title: Nginx PHP-FPM Stops Working, open socket left in connection
body: <p>I have this re-occurring issue with Nginx about once a day, about twice under high traffic loads. The fix is easy, restart the server, but when the error happens, Nginx completely stops working. I have an NGINX PHP-FPM setup.</p>
  <p>It issue starts with:</p>
  <pre><code>020/09/27 09:57:27 [error] 38#38: *430982 upstream timed out (110: Connection timed out) while connecting to upstream, client: x.x.x.x, server: example.com, request: &quot;POST /api/sessions/wri
  </code></pre>
  <p>And then it progress into:</p>
  <pre><code>2020/09/27 10:03:22 [alert] 40#40: *431277 open socket #18 left in connection 51
  2020/09/27 10:03:22 [alert] 38#38: *431298 open socket #34 left in connection 166
  2020/09/27 10:03:22 [alert] 40#40: *431288 open socket #28 left in connection 59
  2020/09/27 10:03:22 [alert] 38#38: *431296 open socket #32 left in connection 169
  2020/09/27 10:03:22 [alert] 38#38: *431257 open socket #36 left in connection 177
  2020/09/27 10:03:22 [alert] 38#38: *431291 open socket #23 left in connection 178
  2020/09/27 10:03:22 [alert] 38#38: *431253 open socket #27 left in connection 188
  2020/09/27 10:03:22 [alert] 38#38: *431300 open socket #31 left in connection 197
  2020/09/27 10:03:22 [alert] 38#38: *431312 open socket #12 left in connection 204
  2020/09/27 10:03:22 [alert] 38#38: *431259 open socket #38 left in connection 206
  2020/09/27 10:03:22 [alert] 37#37: aborting
  2020/09/27 10:03:22 [alert] 38#38: aborting
  2020/09/27 10:03:22 [alert] 40#40: aborting
  2020/09/27 10:03:23 [warn] 21568#21568: 8096 worker_connections exceed open file resource limit: 1024
  2020/09/27 10:08:24 [warn] 21574#21574: *636 upstream server temporarily disabled while connecting to upstream,
  </code></pre>
  <p>Now GET requests still do work. So if I go to the website, it loads. But anything that is POST, PUT or DELETE will fail, so ultimately the users cant do anything but browse.</p>
  <p>Any ideas on why this is happening? And is there a healthcheck that can be used to detect these issues?</p>