Reuse database connection

[dan-cooke]

Hi there,

I cannot seem to re-use my mongodb connection between requests.

I have the following connect function:

import { MongoClient } from 'mongodb';

let mongo: MongoClient;
export const connectToAtlas = async () => {
  if (!process.env.ATLAS_CLUSTER_URI) {
    throw new Error(`Cannot connect to Atlas no URI in env`);
  }
  const client = new MongoClient(process.env.ATLAS_CLUSTER_URI);

  if (!mongo) {
    mongo = await client.connect();
  }

  return mongo.db(`baggers`);
};

However mongo is always undefined when my loader calls this function.

This is making my app slower than nextjs :(

[dan-cooke]

So I followed the example on nextJS https://github.com/vercel/next.js/blob/canary/examples/with-mongodb/lib/mongodb.js

[kiliman]

Which adapter are you using? If you're using serverless like Vercel, you can't reuse connections across each request since requests are short-lived and on different processes.

Only adapters that give your a long-running process like Express will support that.

[dan-cooke]

I am using fly.io

It seems to support this

[kiliman]

Ok, fly.io is a host, and I believe the default template uses Remix App Server (which is a built-in Express server), so my comments still apply.

Anyway, I'm posting an answer.

[kiliman]

Remix App Server and Express adapter purge the require cache on every request (only in DEV).

You should store your client reference on the global object. Here's how the Prisma client is persisted from the Jokes tutorial.

let db: PrismaClient;

declare global {
  var __db: PrismaClient | undefined;
}

// this is needed because in development we don't want to restart
// the server with every change, but we want to make sure we don't
// create a new connection to the DB with every change either.
if (process.env.NODE_ENV === "production") {
  db = new PrismaClient();
  db.$connect();
} else {
  if (!global.__db) {
    global.__db = new PrismaClient();
    global.__db.$connect();
  }
  db = global.__db;
}

export { db };

[dan-cooke]

Awesome yeh, I had looked at the example in the Jokes tutorial, but I had no idea why a global was required. ( I still don't really understand that tbh) so I just ignored it.

My bad.

Thanks!

[MHassanNadeem]

Here is my code for MongoClient, perhaps somebody would find this explicit code for mongodb useful.

import { MongoClient } from "mongodb";
import { config } from "@app/.server/config";

declare global {
  // eslint-disable-next-line no-var
  var __mongoClient: MongoClient | undefined;
}

let mongoClient: MongoClient;

// this is needed because in development we don't want to restart
// the server with every change, but we want to make sure we don't
// create a new connection to the DB with every change either.
if (process.env.NODE_ENV === "production") {
  mongoClient = new MongoClient(config.mongodb.url);
} else {
  if (!global.__mongoClient) {
    global.__mongoClient = new MongoClient(config.mongodb.url);
  }
  mongoClient = global.__mongoClient;
}

export { mongoClient };