Firebase Cloud Function no console.log when admin.firestore() is called - node.js

Question

I have a webhook to recieve facebook messenger events in a cloud function like so:
export const facebookMessengerHook = functions.https.onRequest(async (req: express.Request, res: express.Response) => {
console.log(req);
console.log(req.method);
console.log(req.body);
if (req.method == "POST") {
const body = req.body;
console.log(body);
// Checks this is an event from a page subscription
if (body.object === 'page') {
res.status(200).send('EVENT_RECEIVED');
// Iterates over each entry - there may be multiple if batched
for (const entry of body.entry) {
// will only ever contain one message, so we get index 0
const webhook_data = entry.messaging[0];
console.log(webhook_data);
try {
// v THAT PART HERE v
const user = await admin.firestore().collection('users')
.where('facebookMessengerId', '==', webhook_data.sender.id)
.get();
// ^ THAT PART HERE ^
console.log(user);
} catch (e) {
console.log('No user');
}
}
}
else {
// Returns a '404 Not Found' if event is not from a page subscription
res.sendStatus(404);
}
}
});
It does not log anything, unless I comment out the marked part in the snippet.
Can someone please explain to me why and how to fix this, because I need to make a call to firestore and I also need the console.log for debug purposes?
Thanks for any help!

Answer 1

The problem most probably comes from the fact that by doing
res.status(200).send('EVENT_RECEIVED');
you actually indicate to the Cloud Function platform that the Cloud Function can be terminated before the rest of the asynchronous work (the set of calls to the get() method) is done. See the following official video form more detail. In other words, the Cloud Function is terminated before the promises returned by the get() method are resolved.
So you should modify your code as follows:
//....
if (body.object === 'page') {
// Iterates over each entry - there may be multiple if batched
for (const entry of body.entry) {
// will only ever contain one message, so we get index 0
const webhook_data = entry.messaging[0];
console.log(webhook_data);
try {
const user = await admin.firestore().collection('users')
.where('facebookMessengerId', '==', webhook_data.sender.id)
.get();
console.log(user);
} catch (e) {
console.log('No user');
//Here throw an error to be catched at an upper level
}
}
res.status(200).send('EVENT_RECEIVED');
}
//....
Note that you may use Promise.all() since you issue a series of fetch to the database. But with your code it is impossible to confirm that, because it does not show the exact use of these fetches.