web2py.gluon.cache

1 #!/usr/bin/env python 2 # -*- coding: utf-8 -*- 3 4 """ 5 This file is part of the web2py Web Framework 6 Copyrighted by Massimo Di Pierro <mdipierro@cs.depaul.edu> 7 License: LGPLv3 (http://www.gnu.org/licenses/lgpl.html) 8 9 Basic caching classes and methods 10 ================================= 11 12 - Cache - The generic caching object interfacing with the others 13 - CacheInRam - providing caching in ram 14 - CacheInDisk - provides caches on disk 15 16 Memcache is also available via a different module (see gluon.contrib.memcache) 17 18 When web2py is running on Google App Engine, 19 caching will be provided by the GAE memcache 20 (see gluon.contrib.gae_memcache) 21 """ 22 23 import time 24 import portalocker 25 import shelve 26 import thread 27 import os 28 import logging 29 import re 30 31 logger = logging.getLogger("web2py.cache") 32 33 __all__ = ['Cache'] 34 35 36 DEFAULT_TIME_EXPIRE = 300 37 38

39 -class CacheAbstract(object):

40 """ 41 Abstract class for cache implementations. 42 Main function is now to provide referenced api documentation. 43 44 Use CacheInRam or CacheOnDisk instead which are derived from this class. 45 """ 46 47 cache_stats_name = 'web2py_cache_statistics' 48

49 - def __init__(self, request=None):

50 """ 51 Paremeters 52 ---------- 53 request: 54 the global request object 55 """ 56 raise NotImplementedError

57

58 - def __call__(self, key, f, 59 time_expire = DEFAULT_TIME_EXPIRE):

60 """ 61 Tries retrieve the value corresponding to `key` from the cache of the 62 object exists and if it did not expire, else it called the function `f` 63 and stores the output in the cache corresponding to `key`. In the case 64 the output of the function is returned. 65 66 :param key: the key of the object to be store or retrieved 67 :param f: the function, whose output is to be cached 68 :param time_expire: expiration of the cache in microseconds 69 70 - `time_expire` is used to compare the current time with the time when 71 the requested object was last saved in cache. It does not affect 72 future requests. 73 - Setting `time_expire` to 0 or negative value forces the cache to 74 refresh. 75 76 If the function `f` is `None` the cache is cleared. 77 """ 78 raise NotImplementedError

79

80 - def clear(self, regex=None):

81 """ 82 Clears the cache of all keys that match the provided regular expression. 83 If no regular expression is provided, it clears all entries in cache. 84 85 Parameters 86 ---------- 87 regex: 88 if provided, only keys matching the regex will be cleared. 89 Otherwise all keys are cleared. 90 """ 91 92 raise NotImplementedError

93

94 - def increment(self, key, value=1):

95 """ 96 Increments the cached value for the given key by the amount in value 97 98 Parameters 99 ---------- 100 key: 101 key for the cached object to be incremeneted 102 value: 103 amount of the increment (defaults to 1, can be negative) 104 """ 105 raise NotImplementedError

106

107 - def _clear(self, storage, regex):

108 """ 109 Auxiliary function called by `clear` to search and clear cache entries 110 """ 111 r = re.compile(regex) 112 for (key, value) in storage.items(): 113 if r.match(str(key)): 114 del storage[key]

115

116 -class CacheInRam(CacheAbstract):

117 """ 118 Ram based caching 119 120 This is implemented as global (per process, shared by all threads) 121 dictionary. 122 A mutex-lock mechanism avoid conflicts. 123 """ 124 125 locker = thread.allocate_lock() 126 meta_storage = {} 127

128 - def __init__(self, request=None):

129 self.locker.acquire() 130 self.request = request 131 if request: 132 app = request.application 133 else: 134 app = '' 135 if not app in self.meta_storage: 136 self.storage = self.meta_storage[app] = {CacheAbstract.cache_stats_name: { 137 'hit_total': 0, 138 'misses': 0, 139 }} 140 else: 141 self.storage = self.meta_storage[app] 142 self.locker.release()

143

144 - def clear(self, regex=None):

145 self.locker.acquire() 146 storage = self.storage 147 if regex == None: 148 storage.clear() 149 else: 150 self._clear(storage, regex) 151 152 if not CacheAbstract.cache_stats_name in storage.keys(): 153 storage[CacheAbstract.cache_stats_name] = { 154 'hit_total': 0, 155 'misses': 0, 156 } 157 158 self.locker.release()

159

160 - def __call__(self, key, f, 161 time_expire = DEFAULT_TIME_EXPIRE):

162 """ 163 Attention! cache.ram does not copy the cached object. It just stores a reference to it. 164 Turns out the deepcopying the object has some problems: 165 1) would break backward compatibility 166 2) would be limiting because people may want to cache live objects 167 3) would work unless we deepcopy no storage and retrival which would make things slow. 168 Anyway. You can deepcopy explicitly in the function generating the value to be cached. 169 """ 170 171 dt = time_expire 172 173 self.locker.acquire() 174 item = self.storage.get(key, None) 175 if item and f == None: 176 del self.storage[key] 177 self.storage[CacheAbstract.cache_stats_name]['hit_total'] += 1 178 self.locker.release() 179 180 if f is None: 181 return None 182 if item and (dt == None or item[0] > time.time() - dt): 183 return item[1] 184 value = f() 185 186 self.locker.acquire() 187 self.storage[key] = (time.time(), value) 188 self.storage[CacheAbstract.cache_stats_name]['misses'] += 1 189 self.locker.release() 190 return value

191

192 - def increment(self, key, value=1):

193 self.locker.acquire() 194 try: 195 if key in self.storage: 196 value = self.storage[key][1] + value 197 self.storage[key] = (time.time(), value) 198 except BaseException, e: 199 self.locker.release() 200 raise e 201 self.locker.release() 202 return value

203 204

205 -class CacheOnDisk(CacheAbstract):

206 """ 207 Disk based cache 208 209 This is implemented as a shelve object and it is shared by multiple web2py 210 processes (and threads) as long as they share the same filesystem. 211 The file is locked wen accessed. 212 213 Disk cache provides persistance when web2py is started/stopped but it slower 214 than `CacheInRam` 215 216 Values stored in disk cache must be pickable. 217 """ 218 219 speedup_checks = set() 220

221 - def __init__(self, request, folder=None):

222 self.request = request 223 224 # Lets test if the cache folder exists, if not 225 # we are going to create it 226 folder = folder or os.path.join(request.folder, 'cache') 227 228 if not os.path.exists(folder): 229 os.mkdir(folder) 230 231 ### we need this because of a possible bug in shelve that may 232 ### or may not lock 233 self.locker_name = os.path.join(folder,'cache.lock') 234 self.shelve_name = os.path.join(folder,'cache.shelve') 235 236 locker, locker_locked = None, False 237 speedup_key = (folder,CacheAbstract.cache_stats_name) 238 if not speedup_key in self.speedup_checks or \ 239 not os.path.exists(self.shelve_name): 240 try: 241 locker = open(self.locker_name, 'a') 242 portalocker.lock(locker, portalocker.LOCK_EX) 243 locker_locked = True 244 storage = shelve.open(self.shelve_name) 245 246 if not storage.has_key(CacheAbstract.cache_stats_name): 247 storage[CacheAbstract.cache_stats_name] = { 248 'hit_total': 0, 249 'misses': 0, 250 } 251 storage.sync() 252 self.speedup_checks.add(speedup_key) 253 except ImportError: 254 pass # no module _bsddb, ignoring exception now so it makes a ticket only if used 255 except: 256 logger.error('corrupted file %s, deleting it!' \ 257 % self.shelve_name) 258 os.unlink(self.shelve_name) 259 if locker_locked: 260 portalocker.unlock(locker) 261 if locker: 262 locker.close()

263

264 - def clear(self, regex=None):

265 locker = open(self.locker_name,'a') 266 portalocker.lock(locker, portalocker.LOCK_EX) 267 storage = shelve.open(self.shelve_name) 268 if regex == None: 269 storage.clear() 270 else: 271 self._clear(storage, regex) 272 if not CacheAbstract.cache_stats_name in storage.keys(): 273 storage[CacheAbstract.cache_stats_name] = { 274 'hit_total': 0, 275 'misses': 0, 276 } 277 storage.sync() 278 portalocker.unlock(locker) 279 locker.close()

280

281 - def __call__(self, key, f, 282 time_expire = DEFAULT_TIME_EXPIRE):

283 dt = time_expire 284 285 locker = open(self.locker_name,'a') 286 portalocker.lock(locker, portalocker.LOCK_EX) 287 288 storage = shelve.open(self.shelve_name) 289 290 item = storage.get(key, None) 291 if item and f == None: 292 del storage[key] 293 294 storage[CacheAbstract.cache_stats_name] = { 295 'hit_total': storage[CacheAbstract.cache_stats_name]['hit_total'] + 1, 296 'misses': storage[CacheAbstract.cache_stats_name]['misses'] 297 } 298 299 storage.sync() 300 301 portalocker.unlock(locker) 302 locker.close() 303 304 if f is None: 305 return None 306 if item and (dt == None or item[0] > time.time() - dt): 307 return item[1] 308 value = f() 309 310 locker = open(self.locker_name,'a') 311 portalocker.lock(locker, portalocker.LOCK_EX) 312 313 storage[key] = (time.time(), value) 314 315 storage[CacheAbstract.cache_stats_name] = { 316 'hit_total': storage[CacheAbstract.cache_stats_name]['hit_total'], 317 'misses': storage[CacheAbstract.cache_stats_name]['misses'] + 1 318 } 319 320 storage.sync() 321 322 portalocker.unlock(locker) 323 locker.close() 324 325 return value

326

327 - def increment(self, key, value=1):

328 locker = open(self.locker_name,'a') 329 portalocker.lock(locker, portalocker.LOCK_EX) 330 storage = shelve.open(self.shelve_name) 331 try: 332 if key in storage: 333 value = storage[key][1] + value 334 storage[key] = (time.time(), value) 335 storage.sync() 336 except BaseException, e: 337 portalocker.unlock(locker) 338 locker.close() 339 raise e 340 portalocker.unlock(locker) 341 locker.close() 342 return value

343 344

345 -class Cache(object):

346 """ 347 Sets up generic caching, creating an instance of both CacheInRam and 348 CacheOnDisk. 349 In case of GAE will make use of gluon.contrib.gae_memcache. 350 351 - self.ram is an instance of CacheInRam 352 - self.disk is an instance of CacheOnDisk 353 """ 354

355 - def __init__(self, request):

356 """ 357 Parameters 358 ---------- 359 request: 360 the global request object 361 """ 362 # GAE will have a special caching 363 import settings 364 if settings.global_settings.web2py_runtime_gae: 365 from contrib.gae_memcache import MemcacheClient 366 self.ram=self.disk=MemcacheClient(request) 367 else: 368 # Otherwise use ram (and try also disk) 369 self.ram = CacheInRam(request) 370 try: 371 self.disk = CacheOnDisk(request) 372 except IOError: 373 logger.warning('no cache.disk (IOError)') 374 except AttributeError: 375 # normally not expected anymore, as GAE has already 376 # been accounted for 377 logger.warning('no cache.disk (AttributeError)')

378

379 - def __call__(self, 380 key = None, 381 time_expire = DEFAULT_TIME_EXPIRE, 382 cache_model = None):

383 """ 384 Decorator function that can be used to cache any function/method. 385 386 Example:: 387 388 @cache('key', 5000, cache.ram) 389 def f(): 390 return time.ctime() 391 392 When the function f is called, web2py tries to retrieve 393 the value corresponding to `key` from the cache of the 394 object exists and if it did not expire, else it calles the function `f` 395 and stores the output in the cache corresponding to `key`. In the case 396 the output of the function is returned. 397 398 :param key: the key of the object to be store or retrieved 399 :param time_expire: expiration of the cache in microseconds 400 :param cache_model: `cache.ram`, `cache.disk`, or other 401 (like `cache.memcache` if defined). It defaults to `cache.ram`. 402 403 Notes 404 ----- 405 `time_expire` is used to compare the curret time with the time when the 406 requested object was last saved in cache. It does not affect future 407 requests. 408 Setting `time_expire` to 0 or negative value forces the cache to 409 refresh. 410 411 If the function `f` is an action, we suggest using 412 `request.env.path_info` as key. 413 """ 414 if not cache_model: 415 cache_model = self.ram 416 417 def tmp(func): 418 def action(): 419 return cache_model(key, func, time_expire)

420 action.__name___ = func.__name__ 421 action.__doc__ = func.__doc__ 422 return action

423 424 return tmp 425

Source Code for Module web2py.gluon.cache