Why are multiple connections being created in my database? - database

Question

I am developing a website in NextJs and using MongoDB as a database. This code is what connects to the database and keeps it in cache.
import { MongoClient } from "mongodb";
let cache = {};
export default async function connect() {
if (cache?.client?.isConnected()) {
return cache;
}
const opts = {
useNewUrlParser: true,
useUnifiedTopology: true,
};
return MongoClient.connect(process.env.DATABASE_URL, opts).then((client) => {
cache = {
db: client.db("bd"),
client,
};
return {
client,
db: client.db("bd"),
};
});
}
I imagine that this code should cause only 1 connection to be created but it is creating many more connections. As in the photo below, 18 connections were created and dropped to 6 after I stopped use the site. Why are several connections being created? How do you make it just one?
This is an example of code that I am using on one of the routes to list users.
...
const { db, client } = await connect();
const { userThatMakeRequest } = req;
const { group } = req.query;
const users = await db
.collection("user")
.find(
{
roles: "team-user",
"team.id": userThatMakeRequest?.team?.id,
"group.id": group,
hasAccess: true,
},
{ projection: { password: 0 } }
)
.toArray();
res.status(200).json({
response: users || [],
});

Answer 1

The driver creates 1 or 2 connections to each known server for monitoring purposes. Application connections (the ones used for satisfying queries and writes) are separate.
If you create a client object and perform one query against a 3 node replica set running MongoDB 4.4, you'll end up with 7 total connections.