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

Here's how to access database by URL using Admin SDK:

let app = admin.app();
let ref = app.database('https://secondary_db_url.firebaseio.com').ref();

Here's an example from Admin SDK integration tests: https://github.com/firebase/firebase-admin-node/blob/master/test/integration/database.js#L52

Answer 2

With cloud functions > 1.1 now, here is the documentation link that saved my life on this issue.

https://firebase.google.com/docs/database/usage/sharding#connect_your_app_to_multiple_database_instances

So, it looks like this at the top of my my cloud function index.js :

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

const dev = admin.initializeApp({
  databaseURL: "https://appdev.firebaseio.com"
}, 'dev');

const v2 = admin.initializeApp({
  databaseURL: "https://appv2.firebaseio.com"
}, 'v2');

and then, in my clond functions functions code I can do :

//will change stuff on default database
admin.database().ref().child(`stuff/${stuffId}`).set(myStuff)

//will change stuff on my dev database
admin.database(dev).ref().child(`stuff/${stuffId}`).set(myStuff)

//will change stuff on my v2 database
admin.database(v2).ref().child(`stuff/${stuffId}`).set(myStuff)

Answer 3

So it looks like you are trying to access multiple databases using the javascript web client API. Passing the URL of the database to the API like this doesn't work with the Admin SDK:

admin.database('https://secondary_db_url.firebaseio.com').ref(`/testNode`)

Instead, you have to initialize a second app, give it a name, and pass that app around to the Admin SDK APIs. Here's a complete sample that writes the same data to two different database instances in the same project:

const functions = require('firebase-functions')
const admin = require('firebase-admin')
admin.initializeApp(functions.config().firebase)

const otherConfig = Object.assign({}, functions.config().firebase)
otherConfig.databaseURL = 'https://your-other-db.firebaseio.com/'
const otherApp = admin.initializeApp(otherConfig, 'otherAppName')

exports.foo = functions.https.onRequest((req, res) => {
    const data = { foo: 'bar' }
    const p1 = admin.database().ref('data').set(data)
    const p2 = admin.database(otherApp).ref('data').set(data)
    Promise.all([p1, p2]).then(() => {
        res.send("OK")
    })
    .catch(error => {
        res.status(500).send(error)
    })
})

Answer 4

Updating this while on Firebase Functions v3.14.0. None of this answers worked for me so I implemented this solution

instance Registers a function that triggers on events from a specific Firebase Realtime Database instance

functions.database.instance('my-app-db-2').ref('/foo/bar')

Use the name of the database instance and it works, no need for the url. functions.database.ref used without instance watches the default instance for events.