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<div class="section" id="module-eventlet.greenpool">
<span id="greenpool-green-thread-pools"></span><h1><code class="xref py py-mod docutils literal"><span class="pre">greenpool</span></code> &#8211; Green Thread Pools<a class="headerlink" href="#module-eventlet.greenpool" title="Permalink to this headline"></a></h1>
<dl class="class">
<dt id="eventlet.greenpool.GreenPool">
<em class="property">class </em><code class="descclassname">eventlet.greenpool.</code><code class="descname">GreenPool</code><span class="sig-paren">(</span><em>size=1000</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPool" title="Permalink to this definition"></a></dt>
<dd><p>The GreenPool class is a pool of green threads.</p>
<dl class="method">
<dt id="eventlet.greenpool.GreenPool.free">
<code class="descname">free</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPool.free" title="Permalink to this definition"></a></dt>
<dd><p>Returns the number of greenthreads available for use.</p>
<p>If zero or less, the next call to <a class="reference internal" href="#eventlet.greenpool.GreenPool.spawn" title="eventlet.greenpool.GreenPool.spawn"><code class="xref py py-meth docutils literal"><span class="pre">spawn()</span></code></a> or <a class="reference internal" href="#eventlet.greenpool.GreenPool.spawn_n" title="eventlet.greenpool.GreenPool.spawn_n"><code class="xref py py-meth docutils literal"><span class="pre">spawn_n()</span></code></a> will
block the calling greenthread until a slot becomes available.</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenpool.GreenPool.imap">
<code class="descname">imap</code><span class="sig-paren">(</span><em>function</em>, <em>*iterables</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPool.imap" title="Permalink to this definition"></a></dt>
<dd><p>This is the same as <a class="reference external" href="https://docs.python.org/2/library/itertools.html#itertools.imap" title="(in Python v2.7)"><code class="xref py py-func docutils literal"><span class="pre">itertools.imap()</span></code></a>, and has the same
concurrency and memory behavior as <a class="reference internal" href="#eventlet.greenpool.GreenPool.starmap" title="eventlet.greenpool.GreenPool.starmap"><code class="xref py py-meth docutils literal"><span class="pre">starmap()</span></code></a>.</p>
<p>It&#8217;s quite convenient for, e.g., farming out jobs from a file:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">worker</span><span class="p">(</span><span class="n">line</span><span class="p">):</span>
<span class="k">return</span> <span class="n">do_something</span><span class="p">(</span><span class="n">line</span><span class="p">)</span>
<span class="n">pool</span> <span class="o">=</span> <span class="n">GreenPool</span><span class="p">()</span>
<span class="k">for</span> <span class="n">result</span> <span class="ow">in</span> <span class="n">pool</span><span class="o">.</span><span class="n">imap</span><span class="p">(</span><span class="n">worker</span><span class="p">,</span> <span class="nb">open</span><span class="p">(</span><span class="s2">&quot;filename&quot;</span><span class="p">,</span> <span class="s1">&#39;r&#39;</span><span class="p">)):</span>
<span class="nb">print</span><span class="p">(</span><span class="n">result</span><span class="p">)</span>
</pre></div>
</div>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenpool.GreenPool.resize">
<code class="descname">resize</code><span class="sig-paren">(</span><em>new_size</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPool.resize" title="Permalink to this definition"></a></dt>
<dd><p>Change the max number of greenthreads doing work at any given time.</p>
<p>If resize is called when there are more than <em>new_size</em> greenthreads
already working on tasks, they will be allowed to complete but no new
tasks will be allowed to get launched until enough greenthreads finish
their tasks to drop the overall quantity below <em>new_size</em>. Until
then, the return value of free() will be negative.</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenpool.GreenPool.running">
<code class="descname">running</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPool.running" title="Permalink to this definition"></a></dt>
<dd><p>Returns the number of greenthreads that are currently executing
functions in the GreenPool.</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenpool.GreenPool.spawn">
<code class="descname">spawn</code><span class="sig-paren">(</span><em>function</em>, <em>*args</em>, <em>**kwargs</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPool.spawn" title="Permalink to this definition"></a></dt>
<dd><p>Run the <em>function</em> with its arguments in its own green thread.
Returns the <a class="reference internal" href="greenthread.html#eventlet.greenthread.GreenThread" title="eventlet.greenthread.GreenThread"><code class="xref py py-class docutils literal"><span class="pre">GreenThread</span></code></a>
object that is running the function, which can be used to retrieve the
results.</p>
<p>If the pool is currently at capacity, <code class="docutils literal"><span class="pre">spawn</span></code> will block until one of
the running greenthreads completes its task and frees up a slot.</p>
<p>This function is reentrant; <em>function</em> can call <code class="docutils literal"><span class="pre">spawn</span></code> on the same
pool without risk of deadlocking the whole thing.</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenpool.GreenPool.spawn_n">
<code class="descname">spawn_n</code><span class="sig-paren">(</span><em>function</em>, <em>*args</em>, <em>**kwargs</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPool.spawn_n" title="Permalink to this definition"></a></dt>
<dd><p>Create a greenthread to run the <em>function</em>, the same as
<a class="reference internal" href="#eventlet.greenpool.GreenPool.spawn" title="eventlet.greenpool.GreenPool.spawn"><code class="xref py py-meth docutils literal"><span class="pre">spawn()</span></code></a>. The difference is that <a class="reference internal" href="#eventlet.greenpool.GreenPool.spawn_n" title="eventlet.greenpool.GreenPool.spawn_n"><code class="xref py py-meth docutils literal"><span class="pre">spawn_n()</span></code></a> returns
None; the results of <em>function</em> are not retrievable.</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenpool.GreenPool.starmap">
<code class="descname">starmap</code><span class="sig-paren">(</span><em>function</em>, <em>iterable</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPool.starmap" title="Permalink to this definition"></a></dt>
<dd><p>This is the same as <a class="reference external" href="https://docs.python.org/2/library/itertools.html#itertools.starmap" title="(in Python v2.7)"><code class="xref py py-func docutils literal"><span class="pre">itertools.starmap()</span></code></a>, except that <em>func</em> is
executed in a separate green thread for each item, with the concurrency
limited by the pool&#8217;s size. In operation, starmap consumes a constant
amount of memory, proportional to the size of the pool, and is thus
suited for iterating over extremely long input lists.</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenpool.GreenPool.waitall">
<code class="descname">waitall</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPool.waitall" title="Permalink to this definition"></a></dt>
<dd><p>Waits until all greenthreads in the pool are finished working.</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenpool.GreenPool.waiting">
<code class="descname">waiting</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPool.waiting" title="Permalink to this definition"></a></dt>
<dd><p>Return the number of greenthreads waiting to spawn.</p>
</dd></dl>
</dd></dl>
<dl class="class">
<dt id="eventlet.greenpool.GreenPile">
<em class="property">class </em><code class="descclassname">eventlet.greenpool.</code><code class="descname">GreenPile</code><span class="sig-paren">(</span><em>size_or_pool=1000</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPile" title="Permalink to this definition"></a></dt>
<dd><p>GreenPile is an abstraction representing a bunch of I/O-related tasks.</p>
<p>Construct a GreenPile with an existing GreenPool object. The GreenPile will
then use that pool&#8217;s concurrency as it processes its jobs. There can be
many GreenPiles associated with a single GreenPool.</p>
<p>A GreenPile can also be constructed standalone, not associated with any
GreenPool. To do this, construct it with an integer size parameter instead
of a GreenPool.</p>
<p>It is not advisable to iterate over a GreenPile in a different greenthread
than the one which is calling spawn. The iterator will exit early in that
situation.</p>
<dl class="method">
<dt id="eventlet.greenpool.GreenPile.next">
<code class="descname">next</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPile.next" title="Permalink to this definition"></a></dt>
<dd><p>Wait for the next result, suspending the current greenthread until it
is available. Raises StopIteration when there are no more results.</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenpool.GreenPile.spawn">
<code class="descname">spawn</code><span class="sig-paren">(</span><em>func</em>, <em>*args</em>, <em>**kw</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenpool.GreenPile.spawn" title="Permalink to this definition"></a></dt>
<dd><p>Runs <em>func</em> in its own green thread, with the result available by
iterating over the GreenPile object.</p>
</dd></dl>
</dd></dl>
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