External HTTP REST service

I’am trying to add an exernal REST service for testing purpose.

So first question : Is it possible to do that (calling an external rest service through this “external service” functionality instead of a direct call ?).

If yes, I’d like to add openweathermap.org free weather API.
So I created a new stack, create the external service pointing to openweathermap.org (“hostname” mode)

Then I deployed a dummy service (in nodeJS) linked to openweathermap (with openweathermap alias).

So in my node code I try to call this external service like this :

var options = {
	method: 'GET',
	uri: 'http://openweathermap/data/2.5/weather?q=London&APPID={APIKEY}',
	headers: {
	json: true

but I have the following error :

name: "RequestError",
message: "Error: getaddrinfo EIO",
    cause: {
    code: "EIO",
    errno: "EIO",
    syscall: "getaddrinfo"

I though I could use http://[alias_name_of_external_service]/xxx to call my external service from another container in stack.

Did I missed something?

Thank you for your help.