Source code for cubicweb.web.httpcache
# copyright 2003-2012 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of CubicWeb.
#
# CubicWeb 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 2.1 of the License, or (at your option)
# any later version.
#
# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with CubicWeb. If not, see <http://www.gnu.org/licenses/>.
"""HTTP cache managers"""
__docformat__ = "restructuredtext en"
from calendar import timegm
from datetime import datetime
[docs]class NoHTTPCacheManager(object):
"""default cache manager: set no-cache cache control policy"""
def __init__(self, view):
self.view = view
self.req = view._cw
self.cw_rset = view.cw_rset
def set_headers(self):
self.req.set_header('Cache-control', 'no-cache')
self.req.set_header('Expires', 'Sat, 01 Jan 2000 00:00:00 GMT')
[docs]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)
[docs]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
"""
def etag(self):
if not self.req.cnx: # session without established connection to the repo
return self.view.__regid__
return self.view.__regid__ + '/' + ','.join(sorted(self.req.user.groups))
def max_age(self):
# 0 to actually force revalidation
return 0
def last_modified(self):
"""return view's last modified GMT time"""
return self.view.last_modified()
def set_headers(self):
req = self.req
try:
req.set_header('Etag', 'W/"%s"' % self.etag())
except NoEtag:
super(EtagHTTPCacheManager, self).set_headers()
return
req.set_header('Cache-control',
'must-revalidate,max-age=%s' % self.max_age())
mdate = self.last_modified()
# use a timestamp, not a formatted raw header, and let
# the front-end correctly generate it
# ("%a, %d %b %Y %H:%M:%S GMT" return localized date that
# twisted don't parse correctly)
req.set_header('Last-modified', timegm(mdate.timetuple()), raw=False)
[docs]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.cw_rset is None or len(self.cw_rset) == 0: # entity startup view for instance
return super(EntityHTTPCacheManager, self).etag()
if len(self.cw_rset) > 1:
raise NoEtag()
etag = super(EntityHTTPCacheManager, self).etag()
eid = self.cw_rset[0][0]
if self.req.user.owns(eid):
etag += ',owners'
return str(eid) + '/' + etag
[docs]class NoEtag(Exception):
"""an etag can't be generated"""
__all__ = ('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
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._cw.header_if_modified_since()
if mtime:
tdelta = (ctime - mtime)
if tdelta.days * 24*60*60 + tdelta.seconds <= self.cache_max_age:
return mtime
# mtime = ctime will force page rerendering
return ctime
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.StartupView.http_cache_manager = MaxAgeHTTPCacheManager
viewmod.StartupView.cache_max_age = 60*60*2 # stay in http cache for 2 hours by default
### HTTP Cache validator ############################################
def get_validators(headers_in):
"""return a list of http condition validator relevant to this request
"""
result = []
for header, func in VALIDATORS:
value = headers_in.getHeader(header)
if value is not None:
result.append((func, value))
return result
def if_modified_since(ref_date, headers_out):
last_modified = headers_out.getHeader('last-modified')
if last_modified is None:
return True
return ref_date < last_modified
def if_none_match(tags, headers_out):
etag = headers_out.getHeader('etag')
if etag is None:
return True
return not ((etag in tags) or ('*' in tags))
VALIDATORS = [
('if-modified-since', if_modified_since),
#('if-unmodified-since', if_unmodified_since),
('if-none-match', if_none_match),
#('if-modified-since', if_modified_since),
]
