Random connection errors in Google Cloud Functions

Do you want to request a feature or report a bug?

BUG

What is the current behavior?

We are using Mongoose inside our Google Cloud Functions and we have a lot of errors related to the connection that seems very unstable. We have a lot of traffic in our cloud functions, something like dozens of calls per second. Most of the time the functions run well, but a non-neglectable percentage of our traffic is broken due to a connection error I’m unable to troubleshoot. I’ve tried reproducing with a simple cloud function that connects to Mongoose and runs every minute, and I’ve had 3 times the MongooseServerSelection error in two days. We also have random massive spike of MongoNetworkError: Client network socket disconnected before secure TLS connection was established I cannot explain.

If the current behavior is a bug, please provide the steps to reproduce. This script is the reproduction I used to have the 3 random MongooseServerSelectionError

import type { Connection, Model } from "mongoose";

import mongoose from "mongoose";
import * as functions from "firebase-functions";

const { db } = functions.config();

let connection: Connection = null;
let model: Model<any> | null;

export default async function testMongoose() {
  if (!connection) {
    connection = await mongoose.createConnection(db.url);
    await connection
      .asPromise()
      .catch((error) => logger.error("A db error has occured.", { error })); // This here is never executed in the logs.

    model = connection.model(
      "test_data",
      new mongoose.Schema({ message: String })
    );
  }

  await model.create({ message: "This is a test data." });
}

What is the expected behavior?

We no longer have unknown network errors.

What are the versions of Node.js, Mongoose, and MongoDB you are using? Note that “latest” is not a version. Node 14.X MongoDB v4.2 Mongoose v6.0.12

[axelvaindal]

Just to double check you have whitelisted your IP?

yes, otherwise the calls would fail all the time not just randomly.

[vkarpov15]

@axelvaindal can you try reducing maxPoolSize to 5? That may help.

it’s not really possible for us to say how many connections should be opened for a given number of function invocations without studying your code and access patterns.