What is best way to handle global connection of Mongodb in NodeJs

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Create a Connection singleton module to manage the apps database connection.

MongoClient does not provide a singleton connection pool so you don’t want to call MongoClient.connect() repeatedly in your app. A singleton class to wrap the mongo client works for most apps I’ve seen.

const MongoClient = require('mongodb').MongoClient

class Connection {

    static async open() {
        if (this.db) return this.db
        this.db = await MongoClient.connect(this.url, this.options)
        return this.db
    }

}

Connection.db = null
Connection.url="mongodb://127.0.0.1:27017/test_db"
Connection.options = {
    bufferMaxEntries:   0,
    reconnectTries:     5000,
    useNewUrlParser:    true,
    useUnifiedTopology: true,
}

module.exports = { Connection }

Everywhere you require('./Connection'), the Connection.open() method will be available, as will the Connection.db property if it has been initialised.

const router = require('express').Router()
const { Connection } = require('../lib/Connection.js')

// This should go in the app/server setup, and waited for.
Connection.open()

router.get('/files', async (req, res) => {
   try {
     const files = await Connection.db.collection('files').find({})
     res.json({ files })
   }
   catch (error) {
     res.status(500).json({ error })
   }
})

module.exports = router

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