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<div class="section" id="generators">
<h1>Generators<a class="headerlink" href="#generators" title="Permalink to this headline">¶</a></h1>
<div class="section" id="problem">
<h2>Problem<a class="headerlink" href="#problem" title="Permalink to this headline">¶</a></h2>
<p>Until 0.5.2 Pyroute2 collected all the responses in a list
and returned them at once. It may be ok as long as there is
not so many objects to return. But let’s say there are some
thousands of routes:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ ip ro | wc -l
315417
</pre></div>
</div>
<p>Now we use a script to retrieve the routes:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">from</span> <span class="nn">pyroute2</span> <span class="k">import</span> <span class="n">config</span>
<span class="kn">from</span> <span class="nn">pyroute2</span> <span class="k">import</span> <span class="n">IPRoute</span>
<span class="n">config</span><span class="o">.</span><span class="n">nlm_generator</span> <span class="o">=</span> <span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">lower</span><span class="p">()</span>
<span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">)</span> <span class="o">></span> <span class="mi">1</span>
<span class="k">else</span> <span class="s1">'false'</span><span class="p">)</span> <span class="o">==</span> <span class="s1">'true'</span>
<span class="k">with</span> <span class="n">IPRoute</span><span class="p">()</span> <span class="k">as</span> <span class="n">ipr</span><span class="p">:</span>
<span class="k">for</span> <span class="n">route</span> <span class="ow">in</span> <span class="n">ipr</span><span class="o">.</span><span class="n">get_routes</span><span class="p">():</span>
<span class="k">pass</span>
</pre></div>
</div>
<p>If the library collects all the routes in a list and returns
the list, it may take a lot of memory:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ /usr/bin/time -v python e.py false
Command being timed: "python e.py false"
User time (seconds): 30.42
System time (seconds): 3.63
Percent of CPU this job got: 99%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:34.09
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 2416472
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 604787
Voluntary context switches: 9
Involuntary context switches: 688
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
</pre></div>
</div>
<p>2416472 kbytes of RSS. Pretty much.</p>
</div>
<div class="section" id="solution">
<h2>Solution<a class="headerlink" href="#solution" title="Permalink to this headline">¶</a></h2>
<p>Now we use generator to iterate the results:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ /usr/bin/time -v python e.py true
Command being timed: "python e.py true"
User time (seconds): 18.48
System time (seconds): 0.99
Percent of CPU this job got: 99%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:19.49
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 45132
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 433589
Voluntary context switches: 9
Involuntary context switches: 244
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
</pre></div>
</div>
<p>45132 kbytes of RSS. That’s the difference. Say we have a bit more
routes:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ ip ro | wc -l
678148
</pre></div>
</div>
<p>Without generators the script will simply run ot of memory. But with
the generators:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ /usr/bin/time -v python e.py true
Command being timed: "python e.py true"
User time (seconds): 39.63
System time (seconds): 2.78
Percent of CPU this job got: 99%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:42.75
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 45324
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 925560
Voluntary context switches: 11
Involuntary context switches: 121182
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
</pre></div>
</div>
<p>Again, 45324 kbytes of RSS.</p>
</div>
<div class="section" id="configuration">
<h2>Configuration<a class="headerlink" href="#configuration" title="Permalink to this headline">¶</a></h2>
<p>To turn the generator option on, one should set <code class="docutils literal notranslate"><span class="pre">pyroute2.config.nlm_generator</span></code>
to <code class="docutils literal notranslate"><span class="pre">True</span></code>. By default is <code class="docutils literal notranslate"><span class="pre">False</span></code> not to break existing projects.:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">pyroute2</span> <span class="k">import</span> <span class="n">config</span>
<span class="kn">from</span> <span class="nn">pyroute2</span> <span class="k">import</span> <span class="n">IPRoute</span>
<span class="n">config</span><span class="o">.</span><span class="n">nlm_generator</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">with</span> <span class="n">IPRoute</span><span class="p">()</span> <span class="k">as</span> <span class="n">ipr</span><span class="p">:</span>
<span class="k">for</span> <span class="n">route</span> <span class="ow">in</span> <span class="n">ipr</span><span class="o">.</span><span class="n">get_routes</span><span class="p">():</span>
<span class="n">handle</span><span class="p">(</span><span class="n">route</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="section" id="iproute-and-generators">
<h2>IPRoute and generators<a class="headerlink" href="#iproute-and-generators" title="Permalink to this headline">¶</a></h2>
<p>IPRoute objects will return generators only for methods that employ <code class="docutils literal notranslate"><span class="pre">GET_...</span></code>
requests like <code class="docutils literal notranslate"><span class="pre">get_routes()</span></code>, <code class="docutils literal notranslate"><span class="pre">get_links()</span></code>, <code class="docutils literal notranslate"><span class="pre">link('dump',</span> <span class="pre">...)</span></code>, <code class="docutils literal notranslate"><span class="pre">addr('dump',</span> <span class="pre">...)</span></code>.
Setters will work as usually to apply changes immediately.</p>
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<h3><a href="index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Generators</a><ul>
<li><a class="reference internal" href="#problem">Problem</a></li>
<li><a class="reference internal" href="#solution">Solution</a></li>
<li><a class="reference internal" href="#configuration">Configuration</a></li>
<li><a class="reference internal" href="#iproute-and-generators">IPRoute and generators</a></li>
</ul>
</li>
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