title: Apache reverse proxy "Failed to load resource" 502 Proxy Error
body: <h2>Background</h2>
  
  <p>As the path of least resistance on getting my Web app (served by AllegroServe) to deal with a potential partner's Shibboleth SOS setup I decided to try running Apache in front of AllegroServe, since the partner and Shibboleth support Apache.</p>
  
  <p>Anyway, I took a dead simple approach and just dropped this in httpd.conf after turning on all the recommended modules for reverse proxy:</p>
  
  <pre><code>ProxyPass / http://localhost:8000 retry=1 acquire=3000 timeout=3000 Keepalive=On
  ProxyPassReverse / http://localhost:8000
  </code></pre>
  
  <p>All the options on ProxyPass were added based on something I googled up, but timeout seems not to be the problem because this error comes back in a few milliseconds: "failed to load resource: the server responded with a status of 502 (Proxy Error)" on this bit of HTML in (the only thing that does load) the index.html:</p>
  
  <pre><code>&lt;script type="text/javascript" src="script/soa.js"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>I also tried just loading an image and get the same error, and I put the image in the same directory as index.html in case it was a directory access issue.</p>
  
  <p>I note, FWIW, that the request for soa.js or the image does not make it to AllegroServe (or at least it does not log anything).</p>
  
  <p>btw, AllegroServe is running on port 8000 and I can access localhost:8000 without a problem. And to repeat myself, hitting localhost:8080 works as far as loading the index.html.</p>
  
  <p>I have checked permissions on the directories in question but suspect that is not the issue since it is getting to the index.html (and, again, the follow-up request for the JS (or png file) do not seem even to be reaching AllegroServe.</p>