title: Wordpress Server sending bad request to itself and crashing apache
body: <p>Our Wordpress server has been choking itself. seemingly randomly, for the last 4 or 5 months. After a long process of troubleshooting various things I finally pinpointed it to 4-6 requests that show up in Apache. They're completely empty and they come from our own wordpress server IP. No VHost specified, no request path either. <a href="https://i.stack.imgur.com/VpNzl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VpNzl.png" alt="Apache Status"></a></p>
  
  <p>These requests get stuck in Reading Request, and any subsequent legitimate requests get stuck in Sending Reply until the scoreboard is full. The site effectively goes down until we restart FPM and Apache.</p>
  
  <p>I "fixed" this by banning our server's IP from making requests via htaccess. Our apache now stays up but we get error logs for access denied to 400.shtml (bad request). This works, but of course I really want to figure out what is causing these requests.</p>
  
  <p>I've checked our cron jobs and removed all of the ones from old plugins but the requests still come in anywhere from every hour to every 3 hours. This doesn't match any of the remaining cron frequencies.</p>
  
  <p>Any help is greatly appreciated, I'm at wits end.</p>
  
  <p>Environment details:</p>
  
  <p>Dedicated WHM box, wordpress running on a dedicated IP as a sub account.</p>
  
  <ul>
  <li>Apache 2.4</li>
  <li>PHP 7.2 with Zen OpCache</li>
  <li>nginx reverse proxy (Engintron WHM plugin)</li>
  <li>Cloudflare CDN.</li>
  <li>No other wordpress cache plugins except for cloudflare.</li>
  <li>No load balancers.</li>
  </ul>