or we're out of retries, so we 
 69      # ignore this and go on 
 70   
 71   
 72 -def SetCloseOnExecFlag(fd, enable): 
 73    """Sets or unsets the close-on-exec flag on a file descriptor. 
 74   
 75    @type fd: int 
 76    @param fd: File descriptor 
 77    @type enable: bool 
 78    @param enable: Whether to set or unset it. 
 79   
 80    """ 
 81    flags = fcntl.fcntl(fd, fcntl.F_GETFD) 
 82   
 83    if enable: 
 84      flags |= fcntl.FD_CLOEXEC 
 85    else: 
 86      flags &= ~fcntl.FD_CLOEXEC 
 87   
 88    fcntl.fcntl(fd, fcntl.F_SETFD, flags) 
 89   
 90   
 91 -def SetNonblockFlag(fd, enable): 
 92    """Sets or unsets the O_NONBLOCK flag on on a file descriptor. 
 93   
 94    @type fd: int 
 95    @param fd: File descriptor 
 96    @type enable: bool 
 97    @param enable: Whether to set or unset it 
 98   
 99    """ 
100    flags = fcntl.fcntl(fd, fcntl.F_GETFL) 
101   
102    if enable: 
103      flags |= os.O_NONBLOCK 
104    else: 
105      flags &= ~os.O_NONBLOCK 
106   
107    fcntl.fcntl(fd, fcntl.F_SETFL, flags) 
108   
109   
110 -def RetryOnSignal(fn, *args, **kwargs): 
111    """Calls a function again if it failed due to EINTR. 
112   
113    """ 
114    while True: 
115      try: 
116        return fn(*args, **kwargs) 
117      except EnvironmentError, err: 
118        if err.errno != errno.EINTR: 
119          raise 
120      except (socket.error, select.error), err: 
121        # In python 2.6 and above select.error is an IOError, so it's handled 
122        # above, in 2.5 and below it's not, and it's handled here. 
123        if not (err.args and err.args[0] == errno.EINTR): 
124          raise 
125   
126   
127 -def IgnoreProcessNotFound(fn, *args, **kwargs): 
128    """Ignores ESRCH when calling a process-related function. 
129   
130    ESRCH is raised when a process is not found. 
131   
132    @rtype: bool 
133    @return: Whether process was found 
134   
135    """ 
136    try: 
137      fn(*args, **kwargs) 
138    except EnvironmentError, err: 
139      # Ignore ESRCH 
140      if err.errno == errno.ESRCH: 
141        return False 
142      raise 
143   
144    return True 
145   
146   
147 -def IgnoreSignals(fn, *args, **kwargs): 
148    """Tries to call a function ignoring failures due to EINTR. 
149   
150    """ 
151    try: 
152      return fn(*args, **kwargs) 
153    except EnvironmentError, err: 
154      if err.errno == errno.EINTR: 
155        return None 
156      else: 
157        raise 
158    except (select.error, socket.error), err: 
159      # In python 2.6 and above select.error is an IOError, so it's handled 
160      # above, in 2.5 and below it's not, and it's handled here. 
161      if err.args and err.args[0] == errno.EINTR: 
162        return None 
163      else: 
164        raise 
165   
166   
167 -def GetClosedTempfile(*args, **kwargs): 
168    """Creates a temporary file and returns its path. 
169   
170    """ 
171    (fd, path) = tempfile.mkstemp(*args, **kwargs) 
172    CloseFdNoError(fd) 
173    return path 
174   
175   
176 -def IsExecutable(filename): 
177    """Checks whether a file exists and is executable. 
178   
179    @type filename: string 
180    @param filename: Filename 
181    @rtype: bool 
182   
183    """ 
184    return os.path.isfile(filename) and os.access(filename, os.X_OK) 
185   
186   
187 -def ResetTempfileModule(_time=time.time): 
188    """Resets the random name generator of the tempfile module. 
189   
190    This function should be called after C{os.fork} in the child process to 
191    ensure it creates a newly seeded random generator. Otherwise it would 
192    generate the same random parts as the parent process. If several processes 
193    race for the creation of a temporary file, this could lead to one not getting 
194    a temporary name. 
195   
196    """ 
197    # pylint: disable=W0212 
198    if ((sys.hexversion >= 0x020703F0 and sys.hexversion < 0x03000000) or 
199        sys.hexversion >= 0x030203F0): 
200      # Python 2.7 automatically resets the RNG on pid changes (i.e. forking) 
201      return 
202   
203    try: 
204      lock = tempfile._once_lock 
205      lock.acquire() 
206      try: 
207        # Re-seed random name generator 
208        if tempfile._name_sequence: 
209          tempfile._name_sequence.rng.seed(hash(_time()) ^ os.getpid()) 
210      finally: 
211        lock.release() 
212    except AttributeError: 
213      logging.critical("The tempfile module misses at least one of the" 
214                       " '_once_lock' and '_name_sequence' attributes") 
215