Cloud Functions for Firebase send push to multiple users - firebase

Question

I try to get multiple push notifications to run on Cloud Functions for Firebase without success.
I store my message receipts in a node
message_receipts
-KtvyTN3nbVKoFjHdpJg
hHhs5Aco38X1W8EhaaxrwsQDXwy1:"receipt"
nI25FjUnBfQiCWzdCUIAe8CWTPQ2:"receipt"
To send push notifications I try following on cloud functions:
//*********************************************************************************************************** */
//handle lsit item added by shared user
if (String(msgData.messageType) == 'ListItemAddedBySharedUser') {
return admin.database().ref("message_receipts").child(event.params.messageID).once('value').then(receipts => {
receipts.forEach(function (receipt) {
//Send push to receipt
return admin.database().ref('/users/' + receipt.key).once('value').then(usnap => {
//Send push to users fcmToken
const userSnap = usnap.val()
console.log('sending Push to ' + userSnap.fcmToken)
//create Notification Payload
var payload = {
notification: {
title: msgData.title,
body: msgData.message,
badge: '1',
sound: 'default',
sbID: String(event.data.key),
senderID: msgData.senderID,
listID: msgData.listID,
receiptID: receipt.key,
notificationType: String(msgData.messageType),
}
};
return admin.messaging().sendToDevice(userSnap.fcmToken, payload).then(response => {
console.log("Successfully sent invite message:", response)
console.log(response.results[0].error)
}).catch((err) => { console.log("Error sending Push", err) })
})
})
})
} //*********************************************************************************************************** */
All I get is one notification sent.
I'am very new to java script and cloud functions.
What do I need to do to get all of my users notified?

Answer 1

You need to aggregate all of the asynchronous actions you're taking. Here you're doing a forEach on the message receipts, but then you're returning a single promise. Try something like:
var promises = [];
receipts.forEach(function (receipt) {
//Send push to receipt
promises.push(admin.database().ref('/users/' + receipt.key).once('value').then(usnap => {
/* ... */
}))
})
return Promise.all(promises);
This will aggregate all of your outstanding notifications into a single Promise.all call, which will wait until they all complete.

Answer 2

You can send a batch of messages as described in the documentation:
https://firebase.google.com/docs/cloud-messaging/send-message#send-a-batch-of-messages
// Create a list containing up to 500 messages.
const messages = [];
messages.push({
notification: {title: 'Price drop', body: '5% off all electronics'},
token: registrationToken,
});
messages.push({
notification: {title: 'Price drop', body: '2% off all books'},
topic: 'readers-club',
});
return admin.messaging().sendAll(messages)
.then((response) => {
console.log(response.successCount + ' messages were sent successfully');
});