Source Code for Module ganeti.utils.wrapper

  1  # 
  2  # 
  3   
  4  # Copyright (C) 2006, 2007, 2010, 2011, 2012 Google Inc. 
  5  # All rights reserved. 
  6  # 
  7  # Redistribution and use in source and binary forms, with or without 
  8  # modification, are permitted provided that the following conditions are 
  9  # met: 
 10  # 
 11  # 1. Redistributions of source code must retain the above copyright notice, 
 12  # this list of conditions and the following disclaimer. 
 13  # 
 14  # 2. Redistributions in binary form must reproduce the above copyright 
 15  # notice, this list of conditions and the following disclaimer in the 
 16  # documentation and/or other materials provided with the distribution. 
 17  # 
 18  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 
 19  # IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 
 20  # TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
 21  # PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR 
 22  # CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 
 23  # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 
 24  # PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
 25  # PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
 26  # LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 
 27  # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 
 28  # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 29   
 30  """Utility functions wrapping other functions. 
 31   
 32  """ 
 33   
 34  import sys 
 35  import time 
 36  import socket 
 37  import errno 
 38  import tempfile 
 39  import fcntl 
 40  import os 
 41  import select 
 42  import logging 
 43   
 44   
 45 -def TestDelay(duration): 
 46    """Sleep for a fixed amount of time. 
 47   
 48    @type duration: float 
 49    @param duration: the sleep duration, in seconds 
 50    @rtype: (boolean, str) 
 51    @return: False for negative value, and an accompanying error message; 
 52        True otherwise (and msg is None) 
 53   
 54    """ 
 55    if duration < 0: 
 56      return False, "Invalid sleep duration" 
 57    time.sleep(duration) 
 58    return True, None 
 59   
 60   
 61 -def CloseFdNoError(fd, retries=5): 
 62    """Close a file descriptor ignoring errors. 
 63   
 64    @type fd: int 
 65    @param fd: the file descriptor 
 66    @type retries: int 
 67    @param retries: how many retries to make, in case we get any 
 68        other error than EBADF 
 69   
 70    """ 
 71    try: 
 72      os.close(fd) 
 73    except OSError, err: 
 74      if err.errno != errno.EBADF: 
 75        if retries > 0: 
 76          CloseFdNoError(fd, retries - 1) 
 77      # else either it's closed already or we're out of retries, so we 
 78      # ignore this and go on 
 79   
 80   
 81 -def SetCloseOnExecFlag(fd, enable): 
 82    """Sets or unsets the close-on-exec flag on a file descriptor. 
 83   
 84    @type fd: int 
 85    @param fd: File descriptor 
 86    @type enable: bool 
 87    @param enable: Whether to set or unset it. 
 88   
 89    """ 
 90    flags = fcntl.fcntl(fd, fcntl.F_GETFD) 
 91   
 92    if enable: 
 93      flags |= fcntl.FD_CLOEXEC 
 94    else: 
 95      flags &= ~fcntl.FD_CLOEXEC 
 96   
 97    fcntl.fcntl(fd, fcntl.F_SETFD, flags) 
 98   
 99   
100 -def SetNonblockFlag(fd, enable): 
101    """Sets or unsets the O_NONBLOCK flag on on a file descriptor. 
102   
103    @type fd: int 
104    @param fd: File descriptor 
105    @type enable: bool 
106    @param enable: Whether to set or unset it 
107   
108    """ 
109    flags = fcntl.fcntl(fd, fcntl.F_GETFL) 
110   
111    if enable: 
112      flags |= os.O_NONBLOCK 
113    else: 
114      flags &= ~os.O_NONBLOCK 
115   
116    fcntl.fcntl(fd, fcntl.F_SETFL, flags) 
117   
118   
119 -def RetryOnSignal(fn, *args, **kwargs): 
120    """Calls a function again if it failed due to EINTR. 
121   
122    """ 
123    while True: 
124      try: 
125        return fn(*args, **kwargs) 
126      except EnvironmentError, err: 
127        if err.errno != errno.EINTR: 
128          raise 
129      except (socket.error, select.error), err: 
130        # In python 2.6 and above select.error is an IOError, so it's handled 
131        # above, in 2.5 and below it's not, and it's handled here. 
132        if not (err.args and err.args[0] == errno.EINTR): 
133          raise 
134   
135   
136 -def IgnoreProcessNotFound(fn, *args, **kwargs): 
137    """Ignores ESRCH when calling a process-related function. 
138   
139    ESRCH is raised when a process is not found. 
140   
141    @rtype: bool 
142    @return: Whether process was found 
143   
144    """ 
145    try: 
146      fn(*args, **kwargs) 
147    except EnvironmentError, err: 
148      # Ignore ESRCH 
149      if err.errno == errno.ESRCH: 
150        return False 
151      raise 
152   
153    return True 
154   
155   
156 -def IgnoreSignals(fn, *args, **kwargs): 
157    """Tries to call a function ignoring failures due to EINTR. 
158   
159    """ 
160    try: 
161      return fn(*args, **kwargs) 
162    except EnvironmentError, err: 
163      if err.errno == errno.EINTR: 
164        return None 
165      else: 
166        raise 
167    except (select.error, socket.error), err: 
168      # In python 2.6 and above select.error is an IOError, so it's handled 
169      # above, in 2.5 and below it's not, and it's handled here. 
170      if err.args and err.args[0] == errno.EINTR: 
171        return None 
172      else: 
173        raise 
174   
175   
176 -def GetClosedTempfile(*args, **kwargs): 
177    """Creates a temporary file and returns its path. 
178   
179    """ 
180    (fd, path) = tempfile.mkstemp(*args, **kwargs) 
181    CloseFdNoError(fd) 
182    return path 
183   
184   
185 -def IsExecutable(filename): 
186    """Checks whether a file exists and is executable. 
187   
188    @type filename: string 
189    @param filename: Filename 
190    @rtype: bool 
191   
192    """ 
193    return os.path.isfile(filename) and os.access(filename, os.X_OK) 
194   
195   
196 -def ResetTempfileModule(_time=time.time): 
197    """Resets the random name generator of the tempfile module. 
198   
199    This function should be called after C{os.fork} in the child process to 
200    ensure it creates a newly seeded random generator. Otherwise it would 
201    generate the same random parts as the parent process. If several processes 
202    race for the creation of a temporary file, this could lead to one not getting 
203    a temporary name. 
204   
205    """ 
206    # pylint: disable=W0212 
207    if ((sys.hexversion >= 0x020703F0 and sys.hexversion < 0x03000000) or 
208        sys.hexversion >= 0x030203F0): 
209      # Python 2.7 automatically resets the RNG on pid changes (i.e. forking) 
210      return 
211   
212    try: 
213      lock = tempfile._once_lock 
214      lock.acquire() 
215      try: 
216        # Re-seed random name generator 
217        if tempfile._name_sequence: 
218          tempfile._name_sequence.rng.seed(hash(_time()) ^ os.getpid()) 
219      finally: 
220        lock.release() 
221    except AttributeError: 
222      logging.critical("The tempfile module misses at least one of the" 
223                       " '_once_lock' and '_name_sequence' attributes") 
224