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