Google cloud pub/sub function gives "The requested snapshot version is too old" when querying firestore

In case someone faces this problem, I answer my own question.

After a lot of reading, testing, I've noticed there is a warning in my logs like "Function returned undefined, expected Promise or value". Because I return a promise in my function, I was not paying attention to this.

Adding a return on top of my function fixed my warning, and my function has been running successfully for 5 days.

return exports.GenerateRankings = functions.pubsub.schedule('0 3 * * *') ...

I encountered the same problem, in my case, the code was as follows and the error mentioned in this issue was returned.

const userSnapshots = await this.firestore.collection('Users').where('archive', '==', false).get();
const users = userSnapshots.docs
users.map(async (user) => {
    //code to update user documents
});

Then I changed the code to the following and it worked without returning the error mentioned in this issue.

const userSnapshots = await this.firestore.collection('Users').where('archive', '==', false).get();
const users = userSnapshots.docs
const markPromises = users.map(async (user) => {
    //code to update user documents
});

await Promise.all(markPromises);

I don’t know this is the correct answer to this question but this worked for me.

For my case, I guess the problem was because of the size of data, and time it took to do the data management. I have split data into parts of 5000 elements :

    const store = getFirestore(initializeApp(myConfig));
    const collectionRef = store.collection("users");
    const limit = 5000;
    let docs: Array<QueryDocumentSnapshot<DocumentData>>;
    let querySnapshot: QuerySnapshot<DocumentData>;

    let query = collectionRef.limit(limit);

    do {
        querySnapshot = await query.get();
        docs = querySnapshot.docs; // thanks to @prahack answer
        for (const doc of docs) {
            await manageMyData(doc.id, doc.data());
        }
        if (docs.length > 0) {
            // Get the last visible document
            query = collectionRef.startAfter(docs[docs.length - 1]).limit(limit);
        }
    } while (docs.length > 0);

Without my data managing, i can use part of 10.000 elements (limit = 10000), but with management, i should down to 5000.

I spent hours trying to run a list of actions inside a "pubsub" and then I decided to try the following code and it worked.

this.firestore.collection('Users').where('archive', '==', false).get().then(snap=>{
    // Code Here
});