web/httpcache.py
author Sylvain Thénault <sylvain.thenault@logilab.fr>
Tue, 26 Jan 2010 13:32:54 +0100
changeset 4364 766359c69f2f
parent 4252 6c4f109c2b03
child 4436 294e084f1263
permissions -rw-r--r--
[uicfg] fix autoform_section rtags initialization 1. when a relation is marked as inlined in the 'main' form type, we want its opposite (eg when one the other side of the relation) to be marked as hidden in the 'inlined' form type 2. when no section is specified for the 'inlined' form type, use the same as in the 'main' form type to do this properly, we need two initialization stages. The first one to handle 1., the second to handle what was done before and 2. We can't do this in a single stage because we've to know the bare value of the "opposite" tag.

"""HTTP cache managers


:organization: Logilab
:copyright: 2001-2010 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._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
    """
    # GMT time required
    date_format = "%a, %d %b %Y %H:%M:%S GMT"

    def etag(self):
        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 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.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:
                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