| """ |
| Caching framework. |
| |
| This package defines set of cache backends that all conform to a simple API. |
| In a nutshell, a cache is a set of values -- which can be any object that |
| may be pickled -- identified by string keys. For the complete API, see |
| the abstract BaseCache class in django.core.cache.backends.base. |
| |
| Client code should not access a cache backend directly; instead it should |
| either use the "cache" variable made available here, or it should use the |
| get_cache() function made available here. get_cache() takes a backend URI |
| (e.g. "memcached://127.0.0.1:11211/") and returns an instance of a backend |
| cache class. |
| |
| See docs/cache.txt for information on the public API. |
| """ |
| |
| try: |
| from urlparse import parse_qsl |
| except ImportError: |
| from cgi import parse_qsl |
| |
| from google.appengine._internal.django.conf import settings |
| from google.appengine._internal.django.core import signals |
| from google.appengine._internal.django.core.cache.backends.base import InvalidCacheBackendError, CacheKeyWarning |
| from google.appengine._internal.django.utils import importlib |
| |
| # Name for use in settings file --> name of module in "backends" directory. |
| # Any backend scheme that is not in this dictionary is treated as a Python |
| # import path to a custom backend. |
| BACKENDS = { |
| 'memcached': 'memcached', |
| 'locmem': 'locmem', |
| 'file': 'filebased', |
| 'db': 'db', |
| 'dummy': 'dummy', |
| } |
| |
| def parse_backend_uri(backend_uri): |
| """ |
| Converts the "backend_uri" into a cache scheme ('db', 'memcached', etc), a |
| host and any extra params that are required for the backend. Returns a |
| (scheme, host, params) tuple. |
| """ |
| if backend_uri.find(':') == -1: |
| raise InvalidCacheBackendError("Backend URI must start with scheme://") |
| scheme, rest = backend_uri.split(':', 1) |
| if not rest.startswith('//'): |
| raise InvalidCacheBackendError("Backend URI must start with scheme://") |
| |
| host = rest[2:] |
| qpos = rest.find('?') |
| if qpos != -1: |
| params = dict(parse_qsl(rest[qpos+1:])) |
| host = rest[2:qpos] |
| else: |
| params = {} |
| if host.endswith('/'): |
| host = host[:-1] |
| |
| return scheme, host, params |
| |
| def get_cache(backend_uri): |
| scheme, host, params = parse_backend_uri(backend_uri) |
| if scheme in BACKENDS: |
| name = 'django.core.cache.backends.%s' % BACKENDS[scheme] |
| else: |
| name = scheme |
| module = importlib.import_module(name) |
| return getattr(module, 'CacheClass')(host, params) |
| |
| cache = get_cache(settings.CACHE_BACKEND) |
| |
| # Some caches -- pythont-memcached in particular -- need to do a cleanup at the |
| # end of a request cycle. If the cache provides a close() method, wire it up |
| # here. |
| if hasattr(cache, 'close'): |
| signals.request_finished.connect(cache.close) |
| |