javascript - How to access multiple Realtime Database instances in Cloud Functions for Firebase

Question

I'm using multiple databases in a Firebase project. Cloud functions for the main (default) database work great, however, I cannot make them work for a secondary database. For example I want to make a read request on a node with admin privileges:

//this works
admin.database().ref(nodePath).once('value')...

This works in the main database, however, if I want to execute the command on another database, it doesn't work:

//this doesn't work
admin.database(secondaryDatabaseUrl).ref(nodePath).once('value')...

Although the functions are deployed, I get an error on the console when trying to execute the cloud function.

Here's the code for the cloud function with an https trigger:

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
const secureCompare = require('secure-compare');

exports.testFunction= functions.https.onRequest((req, res) => {
  const key = req.query.key;
  // Exit if the keys don't match
  if (!secureCompare(key, functions.config().cron.key)) {
    console.error('keys do not match');
    res.status(403).send('error1');
    return;
  }
  //test read request
  //the line below crashes the function
  return admin.database('https://secondary_db_url.firebaseio.com').ref(`/testNode`).once('value').then(dataSnapshot=> {
    console.log('value', dataSnapshot.val());
    return;
  }).catch(er => {
    console.error('error', er);
    res.status(403).send('error2');
  });
});

Below is the error log in the Firebase console:

TypeError: ns.ensureApp(...).database is not a function
    at FirebaseNamespace.fn (/user_code/node_modules/firebase-admin/lib/firebase-namespace.js:251:42)
    at exports.testFunction.functions.https.onRequest (/user_code/index.js:16:16)
    at cloudFunction (/user_code/node_modules/firebase-functions/lib/providers/https.js:26:41)
    at /var/tmp/worker/worker.js:671:7
    at /var/tmp/worker/worker.js:655:9
    at _combinedTickCallback (internal/process/next_tick.js:73:7)
    at process._tickDomainCallback (internal/process/next_tick.js:128:9)

If I don't specify the secondary database URL, the function will make the read request on my main database which works great:

//this works
return admin.database().ref(`/testNode`).once('value').then(dataSnapshot=> {
...

I'm using the latest SDK versions: "firebase-admin": "^5.5.1" and "firebase-functions": "^0.7.3"

So, how do I get an instance of a secondary database in cloud functions using admin privileges?

Answer 1

Waitting for answers