1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
|
"Base Cache class."
import warnings
from django.core.exceptions import ImproperlyConfigured, DjangoRuntimeWarning
class InvalidCacheBackendError(ImproperlyConfigured):
pass
class CacheKeyWarning(DjangoRuntimeWarning):
pass
# Memcached does not accept keys longer than this.
MEMCACHE_MAX_KEY_LENGTH = 250
class BaseCache(object):
def __init__(self, params):
timeout = params.get('timeout', 300)
try:
timeout = int(timeout)
except (ValueError, TypeError):
timeout = 300
self.default_timeout = timeout
def add(self, key, value, timeout=None):
"""
Set a value in the cache if the key does not already exist. If
timeout is given, that timeout will be used for the key; otherwise
the default cache timeout will be used.
Returns True if the value was stored, False otherwise.
"""
raise NotImplementedError
def get(self, key, default=None):
"""
Fetch a given key from the cache. If the key does not exist, return
default, which itself defaults to None.
"""
raise NotImplementedError
def set(self, key, value, timeout=None):
"""
Set a value in the cache. If timeout is given, that timeout will be
used for the key; otherwise the default cache timeout will be used.
"""
raise NotImplementedError
def delete(self, key):
"""
Delete a key from the cache, failing silently.
"""
raise NotImplementedError
def get_many(self, keys):
"""
Fetch a bunch of keys from the cache. For certain backends (memcached,
pgsql) this can be *much* faster when fetching multiple values.
Returns a dict mapping each key in keys to its value. If the given
key is missing, it will be missing from the response dict.
"""
d = {}
for k in keys:
val = self.get(k)
if val is not None:
d[k] = val
return d
def has_key(self, key):
"""
Returns True if the key is in the cache and has not expired.
"""
return self.get(key) is not None
def incr(self, key, delta=1):
"""
Add delta to value in the cache. If the key does not exist, raise a
ValueError exception.
"""
if key not in self:
raise ValueError("Key '%s' not found" % key)
new_value = self.get(key) + delta
self.set(key, new_value)
return new_value
def decr(self, key, delta=1):
"""
Subtract delta from value in the cache. If the key does not exist, raise
a ValueError exception.
"""
return self.incr(key, -delta)
def __contains__(self, key):
"""
Returns True if the key is in the cache and has not expired.
"""
# This is a separate method, rather than just a copy of has_key(),
# so that it always has the same functionality as has_key(), even
# if a subclass overrides it.
return self.has_key(key)
def set_many(self, data, timeout=None):
"""
Set a bunch of values in the cache at once from a dict of key/value
pairs. For certain backends (memcached), this is much more efficient
than calling set() multiple times.
If timeout is given, that timeout will be used for the key; otherwise
the default cache timeout will be used.
"""
for key, value in data.items():
self.set(key, value, timeout)
def delete_many(self, keys):
"""
Set a bunch of values in the cache at once. For certain backends
(memcached), this is much more efficient than calling delete() multiple
times.
"""
for key in keys:
self.delete(key)
def clear(self):
"""Remove *all* values from the cache at once."""
raise NotImplementedError
def validate_key(self, key):
"""
Warn about keys that would not be portable to the memcached
backend. This encourages (but does not force) writing backend-portable
cache code.
"""
if len(key) > MEMCACHE_MAX_KEY_LENGTH:
warnings.warn('Cache key will cause errors if used with memcached: '
'%s (longer than %s)' % (key, MEMCACHE_MAX_KEY_LENGTH),
CacheKeyWarning)
for char in key:
if ord(char) < 33 or ord(char) == 127:
warnings.warn('Cache key contains characters that will cause '
'errors if used with memcached: %r' % key,
CacheKeyWarning)
|
