1 """HTTP cache managers

     2 

     3 

     4 :organization: Logilab

     5 :copyright: 2001-2008 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

     6 :contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr

     7 """

     8 __docformat__ = "restructuredtext en"

     9 

    10 from mx.DateTime import DateTimeFromTicks, now, gmtime

    11 

    12 # time delta usable to convert localized time to GMT time

    13 GMTOFFSET = - (now() - gmtime())

    14 

    15 class NoHTTPCacheManager(object):

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

    17     def __init__(self, view):

    18         self.view = view

    19         self.req = view.req

    20         self.rset = view.rset

    21 

    22     def set_headers(self):

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

    24 

    25 class MaxAgeHTTPCacheManager(NoHTTPCacheManager):

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

    27     specified with the `cache_max_age` attribute of the view

    28     """

    29     def set_headers(self):

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

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

    32 

    33 class EtagHTTPCacheManager(NoHTTPCacheManager):

    34     """etag based cache manager for startup views

    35 

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

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

    38       revalidation on each request

    39     """

    40     # GMT time required

    41     date_format = "%a, %d %b %Y %H:%M:%S GMT"

    42 

    43     def etag(self):

    44         return self.view.id + '/' + ','.join(sorted(self.req.user.groups))

    45     

    46     def max_age(self):

    47         # 0 to actually force revalidation

    48         return 0

    49     

    50     def last_modified(self):

    51         return self.view.last_modified()

    52     

    53     def set_headers(self):

    54         req = self.req

    55         try:

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

    57         except NoEtag:

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

    59             return

    60         req.set_header('Cache-control',

    61                        'must-revalidate;max-age=%s' % self.max_age())

    62         mdate = self.last_modified()

    63         req.set_header('Last-modified', mdate.strftime(self.date_format))

    64 

    65 class EntityHTTPCacheManager(EtagHTTPCacheManager):

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

    67 

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

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

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

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

    72     """

    73     def etag(self):

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

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

    76         if len(self.rset) > 1:

    77             raise NoEtag()

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

    79         eid = self.rset[0][0]

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

    81             etag += ',owners'

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

    83 

    84 

    85 class NoEtag(Exception):

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

    87 

    88 __all__ = ('GMTOFFSET',

    89            'NoHTTPCacheManager', 'MaxAgeHTTPCacheManager',

    90            'EtagHTTPCacheManager', 'EntityHTTPCacheManager')

    91 

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

    93 # http cache related logic here

    94 

    95 from cubicweb.common import view

    96 

    97 def set_http_cache_headers(self):

    98     self.http_cache_manager(self).set_headers()

    99 view.View.set_http_cache_headers = set_http_cache_headers

   100 

   101 def last_modified(self):

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

   103     modified. Take care of possible related objects modifications.

   104 

   105     /!\ must return GMT time /!\

   106     """

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

   108     ctime = gmtime()

   109     if self.cache_max_age:

   110         mtime = self.req.header_if_modified_since()

   111         if mtime:

   112             if (ctime - mtime).seconds > self.cache_max_age:

   113                 mtime = ctime

   114         else:

   115             mtime = ctime

   116     else:

   117         mtime = ctime

   118     # mtime = ctime will force page rerendering

   119     return mtime

   120 view.View.last_modified = last_modified

   121 

   122 # configure default caching

   123 view.View.http_cache_manager = NoHTTPCacheManager

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

   125 view.View.cache_max_age = 0

   126 

   127 

   128 view.EntityView.http_cache_manager = EntityHTTPCacheManager

   129 

   130 view.StartupView.http_cache_manager = MaxAgeHTTPCacheManager

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