Firebase function not executed - database

Question

import * as functions from 'firebase-functions';
console.log('I am a log entry0!');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
console.log('I am a log entry1!');
export const onMessageCreate = functions.database
.ref('/users/{userId}/totalScore')
.onUpdate((change) => {
console.log('I am a log entry2!');
//var a = admin.firestore().collection('/users');
})
I have deployed the function and I can see it in the console. But the function is not executed when totalScore is updated in the database....

Answer 1

Your database is Firestore but you use a Cloud Function that is triggered by an update in the Realtime Database. These are two different Firebase services and you need to change your code accordingly.
The following code will work:
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();
exports.onMessageCreate = functions.firestore
.document('users/{userId}')
.onUpdate((change, context) => {
// Get an object representing the document
const newValue = change.after.data();
// ...or the previous value before this update
const previousValue = change.before.data();
if (newValue.totalScore !== previousValue.totalScore) {
console.log('NEW TOTAL SCORE');
}
return null;
//I guess you are going to do more than just logging to the console.
//If you do any asynchronous action, you should return the corresponding promise, see point 3 below
//For example:
//if (newValue.totalScore !== previousValue.totalScore) {
// return db.collection("score").doc(newValue.name).set({score: newValue.totalScore});
//}
});
Note that:
You cannot trigger the onUpdate Cloud Function when a specific field of the document changes. The Cloud Function will be triggered when any field of the Firestore document changes. But you can detect which field(s) have changed, as shown in the above code.
Since version 1.0 you have to initialize with admin.initializeApp();, see https://firebase.google.com/docs/functions/beta-v1-diffList
You need to indicate to the platform when the Cloud Function has finished executing: Since you are not executing any asynchronous operation in your Cloud Function you can use return null;. (For more details on this point, I would suggest you watch the 3 videos about "JavaScript Promises" from the Firebase video series: https://firebase.google.com/docs/functions/video-series/).

Answer 2

I think the update is checked on the ref not on the child
Try this
export const onMessageCreate = functions.database
.ref('/users/{userId}')
.onUpdate((change) => {
console.log('I am a log entry2!');
//var a = admin.firestore().collection('/users');
})
You get the old and new values of the snapshot at that location

Answer 3

If you are using Cloud Firestore then your listener is incorrect. In your case, you are specifying a listener for Realtime Database. We extract firestore from the functions and specify the path to the document we want to have a listener on:
import * as functions from 'firebase-functions';
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
export const onMessageCreate = functions.firestore
.document('users/{userId}')
.onUpdate((change, context) => {
console.log(change.before.data()); // shows the document before update
console.log(change.after.data()); // shows the document after change
return;
})