web/httpcache.py
author Alexandre Fayolle <alexandre.fayolle@logilab.fr>
Fri, 15 Apr 2011 16:05:20 +0200
changeset 7236 b91205ada414
parent 5867 7ef636d24ab2
child 8176 eff4fe02ec64
permissions -rw-r--r--
added test case to monitor speed improvements in the repository code. To use it, add a test in a patch, then hack CW to speed it up in another patch, updating the test if needed. By running the test with and without the second patch applied you can easily see the speed improvements

# copyright 2003-2010 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 time import mktime
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._cw
        self.cw_rset = view.cw_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
    """

    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', '"%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()
        # 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', mktime(mdate.timetuple()), raw=False)


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


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._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