502 Bad Gateway with nginx | Google App Engine | Node JS

Question

I am hosting the web app on Google Cloud Platform with App Engine and I am using ExpressJS and MongoDB, which is hosted on mLab.

Everything worked well until 1/1/201

Answer 1

A 502 is not necessarily an error with nginx itself, it can most often happen when the nginx proxy cannot talk to your app container (usually because your app failed to start). If you get a 502 after migrating to 'env: flex' this is most likely due to some code changes needed in your app as mentioned in Upgrading to the Latest App Engine Flexible Environment Release.

Checking your application logs for errors from NPM will also help to diagnose the exact reason for the failed startup.