Source Code for Module ganeti.utils.livelock

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 29   
 30  """Lockfiles to prove liveliness 
 31   
 32  When requesting resources, like locks, from wconfd, requesters have 
 33  to provide the name of a file they own an exclusive lock on, to prove 
 34  that they are still alive. Provide methods to obtain such a file. 
 35  """ 
 36   
 37  import fcntl 
 38  import os 
 39  import struct 
 40  import time 
 41   
 42  from ganeti.utils.algo import NiceSort 
 43  from ganeti import pathutils 
 44   
 45   
 46 -class LiveLockName(object): 
 47 -  def __init__(self, name): 
 48      self._name = name 
 49   
 50 -  def GetPath(self): 
 51      return self._name 
 52   
 53 -  def close(self): 
 54      """Clean up the lockfile. 
 55   
 56      """ 
 57      os.remove(self._name) 
 58   
 59 -  def __str__(self): 
 60      return "LiveLockName(" + self.GetPath() + ")" 
 61   
 62   
 63 -class LiveLock(object): 
 64    """Utility for a lockfile needed to request resources from WconfD. 
 65   
 66    """ 
 67 -  def __init__(self, name=None): 
 68      if name is None: 
 69        name = "pid%d_" % os.getpid() 
 70      # to avoid reusing existing lock files, extend name 
 71      # by the current time 
 72      name = "%s_%d" % (name, int(time.time())) 
 73      fname = os.path.join(pathutils.LIVELOCK_DIR, name) 
 74      self.lockfile = open(fname, 'w') 
 75      fcntl.fcntl(self.lockfile, fcntl.F_SETLKW, 
 76                  struct.pack('hhllhh', fcntl.F_WRLCK, 0, 0, 0, 0, 0)) 
 77   
 78 -  def GetPath(self): 
 79      return self.lockfile.name 
 80   
 81 -  def close(self): 
 82      """Close the lockfile and clean it up. 
 83   
 84      """ 
 85      self.lockfile.close() 
 86      os.remove(self.lockfile.name) 
 87   
 88 -  def __str__(self): 
 89      return "LiveLock(" + self.GetPath() + ")" 
 90   
 91   
 92 -def GuessLockfileFor(name): 
 93    """For a given name, take the latest file matching. 
 94   
 95    @return: the file with the latest name matching the given 
 96        prefix in LIVELOCK_DIR, or the plain name, if none 
 97        exists. 
 98    """ 
 99    lockfiles = filter(lambda n: n.startswith(name), 
100                       os.listdir(pathutils.LIVELOCK_DIR)) 
101    if len(lockfiles) > 0: 
102      lockfile = NiceSort(lockfiles)[-1] 
103    else: 
104      lockfile = name 
105   
106    return os.path.join(pathutils.LIVELOCK_DIR, lockfile) 
107