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1 import gevent |
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2 import fcntl |
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3 import hashlib |
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4 |
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5 class Settings(object): |
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6 RAND_SIZE = 15 # 120 bits |
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7 |
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8 """ Handles state updates from both the web UI and from the fridge client. |
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9 The fridge client is canonical. It provides the epoch (apart from 'startepoch'), that |
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10 is changed any time the fridge reloads its local config. The fridge only accepts |
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11 updates that have the same epoch. |
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12 |
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13 When the web UI changes it keeps the same epoch but generates a new tag. The fridge sends |
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14 its current known tag and waits for it to change. |
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15 |
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16 content is opaque, presently a dictionary of decoded json |
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17 """ |
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18 |
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19 def __init__(self): |
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20 self.event = gevent.event.Event() |
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21 self.contents = None |
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22 self.epoch = None |
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23 self.tag = None |
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24 |
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25 self.update(self, None, 'startepoch') |
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26 |
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27 def wait(self, epoch_tag = None, timeout = None): |
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28 """ returns false if the timeout was hit """ |
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29 if self.epoch_tag() != epoch_tag: |
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30 # has alredy changed |
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31 return True |
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32 return self.event.wait(timeout) |
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33 |
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34 def epoch_tag(self): |
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35 return '%s-%s' % (self.epoch, self.tag) |
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36 |
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37 def random(self): |
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38 return binascii.hexlify(os.urandom(self.RAND_SIZE)) |
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39 |
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40 def update(self, contents, epoch = None): |
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41 """ replaces settings contents and updates waiters if changed """ |
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42 if epoch: |
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43 if self.epoch == epoch: |
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44 return |
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45 else: |
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46 self.epoch = epoch |
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47 |
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48 self.tag = self.random() |
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49 self.contents = contents |
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50 |
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51 self.event.set() |
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52 self.event.clear() |
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53 |
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54 def get(self): |
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55 """ Returns (contents, epoch-tag) """ |
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56 return self.contents, self.epoch_tag() |
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57 |
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58 |
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59 |
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60 |
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61 |
