1 | "Thread-safe in-memory cache backend." |
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2 | |
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3 | import time |
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4 | try: |
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5 | import cPickle as pickle |
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6 | except ImportError: |
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7 | import pickle |
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8 | |
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9 | from django.core.cache.backends.base import BaseCache |
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10 | from django.utils.synch import RWLock |
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11 | |
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12 | class CacheClass(BaseCache): |
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13 | def __init__(self, _, params): |
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14 | BaseCache.__init__(self, params) |
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15 | self._cache = {} |
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16 | self._expire_info = {} |
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17 | |
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18 | if "nopickle" in params and params["nopickle"] == "True": |
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19 | self.nopickle = True |
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20 | else: |
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21 | self.nopickle = False |
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22 | |
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23 | max_entries = params.get('max_entries', 300) |
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24 | try: |
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25 | self._max_entries = int(max_entries) |
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26 | except (ValueError, TypeError): |
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27 | self._max_entries = 300 |
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28 | |
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29 | cull_frequency = params.get('cull_frequency', 3) |
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30 | try: |
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31 | self._cull_frequency = int(cull_frequency) |
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32 | except (ValueError, TypeError): |
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33 | self._cull_frequency = 3 |
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34 | |
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35 | self._lock = RWLock() |
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36 | |
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37 | def _add(self, key, value, timeout=None): |
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38 | if len(self._cache) >= self._max_entries: |
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39 | self._cull() |
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40 | if timeout is None: |
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41 | timeout = self.default_timeout |
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42 | if key not in self._cache.keys(): |
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43 | self._cache[key] = value |
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44 | self._expire_info[key] = time.time() + timeout |
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45 | |
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46 | def add(self, key, value, timeout=None): |
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47 | self._lock.writer_enters() |
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48 | # Python 2.3 and 2.4 don't allow combined try-except-finally blocks. |
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49 | try: |
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50 | try: |
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51 | self._add(key, pickle.dumps(value), timeout) |
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52 | except pickle.PickleError: |
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53 | pass |
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54 | finally: |
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55 | self._lock.writer_leaves() |
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56 | |
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57 | def get(self, key, default=None): |
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58 | should_delete = False |
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59 | self._lock.reader_enters() |
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60 | try: |
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61 | now = time.time() |
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62 | exp = self._expire_info.get(key) |
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63 | if exp is None: |
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64 | return default |
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65 | elif exp < now: |
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66 | should_delete = True |
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67 | else: |
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68 | if self.nopickle: |
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69 | return self._cache[key] |
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70 | else: |
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71 | try: |
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72 | return pickle.loads(self._cache[key]) |
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73 | except pickle.PickleError: |
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74 | return default |
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75 | finally: |
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76 | self._lock.reader_leaves() |
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77 | if should_delete: |
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78 | self._lock.writer_enters() |
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79 | try: |
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80 | del self._cache[key] |
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81 | del self._expire_info[key] |
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82 | return default |
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83 | finally: |
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84 | self._lock.writer_leaves() |
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85 | |
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86 | def _set(self, key, value, timeout=None): |
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87 | if len(self._cache) >= self._max_entries: |
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88 | self._cull() |
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89 | if timeout is None: |
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90 | timeout = self.default_timeout |
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91 | self._cache[key] = value |
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92 | self._expire_info[key] = time.time() + timeout |
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93 | |
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94 | def set(self, key, value, timeout=None): |
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95 | self._lock.writer_enters() |
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96 | # Python 2.3 and 2.4 don't allow combined try-except-finally blocks. |
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97 | try: |
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98 | if self.nopickle: |
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99 | self._set(key, value, timeout) |
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100 | else: |
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101 | try: |
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102 | self._set(key, pickle.dumps(value), timeout) |
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103 | except pickle.PickleError: |
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104 | pass |
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105 | finally: |
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106 | self._lock.writer_leaves() |
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107 | |
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108 | def has_key(self, key): |
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109 | return key in self._cache |
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110 | |
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111 | def _cull(self): |
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112 | if self._cull_frequency == 0: |
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113 | self._cache.clear() |
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114 | self._expire_info.clear() |
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115 | else: |
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116 | doomed = [k for (i, k) in enumerate(self._cache) if i % self._cull_frequency == 0] |
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117 | for k in doomed: |
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118 | self.delete(k) |
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119 | |
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120 | def _delete(self, key): |
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121 | try: |
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122 | del self._cache[key] |
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123 | except KeyError: |
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124 | pass |
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125 | try: |
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126 | del self._expire_info[key] |
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127 | except KeyError: |
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128 | pass |
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129 | |
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130 | def delete(self, key): |
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131 | self._lock.writer_enters() |
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132 | try: |
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133 | self._delete(key) |
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134 | finally: |
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135 | self._lock.writer_leaves() |
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