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1 """HTTP cache managers |
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2 |
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3 |
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4 :organization: Logilab |
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5 :copyright: 2001-2008 LOGILAB S.A. (Paris, FRANCE), all rights reserved. |
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6 :contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr |
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7 """ |
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8 __docformat__ = "restructuredtext en" |
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9 |
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10 from mx.DateTime import DateTimeFromTicks, now, gmtime |
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11 |
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12 # time delta usable to convert localized time to GMT time |
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13 GMTOFFSET = - (now() - gmtime()) |
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14 |
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15 class NoHTTPCacheManager(object): |
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16 """default cache manager: set no-cache cache control policy""" |
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17 def __init__(self, view): |
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18 self.view = view |
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19 self.req = view.req |
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20 self.rset = view.rset |
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21 |
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22 def set_headers(self): |
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23 self.req.set_header('Cache-control', 'no-cache') |
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24 |
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25 class MaxAgeHTTPCacheManager(NoHTTPCacheManager): |
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26 """max-age cache manager: set max-age cache control policy, with max-age |
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27 specified with the `cache_max_age` attribute of the view |
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28 """ |
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29 def set_headers(self): |
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30 self.req.set_header('Cache-control', |
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31 'max-age=%s' % self.view.cache_max_age) |
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32 |
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33 class EtagHTTPCacheManager(NoHTTPCacheManager): |
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34 """etag based cache manager for startup views |
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35 |
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36 * etag is generated using the view name and the user's groups |
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37 * set policy to 'must-revalidate' and expires to the current time to force |
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38 revalidation on each request |
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39 """ |
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40 # GMT time required |
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41 date_format = "%a, %d %b %Y %H:%M:%S GMT" |
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42 |
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43 def etag(self): |
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44 return self.view.id + '/' + ','.join(sorted(self.req.user.groups)) |
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45 |
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46 def max_age(self): |
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47 # 0 to actually force revalidation |
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48 return 0 |
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49 |
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50 def last_modified(self): |
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51 return self.view.last_modified() |
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52 |
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53 def set_headers(self): |
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54 req = self.req |
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55 try: |
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56 req.set_header('Etag', '"%s"' % self.etag()) |
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57 except NoEtag: |
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58 self.req.set_header('Cache-control', 'no-cache') |
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59 return |
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60 req.set_header('Cache-control', |
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61 'must-revalidate;max-age=%s' % self.max_age()) |
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62 mdate = self.last_modified() |
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63 req.set_header('Last-modified', mdate.strftime(self.date_format)) |
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64 |
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65 class EntityHTTPCacheManager(EtagHTTPCacheManager): |
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66 """etag based cache manager for view displaying a single entity |
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67 |
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68 * etag is generated using entity's eid, the view name and the user's groups |
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69 * get last modified time from the entity definition (this may not be the |
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70 entity's modification time since a view may include some related entities |
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71 with a modification time to consider) using the `last_modified` method |
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72 """ |
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73 def etag(self): |
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74 if self.rset is None or len(self.rset) == 0: # entity startup view for instance |
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75 return super(EntityHTTPCacheManager, self).etag() |
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76 if len(self.rset) > 1: |
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77 raise NoEtag() |
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78 etag = super(EntityHTTPCacheManager, self).etag() |
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79 eid = self.rset[0][0] |
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80 if self.req.user.owns(eid): |
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81 etag += ',owners' |
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82 return str(eid) + '/' + etag |
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83 |
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84 |
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85 class NoEtag(Exception): |
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86 """an etag can't be generated""" |
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87 |
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88 __all__ = ('GMTOFFSET', |
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89 'NoHTTPCacheManager', 'MaxAgeHTTPCacheManager', |
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90 'EtagHTTPCacheManager', 'EntityHTTPCacheManager') |
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91 |
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92 # monkey patching, so view doesn't depends on this module and we have all |
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93 # http cache related logic here |
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94 |
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95 from cubicweb.common import view |
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96 |
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97 def set_http_cache_headers(self): |
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98 self.http_cache_manager(self).set_headers() |
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99 view.View.set_http_cache_headers = set_http_cache_headers |
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100 |
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101 def last_modified(self): |
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102 """return the date/time where this view should be considered as |
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103 modified. Take care of possible related objects modifications. |
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104 |
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105 /!\ must return GMT time /!\ |
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106 """ |
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107 # XXX check view module's file modification time in dev mod ? |
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108 ctime = gmtime() |
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109 if self.cache_max_age: |
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110 mtime = self.req.header_if_modified_since() |
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111 if mtime: |
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112 if (ctime - mtime).seconds > self.cache_max_age: |
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113 mtime = ctime |
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114 else: |
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115 mtime = ctime |
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116 else: |
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117 mtime = ctime |
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118 # mtime = ctime will force page rerendering |
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119 return mtime |
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120 view.View.last_modified = last_modified |
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121 |
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122 # configure default caching |
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123 view.View.http_cache_manager = NoHTTPCacheManager |
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124 # max-age=0 to actually force revalidation when needed |
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125 view.View.cache_max_age = 0 |
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126 |
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127 |
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128 view.EntityView.http_cache_manager = EntityHTTPCacheManager |
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129 |
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130 view.StartupView.http_cache_manager = MaxAgeHTTPCacheManager |
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131 view.StartupView.cache_max_age = 60*60*2 # stay in http cache for 2 hours by default |