502 (BAD GATEWAY) is returned by nginx if it fails to contact your service. This usually happens if your app stopped listening, when instance has been shut down or did not start.
Investigation progress depends on information such as: what app engine service is affected by this issue, name of services, what time the errors started appearing. A simple fix, if you have deployed a new version recently, would be rolling it back. Some of the needed information items are of private nature, and should not be posted in a publicly accessible forum. You are therefore encouraged to open an issue, with more relevant information, in the Public Issue Tracker <https://issuetracker.google.com/>, and set communication to "private", prior to posting private or sensitive information. -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to google-appengine+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/google-appengine/3dcb2a35-aa02-4815-adea-f1d49ecbbe9d%40googlegroups.com.
