title: Worker always offline in Celery flower
body: <p>I have <code>Celery</code> and <a href="https://github.com/mher/flower#celery-flower" rel="noreferrer">Flower</a> running on my server and the tasks run just fine and are correctly registered and updated for me to monitor within the Flower UI, however, the worker status is allways <code>Offline</code> no matter if I restart the workers or Flower itself, and my log file (as given by the <code>--log_file_prefix</code> option) is empty, so no errors, nothing.</p>
  
  <p>The only thing I can see is that the chrome dev tools show a Websocket Handshake error as shown below:
  <img src="https://i.stack.imgur.com/hoVB1.png" alt="flower error in chrome dev tools">
  and a message <code>CAUTION: Provitional headers are shown.</code>
  <img src="https://i.stack.imgur.com/sAbkk.png" alt="enter image description here"></p>
  
  <p>I read that I need to make my server to respond with the <code>Upgrade: websocket</code> and <code>Connection: upgrade</code> headers for the Websocket handshake to be successful. I'm using apache, then I tried so by specifying the following in <code>/etc/apache2/sites-enabled/mysite.conf</code>:</p>
  
  <pre><code>Header set Upgrade "websocket"
  Header set Connection "upgrade"
  </code></pre>
  
  <p>but it didn't work.</p>
  
  <p>Does anyone have a clue on this error? Let me know if you need any more info.</p>
  
  <p>Thanks!!</p>