title: 502 Bad Gateway and "Please try again in 30 seconds" messages
body: <p>First of all I know that http 502 on gcloud means any possible error. 
  Also, <strong>in logs there are no errors</strong> only standard spring boot info and debug messages.</p>
  
  <p>The project I have troubles is a swagger generated spring boot java project (more than 160 java files).</p>
  
  <p>Locally on intellij works well and fast.</p>
  
  <p>After executing <em>mvn clean spring-boot:run</em> on gclod shell the project starts and I see the default generated page on the browser.</p>
  
  <p>After executing <code>mvn  appengine:deploy</code> on gclod shell I always see this message on the browser:
  <em>Error: Server Error The server encountered a temporary error and could not complete your request. Please try again in 30 seconds</em>
  or This error: <em>502 Bad Gateway nginx</em>. Always.</p>
  
  <p>This are the last messages from gcloud console (after mvn  appengine:deploy):</p>
  
  <pre><code>..done.
  [INFO] GCLOUD: Setting traffic split for service [default]...
  [INFO] GCLOUD: ...................................done.
  [INFO] GCLOUD: Deployed service [default] to [https://polishapi-psd2.appspot.com]
  [INFO] GCLOUD:
  [INFO] GCLOUD: You can stream logs from the command line by running:
  [INFO] GCLOUD:   $ gcloud app logs tail -s default
  [INFO] GCLOUD:
  [INFO] GCLOUD: To view your application in the web browser run:
  [INFO] GCLOUD:   $ gcloud app browse
  [INFO] ------------------------------------------------------------------------
  [INFO] BUILD SUCCESS
  [INFO] ------------------------------------------------------------------------
  [INFO] Total time:  16:07 min
  [INFO] Finished at: 2019-12-18T14:11:30+01:00
  [INFO] ------------------------------------------------------------------------
  C:\workspace\PolishAPI-psd2&gt;gcloud app logs tail
  </code></pre>
  
  <p><strong>In logs there are no errors</strong>.
  A basic, super simple, spring boot "hello world" project works but not that swagger generated big one.</p>
  
  <p>How to deal with this problem?
  Thank you.</p>