502 sever error when running Meteor app on GCE


I have already a Meteor app and Google Cloud Engine (GCE) need to deploy on.

Follow this instruction: Deploy Meteor to Google App Engine 2017

I have successfully deployed my app onto GCE but sometimes, I meet this error:

I try to view error.log from nginx. I saw some error like that:

I don’t have any experience about server and network. Let me know or give me some instruction about that. Thanks