firebase Nodejs async cloud function not finishing execution

Question

I am building a firebase cloud function that when I change a value in my db, I get UIDs of all users in db then check a node called wishlists to see if the user has products in one of his wishlists. if the wishlists of the users do not have products the cloud function sends a notification to the user with a msg to fill his wishlist. The function works for one user but when I iterate the user's nodes and call the work that I do for one user, it finishes before completing all the work. I believe that the probléme comes from not handling properly the async functions. Any help is appreciated. Thanks!

const functions = require('firebase-functions');
const admin = require('firebase-admin');
const runtimeOpts = {
timeoutSeconds: 180,
memory: '1GB'
}

admin.initializeApp(functions.config().firebase);
exports.sendAdminNotificationForEmptyWishlists = functions.runWith(runtimeOpts)
.database.ref('/dev/fireNotifCloudFunc')
.onWrite(async () => {   
    // get all users uids
   const ref = admin.database().ref().child('Influencers')
   return ref.once("value")
   .then(function(snapshot) {
       snapshot.forEach( async function(child) {
            await checkUserWishlists(child.key)
       })
   })
   .catch(function(error){
       console.log(error); 
   });
});

//check users wishlists
async function checkUserWishlists(uid){
var ref = admin.database().ref().child('Articles').child(uid)
ref.once("value")
.then(function(snapshot) {
    if(snapshot.exists()){
        const wishlistsNumber = snapshot.numChildren();
        let wishlistCount = 0
        let userHasProduct = false         
        var BreakException = {};
        try {
            snapshot.forEach(function(child) {
                wishlistCount = wishlistCount + 1
                //wishlist node
                if(child.child("articles").exists()){
                    //user have not empty wishlist
                    userHasProduct = true
                    throw BreakException
                }
            });
        }
        catch(err){
            if (err !== BreakException) throw err;
        }
        if((wishlistCount === wishlistsNumber) && !userHasProduct){
            let fcmToken = (async () => {
                fcmToken = await getUserFirestoreFCM(uid).then(()=>{
                    sendPushNotificationToUser(fcmToken,"emptyWishlists")
                return fcmToken
                })
                .catch((error)=>{
                    console.log("error getting fcm token " + error);
                })
            })();
        }
    }
    else{
        console.log("user did not exist in articles node" );
        return 
    }
})
.catch(function(error){
    console.log(error); 
});
}

 async function getUserFirestoreFCM(uid){
   let documentRef = admin.firestore().doc("users_table/" + uid);
   documentRef.get().then(documentSnapshot => {
   if (documentSnapshot.exists) {
      console.log('Document exist')
      return  documentSnapshot.get('fcmToken')
   }
   else {
        console.log('Document dosen\'t exist')
        return 
   }
   })
   .catch(function(error){
       console.log('error geting fcm token from firestore ' + error);
   })
}  

async function sendPushNotificationToUser(fcm,type){

   //get fcm token    
     if(type === "emptyWishlists"){
        //notification content
        const payloadEmptyWishlists = {
        notification: {
        title: `Vos wishlists sont vides !`,
        body: "Hello veuillez ajouter des produits dans vos wishlists pour joindre les 
               influenceurs dans le fil d'acceil, cheers ! ",
        icon: "default",            
        sound: "default"
        }
    };
    const options = {        
        priority: "high",
        timeToLive: 60 * 60 * 24
    };
    //send notif
    return admin.messaging().sendToDevice(fcm, 
          payloadEmptyWishlists,options).then(function(response){
              console.log('Notification sent successfully:',response);
              return
    }) 
    .catch(function(error){
        console.log('Notification sent failed:',error);
    });
  }
}

this is a screeshot from the logs

Your use of async/await with the forEach callback isn't working the way you expect. Read this: https://stackoverflow.com/questions/37576685/using-async-await-with-a-foreach-loop — Doug Stevenson, Dec 09 '19 at 15:56

score 1 · Accepted Answer · answered Dec 12 '19 at 08:37

I think you should not use async/await in forEach loop callaback. This generally is tricky. Searching for good explanation I have found this article. I think its very short and clear.

In this situation I don't think that you need this async/await, but I would have to implement it to be sure. Anyway, if it appear that you still need async there is workaround in mentioned article.

firebase Nodejs async cloud function not finishing execution

1 Answers1