Source code for woob.browser.cache

# Copyright(C) 2012-2016 woob project
# This file is part of woob.
# woob is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# woob is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# GNU Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public License
# along with woob. If not, see <>.

__all__ = ['CacheMixin']

class CacheEntry:
    def __init__(self, response):
        self.response = response
        self.etag = response.headers.get('ETag')
        self.last_modified = response.headers.get('Last-Modified')

    def has_cache_key(self):
        return (self.etag or self.last_modified)

    def update_request(self, request):
        if self.last_modified:
            request.headers['If-Modified-Since'] = self.last_modified
        if self.etag:
            request.headers['If-None-Match'] = self.etag

[docs]class CacheMixin: """Mixin to inherit in a Browser""" cache_is_updatable = True """Whether the cache is updatable If `False`, once a request has been successfully executed, its response will always be returned. If `True`, the `ETag` and `Last-Modified` of the response will be stored along with the cache. When the request is re-executed, instead of simply returning the previous response, the server is queried to check if a newer version of the page exists. If a newer page exists, it is returned instead and overwrites the obsolete page in the cache. """ def __init__(self, *args, **kwargs): super(CacheMixin, self).__init__(*args, **kwargs) self.cache = {} """Cache store object To limit the size of the cache, a :class:`` instance can be used. """
[docs] def make_cache_key(self, request): """Make a key for the cache corresponding to the request.""" body = getattr(request, 'body', None) headers = tuple(request.headers.values()) return (request.method, request.url, body, headers)
[docs] def open_with_cache(self, url, **kwargs): """Perform a request using the cache if possible.""" request = self.build_request(url, **kwargs) key = self.make_cache_key(request) if key in self.cache: if not self.cache_is_updatable: self.logger.debug('cache HIT for %r', request.url) return self.cache[key].response else: self.cache[key].update_request(request) response = super(CacheMixin, self).open(request, **kwargs) if response.status_code == 304: self.logger.debug('cache HIT for %r', request.url) return self.cache[key].response elif response.status_code == 200: entry = CacheEntry(response) if entry.has_cache_key(): self.logger.debug('storing %r response in cache', request.url) self.cache[key] = entry self.logger.debug('cache MISS for %r', request.url) return response