Best way to connect to MongoDB using Node.js [duplicate] - node.js

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How do I manage MongoDB connections in a Node.js web application?
(13 answers)
Closed 4 years ago.
I've read a few guides on how to use Mongo with Node, and they all seem to connect to databases differently. One particular way that worked well for me was:
MongoClient.connect("mongodb://localhost:27017/exampleDb", function(err, db) {
if(err) { return console.dir(err); }
db.createCollection('users', function(err, collection) {});
//Do all server/database operations in here
});
However, this seems inefficient/odd to me, I would have to reconnect to the database every time there is an app.get(), like for making a new user or retrieving information.
Another way that seems better suited to me is
var mongoose = require("mongoose")
var db = mongoose.connect("localhost:27107/users");
db.createCollection('users', function(err, collection) {});
I've seen several sites do something along these lines, but I personally can't get the above to work. I keep getting the error TypeError: db.createCollection is not a function server-side. So, my question is why the above code doesn't work, if the first code is a good alternative, and if there are any other ways to do this.

Answer 1

You can use a global variable to hold the connection (e.g. db), for example:
var db = null // global variable to hold the connection
MongoClient.connect('mongodb://localhost:27017/', function(err, client) {
if(err) { console.error(err) }
db = client.db('test') // once connected, assign the connection to the global variable
})
app.get('/', function(req, res) {
db.collection('test').find({}).toArray(function(err, docs) {
if(err) { console.error(err) }
res.send(JSON.stringify(docs))
})
})
Or, if you prefer, you can also use the Promise object that is returned by MongoClient if it is called without a callback argument:
var conn = MongoClient.connect('mongodb://localhost:27017/') // returns a Promise
app.get('/', function(req, res) {
conn.then(client=> client.db('test').collection('test').find({}).toArray(function(err, docs) {
if(err) { console.error(err) }
res.send(JSON.stringify(docs))
}))
})
Please note that I used the ES6 fat arrow function definition in the second example.
You are absolutely correct that you should not call MongoClient every time. Using a global variable or Promises allows the MongoDB node.js driver to create a connection pool, which achieves at least two good things:
Connections are reused in a pool, so there is no multiple expensive setup/teardown process for the lifetime of your application. You connect once, and let the driver take care of the rest for you.
You can control the amount of connection your application makes into the database, by limiting the size of the connection pool.
Edit 2018-08-24: The MongoClient.connect() method in node.js driver version 3.0 and newer returns a client object instead of a database object. The examples above were modified to keep it up to date with the latest node.js driver version.

Answer 2

I've written a tutorial on how to reuse mongodb connection in express. You can see here. Basically, it's a simple module, which you can use with expressjs like that:
var connection = require('./dbconnection');
// url and optional config.
app.use(connection(app, 'mongourl', {});
And here's the code for the connection:
module.exports = function(app, uri, opts) {
if (typeof uri !== 'string') {
throw new TypeError('Error: Unexpected mongodb connection url');
}
opts = opts || {};
var property = opts.property || 'db';
var connection;
return function expressMongoDb(req, res, next) {
if (!connection) {
connection = MongoClient.connect(uri, opts);
}
connection
.then(function (db) {
req[property] = db;
app.set('mongodb', db);
next();
})
.catch(function (err) {
connection = undefined;
next(err);
});
};
};

Answer 3

You could use it this way:
that's server.js file:
import path from 'path'
import express from 'express'
import bodyParser from 'body-parser'
import morgan from 'morgan'
import db from './server/database'
import routes from './server/routes'
import webpack from 'webpack'
import webpackDevMiddleware from 'webpack-dev-middleware'
import webpackHotMiddleware from 'webpack-hot-middleware'
import webpackConfig from './config/webpack'
const app = express()
const port = process.env.PORT || process.env.NODE_PORT
const compiler = webpack(webpackConfig)
db(λ => {
app.use(webpackDevMiddleware(compiler, { noInfo: true, publicPath: webpackConfig.output.publicPath }))
app.use(webpackHotMiddleware(compiler))
app.use(morgan('dev'))
app.use(bodyParser.json({ limit: '20mb' }))
app.use(bodyParser.urlencoded({ limit: '20mb', extended: false }))
app.use('/static', express.static('static'));
//app.use('/api', jwt)
app.use('/api', routes())
app.set('json spaces', 2)
app.get('*', function(request, response) {
response.sendFile(path.resolve(__dirname, 'index.html'))
})
app.listen(port, (error) => {
if (error) {
console.error(error)
throw error
} else {
console.info(`==> 🌎 Listening on port ${port}. Open up http://localhost:${port}/ in your browser.`)
}
})
})
server/database.js
import mongoose from 'mongoose'
export default callback => {
const { MONGO_URL, MONGO_PORT, MONGO_DB } = process.env
mongoose.connect(`mongodb://${MONGO_URL}:${MONGO_PORT}/${MONGO_DB}`, error => {
if (error) {
console.error('Please make sure your MongoDB configuration is correct and that service is running')
throw error
}
})
callback()
}
Then you'll have to define your mongoose models, for instance:
import mongoose, { Schema } from 'mongoose'
const ideaSchema = new Schema({
title: {
type: String,
required: true
},
slug: {
type: String,
required: true,
unique: true
},
description: {
type: String,
required: true
}
})
export default mongoose.model('Idea', ideaSchema)
And just use controllers this way:
import HttpStatus from 'http-status-codes'
import mongoose from 'mongoose'
import sanitize from 'sanitize-html'
import slug from 'slug'
import Idea from '../models/idea'
const findAllIdeas = (req, res) => {
Idea.find()
.select('user title slug createdAt updatedAt')
.populate({
path: 'user',
select: 'firstName lastName'
})
.then(data => res.status(HttpStatus.OK).json(data))
.catch(error => res.status(HttpStatus.BAD_REQUEST).json(error))
}
export default { findAllIdeas, findIdeaBySlug, createIdea, addComment }
You will not have to connect to mongoDB for each get request.
So your route will look like that. Quite straightforward:
import { Router } from 'express'
import controller from '../controllers/idea'
const router = Router()
router.route('/')
.get(controller.findAllIdeas)
.post(controller.createIdea)
router.route('/:slug')
.get(controller.findIdeaBySlug)
router.route('/comment')
.post(controller.addComment)
export default router

Answer 4

My go-to code is as follows:
mongoose.connect(YOUR_URL ,function(err) {
if (err) {
console.log(err);
}else{
console.log("Connected to DB");
}
});
Also try connecting to just localhost:27107, that may be your problem.