How to get an error message from an App Engine server?

Question

I am running a simple Node Express server with this endpoint

app.get('/', (req, res) => {
  res.send("Success!");
});

When I ran this server locally or through App Engine and contact the endpoint, I receive the expected response "Success!".

To make sure I can receive an error message, I changed the endpoint to

app.get('/', (req, res) => {
  throw new Error("A useful error message")
});

When I run this server locally and contact the endpoint, I receive the message Error: A useful error message as expected. But when I run the server with App Engine and contact the endpoint, I receive the message Internal Server Error. Is there a way to have app engine return the specific error message I threw from the server?

Answer 1

You can check the error message on Stackdriver Logging:

   Error: A useful error message at app.get (/srv/app.js:32:9) at Layer.handle [as handle_request] (/srv/node_modules/express/lib/router/layer.js:95:5) at next (/srv/node_modules/express/lib/router/route.js:137:13) at Route.dispatch (/srv/node_modules/express/lib/router/route.js:112:3) at Layer.handle [as handle_request] (/srv/node_modules/express/lib/router/layer.js:95:5) at /srv/node_modules/express/lib/router/index.js:281:22 at Function.process_params (/srv/node_modules/express/lib/router/index.js:335:12) at next (/srv/node_modules/express/lib/router/index.js:275:10) at expressInit (/srv/node_modules/express/lib/middleware/init.js:40:5) at Layer.handle [as handle_request] (/srv/node_modules/express/lib/router/layer.js:95:5)

Or you can run :

     gcloud app logs read --limit 5

     Error: A useful error message      at app.get (/srv/app.js:32:9)      at Layer.handle [as handle_request] (/srv/node_modules/express/lib/router/layer.js:95:5)      at next (/srv/node_modules/express/lib/router/route.js:137:13)      at Route.dispatch (/srv/node_modules/express/lib/router/route.js:112:3)      at Layer.handle [as handle_request] (/srv/node_modules/express/lib/router/layer.js:95:5)      at /srv/node_modules/express/lib/router/index.js:281:22      at Function.process_params (/srv/node_modules/express/lib/router/index.js:335:12)      at next (/srv/node_modules/express/lib/router/index.js:275:10)      at expressInit (/srv/node_modules/express/lib/middleware/init.js:40:5)      at Layer.handle [as handle_request] (/srv/node_modules/express/lib/router/layer.js:95:5)