Source Code for Module ClusterShell.Engine.Factory

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 2  # Copyright CEA/DAM/DIF (2009, 2010) 
 3  #  Contributor: Stephane THIELL <stephane.thiell@cea.fr> 
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33  # $Id: Factory.py 238 2010-02-25 22:30:31Z st-cea $ 
34   
35  """ 
36  Engine Factory to select the best working event engine for the current 
37  version of Python and Operating System. 
38  """ 
39   
40  import sys 
41   
42  from ClusterShell.Engine.Engine import EngineNotSupportedError 
43   
44  # Available event engines 
45  from ClusterShell.Engine.EPoll import EngineEPoll 
46  from ClusterShell.Engine.Poll import EnginePoll 
47   
48   
49 -class PreferredEngine(object): 
50      """ 
51      Preferred Engine selection metaclass (DP Abstract Factory). 
52      """ 
53   
54      engines = { EngineEPoll.identifier: EngineEPoll, 
55                  EnginePoll.identifier: EnginePoll } 
56   
57 -    def __new__(cls, hint, info): 
58          """ 
59          Create a new preferred Engine. 
60          """ 
61          if not hint or hint == 'auto': 
62              # 2010-02-11: disable automatic EngineEPoll selection as an 
63              # epoll issue has been found (trac ticket #56). 
64              for engine_class in [ EnginePoll ]:  # in order or preference 
65                  try: 
66                      return engine_class(info) 
67                  except EngineNotSupportedError: 
68                      pass 
69              raise RuntimeError("FATAL: No supported Engine found") 
70          else: 
71              # User overriding engine selection 
72              try: 
73                  return cls.engines[hint](info) 
74              except KeyError, exc: 
75                  print >> sys.stderr, "Invalid engine identifier", exc 
76                  raise 
77