`DocumentReference.create()` keeps trying to create an already existing document, leading to a hang in functions

[jellynoone]

[READ] Step 1: Are you in the right place? ✅

[REQUIRED] Step 2: Describe your environment

• Operating System version: MacOS 14.5
• Firebase Product: functions, firestore
• Node.js version: v18.20.3
• NPM version: 10.7.0

[REQUIRED] Step 3: Describe the problem

Steps to reproduce:

1. Create a new demo project via firebase init
2. Select functions and firestore
3. Run emulators through: firebase emulators:start --inspect-functions --project demo-me
4. Visit http://127.0.0.1:5001/demo-me/us-central1/runMeTwice in browser
5. Refresh

Relevant Code:

{
  "name": "functions",
  "description": "Cloud Functions for Firebase",
  "engines": {
    "node": "18"
  },
  "main": "index.js",
  "dependencies": {
    "firebase-admin": "^12.1.0",
    "firebase-functions": "^5.0.0"
  },
  "private": true
}

//@ts-check
const { onRequest } = require("firebase-functions/v2/https");
const logger = require("firebase-functions/logger");
const { firestore, initializeApp } = require("firebase-admin");
const { initializeFirestore } = require("firebase-admin/firestore");

/** @type {firestore.Firestore} */
let _defaultFirestore;
function defaultFirestore() {
    return _defaultFirestore ??= initializeFirestore(initializeApp(), {
        preferRest: true,
    })
}

exports.runMeTwice = onRequest(async (_, res) => {
    try {
        const doc = defaultFirestore().collection("test").doc("smt");
        await doc.create({});
        logger.log("Created");
    } catch (error) {
        logger.log(error);
    } finally {
        res.end();
    }
});

Expected behavior

The second time the function is ran, it should fail.

Actual behavior

The first time the function is run the document is created. The second time, the function never completes.

Additionally, attaching to the node process, it seems the creation process keeps getting retried even though it should fail.

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[jellynoone]

In addition, performing this in a transaction will eventually fail and terminate the function.
However, attaching the debugger it shows, the transaction is still attempted multiple times.
This seems incorrect.

exports.runMeTwice = onRequest(async (_, res) => {
    try {
        const firestore = defaultFirestore();
        await firestore.runTransaction(async (txn) => {
            txn.create(firestore.collection("test").doc("smt"), {});
        })
        logger.log("Created");
    } catch (error) {
        logger.log(error);
    } finally {
        res.end();
    }
});

[cherylEnkidu]

Hi @jellynoone ,

I will take a look at this and get back to you.

[cherylEnkidu]

@jellynoone

While investigating, there are some things can be tried as a workaround:

• Use set() instead
• DocumentReference.create() calls bulkWriter internally. You can try to use bulkWriter and config the retry option

[cherylEnkidu]

This is the code I used to reproduce the issue against production, it throws Document already exists successfully.

const ref = randomCol.doc();
await ref.create({});
const snap1 = await ref.get();

await ref.create({});

Are you testing against production or emulator?

[jellynoone]

I'm testing this against the emulator. Did you try with the provided example?
I think the preferRest: true, configuration option might be significant.

Tested this again against the emulator, without preferRest the function completes with an error. With preferRest the function hangs.

[jellynoone]

@cherylEnkidu Did you perhaps have a chance to reevaluate based on the additional information provided?

[cherylEnkidu]

Hi @jellynoone ,

I will continue the investigation this week, and I will reply the ticket as soon as I get any updates :)

[jellynoone]

Hi @cherylEnkidu were you able to take a look?