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<h1><a href="../../../index.html">Django 1.11.20 documentation</a></h1>
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<h1>Source code for django.middleware.cache</h1><div class="highlight"><pre>
<span></span><span class="sd">"""</span>
<span class="sd">Cache middleware. If enabled, each Django-powered page will be cached based on</span>
<span class="sd">URL. The canonical way to enable cache middleware is to set</span>
<span class="sd">``UpdateCacheMiddleware`` as your first piece of middleware, and</span>
<span class="sd">``FetchFromCacheMiddleware`` as the last::</span>
<span class="sd"> MIDDLEWARE = [</span>
<span class="sd"> 'django.middleware.cache.UpdateCacheMiddleware',</span>
<span class="sd"> ...</span>
<span class="sd"> 'django.middleware.cache.FetchFromCacheMiddleware'</span>
<span class="sd"> ]</span>
<span class="sd">This is counter-intuitive, but correct: ``UpdateCacheMiddleware`` needs to run</span>
<span class="sd">last during the response phase, which processes middleware bottom-up;</span>
<span class="sd">``FetchFromCacheMiddleware`` needs to run last during the request phase, which</span>
<span class="sd">processes middleware top-down.</span>
<span class="sd">The single-class ``CacheMiddleware`` can be used for some simple sites.</span>
<span class="sd">However, if any other piece of middleware needs to affect the cache key, you'll</span>
<span class="sd">need to use the two-part ``UpdateCacheMiddleware`` and</span>
<span class="sd">``FetchFromCacheMiddleware``. This'll most often happen when you're using</span>
<span class="sd">Django's ``LocaleMiddleware``.</span>
<span class="sd">More details about how the caching works:</span>
<span class="sd">* Only GET or HEAD-requests with status code 200 are cached.</span>
<span class="sd">* The number of seconds each page is stored for is set by the "max-age" section</span>
<span class="sd"> of the response's "Cache-Control" header, falling back to the</span>
<span class="sd"> CACHE_MIDDLEWARE_SECONDS setting if the section was not found.</span>
<span class="sd">* This middleware expects that a HEAD request is answered with the same response</span>
<span class="sd"> headers exactly like the corresponding GET request.</span>
<span class="sd">* When a hit occurs, a shallow copy of the original response object is returned</span>
<span class="sd"> from process_request.</span>
<span class="sd">* Pages will be cached based on the contents of the request headers listed in</span>
<span class="sd"> the response's "Vary" header.</span>
<span class="sd">* This middleware also sets ETag, Last-Modified, Expires and Cache-Control</span>
<span class="sd"> headers on the response object.</span>
<span class="sd">"""</span>
<span class="kn">from</span> <span class="nn">django.conf</span> <span class="k">import</span> <span class="n">settings</span>
<span class="kn">from</span> <span class="nn">django.core.cache</span> <span class="k">import</span> <span class="n">DEFAULT_CACHE_ALIAS</span><span class="p">,</span> <span class="n">caches</span>
<span class="kn">from</span> <span class="nn">django.utils.cache</span> <span class="k">import</span> <span class="p">(</span>
<span class="n">get_cache_key</span><span class="p">,</span> <span class="n">get_max_age</span><span class="p">,</span> <span class="n">has_vary_header</span><span class="p">,</span> <span class="n">learn_cache_key</span><span class="p">,</span>
<span class="n">patch_response_headers</span><span class="p">,</span>
<span class="p">)</span>
<span class="kn">from</span> <span class="nn">django.utils.deprecation</span> <span class="k">import</span> <span class="n">MiddlewareMixin</span>
<div class="viewcode-block" id="UpdateCacheMiddleware"><a class="viewcode-back" href="../../../ref/middleware.html#django.middleware.cache.UpdateCacheMiddleware">[docs]</a><span class="k">class</span> <span class="nc">UpdateCacheMiddleware</span><span class="p">(</span><span class="n">MiddlewareMixin</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Response-phase cache middleware that updates the cache if the response is</span>
<span class="sd"> cacheable.</span>
<span class="sd"> Must be used as part of the two-part update/fetch cache middleware.</span>
<span class="sd"> UpdateCacheMiddleware must be the first piece of middleware in MIDDLEWARE</span>
<span class="sd"> so that it'll get called last during the response phase.</span>
<span class="sd"> """</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">get_response</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cache_timeout</span> <span class="o">=</span> <span class="n">settings</span><span class="o">.</span><span class="n">CACHE_MIDDLEWARE_SECONDS</span>
<span class="bp">self</span><span class="o">.</span><span class="n">key_prefix</span> <span class="o">=</span> <span class="n">settings</span><span class="o">.</span><span class="n">CACHE_MIDDLEWARE_KEY_PREFIX</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cache_alias</span> <span class="o">=</span> <span class="n">settings</span><span class="o">.</span><span class="n">CACHE_MIDDLEWARE_ALIAS</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cache</span> <span class="o">=</span> <span class="n">caches</span><span class="p">[</span><span class="bp">self</span><span class="o">.</span><span class="n">cache_alias</span><span class="p">]</span>
<span class="bp">self</span><span class="o">.</span><span class="n">get_response</span> <span class="o">=</span> <span class="n">get_response</span>
<span class="k">def</span> <span class="nf">_should_update_cache</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">request</span><span class="p">,</span> <span class="n">response</span><span class="p">):</span>
<span class="k">return</span> <span class="nb">hasattr</span><span class="p">(</span><span class="n">request</span><span class="p">,</span> <span class="s1">'_cache_update_cache'</span><span class="p">)</span> <span class="ow">and</span> <span class="n">request</span><span class="o">.</span><span class="n">_cache_update_cache</span>
<span class="k">def</span> <span class="nf">process_response</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">request</span><span class="p">,</span> <span class="n">response</span><span class="p">):</span>
<span class="sd">"""Sets the cache, if needed."""</span>
<span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">_should_update_cache</span><span class="p">(</span><span class="n">request</span><span class="p">,</span> <span class="n">response</span><span class="p">):</span>
<span class="c1"># We don't need to update the cache, just return.</span>
<span class="k">return</span> <span class="n">response</span>
<span class="k">if</span> <span class="n">response</span><span class="o">.</span><span class="n">streaming</span> <span class="ow">or</span> <span class="n">response</span><span class="o">.</span><span class="n">status_code</span> <span class="ow">not</span> <span class="ow">in</span> <span class="p">(</span><span class="mi">200</span><span class="p">,</span> <span class="mi">304</span><span class="p">):</span>
<span class="k">return</span> <span class="n">response</span>
<span class="c1"># Don't cache responses that set a user-specific (and maybe security</span>
<span class="c1"># sensitive) cookie in response to a cookie-less request.</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">request</span><span class="o">.</span><span class="n">COOKIES</span> <span class="ow">and</span> <span class="n">response</span><span class="o">.</span><span class="n">cookies</span> <span class="ow">and</span> <span class="n">has_vary_header</span><span class="p">(</span><span class="n">response</span><span class="p">,</span> <span class="s1">'Cookie'</span><span class="p">):</span>
<span class="k">return</span> <span class="n">response</span>
<span class="c1"># Try to get the timeout from the "max-age" section of the "Cache-</span>
<span class="c1"># Control" header before reverting to using the default cache_timeout</span>
<span class="c1"># length.</span>
<span class="n">timeout</span> <span class="o">=</span> <span class="n">get_max_age</span><span class="p">(</span><span class="n">response</span><span class="p">)</span>
<span class="k">if</span> <span class="n">timeout</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">timeout</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">cache_timeout</span>
<span class="k">elif</span> <span class="n">timeout</span> <span class="o">==</span> <span class="mi">0</span><span class="p">:</span>
<span class="c1"># max-age was set to 0, don't bother caching.</span>
<span class="k">return</span> <span class="n">response</span>
<span class="n">patch_response_headers</span><span class="p">(</span><span class="n">response</span><span class="p">,</span> <span class="n">timeout</span><span class="p">)</span>
<span class="k">if</span> <span class="n">timeout</span> <span class="ow">and</span> <span class="n">response</span><span class="o">.</span><span class="n">status_code</span> <span class="o">==</span> <span class="mi">200</span><span class="p">:</span>
<span class="n">cache_key</span> <span class="o">=</span> <span class="n">learn_cache_key</span><span class="p">(</span><span class="n">request</span><span class="p">,</span> <span class="n">response</span><span class="p">,</span> <span class="n">timeout</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">key_prefix</span><span class="p">,</span> <span class="n">cache</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">cache</span><span class="p">)</span>
<span class="k">if</span> <span class="nb">hasattr</span><span class="p">(</span><span class="n">response</span><span class="p">,</span> <span class="s1">'render'</span><span class="p">)</span> <span class="ow">and</span> <span class="n">callable</span><span class="p">(</span><span class="n">response</span><span class="o">.</span><span class="n">render</span><span class="p">):</span>
<span class="n">response</span><span class="o">.</span><span class="n">add_post_render_callback</span><span class="p">(</span>
<span class="k">lambda</span> <span class="n">r</span><span class="p">:</span> <span class="bp">self</span><span class="o">.</span><span class="n">cache</span><span class="o">.</span><span class="n">set</span><span class="p">(</span><span class="n">cache_key</span><span class="p">,</span> <span class="n">r</span><span class="p">,</span> <span class="n">timeout</span><span class="p">)</span>
<span class="p">)</span>
<span class="k">else</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cache</span><span class="o">.</span><span class="n">set</span><span class="p">(</span><span class="n">cache_key</span><span class="p">,</span> <span class="n">response</span><span class="p">,</span> <span class="n">timeout</span><span class="p">)</span>
<span class="k">return</span> <span class="n">response</span></div>
<div class="viewcode-block" id="FetchFromCacheMiddleware"><a class="viewcode-back" href="../../../ref/middleware.html#django.middleware.cache.FetchFromCacheMiddleware">[docs]</a><span class="k">class</span> <span class="nc">FetchFromCacheMiddleware</span><span class="p">(</span><span class="n">MiddlewareMixin</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Request-phase cache middleware that fetches a page from the cache.</span>
<span class="sd"> Must be used as part of the two-part update/fetch cache middleware.</span>
<span class="sd"> FetchFromCacheMiddleware must be the last piece of middleware in MIDDLEWARE</span>
<span class="sd"> so that it'll get called last during the request phase.</span>
<span class="sd"> """</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">get_response</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">key_prefix</span> <span class="o">=</span> <span class="n">settings</span><span class="o">.</span><span class="n">CACHE_MIDDLEWARE_KEY_PREFIX</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cache_alias</span> <span class="o">=</span> <span class="n">settings</span><span class="o">.</span><span class="n">CACHE_MIDDLEWARE_ALIAS</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cache</span> <span class="o">=</span> <span class="n">caches</span><span class="p">[</span><span class="bp">self</span><span class="o">.</span><span class="n">cache_alias</span><span class="p">]</span>
<span class="bp">self</span><span class="o">.</span><span class="n">get_response</span> <span class="o">=</span> <span class="n">get_response</span>
<span class="k">def</span> <span class="nf">process_request</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">request</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Checks whether the page is already cached and returns the cached</span>
<span class="sd"> version if available.</span>
<span class="sd"> """</span>
<span class="k">if</span> <span class="n">request</span><span class="o">.</span><span class="n">method</span> <span class="ow">not</span> <span class="ow">in</span> <span class="p">(</span><span class="s1">'GET'</span><span class="p">,</span> <span class="s1">'HEAD'</span><span class="p">):</span>
<span class="n">request</span><span class="o">.</span><span class="n">_cache_update_cache</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">return</span> <span class="kc">None</span> <span class="c1"># Don't bother checking the cache.</span>
<span class="c1"># try and get the cached GET response</span>
<span class="n">cache_key</span> <span class="o">=</span> <span class="n">get_cache_key</span><span class="p">(</span><span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">key_prefix</span><span class="p">,</span> <span class="s1">'GET'</span><span class="p">,</span> <span class="n">cache</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">cache</span><span class="p">)</span>
<span class="k">if</span> <span class="n">cache_key</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">request</span><span class="o">.</span><span class="n">_cache_update_cache</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">return</span> <span class="kc">None</span> <span class="c1"># No cache information available, need to rebuild.</span>
<span class="n">response</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">cache</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">cache_key</span><span class="p">)</span>
<span class="c1"># if it wasn't found and we are looking for a HEAD, try looking just for that</span>
<span class="k">if</span> <span class="n">response</span> <span class="ow">is</span> <span class="kc">None</span> <span class="ow">and</span> <span class="n">request</span><span class="o">.</span><span class="n">method</span> <span class="o">==</span> <span class="s1">'HEAD'</span><span class="p">:</span>
<span class="n">cache_key</span> <span class="o">=</span> <span class="n">get_cache_key</span><span class="p">(</span><span class="n">request</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">key_prefix</span><span class="p">,</span> <span class="s1">'HEAD'</span><span class="p">,</span> <span class="n">cache</span><span class="o">=</span><span class="bp">self</span><span class="o">.</span><span class="n">cache</span><span class="p">)</span>
<span class="n">response</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">cache</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">cache_key</span><span class="p">)</span>
<span class="k">if</span> <span class="n">response</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">request</span><span class="o">.</span><span class="n">_cache_update_cache</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">return</span> <span class="kc">None</span> <span class="c1"># No cache information available, need to rebuild.</span>
<span class="c1"># hit, return cached response</span>
<span class="n">request</span><span class="o">.</span><span class="n">_cache_update_cache</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">return</span> <span class="n">response</span></div>
<span class="k">class</span> <span class="nc">CacheMiddleware</span><span class="p">(</span><span class="n">UpdateCacheMiddleware</span><span class="p">,</span> <span class="n">FetchFromCacheMiddleware</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Cache middleware that provides basic behavior for many simple sites.</span>
<span class="sd"> Also used as the hook point for the cache decorator, which is generated</span>
<span class="sd"> using the decorator-from-middleware utility.</span>
<span class="sd"> """</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">get_response</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">cache_timeout</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">get_response</span> <span class="o">=</span> <span class="n">get_response</span>
<span class="c1"># We need to differentiate between "provided, but using default value",</span>
<span class="c1"># and "not provided". If the value is provided using a default, then</span>
<span class="c1"># we fall back to system defaults. If it is not provided at all,</span>
<span class="c1"># we need to use middleware defaults.</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">key_prefix</span> <span class="o">=</span> <span class="n">kwargs</span><span class="p">[</span><span class="s1">'key_prefix'</span><span class="p">]</span>
<span class="k">if</span> <span class="n">key_prefix</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">key_prefix</span> <span class="o">=</span> <span class="s1">''</span>
<span class="k">except</span> <span class="ne">KeyError</span><span class="p">:</span>
<span class="n">key_prefix</span> <span class="o">=</span> <span class="n">settings</span><span class="o">.</span><span class="n">CACHE_MIDDLEWARE_KEY_PREFIX</span>
<span class="bp">self</span><span class="o">.</span><span class="n">key_prefix</span> <span class="o">=</span> <span class="n">key_prefix</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">cache_alias</span> <span class="o">=</span> <span class="n">kwargs</span><span class="p">[</span><span class="s1">'cache_alias'</span><span class="p">]</span>
<span class="k">if</span> <span class="n">cache_alias</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">cache_alias</span> <span class="o">=</span> <span class="n">DEFAULT_CACHE_ALIAS</span>
<span class="k">except</span> <span class="ne">KeyError</span><span class="p">:</span>
<span class="n">cache_alias</span> <span class="o">=</span> <span class="n">settings</span><span class="o">.</span><span class="n">CACHE_MIDDLEWARE_ALIAS</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cache_alias</span> <span class="o">=</span> <span class="n">cache_alias</span>
<span class="k">if</span> <span class="n">cache_timeout</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">cache_timeout</span> <span class="o">=</span> <span class="n">settings</span><span class="o">.</span><span class="n">CACHE_MIDDLEWARE_SECONDS</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cache_timeout</span> <span class="o">=</span> <span class="n">cache_timeout</span>
<span class="bp">self</span><span class="o">.</span><span class="n">cache</span> <span class="o">=</span> <span class="n">caches</span><span class="p">[</span><span class="bp">self</span><span class="o">.</span><span class="n">cache_alias</span><span class="p">]</span>
</pre></div>
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