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<h1>SQLAlchemy 0.9 Documentation</h1>
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<h1>Source code for examples.dogpile_caching.environment</h1><div class="highlight"><pre>
<span class="sd">"""environment.py</span>
<span class="sd">Establish data / cache file paths, and configurations,</span>
<span class="sd">bootstrap fixture data if necessary.</span>
<span class="sd">"""</span>
<span class="kn">from</span> <span class="nn">.</span> <span class="kn">import</span> <span class="n">caching_query</span>
<span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="kn">import</span> <span class="n">create_engine</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.orm</span> <span class="kn">import</span> <span class="n">scoped_session</span><span class="p">,</span> <span class="n">sessionmaker</span>
<span class="kn">from</span> <span class="nn">sqlalchemy.ext.declarative</span> <span class="kn">import</span> <span class="n">declarative_base</span>
<span class="kn">from</span> <span class="nn">dogpile.cache.region</span> <span class="kn">import</span> <span class="n">make_region</span>
<span class="kn">import</span> <span class="nn">os</span>
<span class="kn">from</span> <span class="nn">hashlib</span> <span class="kn">import</span> <span class="n">md5</span>
<span class="kn">import</span> <span class="nn">sys</span>
<span class="n">py2k</span> <span class="o">=</span> <span class="n">sys</span><span class="o">.</span><span class="n">version_info</span> <span class="o"><</span> <span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
<span class="k">if</span> <span class="n">py2k</span><span class="p">:</span>
<span class="nb">input</span> <span class="o">=</span> <span class="nb">raw_input</span>
<span class="c"># dogpile cache regions. A home base for cache configurations.</span>
<span class="n">regions</span> <span class="o">=</span> <span class="p">{}</span>
<span class="c"># scoped_session. Apply our custom CachingQuery class to it,</span>
<span class="c"># using a callable that will associate the dictionary</span>
<span class="c"># of regions with the Query.</span>
<span class="n">Session</span> <span class="o">=</span> <span class="n">scoped_session</span><span class="p">(</span>
<span class="n">sessionmaker</span><span class="p">(</span>
<span class="n">query_cls</span><span class="o">=</span><span class="n">caching_query</span><span class="o">.</span><span class="n">query_callable</span><span class="p">(</span><span class="n">regions</span><span class="p">)</span>
<span class="p">)</span>
<span class="p">)</span>
<span class="c"># global declarative base class.</span>
<span class="n">Base</span> <span class="o">=</span> <span class="n">declarative_base</span><span class="p">()</span>
<span class="n">root</span> <span class="o">=</span> <span class="s">"./dogpile_data/"</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">exists</span><span class="p">(</span><span class="n">root</span><span class="p">):</span>
<span class="nb">input</span><span class="p">(</span><span class="s">"Will create datafiles in </span><span class="si">%r</span><span class="s">.</span><span class="se">\n</span><span class="s">"</span>
<span class="s">"To reset the cache + database, delete this directory.</span><span class="se">\n</span><span class="s">"</span>
<span class="s">"Press enter to continue.</span><span class="se">\n</span><span class="s">"</span> <span class="o">%</span> <span class="n">root</span>
<span class="p">)</span>
<span class="n">os</span><span class="o">.</span><span class="n">makedirs</span><span class="p">(</span><span class="n">root</span><span class="p">)</span>
<span class="n">dbfile</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="s">"dogpile_demo.db"</span><span class="p">)</span>
<span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s">'sqlite:///</span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="n">dbfile</span><span class="p">,</span> <span class="n">echo</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">Session</span><span class="o">.</span><span class="n">configure</span><span class="p">(</span><span class="n">bind</span><span class="o">=</span><span class="n">engine</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">md5_key_mangler</span><span class="p">(</span><span class="n">key</span><span class="p">):</span>
<span class="sd">"""Receive cache keys as long concatenated strings;</span>
<span class="sd"> distill them into an md5 hash.</span>
<span class="sd"> """</span>
<span class="k">return</span> <span class="n">md5</span><span class="p">(</span><span class="n">key</span><span class="o">.</span><span class="n">encode</span><span class="p">(</span><span class="s">'ascii'</span><span class="p">))</span><span class="o">.</span><span class="n">hexdigest</span><span class="p">()</span>
<span class="c"># configure the "default" cache region.</span>
<span class="n">regions</span><span class="p">[</span><span class="s">'default'</span><span class="p">]</span> <span class="o">=</span> <span class="n">make_region</span><span class="p">(</span>
<span class="c"># the "dbm" backend needs</span>
<span class="c"># string-encoded keys</span>
<span class="n">key_mangler</span><span class="o">=</span><span class="n">md5_key_mangler</span>
<span class="p">)</span><span class="o">.</span><span class="n">configure</span><span class="p">(</span>
<span class="c"># using type 'file' to illustrate</span>
<span class="c"># serialized persistence. Normally</span>
<span class="c"># memcached or similar is a better choice</span>
<span class="c"># for caching.</span>
<span class="s">'dogpile.cache.dbm'</span><span class="p">,</span>
<span class="n">expiration_time</span><span class="o">=</span><span class="mi">3600</span><span class="p">,</span>
<span class="n">arguments</span><span class="o">=</span><span class="p">{</span>
<span class="s">"filename"</span><span class="p">:</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">root</span><span class="p">,</span> <span class="s">"cache.dbm"</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">)</span>
<span class="c"># optional; call invalidate() on the region</span>
<span class="c"># once created so that all data is fresh when</span>
<span class="c"># the app is restarted. Good for development,</span>
<span class="c"># on a production system needs to be used carefully</span>
<span class="c"># regions['default'].invalidate()</span>
<span class="n">installed</span> <span class="o">=</span> <span class="bp">False</span>
<span class="k">def</span> <span class="nf">bootstrap</span><span class="p">():</span>
<span class="k">global</span> <span class="n">installed</span>
<span class="kn">from</span> <span class="nn">.</span> <span class="kn">import</span> <span class="n">fixture_data</span>
<span class="k">if</span> <span class="ow">not</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">exists</span><span class="p">(</span><span class="n">dbfile</span><span class="p">):</span>
<span class="n">fixture_data</span><span class="o">.</span><span class="n">install</span><span class="p">()</span>
<span class="n">installed</span> <span class="o">=</span> <span class="bp">True</span></pre></div>
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