title: Why does a Flask app create two process?
body: <p>As far as I understood Flask should create a thread and a second thread to run on it, but what I see is there are always two processes, not threads, running. 
  Even for the simplest app.</p>
  
  <pre><code>from flask import Flask
  from flask import render_template, request, flash, session, redirect
  
  app = Flask(__name__)
  
  @app.route('/')
  def hello_world():
      return 'Hello World!'
  
  app.run(host="192.168.21.73", port=5000, debug=True)
  </code></pre>
  
  <p>You can see two process running:</p>
  
  <pre><code>ps -x
  5026 ttyO0    S+     0:01 /usr/bin/python ./test_flask.py
  5031 ttyO0    Sl+    0:45 /usr/bin/python ./test_flask.py
  </code></pre>
  
  <p>What is happening here?</p>