scheduler.py

Fri, 26 Jan 2018 10:31:08 +0000

author
Tuomo Valkonen <tuomov@iki.fi>
date
Fri, 26 Jan 2018 10:31:08 +0000
changeset 71
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parent 69
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child 75
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permissions
-rw-r--r--

Changed retry timing to start form end of previous attempt instead of beginning

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1 #
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2 # Scheduler for Borgend
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3 #
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4 # This module simply provide a way for other threads to until a given time
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5 #
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6
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7 import time
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8 import borgend
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9 from threading import Condition, Lock, Thread
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10
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11 logger=borgend.logger.getChild(__name__)
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12
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13 class QueuedEvent:
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14 def __init__(self, cond, name=None):
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15 self.next=None
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16 self.prev=None
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17 self.name=name
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18 self.cond=cond
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19
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20 def __lt__(self, other):
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21 raise NotImplementedError
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22
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23 def insert_after(self, ev):
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24 if not self.next or ev<self.next:
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25 self.insert_immediately_after(ev)
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26 else:
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27 self.next.insert_after(ev)
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28
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29 def insert_immediately_after(self, ev):
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30 assert(ev.next is None and ev.prev is None)
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31 ev.prev=self
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32 ev.next=self.next
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33 self.next=ev
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34
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35 def insert_immediately_before(self, ev):
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36 assert(ev.next is None and ev.prev is None)
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37 ev.next=self
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38 ev.prev=self.prev
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39 self.prev=ev
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40
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41 def unlink(self):
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42 n=self.next
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43 p=self.prev
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44 if n:
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45 n.prev=p
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46 if p:
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47 p.next=n
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48
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49 class ScheduledEvent(QueuedEvent):
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50 def __init__(self, when, cond, name=None):
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51 super().__init__(cond, name=name)
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52 self.when=when
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53
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54 def __lt__(self, other):
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55 return self.when < other.when
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56
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57 class TerminableThread(Thread):
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58 def __init__(self, *args, **kwargs):
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59 super().__init__(*args, **kwargs)
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60 self._terminate=False
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61 self._cond=Condition()
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62
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63 def terminate(self):
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64 with self._cond:
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65 _terminate=True
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66 self._cond.notify()
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67
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68 class QueueThread(TerminableThread):
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69 def __init__(self, *args, **kwargs):
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70 super().__init__(*args, **kwargs)
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71 self.daemon = True
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72 self._list = None
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73
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74 def _insert(self, ev):
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75 if not self._list:
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76 self._list=ev
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77 elif ev<self._list:
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78 self._list.insert_immediately_before(ev)
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79 self._list=ev
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80 else:
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81 self._list.insert_after(ev)
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82
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83 self._cond.notify()
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84
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85 def _unlink(self, ev):
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86 if ev==self._list:
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87 self._list=ev.next
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88 ev.unlink()
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89
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90
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91 class Scheduler(QueueThread):
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92 # Default to precision of 60 seconds: the scheduler thread will never
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93 # sleep longer than that, to get quickly back on track with the schedule
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94 # when the computer wakes up from sleep
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95 def __init__(self, precision=60):
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96 self.precision = precision
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97 self._next_event_time = None
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98 super().__init__(target = self._scheduler_thread, name = 'Scheduler')
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99
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100 def _scheduler_thread(self):
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101 with self._cond:
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102 while not self._terminate:
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103 now = time.monotonic()
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104 if not self._list:
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105 timeout = None
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106 else:
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107 # Wait at most precision seconds, or until next event if it
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108 # comes earlier
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109 timeout=min(self.precision, self._list.when-now)
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110
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111 if not timeout or timeout>0:
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112 self._cond.wait(timeout)
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113 now = time.monotonic()
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114
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115 while self._list and self._list.when <= now:
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116 ev=self._list
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117 logger.debug("Scheduler activating %s" % (ev.name or "(unknown)"))
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118 # We are only allowed to remove ev from list when ev.cond allows
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119 with ev.cond:
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120 self._list=ev.next
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121 ev.unlink()
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122 ev.cond.notifyAll()
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123
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124 def _wait(self, ev):
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125 with self._cond:
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126 self._insert(ev)
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127
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128 # This will release the lock on cond, allowing queue manager (scheduler)
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129 # thread to notify us if we are already to be released
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130 ev.cond.wait()
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131
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132 # If we were woken up by some other event, not the scheduler,
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133 # ensure the event is removed
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134 with self._cond:
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135 self._unlink(ev)
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136
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137 # cond has to be acquired on entry!
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138 def wait_until(self, when, cond, name=None):
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139 self._wait(ScheduledEvent(when, cond, name))
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140

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