title: App engine: I'm seeing 500 status and 204 error code
body: <p>I'm seeing a lot of requests with 500 response code. There are only one line on file log:</p>
  
  <blockquote>
    <p>A problem was encountered with the process that handled this request,
    causing it to exit. This is likely to cause a new process to be used
    for the next request to your application. (Error code 204)</p>
  </blockquote>
  
  <p>Also, I can see a weird appengine's auto log line. I'm using Python 2.7 with threading on and 5 idle instances:</p>
  
  <blockquote>
    <p>190.210.97.5 - - [04/Sep/2015:10:00:21 -0700] "POST /api/v1/ecclaro/sondeos/event HTTP/1.1" 500 0 - "Java/1.6.0_24"
    "xxxxxxxxxxx.appspot.com" ms=4301 cpu_ms=0 pending_ms=942
    exit_code=204 instance=00c61b117c96c7c9c0bec141a97c4d4f8ebb5189
    app_engine_release=1.9.26</p>
  </blockquote>
  
  <p>This happens more often when the traffic on my application is increasing. And often happen with some resources. I don't know to do. Because I can't see low level error logs. My assumption is it's a runtime failure of python but I don't know.</p>
  
  <p>Anyone got any ideas?</p>
  
  <p>Regards</p>