async/await doesn't seem to work with firebase forEach. This code runs console.log for the first child of the snapshot and then just hangs. Is this a bug or am I missing something?
main()
async function main() {
const snap = await root.ref('somepath')
.once('value')
snap.forEach(async val => {
await console.log(val.key)
})
}
It's an unintentional consequence of a feature, sometimes knows as a bug. From the firebase documentation:
an async function always returns a Promise. And a promise is true-y value:
!!Promise.resolve===true.
As a workaround, try this solution:
main()
async function main() {
const snap = await root.ref('somepath')
.once('value')
snap.forEach(function wrapper(){async val => {
await console.log(val.key)
}})
It won't wait for the promise to complete before moving to the next snapshot though. That would require a bit more code, but that may not be what you need anyways.
I use something like this:
import * as admin from "firebase-admin";
type FunctionOnDataSnapshot = (childSnapshot: admin.database.DataSnapshot) => Promise<any>;
export const asyncForEach = async (dataSnapshot: admin.database.DataSnapshot, childFunction: FunctionOnDataSnapshot) => {
const toWait = [];
dataSnapshot.forEach(childSnapshot => {
toWait.push(childFunction((childSnapshot)));
});
await Promise.all(toWait);
};
Related
Let's say we have firebase project in which we have to use RTDB.
In RTDB we have created multiple databases.
I created a cloud trigger function i.e .onCreate so that my both databases get updated whenever I update any of two. When I am creating anything in default database it is working completely fine but when I am trying to update through other database (other than default one) it doesn't update default one. So could you please help me on this?
/* eslint-disable */
import * as functions from "firebase-functions";
import * as admin from "firebase-admin";
admin.initializeApp();
//this method is updating on creating data on database mentioned in instance id
export const newTest1=functions.database.instance('flysample-75b81-227ae').ref('/msg')
.onCreate((snapshot, context) => {
let app = admin.app();
app.database('https://flysample-75b81.firebaseio.com/').ref('/db1').set({Name:"Database1"})
app.database('https://flysample-75b81-227ae.firebaseio.com/').ref('/db1').set({Name:"Database1"})
return "done";
});
//this method is updating only by creating data on default database
export const newTest2=functions.database.ref('/msg')
.onCreate((snapshot, context) => {
let app = admin.app();
app.database('https://flysample-75b81.firebaseio.com/').ref('/db1').set({Name:"Database1"})
app.database('https://flysample-75b81-227ae.firebaseio.com/').ref('/db1').set({Name:"Database1"})
return "done";
});
//below 2 method works fine but i want to do this by single function
export const myFunTest1 = functions.database.instance('flysample-75b81').ref('/name')
.onCreate((snapshot, context) => {
let app = admin.app();
app.database('https://flysample-75b81.firebaseio.com/').ref('/db1').set({Name:"Database1"})
app.database('https://flysample-75b81-227ae.firebaseio.com/').ref('/db1').set({Name:"Database1"})
return "done";
});
export const myFunTest2 = functions.database.instance('flysample-75b81-227ae').ref('/name')
.onCreate((snapshot, context) => {
let app = admin.app();
app.database('https://flysample-75b81.firebaseio.com/').ref('/db1').set({Name:"Database1"})
app.database('https://flysample-75b81-227ae.firebaseio.com/').ref('/db1').set({Name:"Database1"})
return "done";
});
Your code is completely ignoring the asynchronous nature of writing to the database, which means there is no guarantee that any of the database writes completes before the instance gets terminated.
To ensure the writes don't get interrupted, wait for them to complete before returning a result with something like this:
export const newTest2=functions.database.ref('/msg')
.onCreate((snapshot, context) => {
let app = admin.app();
return Promise.all([
app.database('https://flysample-75b81.firebaseio.com/').ref('/db1').set({Name:"Database1"})
app.database('https://flysample-75b81-227ae.firebaseio.com/').ref('/db1').set({Name:"Database1"})
]).then(() => {
return "done";
});
});
So, I don't really know how to write JS, I am developing a mobile app in Flutter, and I would be grateful for some help and clarifications regarding Future/Promises in JS.
I got a collection of posts for each user, and I want to create an .onCreate function which when a user posts a new post (a new document is created inside the 'posts/userId/user_posts' collection), then it gets all the user's followers (from a collection 'user_followers/userUid') and for each follower, it writes the postUid and postOwnerUid to that follower's newsFeed collection ('user_news_feed/followerId').
This is what I got right now, but I am walking blind, since I really don't know JS and I don't know how can I await a write function while inside a get function.
And how do I prevent Cloud Timeouts? If for instance the user has 1000 followers, how can I prevent Firebase from shutting down my function and making sure all the followers are notified?
exports.writeToUserNewsFeed = functions.firestore
.document('posts/{userId}/user_posts/{postId}')
.onCreate((snap, context) => {
const postData = snap.data();
const postUid = postData['post_uid'];
const userUid = postData['user_uid'];
const postCreationDate = postData['post_creation_date'];
var docRef = db.collection('user_followers').doc(userUid).collection('followers');
docRef.get().then((querySnapshot) => {
querySnapshot.forEach((doc) => {
db.collection('user_news_feed')
.doc(doc.data['uid'])
.collection('feed')
.document(postUid)
.set({
'post_uid': postUid,
'user_uid': userUid,
'post_uid': postCreationDate,
});
});
});
});
As explained in the doc, in a background Cloud Function like an onCreate() for Firestore, you need to return a Promise when all the asynchronous work is completed. So in your case, one possibility is to use Promise.all() because you don't know upfront how many documents are in the followers subcollection. Since Promise.all() returns a single Promise you can include it in the Promise chain that you need to return in the Cloud Function.
exports.writeToUserNewsFeed = functions.firestore
.document('posts/{userId}/user_posts/{postId}')
.onCreate((snap, context) => {
const postData = snap.data();
const postUid = postData['post_uid'];
const userUid = postData['user_uid'];
const postCreationDate = postData['post_creation_date'];
var followersColRef = db.collection('user_followers').doc(userUid).collection('followers');
return followersColRef.get().then((querySnapshot) => { // <= See return here
const promises = [];
querySnapshot.forEach((doc) => {
promises.push(
db.collection('user_news_feed')
.doc(doc.data['uid'])
.collection('feed')
.doc(postUid)
.set({
'post_uid': postUid,
'user_uid': userUid,
'post_uid': postCreationDate,
})
);
});
return Promise.all(promises); // <= See return here
})
.catch(error => {
console.log(error);
return null;
})
});
Note that instead of using Promise.all() you could also use a batched write but there is a limit of 500 operations for a batched write.
Trying to read a pushToken from a given user in the users collection (after an update operation on another collection) returns undefined
exports.addDenuncia = functions.firestore
.document('Denuncias/{denunciaID}')
.onWrite((snap, context) => {
const doc = snap.after.data()
const classificadoId = doc.cid
const idTo = doc.peerId
db.collection('Classificados').doc(classificadoId)
.update({
aprovado: false
})
.then(r => {
getToken(idTo).then(token => {
// sendMsg...
})
}).catch(updateErr => {
console.log("updateErr: " + updateErr)
})
async function getToken(id) {
let response = "getTokenResponse"
console.log("id in getToken: " + id)
return db.collection('users').doc(id).get()
.then(user => {
console.log("user in getToken: " + user.data())
response = user.data().pushToken
})
.catch(e => {
console.log("error get userToken: " + e)
response = e
});
return response
}
return null
});
And this is from the FB console log:
-1:43:33.906 AM Function execution started
-1:43:36.799 AM Function execution took 2894 ms, finished with status: 'ok'
-1:43:43.797 AM id in getToken: Fm1RwJaVfmZoSgNEFHq4sbBgoEh1
-1:43:49.196 AM user in getToken: undefined
-1:43:49.196 AM error get userToken: TypeError: Cannot read property 'pushToken' of undefined
-1:43:49.196 AM returned token: undefined
And we can see in this screenshot from the db that the doc does exist:
Hope someone can point me to what I'm doing wrong here.
added screenshot of second example of #Renaud as deployed:
As Doug wrote in his comment, you need to "return a promise from the top level function that resolves when all the async work is complete". He also explains that very well in the official video series: https://firebase.google.com/docs/functions/video-series/ (in particular the 3 videos titled "Learn JavaScript Promises"). You should definitely watch them, highly recommended!
So, the following modifications to your code should work (untested):
exports.addDenuncia = functions.firestore
.document('Denuncias/{denunciaID}')
.onWrite(async (snap, context) => { // <- note the async keyword
try {
const doc = snap.after.data()
const classificadoId = doc.cid
const idTo = doc.peerId
await db.collection('Classificados').doc(classificadoId)
.update({
aprovado: false
});
const userToSnapshot = await db.collection('users').doc(idTo).get();
const token = userToSnapshot.data().pushToken;
await sendMsg(token); // <- Here you should take extra care to correctly deal with the asynchronous character of the sendMsg operation
return null; // <-- This return is key, in order to indicate to the Cloud Function platform that all the asynchronous work is done
} catch (error) {
console.log(error);
return null;
}
});
Since you use an async function in your code, I've used the async/await syntax but we could very well write it by chaining the promises with the then() method, as shown below.
Also, I am not sure, in your case, that it adds any value to put the code that gets the token in a function (unless you want to call it from other Cloud Functions but then you should move it out of the addDenuncia Cloud Function). That's why it has been replaced by two lines of code within the main try block.
Version with chaining promises via the then() method
In this version we chain the different promises returned by the asynchronous methods with the then() method. Compared to the async/await version above, it shows very clearly what means "to return a promise from the top level function that resolves when all the asynchronous work is complete".
exports.addDenuncia = functions.firestore
.document('Denuncias/{denunciaID}')
.onWrite((snap, context) => { // <- no more async keyword
const doc = snap.after.data()
const classificadoId = doc.cid
const idTo = doc.peerId
return db.collection('Classificados').doc(classificadoId) // <- we return a promise from the top level function
.update({
aprovado: false
})
.then(() => {
return db.collection('users').doc(idTo).get();
})
.then(userToSnapshot => {
if {!userToSnapshot.exists) {
throw new Error('No document for the idTo user');
}
const token = userToSnapshot.data().pushToken;
return sendMsg(token); // Again, here we make the assumption that sendMsg is an asynchronous function
})
.catch(error => {
console.log(error);
return null;
})
});
as far as I know, background trigger cloud function should return a promise,right? but what if I want to do nothing in the one of my execution path ?
export const updateDataWhenUserUnattendTheEvent = functions.firestore
.document('events/{eventId}/Attendee/{userId}')
.onDelete((snap, context) => {
const eventID = context.params.eventId
const eventRef = snap.ref.firestore.collection('events').doc(eventID)
const db = admin.firestore()
return db.runTransaction(async t => {
const doc = await t.get(eventRef)
if (doc) {
const eventRankPoint = doc.data().rankPoint
let eventCapacity = doc.data().capacity
return t.update(eventRef,{
isFullCapacity : false,
capacity : eventCapacity + 1,
rankPoint: eventRankPoint - 1
})
} else {
// what should I write in here? empty promise?
return new Promise()
}
})
})
I want to my function worked only if the document is exist. so what should I do ? I write new Promise but .... I don't know what to do actually. thanks in advance
You can just return null if there's no asynchronous work to perform in some code path of your functions. You only truly need a promise if it tracks some async work.
Alternatively, you could return a promise that's resolved immediately with Promise.resolve(null)
Because db.runTransaction is an async function it will return a Promise all the time.
You can drop the else statement and the method will perform as expected because runTransaction will return Promise<void> which is a valid response for Cloud Functions
export const updateDataWhenUserUnattendTheEvent = functions.firestore
.document('events/{eventId}/Attendee/{userId}')
.onDelete((snap, context) => {
const eventID = context.params.eventId;
const eventRef = snap.ref.firestore.collection('events').doc(eventID);
const db = admin.firestore();
return db.runTransaction(async t => {
const doc = await t.get(eventRef);
if (doc) {
const eventRankPoint = doc.data().rankPoint;
let eventCapacity = doc.data().capacity ;
return t.update(eventRef,{
isFullCapacity : false,
capacity : eventCapacity + 1,
rankPoint: eventRankPoint - 1
});
}
});
});
You can also make the onDelete function async which means you can force it to always return a Promise - the below is valid and will exit the function correctly.
export const updateDataWhenUserUnattendTheEvent = functions.firestore
.document('events/{eventId}/Attendee/{userId}')
.onDelete(async (snap, context) => {
// Do Nothing
return;
});
I have observed this behavior occasionally with both onCreate and onDelete triggers.
Both the executions happened for the same document created in firestore. There's only one document there so I don't understand how it could trigger the handler twice. the handler itself is very simple:
module.exports = functions.firestore.document('notes/{noteId}').onCreate((event) => {
const db = admin.firestore();
const params = event.params;
const data = event.data.data();
// empty
});
this doesn't happen all the time. What am I missing?
See the Cloud Firestore Triggers Limitations and Guarantees:
Delivery of function invocations is not currently guaranteed. As the
Cloud Firestore and Cloud Functions integration improves, we plan to
guarantee "at least once" delivery. However, this may not always be
the case during beta. This may also result in multiple invocations
for a single event, so for the highest quality functions ensure that
the functions are written to be idempotent.
There is a Firecast video with tips for implementing idempotence.
Also two Google Blog posts: the first, the second.
Based on #saranpol's answer we use the below for now. We have yet to check if we actually get any duplicate event ids though.
const alreadyTriggered = eventId => {
// Firestore doesn't support forward slash in ids and the eventId often has it
const validEventId = eventId.replace('/', '')
const firestore = firebase.firestore()
return firestore.runTransaction(async transaction => {
const ref = firestore.doc(`eventIds/${validEventId}`)
const doc = await transaction.get(ref)
if (doc.exists) {
console.error(`Already triggered function for event: ${validEventId}`)
return true
} else {
transaction.set(ref, {})
return false
}
})
}
// Usage
if (await alreadyTriggered(context.eventId)) {
return
}
In my case I try to use eventId and transaction to prevent onCreate sometimes triggered twice
(you may need to save eventId in list and check if it exist if your function actually triggered often)
const functions = require('firebase-functions')
const admin = require('firebase-admin')
const db = admin.firestore()
exports = module.exports = functions.firestore.document('...').onCreate((snap, context) => {
const prize = 1000
const eventId = context.eventId
if (!eventId) {
return false
}
// increment money
const p1 = () => {
const ref = db.doc('...')
return db.runTransaction(t => {
return t.get(ref).then(doc => {
let money_total = 0
if (doc.exists) {
const eventIdLast = doc.data().event_id_last
if (eventIdLast === eventId) {
throw 'duplicated event'
}
const m0 = doc.data().money_total
if(m0 !== undefined) {
money_total = m0 + prize
}
} else {
money_total = prize
}
return t.set(ref, {
money_total: money_total,
event_id_last: eventId
}, {merge: true})
})
})
}
// will execute p2 p3 p4 if p1 success
const p2 = () => {
...
}
const p3 = () => {
...
}
const p4 = () => {
...
}
return p1().then(() => {
return Promise.all([p2(), p3(), p4()])
}).catch((error) => {
console.log(error)
})
})
Late to the party, I had this issue but having a min instance solved the issue for me
Upon looking #xaxsis attached screenshot, my function took almost the amount of time about 15 seconds for the first request and about 1/4 of that for the second request