|
0
|
1 |
"Base Cache class." |
|
|
2 |
|
|
|
3 |
from django.core.exceptions import ImproperlyConfigured |
|
|
4 |
|
|
|
5 |
class InvalidCacheBackendError(ImproperlyConfigured): |
|
|
6 |
pass |
|
|
7 |
|
|
|
8 |
class BaseCache(object): |
|
|
9 |
def __init__(self, params): |
|
|
10 |
timeout = params.get('timeout', 300) |
|
|
11 |
try: |
|
|
12 |
timeout = int(timeout) |
|
|
13 |
except (ValueError, TypeError): |
|
|
14 |
timeout = 300 |
|
|
15 |
self.default_timeout = timeout |
|
|
16 |
|
|
|
17 |
def add(self, key, value, timeout=None): |
|
|
18 |
""" |
|
|
19 |
Set a value in the cache if the key does not already exist. If |
|
|
20 |
timeout is given, that timeout will be used for the key; otherwise |
|
|
21 |
the default cache timeout will be used. |
|
|
22 |
|
|
|
23 |
Returns True if the value was stored, False otherwise. |
|
|
24 |
""" |
|
|
25 |
raise NotImplementedError |
|
|
26 |
|
|
|
27 |
def get(self, key, default=None): |
|
|
28 |
""" |
|
|
29 |
Fetch a given key from the cache. If the key does not exist, return |
|
|
30 |
default, which itself defaults to None. |
|
|
31 |
""" |
|
|
32 |
raise NotImplementedError |
|
|
33 |
|
|
|
34 |
def set(self, key, value, timeout=None): |
|
|
35 |
""" |
|
|
36 |
Set a value in the cache. If timeout is given, that timeout will be |
|
|
37 |
used for the key; otherwise the default cache timeout will be used. |
|
|
38 |
""" |
|
|
39 |
raise NotImplementedError |
|
|
40 |
|
|
|
41 |
def delete(self, key): |
|
|
42 |
""" |
|
|
43 |
Delete a key from the cache, failing silently. |
|
|
44 |
""" |
|
|
45 |
raise NotImplementedError |
|
|
46 |
|
|
|
47 |
def get_many(self, keys): |
|
|
48 |
""" |
|
|
49 |
Fetch a bunch of keys from the cache. For certain backends (memcached, |
|
|
50 |
pgsql) this can be *much* faster when fetching multiple values. |
|
|
51 |
|
|
|
52 |
Returns a dict mapping each key in keys to its value. If the given |
|
|
53 |
key is missing, it will be missing from the response dict. |
|
|
54 |
""" |
|
|
55 |
d = {} |
|
|
56 |
for k in keys: |
|
|
57 |
val = self.get(k) |
|
|
58 |
if val is not None: |
|
|
59 |
d[k] = val |
|
|
60 |
return d |
|
|
61 |
|
|
|
62 |
def has_key(self, key): |
|
|
63 |
""" |
|
|
64 |
Returns True if the key is in the cache and has not expired. |
|
|
65 |
""" |
|
|
66 |
return self.get(key) is not None |
|
|
67 |
|
|
|
68 |
def incr(self, key, delta=1): |
|
|
69 |
""" |
|
|
70 |
Add delta to value in the cache. If the key does not exist, raise a |
|
|
71 |
ValueError exception. |
|
|
72 |
""" |
|
|
73 |
if key not in self: |
|
29
|
74 |
raise ValueError("Key '%s' not found" % key) |
|
0
|
75 |
new_value = self.get(key) + delta |
|
|
76 |
self.set(key, new_value) |
|
|
77 |
return new_value |
|
|
78 |
|
|
|
79 |
def decr(self, key, delta=1): |
|
|
80 |
""" |
|
|
81 |
Subtract delta from value in the cache. If the key does not exist, raise |
|
|
82 |
a ValueError exception. |
|
|
83 |
""" |
|
|
84 |
return self.incr(key, -delta) |
|
|
85 |
|
|
|
86 |
def __contains__(self, key): |
|
|
87 |
""" |
|
|
88 |
Returns True if the key is in the cache and has not expired. |
|
|
89 |
""" |
|
|
90 |
# This is a separate method, rather than just a copy of has_key(), |
|
|
91 |
# so that it always has the same functionality as has_key(), even |
|
|
92 |
# if a subclass overrides it. |
|
|
93 |
return self.has_key(key) |
|
29
|
94 |
|
|
|
95 |
def set_many(self, data, timeout=None): |
|
|
96 |
""" |
|
|
97 |
Set a bunch of values in the cache at once from a dict of key/value |
|
|
98 |
pairs. For certain backends (memcached), this is much more efficient |
|
|
99 |
than calling set() multiple times. |
|
|
100 |
|
|
|
101 |
If timeout is given, that timeout will be used for the key; otherwise |
|
|
102 |
the default cache timeout will be used. |
|
|
103 |
""" |
|
|
104 |
for key, value in data.items(): |
|
|
105 |
self.set(key, value, timeout) |
|
|
106 |
|
|
|
107 |
def delete_many(self, keys): |
|
|
108 |
""" |
|
|
109 |
Set a bunch of values in the cache at once. For certain backends |
|
|
110 |
(memcached), this is much more efficient than calling delete() multiple |
|
|
111 |
times. |
|
|
112 |
""" |
|
|
113 |
for key in keys: |
|
|
114 |
self.delete(key) |
|
|
115 |
|
|
|
116 |
def clear(self): |
|
|
117 |
"""Remove *all* values from the cache at once.""" |
|
|
118 |
raise NotImplementedError |