SvelteKit With MongoDB ReferenceError: global is not defined

Question

I'm trying to setup MongoDB connection library function. I know this function is solid, its used in a whole lot of places (search for Global is used here to maintain a cached connection across hot reloads) and you'll find a whole lot of uses including next.js releases. Note, the purpose of global storage for the database connection is to reduce the overall # of db connections in use at any one time.

What I'm not understanding is the error I'm getting when I import this library via import { connectToDatabase } from '$lib/database';

database.js

// https://github.com/mongodb-developer/mongodb-next-todo/blob/main/util/mongodb.js
import { ENV_OBJ } from "$lib/env";
import { MongoClient } from "mongodb";

const uri = ENV_OBJ.MONGODB_URI;

if (!uri) {
    throw new Error("Please define the Mongodb uri environment variable inside .env");
}

/**
 * Global is used here to maintain a cached connection across hot reloads
 * in development. This prevents connections growing exponentially
 * during API Route usage.
 */
let cached = global.mongo

if (!cached) {
    cached = global.mongo = { conn: null, promise: null }
}

export const connectToDatabase = async() => {
    if (cached.conn) {
        return cached.conn;
    }

    if (!cached.promise) {
        const options = {
            useNewUrlParser: true,
            useUnifiedTopology: true
        };

        cached.promise = MongoClient.connect(MONGODB_URI, opts).then((client) => {
            return {
                client,
                db: client.db(MONGODB_DB),
            }
        })
    }
    cached.conn = await cached.promise;
    return cached.conn;
}

The errors:

global is not defined

ReferenceError: global is not defined
    at node_modules/mongodb/lib/promise_provider.js (http://localhost:3000/node_modules/.vite/mongodb.js?v=3885e04e:548:25)
    at __require2 (http://localhost:3000/node_modules/.vite/chunk-6ODJH7E3.js?v=3885e04e:10:44)
    at node_modules/mongodb/lib/utils.js (http://localhost:3000/node_modules/.vite/mongodb.js?v=3885e04e:6524:30)
    at __require2 (http://localhost:3000/node_modules/.vite/chunk-6ODJH7E3.js?v=3885e04e:10:44)
    at node_modules/mongodb/lib/cursor/abstract_cursor.js (http://localhost:3000/node_modules/.vite/mongodb.js?v=3885e04e:10873:19)
    at __require2 (http://localhost:3000/node_modules/.vite/chunk-6ODJH7E3.js?v=3885e04e:10:44)
    at node_modules/mongodb/lib/index.js (http://localhost:3000/node_modules/.vite/mongodb.js?v=3885e04e:25281:29)
    at __require2 (http://localhost:3000/node_modules/.vite/chunk-6ODJH7E3.js?v=3885e04e:10:44)
    at http://localhost:3000/node_modules/.vite/mongodb.js?v=3885e04e:25616:23

Note, I do see a file in my generated minimal sveltekit repo called global.d.ts I'm not sure of its purpose. It contains only:

 /// <reference types="@sveltejs/kit" /> 

Any ideas on what's causing the error?

Reference: "@sveltejs/kit": "version": "1.0.0-next.118",

Edit: After spending a whole lot of time on this issue, the global not defined error seems to come from import { MongoClient } from "mongodb"; If I add appropriate console.logs, I can see that the MongoClient function works fine on the server, but then I get the global error on the client. The server indicates no errors at all.

Answer 1

So it turns out I was calling import { connectToDatabase } from '$lib/database' not in a .js helper file or api style (.js) endpoints. I was attempting to use that import and make a database call directly from the <script> portion of a xxx.svelte file.

Definite no go. That generates an immediate global not defined error.