I am trying to access a Firebase database from inside of a Kubernetes cluster, the only I think of is using a k8s service of type externalName. So I tried with below configuration.

Kuberentes Service:

kind : Service
apiVersion: v1
metadata :
  name : firebase-database-service
  labels :
    app : firebase-database-service
  spec:
    type : ExternalName
    externalName : myapp.firebaseio.com
    ports:
      - port : 443
        targetPort: 443

And below is my simple node app for demonstration.

var firebase        = require('firebase');
var os              = require("os");
var co              = require('co');
var hostName        = os.hostname();

var config = {
    apiKey: "API_KEY",
    databaseURL: "https://firebase-database-service",
};

var dashboard   = firebase.initializeApp(config, 'Dashboard');
dashboard.auth().signInWithEmailAndPassword("username", "password");
let uid = hostName.split('.').join('_') + "_" + process.pid;
let ref = "/data/"+ uid;

setInterval(co.wrap(function* (){
    try {
        dashboard.database().ref(ref + '/loadavg').set(os.loadavg());
    } catch (e) {
        console.error(e);
    }
}), 3000);

and I ended up with the below error.

FIREBASE FATAL ERROR: Cannot parse Firebase url. Please use https://<YOUR FIREBASE>.firebaseio.com 
at Error (native)
at xc (/Users/AAravindan/dev/realtime-screener/projects/test-kube-firebase/node_modules/firebase/database-node.js:55:277)
at yc (/Users/AAravindan/dev/realtime-screener/projects/test-kube-firebase/node_modules/firebase/database-node.js:57:20)
at Object.firebase.INTERNAL.registerService.Reference [as database] (/Users/AAravindan/dev/realtime-screener/projects/test-kube-firebase/node_modules/firebase/database-node.js:255:241)
at P.N (/Users/AAravindan/dev/realtime-screener/projects/test-kube-firebase/node_modules/firebase/app-node.js:18:94)
at Timeout.<anonymous> (/Users/AAravindan/dev/realtime-screener/projects/test-kube-firebase/index.js:19:19)
at next (native)
at onFulfilled (/Users/AAravindan/dev/realtime-screener/projects/test-kube-firebase/node_modules/co/index.js:65:19)
at /Users/AAravindan/dev/realtime-screener/projects/test-kube-firebase/node_modules/co/index.js:54:5
at Timeout.co (/Users/AAravindan/dev/realtime-screener/projects/test-kube-firebase/node_modules/co/index.js:50:10)

Is there any way to access firebase from kubernetes cluster.

Here is a sample project if you want to take a look.

Sample Project