/usr/lib/python2.7/dist-packages/webassets/cache.py is in python-webassets 3:0.10.1-2.
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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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 | """Caches are used for multiple things:
- To speed up asset building. Filter operations every step
of the way can be cached, so that individual parts of a
build that haven't changed can be reused.
- Bundle definitions are cached when a bundle is built so we
can determine whether they have changed and whether a rebuild
is required.
This data is not all stored in the same cache necessarily. The
classes in this module provide the "environment.cache" object, but
also serve in other places.
"""
import os
from os import path
import errno
import tempfile
import warnings
from webassets import six
from webassets.merge import BaseHunk
from webassets.filter import Filter, freezedicts
from webassets.utils import md5_constructor, pickle
import types
__all__ = ('FilesystemCache', 'MemoryCache', 'get_cache',)
def make_hashable(data):
"""Ensures ``data`` can be hashed().
Mostly needs to support dict. The other special types we use
as hash keys (Hunks, Filters) already have a proper hash() method.
See also ``make_md5``.
Note that we do not actually hash the data for the memory cache.
"""
return freezedicts(data)
def make_md5(*data):
"""Make a md5 hash based on``data``.
Specifically, this knows about ``Hunk`` objects, and makes sure
the actual content is hashed.
This is very conservative, and raises an exception if there are
data types that it does not explicitly support. This is because
we had in the past some debugging headaches with the cache not
working for this very reason.
MD5 is faster than sha, and we don't care so much about collisions.
We care enough however not to use hash().
"""
def walk(obj):
if isinstance(obj, (tuple, list, frozenset)):
for item in obj:
for d in walk(item): yield d
elif isinstance(obj, (dict)):
for k in sorted(obj.keys()):
for d in walk(k): yield d
for d in walk(obj[k]): yield d
elif isinstance(obj, BaseHunk):
yield obj.data().encode('utf-8')
elif isinstance(obj, int):
yield str(obj).encode('utf-8')
elif isinstance(obj, six.text_type):
yield obj.encode('utf-8')
elif isinstance(obj, six.binary_type):
yield obj
elif hasattr(obj, "id"):
for i in walk(obj.id()):
yield i
elif obj is None:
yield "None".encode('utf-8')
elif isinstance(obj, types.FunctionType):
yield str(hash(obj)).encode('utf-8')
else:
raise ValueError('Cannot MD5 type %s' % type(obj))
md5 = md5_constructor()
for d in walk(data):
md5.update(d)
return md5.hexdigest()
def safe_unpickle(string):
"""Unpickle the string, or return ``None`` if that fails."""
try:
return pickle.loads(string)
except:
return None
class BaseCache(object):
"""Abstract base class.
The cache key must be something that is supported by the Python hash()
function. The cache value may be a string, or anything that can be pickled.
Since the cache is used for multiple purposes, all webassets-internal code
should always tag its keys with an id, like so:
key = ("tag", actual_key)
One cache instance can only be used safely with a single Environment.
"""
def get(self, key):
"""Should return the cache contents, or False.
"""
raise NotImplementedError()
def set(self, key, value):
raise NotImplementedError()
class MemoryCache(BaseCache):
"""Caches stuff in the process memory.
WARNING: Do NOT use this in a production environment, where you
are likely going to have multiple processes serving the same app!
Note that the keys are used as-is, not passed through hash() (which is
a difference: http://stackoverflow.com/a/9022664/15677). However, the
reason we don't is because the original value is nicer to debug.
"""
def __init__(self, capacity):
self.capacity = capacity
self.keys = []
self.cache = {}
def __eq__(self, other):
"""Return equality with the config values that instantiate
this instance.
"""
return False == other or \
None == other or \
id(self) == id(other)
def get(self, key):
key = make_md5(make_hashable(key))
return self.cache.get(key, None)
def set(self, key, value):
key = make_md5(make_hashable(key))
self.cache[key] = value
try:
self.keys.remove(key)
except ValueError:
pass
self.keys.append(key)
# limit cache to the given capacity
to_delete = self.keys[0:max(0, len(self.keys)-self.capacity)]
self.keys = self.keys[len(to_delete):]
for item in to_delete:
del self.cache[item]
class FilesystemCache(BaseCache):
"""Uses a temporary directory on the disk.
"""
V = 2 # We have changed the cache format once
def __init__(self, directory):
self.directory = directory
def __eq__(self, other):
"""Return equality with the config values
that instantiate this instance.
"""
return True == other or \
self.directory == other or \
id(self) == id(other)
def get(self, key):
filename = path.join(self.directory, '%s' % make_md5(self.V, key))
try:
f = open(filename, 'rb')
except IOError as e:
if e.errno != errno.ENOENT:
raise
return None
try:
result = f.read()
finally:
f.close()
unpickled = safe_unpickle(result)
if unpickled is None:
warnings.warn('Ignoring corrupted cache file %s' % filename)
return unpickled
def set(self, key, data):
md5 = '%s' % make_md5(self.V, key)
filename = path.join(self.directory, md5)
fd, temp_filename = tempfile.mkstemp(prefix='.' + md5,
dir=self.directory)
try:
with os.fdopen(fd, 'wb') as f:
pickle.dump(data, f)
f.flush()
os.rename(temp_filename, filename)
except:
os.unlink(temp_filename)
raise
def get_cache(option, ctx):
"""Return a cache instance based on ``option``.
"""
if not option:
return None
if isinstance(option, BaseCache):
return option
elif isinstance(option, type) and issubclass(option, BaseCache):
return option()
if option is True:
directory = path.join(ctx.directory, '.webassets-cache')
# Auto-create the default directory
if not path.exists(directory):
os.makedirs(directory)
else:
directory = option
return FilesystemCache(directory)
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