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   <h1>Source code for apache_beam.utils.thread_pool_executor</h1><div class="highlight"><pre>
 <span></span><span class="c1">#</span>
 <span class="c1"># Licensed to the Apache Software Foundation (ASF) under one or more</span>
 <span class="c1"># contributor license agreements.  See the NOTICE file distributed with</span>
 <span class="c1"># this work for additional information regarding copyright ownership.</span>
 <span class="c1"># The ASF licenses this file to You under the Apache License, Version 2.0</span>
 <span class="c1"># (the &quot;License&quot;); you may not use this file except in compliance with</span>
 <span class="c1"># the License.  You may obtain a copy of the License at</span>
 <span class="c1">#</span>
 <span class="c1">#    http://www.apache.org/licenses/LICENSE-2.0</span>
 <span class="c1">#</span>
 <span class="c1"># Unless required by applicable law or agreed to in writing, software</span>
 <span class="c1"># distributed under the License is distributed on an &quot;AS IS&quot; BASIS,</span>
 <span class="c1"># WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.</span>
 <span class="c1"># See the License for the specific language governing permissions and</span>
 <span class="c1"># limitations under the License.</span>
 <span class="c1">#</span>

 <span class="c1"># pytype: skip-file</span>

 <span class="kn">import</span> <span class="nn">queue</span>
 <span class="kn">import</span> <span class="nn">threading</span>
 <span class="kn">import</span> <span class="nn">weakref</span>
 <span class="kn">from</span> <span class="nn">concurrent.futures</span> <span class="kn">import</span> <span class="n">_base</span>


 <span class="k">class</span> <span class="nc">_WorkItem</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
   <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">future</span><span class="p">,</span> <span class="n">fn</span><span class="p">,</span> <span class="n">args</span><span class="p">,</span> <span class="n">kwargs</span><span class="p">):</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_future</span> <span class="o">=</span> <span class="n">future</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_fn</span> <span class="o">=</span> <span class="n">fn</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_fn_args</span> <span class="o">=</span> <span class="n">args</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_fn_kwargs</span> <span class="o">=</span> <span class="n">kwargs</span>

   <span class="k">def</span> <span class="nf">run</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
     <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_future</span><span class="o">.</span><span class="n">set_running_or_notify_cancel</span><span class="p">():</span>
       <span class="c1"># If the future wasn&#39;t cancelled, then attempt to execute it.</span>
       <span class="k">try</span><span class="p">:</span>
         <span class="bp">self</span><span class="o">.</span><span class="n">_future</span><span class="o">.</span><span class="n">set_result</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_fn</span><span class="p">(</span><span class="o">*</span><span class="bp">self</span><span class="o">.</span><span class="n">_fn_args</span><span class="p">,</span> <span class="o">**</span><span class="bp">self</span><span class="o">.</span><span class="n">_fn_kwargs</span><span class="p">))</span>
       <span class="k">except</span> <span class="ne">BaseException</span> <span class="k">as</span> <span class="n">exc</span><span class="p">:</span>
         <span class="bp">self</span><span class="o">.</span><span class="n">_future</span><span class="o">.</span><span class="n">set_exception</span><span class="p">(</span><span class="n">exc</span><span class="p">)</span>


 <span class="k">class</span> <span class="nc">_Worker</span><span class="p">(</span><span class="n">threading</span><span class="o">.</span><span class="n">Thread</span><span class="p">):</span>
   <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">idle_worker_queue</span><span class="p">,</span> <span class="n">work_item</span><span class="p">):</span>
     <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_idle_worker_queue</span> <span class="o">=</span> <span class="n">idle_worker_queue</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_work_item</span> <span class="o">=</span> <span class="n">work_item</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_wake_semaphore</span> <span class="o">=</span> <span class="n">threading</span><span class="o">.</span><span class="n">Semaphore</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_lock</span> <span class="o">=</span> <span class="n">threading</span><span class="o">.</span><span class="n">Lock</span><span class="p">()</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_shutdown</span> <span class="o">=</span> <span class="kc">False</span>

   <span class="k">def</span> <span class="nf">run</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
     <span class="k">while</span> <span class="kc">True</span><span class="p">:</span>
       <span class="bp">self</span><span class="o">.</span><span class="n">_work_item</span><span class="o">.</span><span class="n">run</span><span class="p">()</span>
       <span class="bp">self</span><span class="o">.</span><span class="n">_work_item</span> <span class="o">=</span> <span class="kc">None</span>

       <span class="bp">self</span><span class="o">.</span><span class="n">_idle_worker_queue</span><span class="o">.</span><span class="n">put</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span>
       <span class="bp">self</span><span class="o">.</span><span class="n">_wake_semaphore</span><span class="o">.</span><span class="n">acquire</span><span class="p">()</span>
       <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_work_item</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
         <span class="k">return</span>

   <span class="k">def</span> <span class="nf">assign_work</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">work_item</span><span class="p">):</span>
 <span class="w">    </span><span class="sd">&quot;&quot;&quot;Assigns the work item and wakes up the thread.</span>

 <span class="sd">    This method must only be called while the worker is idle.</span>
 <span class="sd">    &quot;&quot;&quot;</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_work_item</span> <span class="o">=</span> <span class="n">work_item</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_wake_semaphore</span><span class="o">.</span><span class="n">release</span><span class="p">()</span>

   <span class="k">def</span> <span class="nf">shutdown</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
 <span class="w">    </span><span class="sd">&quot;&quot;&quot;Wakes up this thread with a &#39;None&#39; work item signalling to shutdown.&quot;&quot;&quot;</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_wake_semaphore</span><span class="o">.</span><span class="n">release</span><span class="p">()</span>


 <div class="viewcode-block" id="UnboundedThreadPoolExecutor"><a class="viewcode-back" href="../../../apache_beam.utils.thread_pool_executor.html#apache_beam.utils.thread_pool_executor.UnboundedThreadPoolExecutor">[docs]</a><span class="k">class</span> <span class="nc">UnboundedThreadPoolExecutor</span><span class="p">(</span><span class="n">_base</span><span class="o">.</span><span class="n">Executor</span><span class="p">):</span>
   <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_idle_worker_queue</span> <span class="o">=</span> <span class="n">queue</span><span class="o">.</span><span class="n">Queue</span><span class="p">()</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_max_idle_threads</span> <span class="o">=</span> <span class="mi">16</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_workers</span> <span class="o">=</span> <span class="n">weakref</span><span class="o">.</span><span class="n">WeakSet</span><span class="p">()</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_shutdown</span> <span class="o">=</span> <span class="kc">False</span>
     <span class="bp">self</span><span class="o">.</span><span class="n">_lock</span> <span class="o">=</span> <span class="n">threading</span><span class="o">.</span><span class="n">Lock</span><span class="p">()</span>  <span class="c1"># Guards access to _workers and _shutdown</span>

 <div class="viewcode-block" id="UnboundedThreadPoolExecutor.submit"><a class="viewcode-back" href="../../../apache_beam.utils.thread_pool_executor.html#apache_beam.utils.thread_pool_executor.UnboundedThreadPoolExecutor.submit">[docs]</a>  <span class="k">def</span> <span class="nf">submit</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">fn</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
 <span class="w">    </span><span class="sd">&quot;&quot;&quot;Attempts to submit the work item.</span>

 <span class="sd">    A runtime error is raised if the pool has been shutdown.</span>
 <span class="sd">    &quot;&quot;&quot;</span>
     <span class="n">future</span> <span class="o">=</span> <span class="n">_base</span><span class="o">.</span><span class="n">Future</span><span class="p">()</span>
     <span class="n">work_item</span> <span class="o">=</span> <span class="n">_WorkItem</span><span class="p">(</span><span class="n">future</span><span class="p">,</span> <span class="n">fn</span><span class="p">,</span> <span class="n">args</span><span class="p">,</span> <span class="n">kwargs</span><span class="p">)</span>
     <span class="k">with</span> <span class="bp">self</span><span class="o">.</span><span class="n">_lock</span><span class="p">:</span>
       <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_shutdown</span><span class="p">:</span>
         <span class="k">raise</span> <span class="ne">RuntimeError</span><span class="p">(</span>
             <span class="s1">&#39;Cannot schedule new tasks after thread pool has been shutdown.&#39;</span><span class="p">)</span>
       <span class="k">try</span><span class="p">:</span>
         <span class="bp">self</span><span class="o">.</span><span class="n">_idle_worker_queue</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">block</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span><span class="o">.</span><span class="n">assign_work</span><span class="p">(</span><span class="n">work_item</span><span class="p">)</span>

         <span class="c1"># If we have more idle threads then the max allowed, shutdown a thread.</span>
         <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_idle_worker_queue</span><span class="o">.</span><span class="n">qsize</span><span class="p">()</span> <span class="o">&gt;</span> <span class="bp">self</span><span class="o">.</span><span class="n">_max_idle_threads</span><span class="p">:</span>
           <span class="k">try</span><span class="p">:</span>
             <span class="bp">self</span><span class="o">.</span><span class="n">_idle_worker_queue</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">block</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span><span class="o">.</span><span class="n">shutdown</span><span class="p">()</span>
           <span class="k">except</span> <span class="n">queue</span><span class="o">.</span><span class="n">Empty</span><span class="p">:</span>
             <span class="k">pass</span>
       <span class="k">except</span> <span class="n">queue</span><span class="o">.</span><span class="n">Empty</span><span class="p">:</span>
         <span class="n">worker</span> <span class="o">=</span> <span class="n">_Worker</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_idle_worker_queue</span><span class="p">,</span> <span class="n">work_item</span><span class="p">)</span>
         <span class="n">worker</span><span class="o">.</span><span class="n">daemon</span> <span class="o">=</span> <span class="kc">True</span>
         <span class="n">worker</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
         <span class="bp">self</span><span class="o">.</span><span class="n">_workers</span><span class="o">.</span><span class="n">add</span><span class="p">(</span><span class="n">worker</span><span class="p">)</span>
     <span class="k">return</span> <span class="n">future</span></div>

 <div class="viewcode-block" id="UnboundedThreadPoolExecutor.shutdown"><a class="viewcode-back" href="../../../apache_beam.utils.thread_pool_executor.html#apache_beam.utils.thread_pool_executor.UnboundedThreadPoolExecutor.shutdown">[docs]</a>  <span class="k">def</span> <span class="nf">shutdown</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">wait</span><span class="o">=</span><span class="kc">True</span><span class="p">):</span>
     <span class="k">with</span> <span class="bp">self</span><span class="o">.</span><span class="n">_lock</span><span class="p">:</span>
       <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_shutdown</span><span class="p">:</span>
         <span class="k">return</span>

       <span class="bp">self</span><span class="o">.</span><span class="n">_shutdown</span> <span class="o">=</span> <span class="kc">True</span>

       <span class="k">for</span> <span class="n">worker</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">_workers</span><span class="p">:</span>
         <span class="n">worker</span><span class="o">.</span><span class="n">shutdown</span><span class="p">()</span>

       <span class="k">if</span> <span class="n">wait</span><span class="p">:</span>
         <span class="k">for</span> <span class="n">worker</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">_workers</span><span class="p">:</span>
           <span class="n">worker</span><span class="o">.</span><span class="n">join</span><span class="p">()</span></div></div>


 <span class="k">class</span> <span class="nc">_SharedUnboundedThreadPoolExecutor</span><span class="p">(</span><span class="n">UnboundedThreadPoolExecutor</span><span class="p">):</span>
   <span class="k">def</span> <span class="nf">shutdown</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">wait</span><span class="o">=</span><span class="kc">True</span><span class="p">):</span>
     <span class="c1"># Prevent shutting down the shared thread pool</span>
     <span class="k">pass</span>


 <span class="n">_SHARED_UNBOUNDED_THREAD_POOL_EXECUTOR</span> <span class="o">=</span> <span class="n">_SharedUnboundedThreadPoolExecutor</span><span class="p">()</span>


 <div class="viewcode-block" id="shared_unbounded_instance"><a class="viewcode-back" href="../../../apache_beam.utils.thread_pool_executor.html#apache_beam.utils.thread_pool_executor.shared_unbounded_instance">[docs]</a><span class="k">def</span> <span class="nf">shared_unbounded_instance</span><span class="p">():</span>
   <span class="k">return</span> <span class="n">_SHARED_UNBOUNDED_THREAD_POOL_EXECUTOR</span></div>
 </pre></div>

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