Source Code for Module ganeti.utils.wrapper

  1  # 
  2  # 
  3   
  4  # Copyright (C) 2006, 2007, 2010, 2011 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 time 
 26  import socket 
 27  import errno 
 28  import tempfile 
 29  import fcntl 
 30  import os 
 31  import select 
 32  import logging 
 33   
 34   
 35 -def TestDelay(duration): 
 36    """Sleep for a fixed amount of time. 
 37   
 38    @type duration: float 
 39    @param duration: the sleep duration 
 40    @rtype: boolean 
 41    @return: False for negative value, True otherwise 
 42   
 43    """ 
 44    if duration < 0: 
 45      return False, "Invalid sleep duration" 
 46    time.sleep(duration) 
 47    return True, None 
 48   
 49   
 50 -def CloseFdNoError(fd, retries=5): 
 51    """Close a file descriptor ignoring errors. 
 52   
 53    @type fd: int 
 54    @param fd: the file descriptor 
 55    @type retries: int 
 56    @param retries: how many retries to make, in case we get any 
 57        other error than EBADF 
 58   
 59    """ 
 60    try: 
 61      os.close(fd) 
 62    except OSError, err: 
 63      if err.errno != errno.EBADF: 
 64        if retries > 0: 
 65          CloseFdNoError(fd, retries - 1) 
 66      # else either it's closed already or we're out of retries, so we 
 67      # ignore this and go on 
 68   
 69   
 70 -def SetCloseOnExecFlag(fd, enable): 
 71    """Sets or unsets the close-on-exec flag on a file descriptor. 
 72   
 73    @type fd: int 
 74    @param fd: File descriptor 
 75    @type enable: bool 
 76    @param enable: Whether to set or unset it. 
 77   
 78    """ 
 79    flags = fcntl.fcntl(fd, fcntl.F_GETFD) 
 80   
 81    if enable: 
 82      flags |= fcntl.FD_CLOEXEC 
 83    else: 
 84      flags &= ~fcntl.FD_CLOEXEC 
 85   
 86    fcntl.fcntl(fd, fcntl.F_SETFD, flags) 
 87   
 88   
 89 -def SetNonblockFlag(fd, enable): 
 90    """Sets or unsets the O_NONBLOCK flag on on a file descriptor. 
 91   
 92    @type fd: int 
 93    @param fd: File descriptor 
 94    @type enable: bool 
 95    @param enable: Whether to set or unset it 
 96   
 97    """ 
 98    flags = fcntl.fcntl(fd, fcntl.F_GETFL) 
 99   
100    if enable: 
101      flags |= os.O_NONBLOCK 
102    else: 
103      flags &= ~os.O_NONBLOCK 
104   
105    fcntl.fcntl(fd, fcntl.F_SETFL, flags) 
106   
107   
108 -def RetryOnSignal(fn, *args, **kwargs): 
109    """Calls a function again if it failed due to EINTR. 
110   
111    """ 
112    while True: 
113      try: 
114        return fn(*args, **kwargs) 
115      except EnvironmentError, err: 
116        if err.errno != errno.EINTR: 
117          raise 
118      except (socket.error, select.error), err: 
119        # In python 2.6 and above select.error is an IOError, so it's handled 
120        # above, in 2.5 and below it's not, and it's handled here. 
121        if not (err.args and err.args[0] == errno.EINTR): 
122          raise 
123   
124   
125 -def IgnoreProcessNotFound(fn, *args, **kwargs): 
126    """Ignores ESRCH when calling a process-related function. 
127   
128    ESRCH is raised when a process is not found. 
129   
130    @rtype: bool 
131    @return: Whether process was found 
132   
133    """ 
134    try: 
135      fn(*args, **kwargs) 
136    except EnvironmentError, err: 
137      # Ignore ESRCH 
138      if err.errno == errno.ESRCH: 
139        return False 
140      raise 
141   
142    return True 
143   
144   
145 -def IgnoreSignals(fn, *args, **kwargs): 
146    """Tries to call a function ignoring failures due to EINTR. 
147   
148    """ 
149    try: 
150      return fn(*args, **kwargs) 
151    except EnvironmentError, err: 
152      if err.errno == errno.EINTR: 
153        return None 
154      else: 
155        raise 
156    except (select.error, socket.error), err: 
157      # In python 2.6 and above select.error is an IOError, so it's handled 
158      # above, in 2.5 and below it's not, and it's handled here. 
159      if err.args and err.args[0] == errno.EINTR: 
160        return None 
161      else: 
162        raise 
163   
164   
165 -def GetClosedTempfile(*args, **kwargs): 
166    """Creates a temporary file and returns its path. 
167   
168    """ 
169    (fd, path) = tempfile.mkstemp(*args, **kwargs) 
170    CloseFdNoError(fd) 
171    return path 
172   
173   
174 -def ResetTempfileModule(): 
175    """Resets the random name generator of the tempfile module. 
176   
177    This function should be called after C{os.fork} in the child process to 
178    ensure it creates a newly seeded random generator. Otherwise it would 
179    generate the same random parts as the parent process. If several processes 
180    race for the creation of a temporary file, this could lead to one not getting 
181    a temporary name. 
182   
183    """ 
184    # pylint: disable-msg=W0212 
185    if hasattr(tempfile, "_once_lock") and hasattr(tempfile, "_name_sequence"): 
186      tempfile._once_lock.acquire() 
187      try: 
188        # Reset random name generator 
189        tempfile._name_sequence = None 
190      finally: 
191        tempfile._once_lock.release() 
192    else: 
193      logging.critical("The tempfile module misses at least one of the" 
194                       " '_once_lock' and '_name_sequence' attributes") 
195