Source Code for Module haizea.pluggable.policies.preemption

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 2  # Copyright 2006-2009, University of Chicago                                 # 
 3  # Copyright 2008-2009, Distributed Systems Architecture Group, Universidad   # 
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18   
19  """This module provides pluggable lease preemption policies. See the documentation 
20  for haizea.core.schedule.policy.PreemptabilityPolicy for more details on 
21  lease preemption policies. 
22  """ 
23   
24  from haizea.core.leases import Lease 
25  from haizea.core.scheduler.policy import PreemptabilityPolicy 
26   
27   
28 -class NoPreemptionPolicy(PreemptabilityPolicy): 
29      """Simple preemption policy: preemption is never allowed. 
30      """ 
31 -    def __init__(self, slottable): 
32          """Constructor 
33           
34          Argument 
35          slottable -- A fully constructed SlotTable 
36          """         
37          PreemptabilityPolicy.__init__(self, slottable) 
38       
39 -    def get_lease_preemptability_score(self, preemptor, preemptee, time): 
40          """Computes the lease preemptability score 
41           
42          See class documentation for details on what policy is implemented here. 
43          See documentation of PreemptabilityPolicy.get_lease_preemptability_score 
44          for more details on this function. 
45           
46          Arguments: 
47          preemptor -- Preemptor lease 
48          preemptee -- Preemptee lease 
49          time -- Time at which preemption would take place 
50          """                     
51          return -1 
52   
53 -class ARPreemptsEverythingPolicy(PreemptabilityPolicy): 
54      """A simple preemption policy where AR leases can always preempt 
55      every other type of lease. Given two possible leases to preempt, 
56      the "youngest" one is preferred (i.e., the one that was most recently 
57      submitted). 
58      """     
59 -    def __init__(self, slottable): 
60          """Constructor 
61           
62          Argument 
63          slottable -- A fully constructed SlotTable 
64          """         
65          PreemptabilityPolicy.__init__(self, slottable) 
66       
67 -    def get_lease_preemptability_score(self, preemptor, preemptee, time): 
68          """Computes the lease preemptability score 
69           
70          See class documentation for details on what policy is implemented here. 
71          See documentation of PreemptabilityPolicy.get_lease_preemptability_score 
72          for more details on this function. 
73           
74          Arguments: 
75          preemptor -- Preemptor lease 
76          preemptee -- Preemptee lease 
77          time -- Time at which preemption would take place 
78          """         
79          if preemptor.get_type() == Lease.ADVANCE_RESERVATION and preemptee.get_type() == Lease.BEST_EFFORT: 
80              return self._get_aging_factor(preemptee, time) 
81          else: 
82              return -1 
83