Firebase functions just dying out with no explanation or error - firebase

Question

I'm trying to implement a messaging application using Firebase Firestore and Firebase Cloud Functions.
In essence, chat messages are stored as individual documents in a subcollection. At first, I implemented this as directly adding a document from the client and listening on the collection and updating the clients when a change happens but later I decided to switch to using Cloud functions so that I can add some functionality that's better done on the server side(filtering etc.).
So I created a function for sending messages, which creates the documents on behalf of the users when the users call the function from the app(i.e. tap the send button).
The function worked and I was able to monitor the processes through the logs. Unfortunately, the functions began to die out without error, the console was reporting that the functions are executed successfully and it usually took less than a second to execute.
I suspect that it has something to do with the promises that probably continue to run but this is the same code that was working but failing today.
If I try a few more times, the functions seem to be working again. Do I need to keep the functions "warm"? Are cloud functions not reliable enough to handle this kind of tasks? When I say my user that a message is sent, I need to be able to confirm that it is sent and communicate it with the users if it failed.
It's hard to debug the issue because no errors are thrown(not even info message, it's just as if didn't happen), it just says that the function successfully finished execution and nothing happened.
Am I missing something here? Thank you.
exports.sendMessage = functions.https.onCall((data, context) => {
if (context.auth.uid == undefined) {
console.warn("SEND MESSAGE: USER NOT SIGNED IN");
return;
}
console.log("Sending message:", data)
const matchId = data["matchId"];
const message = data["message"]
const uid = context.auth.uid
admin.firestore().collection(MatchingUsers).doc(matchId).collection(UserMessages).add({
type: "text",
from: uid,
message: message,
timestamp: admin.firestore.Timestamp.now()
}).then(result => {
console.log("Message sent")
}).catch(err => {
console.log("Error sending mesage:", err)
})
})

Answer 1

As explained in the documentation of the HTTP Callable Cloud Functions:
To return data after an asynchronous operation, return a promise.
Then follows an example:
const sanitizedMessage = sanitizer.sanitizeText(text); // Sanitize the message.
return admin.database().ref('/messages').push({
text: sanitizedMessage,
author: { uid, name, picture, email },
}).then(() => {
console.log('New Message written');
// Returning the sanitized message to the client.
return { text: sanitizedMessage };
})
So you need to adapt your code as follows:
exports.sendMessage = functions.https.onCall((data, context) => {
if (context.auth.uid == undefined) {
console.warn("SEND MESSAGE: USER NOT SIGNED IN");
//Here send back an error as explained here: https://firebase.google.com/docs/functions/callable#handle_errors
}
console.log("Sending message:", data)
const matchId = data["matchId"];
const message = data["message"]
const uid = context.auth.uid
//Note the return on next line
return admin.firestore().collection(MatchingUsers).doc(matchId).collection(UserMessages).add({
type: "text",
from: uid,
message: message,
timestamp: admin.firestore.Timestamp.now()
}).then(result => {
console.log("Message sent");
return { text: "Message sent" };
}).catch(err => {
console.log("Error sending mesage:", err);
//Here, again, send back an error as explained here: https://firebase.google.com/docs/functions/callable#handle_errors
})
})
If you don't want to return a value to the client, you could do as follows, returning null when the Promise returned by the add() asynchronous method resolves. (Not tested but it should work).
exports.sendMessage = functions.https.onCall((data, context) => {
if (context.auth.uid == undefined) {
console.warn("SEND MESSAGE: USER NOT SIGNED IN");
return null;
}
console.log("Sending message:", data)
const matchId = data["matchId"];
const message = data["message"]
const uid = context.auth.uid
//Note the return on next line
return admin.firestore().collection(MatchingUsers).doc(matchId).collection(UserMessages).add({
type: "text",
from: uid,
message: message,
timestamp: admin.firestore.Timestamp.now()
}).then(result => {
console.log("Message sent"); //Actually, if you don't need this console.log() you can remove this entire then() block, returning the promise from add() is enough
return null;
}).catch(err => {
console.log("Error sending mesage:", err);
return null;
})
})