title: How to get trace ID from code?
body: <p>I am running a Java application on Google App Engine standard environment.</p>
  
  <p>Looking at the logs (in particular <code>request_log</code>), I can see a couple of interesting IDs such as <code>trace_id</code> and <code>request_id</code> for each request.</p>
  
  <p>Couple of questions:</p>
  
  <ul>
  <li>How are they different? Are they unique?</li>
  <li>How to obtain them in application code (for the current request)? I would like to log them to a different Stackdriver dataset and be able to correlate the data</li>
  </ul>