1 # copyright 2003-2012 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

     2 # contact http://www.logilab.fr/ -- mailto:contact@logilab.fr

     3 #

     4 # This file is part of CubicWeb.

     5 #

     6 # CubicWeb is free software: you can redistribute it and/or modify it under the

     7 # terms of the GNU Lesser General Public License as published by the Free

     8 # Software Foundation, either version 2.1 of the License, or (at your option)

     9 # any later version.

    10 #

    11 # CubicWeb is distributed in the hope that it will be useful, but WITHOUT

    12 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

    13 # FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more

    14 # details.

    15 #

    16 # You should have received a copy of the GNU Lesser General Public License along

    17 # with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.

    18 """HTTP cache managers"""

    19 

    20 __docformat__ = "restructuredtext en"

    21 

    22 from time import mktime

    23 from datetime import datetime

    24 

    25 class NoHTTPCacheManager(object):

    26     """default cache manager: set no-cache cache control policy"""

    27     def __init__(self, view):

    28         self.view = view

    29         self.req = view._cw

    30         self.cw_rset = view.cw_rset

    31 

    32     def set_headers(self):

    33         self.req.set_header('Cache-control', 'no-cache')

    34         self.req.set_header('Expires', 'Sat, 01 Jan 2000 00:00:00 GMT')

    35 

    36 

    37 class MaxAgeHTTPCacheManager(NoHTTPCacheManager):

    38     """max-age cache manager: set max-age cache control policy, with max-age

    39     specified with the `cache_max_age` attribute of the view

    40     """

    41     def set_headers(self):

    42         self.req.set_header('Cache-control',

    43                             'max-age=%s' % self.view.cache_max_age)

    44 

    45 

    46 class EtagHTTPCacheManager(NoHTTPCacheManager):

    47     """etag based cache manager for startup views

    48 

    49     * etag is generated using the view name and the user's groups

    50     * set policy to 'must-revalidate' and expires to the current time to force

    51       revalidation on each request

    52     """

    53 

    54     def etag(self):

    55         if not self.req.cnx: # session without established connection to the repo

    56             return self.view.__regid__

    57         return self.view.__regid__ + '/' + ','.join(sorted(self.req.user.groups))

    58 

    59     def max_age(self):

    60         # 0 to actually force revalidation

    61         return 0

    62 

    63     def last_modified(self):

    64         """return view's last modified GMT time"""

    65         return self.view.last_modified()

    66 

    67     def set_headers(self):

    68         req = self.req

    69         try:

    70             req.set_header('Etag', '"%s"' % self.etag())

    71         except NoEtag:

    72             super(EtagHTTPCacheManager, self).set_headers()

    73             return

    74         req.set_header('Cache-control',

    75                        'must-revalidate,max-age=%s' % self.max_age())

    76         mdate = self.last_modified()

    77         # use a timestamp, not a formatted raw header, and let

    78         # the front-end correctly generate it

    79         # ("%a, %d %b %Y %H:%M:%S GMT" return localized date that

    80         # twisted don't parse correctly)

    81         req.set_header('Last-modified', mktime(mdate.timetuple()), raw=False)

    82 

    83 

    84 class EntityHTTPCacheManager(EtagHTTPCacheManager):

    85     """etag based cache manager for view displaying a single entity

    86 

    87     * etag is generated using entity's eid, the view name and the user's groups

    88     * get last modified time from the entity definition (this may not be the

    89       entity's modification time since a view may include some related entities

    90       with a modification time to consider) using the `last_modified` method

    91     """

    92     def etag(self):

    93         if self.cw_rset is None or len(self.cw_rset) == 0: # entity startup view for instance

    94             return super(EntityHTTPCacheManager, self).etag()

    95         if len(self.cw_rset) > 1:

    96             raise NoEtag()

    97         etag = super(EntityHTTPCacheManager, self).etag()

    98         eid = self.cw_rset[0][0]

    99         if self.req.user.owns(eid):

   100             etag += ',owners'

   101         return str(eid) + '/' + etag

   102 

   103 

   104 class NoEtag(Exception):

   105     """an etag can't be generated"""

   106 

   107 __all__ = ('GMTOFFSET',

   108            'NoHTTPCacheManager', 'MaxAgeHTTPCacheManager',

   109            'EtagHTTPCacheManager', 'EntityHTTPCacheManager')

   110 

   111 # monkey patching, so view doesn't depends on this module and we have all

   112 # http cache related logic here

   113 

   114 from cubicweb import view as viewmod

   115 

   116 def set_http_cache_headers(self):

   117     self.http_cache_manager(self).set_headers()

   118 viewmod.View.set_http_cache_headers = set_http_cache_headers

   119 

   120 

   121 def last_modified(self):

   122     """return the date/time where this view should be considered as

   123     modified. Take care of possible related objects modifications.

   124 

   125     /!\ must return GMT time /!\

   126     """

   127     # XXX check view module's file modification time in dev mod ?

   128     ctime = datetime.utcnow()

   129     if self.cache_max_age:

   130         mtime = self._cw.header_if_modified_since()

   131         if mtime:

   132             tdelta = (ctime - mtime)

   133             if tdelta.days * 24*60*60 + tdelta.seconds <= self.cache_max_age:

   134                 return mtime

   135     # mtime = ctime will force page rerendering

   136     return ctime

   137 viewmod.View.last_modified = last_modified

   138 

   139 

   140 # configure default caching

   141 viewmod.View.http_cache_manager = NoHTTPCacheManager

   142 # max-age=0 to actually force revalidation when needed

   143 viewmod.View.cache_max_age = 0

   144 

   145 viewmod.StartupView.http_cache_manager = MaxAgeHTTPCacheManager

   146 viewmod.StartupView.cache_max_age = 60*60*2 # stay in http cache for 2 hours by default

   147 

   148 

   149 ### HTTP Cache validator ############################################

   150 

   151 

   152 

   153 def get_validators(headers_in):

   154     """return a list of http condition validator relevant to this request

   155     """

   156     result = []

   157     for header, func in VALIDATORS:

   158         value = headers_in.getHeader(header)

   159         if value is not None:

   160             result.append((func, value))

   161     return result

   162 

   163 

   164 def if_modified_since(ref_date, headers_out):

   165     last_modified = headers_out.getHeader('last-modified')

   166     if last_modified is None:

   167         return True

   168     return ref_date < last_modified

   169 

   170 def if_none_match(tags, headers_out):

   171     etag = headers_out.getHeader('etag')

   172     if etag is None:

   173         return True

   174     return not ((etag in tags) or ('*' in tags))

   175 

   176 VALIDATORS = [

   177     ('if-modified-since', if_modified_since),

   178     #('if-unmodified-since', if_unmodified_since),

   179     ('if-none-match', if_none_match),

   180     #('if-modified-since', if_modified_since),

   181 ]