#!/usr/bin/env python # -*- coding: utf-8 -*- """ This file is part of the web2py Web Framework Copyrighted by Massimo Di Pierro License: LGPLv3 (http://www.gnu.org/licenses/lgpl.html) Basic caching classes and methods ================================= - Cache - The generic caching object interfacing with the others - CacheInRam - providing caching in ram - CacheOnDisk - provides caches on disk Memcache is also available via a different module (see gluon.contrib.memcache) When web2py is running on Google App Engine, caching will be provided by the GAE memcache (see gluon.contrib.gae_memcache) """ import traceback import time import portalocker import shelve import thread import os import logging import re import hashlib import datetime try: import settings have_settings = True except ImportError: have_settings = False logger = logging.getLogger("web2py.cache") __all__ = ['Cache', 'lazy_cache'] DEFAULT_TIME_EXPIRE = 300 class CacheAbstract(object): """ Abstract class for cache implementations. Main function is now to provide referenced api documentation. Use CacheInRam or CacheOnDisk instead which are derived from this class. Attentions, Michele says: There are signatures inside gdbm files that are used directly by the python gdbm adapter that often are lagging behind in the detection code in python part. On every occasion that a gdbm store is probed by the python adapter, the probe fails, because gdbm file version is newer. Using gdbm directly from C would work, because there is backward compatibility, but not from python! The .shelve file is discarded and a new one created (with new signature) and it works until it is probed again... The possible consequences are memory leaks and broken sessions. """ cache_stats_name = 'web2py_cache_statistics' def __init__(self, request=None): """ Parameters ---------- request: the global request object """ raise NotImplementedError def __call__(self, key, f, time_expire=DEFAULT_TIME_EXPIRE): """ Tries retrieve the value corresponding to `key` from the cache of the object exists and if it did not expire, else it called the function `f` and stores the output in the cache corresponding to `key`. In the case the output of the function is returned. :param key: the key of the object to be store or retrieved :param f: the function, whose output is to be cached :param time_expire: expiration of the cache in microseconds - `time_expire` is used to compare the current time with the time when the requested object was last saved in cache. It does not affect future requests. - Setting `time_expire` to 0 or negative value forces the cache to refresh. If the function `f` is `None` the cache is cleared. """ raise NotImplementedError def clear(self, regex=None): """ Clears the cache of all keys that match the provided regular expression. If no regular expression is provided, it clears all entries in cache. Parameters ---------- regex: if provided, only keys matching the regex will be cleared. Otherwise all keys are cleared. """ raise NotImplementedError def increment(self, key, value=1): """ Increments the cached value for the given key by the amount in value Parameters ---------- key: key for the cached object to be incremeneted value: amount of the increment (defaults to 1, can be negative) """ raise NotImplementedError def _clear(self, storage, regex): """ Auxiliary function called by `clear` to search and clear cache entries """ r = re.compile(regex) for (key, value) in storage.items(): if r.match(str(key)): del storage[key] class CacheInRam(CacheAbstract): """ Ram based caching This is implemented as global (per process, shared by all threads) dictionary. A mutex-lock mechanism avoid conflicts. """ locker = thread.allocate_lock() meta_storage = {} def __init__(self, request=None): self.initialized = False self.request = request self.storage = {} def initialize(self): if self.initialized: return else: self.initialized = True self.locker.acquire() request = self.request if request: app = request.application else: app = '' if not app in self.meta_storage: self.storage = self.meta_storage[app] = { CacheAbstract.cache_stats_name: {'hit_total': 0, 'misses': 0}} else: self.storage = self.meta_storage[app] self.locker.release() def clear(self, regex=None): self.initialize() self.locker.acquire() storage = self.storage if regex is None: storage.clear() else: self._clear(storage, regex) if not CacheAbstract.cache_stats_name in storage.keys(): storage[CacheAbstract.cache_stats_name] = { 'hit_total': 0, 'misses': 0} self.locker.release() def __call__(self, key, f, time_expire=DEFAULT_TIME_EXPIRE, destroyer=None): """ Attention! cache.ram does not copy the cached object. It just stores a reference to it. Turns out the deepcopying the object has some problems: 1) would break backward compatibility 2) would be limiting because people may want to cache live objects 3) would work unless we deepcopy no storage and retrival which would make things slow. Anyway. You can deepcopy explicitly in the function generating the value to be cached. """ self.initialize() dt = time_expire now = time.time() self.locker.acquire() item = self.storage.get(key, None) if item and f is None: del self.storage[key] if destroyer: destroyer(item[1]) self.storage[CacheAbstract.cache_stats_name]['hit_total'] += 1 self.locker.release() if f is None: return None if item and (dt is None or item[0] > now - dt): return item[1] elif item and (item[0] < now - dt) and destroyer: destroyer(item[1]) value = f() self.locker.acquire() self.storage[key] = (now, value) self.storage[CacheAbstract.cache_stats_name]['misses'] += 1 self.locker.release() return value def increment(self, key, value=1): self.initialize() self.locker.acquire() try: if key in self.storage: value = self.storage[key][1] + value self.storage[key] = (time.time(), value) except BaseException, e: self.locker.release() raise e self.locker.release() return value class CacheOnDisk(CacheAbstract): """ Disk based cache This is implemented as a shelve object and it is shared by multiple web2py processes (and threads) as long as they share the same filesystem. The file is locked when accessed. Disk cache provides persistance when web2py is started/stopped but it slower than `CacheInRam` Values stored in disk cache must be pickable. """ def _close_shelve_and_unlock(self): try: if self.storage: self.storage.close() finally: if self.locker and self.locked: portalocker.unlock(self.locker) self.locker.close() self.locked = False def _open_shelve_and_lock(self): """Open and return a shelf object, obtaining an exclusive lock on self.locker first. Replaces the close method of the returned shelf instance with one that releases the lock upon closing.""" storage = None locker = None locked = False try: locker = locker = open(self.locker_name, 'a') portalocker.lock(locker, portalocker.LOCK_EX) locked = True try: storage = shelve.open(self.shelve_name) except: logger.error('corrupted cache file %s, will try rebuild it' % (self.shelve_name)) storage = None if not storage and os.path.exists(self.shelve_name): os.unlink(self.shelve_name) storage = shelve.open(self.shelve_name) if not CacheAbstract.cache_stats_name in storage.keys(): storage[CacheAbstract.cache_stats_name] = { 'hit_total': 0, 'misses': 0} storage.sync() except Exception, e: if storage: storage.close() storage = None if locked: portalocker.unlock(locker) locker.close() locked = False raise RuntimeError( 'unable to create/re-create cache file %s' % self.shelve_name) self.locker = locker self.locked = locked self.storage = storage return storage def __init__(self, request=None, folder=None): self.initialized = False self.request = request self.folder = folder self.storage = {} def initialize(self): if self.initialized: return else: self.initialized = True folder = self.folder request = self.request # Lets test if the cache folder exists, if not # we are going to create it folder = folder or os.path.join(request.folder, 'cache') if not os.path.exists(folder): os.mkdir(folder) ### we need this because of a possible bug in shelve that may ### or may not lock self.locker_name = os.path.join(folder, 'cache.lock') self.shelve_name = os.path.join(folder, 'cache.shelve') def clear(self, regex=None): self.initialize() storage = self._open_shelve_and_lock() try: if regex is None: storage.clear() else: self._clear(storage, regex) storage.sync() finally: self._close_shelve_and_unlock() def __call__(self, key, f, time_expire=DEFAULT_TIME_EXPIRE): self.initialize() dt = time_expire storage = self._open_shelve_and_lock() try: item = storage.get(key, None) storage[CacheAbstract.cache_stats_name]['hit_total'] += 1 if item and f is None: del storage[key] storage.sync() now = time.time() if f is None: value = None elif item and (dt is None or item[0] > now - dt): value = item[1] else: value = f() storage[key] = (now, value) storage[CacheAbstract.cache_stats_name]['misses'] += 1 storage.sync() finally: self._close_shelve_and_unlock() return value def increment(self, key, value=1): self.initialize() storage = self._open_shelve_and_lock() try: if key in storage: value = storage[key][1] + value storage[key] = (time.time(), value) storage.sync() finally: self._close_shelve_and_unlock() return value class CacheAction(object): def __init__(self, func, key, time_expire, cache, cache_model): self.__name__ = func.__name__ self.__doc__ = func.__doc__ self.func = func self.key = key self.time_expire = time_expire self.cache = cache self.cache_model = cache_model def __call__(self, *a, **b): if not self.key: key2 = self.__name__ + ':' + repr(a) + ':' + repr(b) else: key2 = self.key.replace('%(name)s', self.__name__)\ .replace('%(args)s', str(a)).replace('%(vars)s', str(b)) cache_model = self.cache_model if not cache_model or isinstance(cache_model, str): cache_model = getattr(self.cache, cache_model or 'ram') return cache_model(key2, lambda a=a, b=b: self.func(*a, **b), self.time_expire) class Cache(object): """ Sets up generic caching, creating an instance of both CacheInRam and CacheOnDisk. In case of GAE will make use of gluon.contrib.gae_memcache. - self.ram is an instance of CacheInRam - self.disk is an instance of CacheOnDisk """ autokey = ':%(name)s:%(args)s:%(vars)s' def __init__(self, request): """ Parameters ---------- request: the global request object """ # GAE will have a special caching if have_settings and settings.global_settings.web2py_runtime_gae: from contrib.gae_memcache import MemcacheClient self.ram = self.disk = MemcacheClient(request) else: # Otherwise use ram (and try also disk) self.ram = CacheInRam(request) try: self.disk = CacheOnDisk(request) except IOError: logger.warning('no cache.disk (IOError)') except AttributeError: # normally not expected anymore, as GAE has already # been accounted for logger.warning('no cache.disk (AttributeError)') def action(self, time_expire=DEFAULT_TIME_EXPIRE, cache_model=None, prefix=None, session=False, vars=True, lang=True, user_agent=False, public=True, valid_statuses=None, quick=None): """ Experimental! Currently only HTTP 1.1 compliant reference : http://code.google.com/p/doctype-mirror/wiki/ArticleHttpCaching time_expire: same as @cache cache_model: same as @cache prefix: add a prefix to the calculated key session: adds response.session_id to the key vars: adds request.env.query_string lang: adds T.accepted_language user_agent: if True, adds is_mobile and is_tablet to the key. Pass a dict to use all the needed values (uses str(.items())) (e.g. user_agent=request.user_agent()) used only if session is not True public: if False forces the Cache-Control to be 'private' valid_statuses: by default only status codes starting with 1,2,3 will be cached. pass an explicit list of statuses on which turn the cache on quick: Session,Vars,Lang,User-agent,Public: fast overrides with initial strings, e.g. 'SVLP' or 'VLP', or 'VLP' """ from gluon import current from gluon.http import HTTP def wrap(func): def wrapped_f(): if current.request.env.request_method != 'GET': return func() if time_expire: cache_control = 'max-age=%(time_expire)s, s-maxage=%(time_expire)s' % dict(time_expire=time_expire) if quick: session_ = True if 'S' in quick else False vars_ = True if 'V' in quick else False lang_ = True if 'L' in quick else False user_agent_ = True if 'U' in quick else False public_ = True if 'P' in quick else False else: session_, vars_, lang_, user_agent_, public_ = session, vars, lang, user_agent, public if not session_ and public_: cache_control += ', public' expires = (current.request.utcnow + datetime.timedelta(seconds=time_expire)).strftime('%a, %d %b %Y %H:%M:%S GMT') vary = None else: cache_control += ', private' expires = 'Fri, 01 Jan 1990 00:00:00 GMT' if cache_model: #figure out the correct cache key cache_key = [current.request.env.path_info, current.response.view] if session_: cache_key.append(current.response.session_id) elif user_agent_: if user_agent_ is True: cache_key.append("%(is_mobile)s_%(is_tablet)s" % current.request.user_agent()) else: cache_key.append(str(user_agent_.items())) if vars_: cache_key.append(current.request.env.query_string) if lang_: cache_key.append(current.T.accepted_language) cache_key = hashlib.md5('__'.join(cache_key)).hexdigest() if prefix: cache_key = prefix + cache_key try: #action returns something rtn = cache_model(cache_key, lambda : func(), time_expire=time_expire) http, status = None, current.response.status except HTTP, e: #action raises HTTP (can still be valid) rtn = cache_model(cache_key, lambda : e.body, time_expire=time_expire) http, status = HTTP(e.status, rtn, **e.headers), e.status else: #action raised a generic exception http = None else: #no server-cache side involved try: #action returns something rtn = func() http, status = None, current.response.status except HTTP, e: #action raises HTTP (can still be valid) status = e.status http = HTTP(e.status, e.body, **e.headers) else: #action raised a generic exception http = None send_headers = False if http and isinstance(valid_statuses, list): if status in valid_statuses: send_headers = True elif valid_statuses is None: if str(status)[0] in '123': send_headers = True if send_headers: headers = { 'Pragma' : None, 'Expires' : expires, 'Cache-Control' : cache_control } current.response.headers.update(headers) if cache_model and not send_headers: #we cached already the value, but the status is not valid #so we need to delete the cached value cache_model(cache_key, None) if http: if send_headers: http.headers.update(current.response.headers) raise http return rtn wrapped_f.__name__ = func.__name__ wrapped_f.__doc__ = func.__doc__ return wrapped_f return wrap def __call__(self, key=None, time_expire=DEFAULT_TIME_EXPIRE, cache_model=None): """ Decorator function that can be used to cache any function/method. Example:: @cache('key', 5000, cache.ram) def f(): return time.ctime() When the function f is called, web2py tries to retrieve the value corresponding to `key` from the cache of the object exists and if it did not expire, else it calles the function `f` and stores the output in the cache corresponding to `key`. In the case the output of the function is returned. :param key: the key of the object to be store or retrieved :param time_expire: expiration of the cache in microseconds :param cache_model: "ram", "disk", or other (like "memcache" if defined). It defaults to "ram". Notes ----- `time_expire` is used to compare the curret time with the time when the requested object was last saved in cache. It does not affect future requests. Setting `time_expire` to 0 or negative value forces the cache to refresh. If the function `f` is an action, we suggest using @cache.client instead """ def tmp(func, cache=self, cache_model=cache_model): return CacheAction(func, key, time_expire, self, cache_model) return tmp @staticmethod def with_prefix(cache_model, prefix): """ allow replacing cache.ram with cache.with_prefix(cache.ram,'prefix') it will add prefix to all the cache keys used. """ return lambda key, f, time_expire=DEFAULT_TIME_EXPIRE, prefix=prefix:\ cache_model(prefix + key, f, time_expire) def lazy_cache(key=None, time_expire=None, cache_model='ram'): """ can be used to cache any function including in modules, as long as the cached function is only called within a web2py request if a key is not provided, one is generated from the function name the time_expire defaults to None (no cache expiration) if cache_model is "ram" then the model is current.cache.ram, etc. """ def decorator(f, key=key, time_expire=time_expire, cache_model=cache_model): key = key or repr(f) def g(*c, **d): from gluon import current return current.cache(key, time_expire, cache_model)(f)(*c, **d) g.__name__ = f.__name__ return g return decorator