How do I manage MongoDB connections in a Node.js w

Question

I'm using the node-mongodb-native driver with MongoDB to write a website.

I have some questions about how to manage connections:

1. Is it enough using only one MongoDB connection for all requests? Are there any performance issues? If not, can I setup a global connection to use in the whole application?

2. If not, is it good if I open a new connection when request arrives, and close it when handled the request? Is it expensive to open and close a connection?

3. Should I use a global connection pool? I hear the driver has a native connection pool. Is it a good choice?

4. If I use a connection pool, how many connections should be used?

5. Are there other things I should notice?

Answer 1

You should create a connection as service then reuse it when need.

// db.service.js
import { MongoClient } from "mongodb";
import database from "../config/database";

const dbService = {
  db: undefined,
  connect: callback => {
    MongoClient.connect(database.uri, function(err, data) {
      if (err) {
        MongoClient.close();
        callback(err);
      }
      dbService.db = data;
      console.log("Connected to database");
      callback(null);
    });
  }
};

export default dbService;

my App.js sample

// App Start
dbService.connect(err => {
  if (err) {
    console.log("Error: ", err);
    process.exit(1);
  }

  server.listen(config.port, () => {
    console.log(`Api runnning at ${config.port}`);
  });
});

and use it wherever you want with

import dbService from "db.service.js"
const db = dbService.db

Answer 2

http://mongoosejs.com/docs/api.html

Check out the source of Mongoose. They open a connection and bind it to a Model object so when the model Object is required, a connection is made to the DB. The driver takes care of connection pooling.

Answer 3

I have implemented below code in my project to implement connection pooling in my code so it will create a minimum connection in my project and reuse available connection

/* Mongo.js*/

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/yourdatabasename"; 
var assert = require('assert');

var connection=[];
// Create the database connection
establishConnection = function(callback){

                MongoClient.connect(url, { poolSize: 10 },function(err, db) {
                    assert.equal(null, err);

                        connection = db
                        if(typeof callback === 'function' && callback())
                            callback(connection)

                    }

                )



}

function getconnection(){
    return connection
}

module.exports = {

    establishConnection:establishConnection,
    getconnection:getconnection
}

/*app.js*/
// establish one connection with all other routes will use.
var db = require('./routes/mongo')

db.establishConnection();

//you can also call with callback if you wanna create any collection at starting
/*
db.establishConnection(function(conn){
  conn.createCollection("collectionName", function(err, res) {
    if (err) throw err;
    console.log("Collection created!");
  });
};
*/

// anyother route.js

var db = require('./mongo')

router.get('/', function(req, res, next) {
    var connection = db.getconnection()
    res.send("Hello");

});

Answer 4

I have been using generic-pool with redis connections in my app - I highly recommend it. Its generic and I definitely know it works with mysql so I don't think you'll have any problems with it and mongo

https://github.com/coopernurse/node-pool