+
−"""HTTP cache managers
+
−
+
−
+
−:organization: Logilab
+
−:copyright: 2001-2009 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.
+
−:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
+
−:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses
+
−"""
+
−__docformat__ = "restructuredtext en"
+
−
+
−from datetime import datetime
+
−
+
−# time delta usable to convert localized time to GMT time
+
−GMTOFFSET = - (datetime.now() - datetime.utcnow())
+
−
+
−class NoHTTPCacheManager(object):
+
−    """default cache manager: set no-cache cache control policy"""
+
−    def __init__(self, view):
+
−        self.view = view
+
−        self.req = view.req
+
−        self.rset = view.rset
+
−
+
−    def set_headers(self):
+
−        self.req.set_header('Cache-control', 'no-cache')
+
−
+
−class MaxAgeHTTPCacheManager(NoHTTPCacheManager):
+
−    """max-age cache manager: set max-age cache control policy, with max-age
+
−    specified with the `cache_max_age` attribute of the view
+
−    """
+
−    def set_headers(self):
+
−        self.req.set_header('Cache-control',
+
−                            'max-age=%s' % self.view.cache_max_age)
+
−
+
−class EtagHTTPCacheManager(NoHTTPCacheManager):
+
−    """etag based cache manager for startup views
+
−
+
−    * etag is generated using the view name and the user's groups
+
−    * set policy to 'must-revalidate' and expires to the current time to force
+
−      revalidation on each request
+
−    """
+
−    # GMT time required
+
−    date_format = "%a, %d %b %Y %H:%M:%S GMT"
+
−
+
−    def etag(self):
+
−        return self.view.id + '/' + ','.join(sorted(self.req.user.groups))
+
−
+
−    def max_age(self):
+
−        # 0 to actually force revalidation
+
−        return 0
+
−
+
−    def last_modified(self):
+
−        return self.view.last_modified()
+
−
+
−    def set_headers(self):
+
−        req = self.req
+
−        try:
+
−            req.set_header('Etag', '"%s"' % self.etag())
+
−        except NoEtag:
+
−            self.req.set_header('Cache-control', 'no-cache')
+
−            return
+
−        req.set_header('Cache-control',
+
−                       'must-revalidate;max-age=%s' % self.max_age())
+
−        mdate = self.last_modified()
+
−        req.set_header('Last-modified', mdate.strftime(self.date_format))
+
−
+
−class EntityHTTPCacheManager(EtagHTTPCacheManager):
+
−    """etag based cache manager for view displaying a single entity
+
−
+
−    * etag is generated using entity's eid, the view name and the user's groups
+
−    * get last modified time from the entity definition (this may not be the
+
−      entity's modification time since a view may include some related entities
+
−      with a modification time to consider) using the `last_modified` method
+
−    """
+
−    def etag(self):
+
−        if self.rset is None or len(self.rset) == 0: # entity startup view for instance
+
−            return super(EntityHTTPCacheManager, self).etag()
+
−        if len(self.rset) > 1:
+
−            raise NoEtag()
+
−        etag = super(EntityHTTPCacheManager, self).etag()
+
−        eid = self.rset[0][0]
+
−        if self.req.user.owns(eid):
+
−            etag += ',owners'
+
−        return str(eid) + '/' + etag
+
−
+
−
+
−class NoEtag(Exception):
+
−    """an etag can't be generated"""
+
−
+
−__all__ = ('GMTOFFSET',
+
−           'NoHTTPCacheManager', 'MaxAgeHTTPCacheManager',
+
−           'EtagHTTPCacheManager', 'EntityHTTPCacheManager')
+
−
+
−# monkey patching, so view doesn't depends on this module and we have all
+
−# http cache related logic here
+
−
+
−from cubicweb import view as viewmod
+
−
+
−def set_http_cache_headers(self):
+
−    self.http_cache_manager(self).set_headers()
+
−viewmod.View.set_http_cache_headers = set_http_cache_headers
+
−
+
−def last_modified(self):
+
−    """return the date/time where this view should be considered as
+
−    modified. Take care of possible related objects modifications.
+
−
+
−    /!\ must return GMT time /!\
+
−    """
+
−    # XXX check view module's file modification time in dev mod ?
+
−    ctime = datetime.utcnow()
+
−    if self.cache_max_age:
+
−        mtime = self.req.header_if_modified_since()
+
−        if mtime:
+
−            tdelta = (ctime - mtime)
+
−            if tdelta.days * 24*60*60 + tdelta.seconds > self.cache_max_age:
+
−                mtime = ctime
+
−        else:
+
−            mtime = ctime
+
−    else:
+
−        mtime = ctime
+
−    # mtime = ctime will force page rerendering
+
−    return mtime
+
−viewmod.View.last_modified = last_modified
+
−
+
−# configure default caching
+
−viewmod.View.http_cache_manager = NoHTTPCacheManager
+
−# max-age=0 to actually force revalidation when needed
+
−viewmod.View.cache_max_age = 0
+
−
+
−
+
−viewmod.EntityView.http_cache_manager = EntityHTTPCacheManager
+
−
+
−viewmod.StartupView.http_cache_manager = MaxAgeHTTPCacheManager
+
−viewmod.StartupView.cache_max_age = 60*60*2 # stay in http cache for 2 hours by default