I have a project where I use Next.js on the front-end and Express.js on the back.
Front-end side
The 'pages' file contains 'index.js'. In it, I am sending the following request.
import Home from "./home/home";
import axios from "axios";
import { useState } from "react";
export default function Index({ data }) {
const [products, setProducts] = useState(data);
const [start, setStart] = useState(1);
const getMoreProducts = async () => {
setStart(start + 1);
const { newProducts } = await axios.get(
`${process.env.NEXT_PUBLIC_BACK_END}/test`
);
setProducts([...products, ...newProducts]);
};
return (
<div>
<Home data={products} />
<button onClick={getMoreProducts}> Load more {start}</button>
</div>
);
}
export async function getServerSideProps(context) {
// Fetch data from external API
const { data } = await axios.get(
`${process.env.NEXT_PUBLIC_BACK_END}/productlist/pagination`,
{
params: {
page: 1,
limit: 5,
},
}
);
return {
props: {
data: data || {},
},
};
// Pass data to the page via props
}
Back-end side
const express = require("express");
var cors = require('cors')
const app = express();
require("dotenv").config();
const mongoose = require("mongoose");
mongoose.connect(
"*********",
{ useNewUrlParser: true }
);
const db = mongoose.connection;
db.on("error", (err) => console.error(err));
db.once("open", () => console.log("Connected to Database "));
app.use(express.json());
const productlistRouter = require("./routes/productlist");
const test = require("./routes/test");
app.use("/productlist", productlistRouter);
app.use("/test", test);
app.use(cors())
app.listen(3000, () => console.log("Server is running"));
And here is my Route code :
const express = require("express");
const router = express.Router();
const Product = require("../models/product");
const cors = require("cors");
const corsOptions = {
headers: [
{ key: "Access-Control-Allow-Credentials", value: "true" },
{ key: "Access-Control-Allow-Origin", value: "*" },
// ...
],
origin: "*",
optionsSuccessStatus: 200, // some legacy browsers (IE11, various SmartTVs) choke on 204
};
router.get("/showall", async (req, res) => {
try {
const product = await Product.find();
res.json(product);
} catch (err) {
res.status(500).json({ message: err.message });
}
});
router.get("/pagination", cors(corsOptions), async (req, res) => {
const page = req.query.page;
const limit = req.query.limit;
const startIndex = (page - 1) * limit;
const endIndex = page * limit;
const products = await Product.find();
const result = products.slice(startIndex, endIndex);
res.json(result);
});
So, When the page is first built with Next.js, the api works, but when I click the 'Load more' button, it gives a CORS error. When I use the same query with 'postman' and other tools, it does not give any error.
On the Next.js side, it works when I send a query to another 3rd party API., but it doesn't work when I send it to my own back-end. And no matter what page or component I do this in, only the APIs that are created at the build time are working.
What could be the reason for this? and how can i solve it? I've read and searched a few articles about cors, but I still haven't found a solution for days.
CORS should be placed on top level as javascript is executed one by one line. Place app.use(cors()) just above the line of app.use("/productlist", productlistRouter);
I have built my portfolio webpage with next.js now I need to test it. to test the express server I use supertest. But the problem is I need to refactor express to use it. Because supertest need to access to app() before listening.
I started the way how I used to implement in node.js app. Put the express code in app.js and call it in index.js.
const express = require("express");
const server = express();
const authService = require("./services/auth");
const bodyParser = require("body-parser");
//put all the middlewares here
module.exports = server;
and then in index.js
const server = require("express")();
// const { parse } = require("url");
const next = require("next");
const routes = require("../routes");
const path = require("path");
require("./mongodb");
const dev = process.env.NODE_ENV !== "production";
const app = next({ dev });
// const handle = app.getRequestHandler(); //this is built in next route handler
const handle = routes.getRequestHandler(app);
app
.prepare()
.then(() => {
const server = require("./app");
//I required this outside too but it did not solve the issue
server.listen(3000, (err) => {
if (err) throw err;
console.log("> Ready on http://localhost:3000");
});
})
.catch((ex) => {
console.error(ex.stack);
process.exit(1);
});
with this set up, express is listening, I am able connect to mongodb, during the start up there is no issue.
When i request to localhost:3000, there is no response from localhost, it is spinning till timeout
Create a test client:
// test-client.ts
import { createServer, RequestListener } from "http";
import { NextApiHandler } from "next";
import { apiResolver } from "next/dist/next-server/server/api-utils";
import request from "supertest";
export const testClient = (handler: NextApiHandler) => {
const listener: RequestListener = (req, res) => {
return apiResolver(
req,
res,
undefined,
handler,
{
previewModeEncryptionKey: "",
previewModeId: "",
previewModeSigningKey: "",
},
false
);
};
return request(createServer(listener));
};
Test your APIs with:
// user.test.ts
import viewerApiHandler from "../api/user";
import { testClient } from "../utils/test-client";
const request = testClient(viewerApiHandler);
describe("/user", () => {
it("should return current user", async () => {
const res = await request.get("/user");
expect(res.status).toBe(200);
expect(res.body).toStrictEqual({ name: "Jane Doe" });
});
});
For those who want to add query parameters, here's the answer:
import { createServer, RequestListener } from 'http'
import { NextApiHandler } from 'next'
import { apiResolver } from 'next/dist/server/api-utils/node'
import request from 'supertest'
export const handlerRequester = (handler: NextApiHandler) => {
const listener: RequestListener = (req, res) => {
let query = {}
let queryUrl = req.url.split('?')[1]
if (queryUrl) {
queryUrl
.split('&')
.map((p) => [p.split('=')[0], p.split('=')[1]])
.forEach((k) => {
query[k[0]] = k[1]
})
}
return apiResolver(
req,
res,
query,
handler,
{
previewModeEncryptionKey: '',
previewModeId: '',
previewModeSigningKey: '',
},
false
)
}
const server = createServer(listener)
return [request(server), server]
}
I've just released a new npm package which handle this case here:
https://www.npmjs.com/package/nextjs-http-supertest
Feel free to test it and give me feedback !
I've been reading and reading and still am confused on what is the best way to share the same database (MongoDb) connection across whole NodeJs app. As I understand connection should be open when app starts and reused between modules. My current idea of the best way is that server.js (main file where everything starts) connects to database and creates object variable that is passed to modules. Once connected this variable will be used by modules code as necessary and this connection stays open. E.g.:
var MongoClient = require('mongodb').MongoClient;
var mongo = {}; // this is passed to modules and code
MongoClient.connect("mongodb://localhost:27017/marankings", function(err, db) {
if (!err) {
console.log("We are connected");
// these tables will be passed to modules as part of mongo object
mongo.dbUsers = db.collection("users");
mongo.dbDisciplines = db.collection("disciplines");
console.log("aaa " + users.getAll()); // displays object and this can be used from inside modules
} else
console.log(err);
});
var users = new(require("./models/user"))(app, mongo);
console.log("bbb " + users.getAll()); // not connected at the very first time so displays undefined
then another module models/user looks like that:
Users = function(app, mongo) {
Users.prototype.addUser = function() {
console.log("add user");
}
Users.prototype.getAll = function() {
return "all users " + mongo.dbUsers;
}
}
module.exports = Users;
Now I have horrible feeling that this is wrong so are there any obvious problems with this approach and if so how to make it better?
You can create a mongoUtil.js module that has functions to both connect to mongo and return a mongo db instance:
const MongoClient = require( 'mongodb' ).MongoClient;
const url = "mongodb://localhost:27017";
var _db;
module.exports = {
connectToServer: function( callback ) {
MongoClient.connect( url, { useNewUrlParser: true }, function( err, client ) {
_db = client.db('test_db');
return callback( err );
} );
},
getDb: function() {
return _db;
}
};
To use it, you would do this in your app.js:
var mongoUtil = require( 'mongoUtil' );
mongoUtil.connectToServer( function( err, client ) {
if (err) console.log(err);
// start the rest of your app here
} );
And then, when you need access to mongo somewhere else, like in another .js file, you can do this:
var mongoUtil = require( 'mongoUtil' );
var db = mongoUtil.getDb();
db.collection( 'users' ).find();
The reason this works is that in node, when modules are require'd, they only get loaded/sourced once so you will only ever end up with one instance of _db and mongoUtil.getDb() will always return that same instance.
Note, code not tested.
There are many ways this could be tweaked to accept configuration objects in places, but overall it's similar to how you have your code laid out, albeit with more modern JS syntax. Could easily be rewritten to prototypes and callbacks, if that's your requirement.
mongo.js
const { MongoClient } = require('mongodb');
const config = require('./config');
const Users = require('./Users');
const conf = config.get('mongodb');
class MongoBot {
constructor() {
const url = `mongodb://${conf.hosts.join(',')}`;
this.client = new MongoClient(url, conf.opts);
}
async init() {
await this.client.connect();
console.log('connected');
this.db = this.client.db(conf.db);
this.Users = new Users(this.db);
}
}
module.exports = new MongoBot();
Users.js
class User {
constructor(db) {
this.collection = db.collection('users');
}
async addUser(user) {
const newUser = await this.collection.insertOne(user);
return newUser;
}
}
module.exports = User;
app.js
const mongo = require('./mongo');
async function start() {
// other app startup stuff...
await mongo.init();
// other app startup stuff...
}
start();
someFile.js
const { Users } = require('./mongo');
async function someFunction(userInfo) {
const user = await Users.addUser(userInfo);
return user;
}
Here's how I do it with contemporary syntax, based on go-oleg's example. Mine is tested and functional.
I put some comments in the code.
./db/mongodb.js
const MongoClient = require('mongodb').MongoClient
const uri = 'mongodb://user:password#localhost:27017/dbName'
let _db
const connectDB = async (callback) => {
try {
MongoClient.connect(uri, (err, db) => {
_db = db
return callback(err)
})
} catch (e) {
throw e
}
}
const getDB = () => _db
const disconnectDB = () => _db.close()
module.exports = { connectDB, getDB, disconnectDB }
./index.js
// Load MongoDB utils
const MongoDB = require('./db/mongodb')
// Load queries & mutations
const Users = require('./users')
// Improve debugging
process.on('unhandledRejection', (reason, p) => {
console.log('Unhandled Rejection at:', p, 'reason:', reason)
})
const seedUser = {
name: 'Bob Alice',
email: 'test#dev.null',
bonusSetting: true
}
// Connect to MongoDB and put server instantiation code inside
// because we start the connection first
MongoDB.connectDB(async (err) => {
if (err) throw err
// Load db & collections
const db = MongoDB.getDB()
const users = db.collection('users')
try {
// Run some sample operations
// and pass users collection into models
const newUser = await Users.createUser(users, seedUser)
const listUsers = await Users.getUsers(users)
const findUser = await Users.findUserById(users, newUser._id)
console.log('CREATE USER')
console.log(newUser)
console.log('GET ALL USERS')
console.log(listUsers)
console.log('FIND USER')
console.log(findUser)
} catch (e) {
throw e
}
const desired = true
if (desired) {
// Use disconnectDB for clean driver disconnect
MongoDB.disconnectDB()
process.exit(0)
}
// Server code anywhere above here inside connectDB()
})
./users/index.js
const ObjectID = require('mongodb').ObjectID
// Notice how the users collection is passed into the models
const createUser = async (users, user) => {
try {
const results = await users.insertOne(user)
return results.ops[0]
} catch (e) {
throw e
}
}
const getUsers = async (users) => {
try {
const results = await users.find().toArray()
return results
} catch (e) {
throw e
}
}
const findUserById = async (users, id) => {
try {
if (!ObjectID.isValid(id)) throw 'Invalid MongoDB ID.'
const results = await users.findOne(ObjectID(id))
return results
} catch (e) {
throw e
}
}
// Export garbage as methods on the Users object
module.exports = { createUser, getUsers, findUserById }
If you are using Express, then you can use mongo-express-req module that allows you to get db connection in request object.
Install
npm install --save mongo-express-req
server.js
var app = require('express')();
var mongoExpressReq = require('mongo-express-req');
app.use(mongoExpressReq('mongodb://localhost/test'));
routes/users.js
app.get('/', function (req, res, next) {
req.db // => Db object
});
Note: mongo-express-req is fork of not maintained express-mongo-db.
A tested solution based on the accepted answer:
mongodbutil.js:
var MongoClient = require( 'mongodb' ).MongoClient;
var _db;
module.exports = {
connectToServer: function( callback ) {
MongoClient.connect( "<connection string>", function( err, client ) {
_db = client.db("<database name>");
return callback( err );
} );
},
getDb: function() {
return _db;
}
};
app.js:
var createError = require('http-errors');
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');
var app = express();
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');
app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
var mongodbutil = require( './mongodbutil' );
mongodbutil.connectToServer( function( err ) {
//app goes online once this callback occurs
var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');
var companiesRouter = require('./routes/companies');
var activitiesRouter = require('./routes/activities');
var registerRouter = require('./routes/register');
app.use('/', indexRouter);
app.use('/users', usersRouter);
app.use('/companies', companiesRouter);
app.use('/activities', activitiesRouter);
app.use('/register', registerRouter);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
next(createError(404));
});
// error handler
app.use(function(err, req, res, next) {
res.locals.message = err.message;
res.locals.error = req.app.get('env') === 'development' ? err : {};
res.status(err.status || 500);
res.render('error');
});
//end of calback
});
module.exports = app;
activities.js -- a route:
var express = require('express');
var router = express.Router();
var mongodbutil = require( '../mongodbutil' );
var db = mongodbutil.getDb();
router.get('/', (req, res, next) => {
db.collection('activities').find().toArray((err, results) => {
if (err) return console.log(err)
res.render('activities', {activities: results, title: "Activities"})
});
});
router.post('/', (req, res) => {
db.collection('activities').save(req.body, (err, result) => {
if (err) return console.log(err)
res.redirect('/activities')
})
});
module.exports = router;
Here is my setup in 2020:
./utils/database.js
const { MongoClient } = require('mongodb');
class Mongo {
constructor () {
this.client = new MongoClient("mongodb://127.0.0.1:27017/my-app", {
useNewUrlParser: true,
useUnifiedTopology: true
});
}
async main () {
await this.client.connect();
console.log('Connected to MongoDB');
this.db = this.client.db();
}
}
module.exports = new Mongo();
/app.js
const mongo = require('./utils/database');
const express = require('express');
const app = express();
const boot = async () => {
await mongo.main();
app.listen(3000);
};
boot();
go-oleg is basically right, but in these days you (probably) dont want use "mongodb" itself, rather use some framework, which will do a lot of "dirty work" for you.
For example, mongoose is one of the most common. This is what we have in our initial server.js file :
const mongoose = require('mongoose');
const options = {server: {socketOptions: {keepAlive: 1}}};
mongoose.connect(config.db, options);
This is everything what is needed to set it up. Now use this anywhere in your code
const mongoose = require('mongoose');
And you get that instance you set up with mongoose.connect
I´m late to the party, but hopefully this answer will help someone, this is a functional code:
db.js
const MongoClient = require("mongodb").MongoClient
const urlMongo = "mongodb://localhost:27017"
var db;
function connectToServer( callback ) {
MongoClient.connect(urlMongo, { useUnifiedTopology: true , useNewUrlParser: true }, function( err, client ) {
db = client.db('auth');
return callback( err );
})
}
function getDb() {
return db
}
module.exports = {connectToServer, getDb}
We export one function to connect to the mongo and another to get de instanceof the connection.
app.js
const express = require('express')
const app = express()
const mongo = require('./db.js');
mongo.connectToServer( function( err) {
if (err) console.log(err);
const auth = require('./modulos')
app.post('/login', (req, res) => { auth.login(req, res)})
app.listen(3000, function () { console.log('Corriendo en puerto 3000')})
});
We must do the require of the auth module after we initiallize the connection, otherwise the getDb function will return undefined.
module.js
const db = require('../db.js').getDb()
const usuariosCollection = db.collection('usuarios')
function login(req, res){
usuariosCollection.find({ 'username': 'Fran' }).toArray(function (err, doc) {
...
})
}
As this is tagged with Express, I thought I would mention that Express has a built in feature to share data between routes. There is an object called app.locals. We can attach properties to it and access it from inside our routes. You simply instantiate your mongo connection in your app.js file.
var app = express();
MongoClient.connect('mongodb://localhost:27017/')
.then(client =>{
const db = client.db('your-db');
const collection = db.collection('your-collection');
app.locals.collection = collection;
});
// view engine setup
app.set('views', path.join(__dirname, 'views'));
This database connection can now be accessed within your routes as below without the need for creating and requiring additional modules.
app.get('/', (req, res) => {
const collection = req.app.locals.collection;
collection.find({}).toArray()
.then(response => res.status(200).json(response))
.catch(error => console.error(error));
});
This method ensures that you have a database connection open for the duration of your app unless you choose to close it at any time. It's easily accessible with req.app.locals.your-collection and doesn't require additional modules.
Initialize the connection as a promise:
const MongoClient = require('mongodb').MongoClient
const uri = 'mongodb://...'
const client = new MongoClient(uri)
const connection = client.connect() // initialized connection
And then call the connection whenever you wish you perform an action on the database:
// if I want to insert into the database...
const connect = connection
connect.then(() => {
const doc = { id: 3 }
const db = client.db('database_name')
const coll = db.collection('collection_name')
coll.insertOne(doc, (err, result) => {
if(err) throw err
})
})
Here's a suggestion using TypeScript and ES6 features and syntax:
db.ts
import { Db, MongoClient } from 'mongodb'
let client: MongoClient
let db: Db
const connectToDatabase = async () => {
client = new MongoClient('databaseURI')
await client.connect()
db = client.db('dbname')
}
export {
connectToDatabase,
client,
db,
}
index.ts
import express from 'express'
import { someRouter } from './routes/someRoute'
import { connectToDatabase } from './db'
connectToDatabase().then(() => {
const app = express()
app.use('/someRoute', someRouter)
const port = process.env.PORT || 5000
app.listen(port, () => {
console.log(`Server is listening on port ${port}`)
})
})
routes/someRoute.ts
import express from 'express'
import { db } from '../db'
const someRouter = express.Router()
someRouter.route('/')
.get(async (req, res) => {
const results = await db.collection('collectionName').find().toArray()
return res.send(results)
})
export {
someRouter,
}
we can create a dbconnection file like dbconnection.js
const MongoClient = require('mongodb').MongoClient
const mongo_url = process.env.MONGO_URL;
module.exports = {
connect: async function(callback) {
var connection;
await new Promise((resolve, reject) => {
MongoClient.connect(mongo_url, {
useNewUrlParser: true
}, (err, database) => {
if (err)
reject();
else {
connection = database;
resolve();
}
});
});
return connection;
}
};
and then use this file in the your app like
var connection = require('../dbconnection');
and then use like this inside your async function
db = await connection.connect();
hope this will work
I find this works well :)
mongoUtil.ts
import { MongoClient } from 'mongodb';
const uri =
'MONGOSTRING';
let connPoolPromise: any = null;
const mongoPoolPromise = () => {
if (connPoolPromise) return connPoolPromise;
connPoolPromise = new Promise((resolve, reject) => {
const conn = new MongoClient(uri, {
useNewUrlParser: true,
useUnifiedTopology: true,
});
if (conn.isConnected()) {
return resolve(conn);
} else {
conn
.connect()
.then(() => {
return resolve(conn.db('DATABASENAME'));
})
.catch(err => {
console.log(err);
reject(err);
});
}
});
return connPoolPromise;
};
export = {
mongoPoolPromise,
};
anyFile.ts
const { mongoPoolPromise } = require('./mongoUtil');
async function getProducts() {
const db = await mongoPoolPromise();
const data = await db
.collection('myCollection')
.find({})
.toArray();
console.log(data);
return data;
}
export { getProducts };
I'm a bit late for this, but I'll add my solution too. It's a much noobier approach compared to the answers here.
Anyway if you are using MongoDB version 4.0 and Node.js 3.0 (or higher versions) you can use isConnected() function from the MongoClient.
const MongoClient = require('mongodb').MongoClient;
const uri = "<your connection url>";
const client = new MongoClient(uri, { useNewUrlParser: true });
if (client.isConnected()) {
execute();
} else {
client.connect().then(function () {
execute();
});
}
function execute() {
// Do anything here
// Ex: client.db("mydb").collection("mycol");
}
This worked fine for me. Hope it helps.
Based on accepted answers, I use a simple approach. But use this only if you want to use db inside function which will be executed after some time. For ex: In express route functions, it is the easiest approach you can take.
mongo.js
const MongoClient = require("mongodb").MongoClient
var db
const connectDb = (callback) => {
if (db) return callback()
MongoClient.connect( uri, {ops},
(err, database) => {
if (err) return console.log(err)
db = database.db("dbName")
console.log("Database Connected")
callback()
}
)
}
const getDb = (collectionToGet) => {
return db.collection(collectionToGet)
}
module.exports = {
connectDb,
getDb,
}
Now, in other files where you want the db object,
user.js
const { connectDb, getDb } = require('mongo.js')
var db // store db object in this object
connectDb(() => ( db = getDb("user") ))
app.get('/', (req, res) => {
// do something with req
db.insert({})
// do something with res
}
If you opt for using mongoose in your application edit your app.js file with the following snippet
app.js
const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/Your_Data_Base_Name', {useNewUrlParser:true})
.then((res) => {
console.log(' ########### Connected to mongDB ###########');
})
.catch((err) => {
console.log('Error in connecting to mongoDb' + err);
});`
Next Step:
Define Models for your application require them and perform CRUD operation directly for example
blogSchema.js
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const blogSchema = new Schema({
_id : mongoose.Schema.Types.ObjectId,
title : {
type : 'String',
unique : true,
required : true
},
description : String,
comments : [{type : mongoose.Schema.Types.ObjectId, ref: 'Comment'}]
});
module.exports = mongoose.model('Blog', blogSchema);
Usage
createBlog.js
const Blog = require('../models/blogSchema');
exports.createBlog = (req, res, next) => {
const blog = new Blog({
_id : new mongoose.Types.ObjectId,
title : req.body.title,
description : req.body.description,
});
blog.save((err, blog) => {
if(err){
console.log('Server Error save fun failed');
res.status(500).json({
msg : "Error occured on server side",
err : err
})
}else{
//do something....
}
U don't need to connect to mogoDB always ....
var MongoClient = require('mongodb').MongoClient;
var url = 'mongodb://localhost:27017/';
var Pro1;
module.exports = {
DBConnection:async function()
{
Pro1 = new Promise(async function(resolve,reject){
MongoClient.connect(url, { useNewUrlParser: true },function(err, db) {
if (err) throw err;
resolve(db);
});
});
},
getDB:async function(Blockchain , Context)
{
bc = Blockchain;
contx = Context;
Pro1.then(function(_db)
{
var dbo = _db.db('dbname');
dbo.collection('collectionname').find().limit(1).skip(0).toArray(function(err,result) {
if (err) throw err;
console.log(result);
});
});
},
closeDB:async function()
{
Pro1.then(function(_db){
_db.close();
});
}
};
const express = require('express')
const server = express()
const mongoClient = require('./MongoDB.js').client
const port = 3000
;(async () => {
await mongoClient.connect()
server.listen(port, () => console.log(`Server is listening on port ${port}!`))
})().catch(console.error)
You can use the Singleton Design Pattern to achive cross file usage of your MongoDB connection.
Init.mjs
/* ################ Controller ################ */
import ctrlLib from '../../controller/lib.mjs';
/* ################ MongoDB ################ */
import mongodb from 'mongodb';
/* ################ Logs ################ */
import log from 'fancy-log';
import chalk from 'chalk';
/** Init MongoDB connection */
export class Init {
/**
* Check if its first time usage of this class.
If true set class instance to this that we always get same instance.
* Then get MongoDB details from config.yml and set as global.
* In the last step we return the class instance.
*/
constructor() {
if (Init.instance == null) Init.instance = this;
const config = ctrlLib.getConfig();
this.MongoURL = config.MongoDB.url;
this.MongoName = config.MongoDB.dbname;
({MongoClient: this.MongoClient} = mongodb);
return Init.instance;
}; // constructor(){
/** Connect to Database and return connection */
async connect() {
try {
const client = await this.MongoClient.connect(
this.MongoURL, {useNewUrlParser: true, useUnifiedTopology: true},
);
this.connection = {'db': client.db(this.MongoName), 'client': client};
return this.connection;
} // try {
catch (e) {
log( `${chalk.red.bold('❌ ERROR')} while try to connect to MongoDB DB
${chalk.white.bold('Error:\n')} ${e}` );
} // catch (e) {
}; // async connect() {
/**
* Return connection for cross file usage
* #return {object}
*/
getConnection() {return this.connection;};
}; // export class Init {
app.mjs
Make sure to 1x time create your MongoDB connection anywhere inside of your project that you can use it later in other files.
/* ################ Services ################ */
import {Init} from './Init.mjs';
(async ()=>{
await new Init().connect();
})().catch(e=>{log('app.mjs - Catch error: ' + e);});
anyOtherFile.mjs
/* ################ Services ################ */
import {Init} from './Init.mjs';
/** Subclass of Search which contains lib functions */
class Lib {
/**
* Find data by using search query and return result.
* #param {string} collection - Name of collection
* #param {object} query - Search query
*/
async findOne(collection, query) {
const connection = new Init().getConnection();
return await connection.db.collection(collection).findOne(query);
}; // async findOne() {
}; // class Lib {
Updated for 2022 MongoClient new updates
MongoUtil.js (For database connection and return database instance)
const { MongoClient } = require('mongodb');
const uri = "your database connection url";
var _db;
module.exports = {
connectToServer: function (callback) {
MongoClient.connect(uri, { useNewUrlParser: true }, function (err, client) {
_db = client.db('testdb');
return callback(err);
});
},
getDb: function () { //this returns database instance
return _db;
}
};
app.js (You can use in any routes or js by importing mongoUtil)
var mongoUtil = require('./mongoUtil');
mongoUtil.connectToServer(function (err, client) {
if (err) console.log(err);
console.log(`server is running`);
insertData(); //or do functions and db queries in any js
});
async function insertData() { //Functions should be async
var database = mongoUtil.getDb();
var movies = database.collection('movies');
const doc = {
title: "Movie title",
content: "Movie content",
}
const result = await movies.insertOne(doc);
console.log(`A document was inserted with the _id: ${result.insertedId}`);
}
I tried #go-oleg answer and it works pretty well. Inside getDb() , I make sure _db must be defined. And if not defined, I call the connectToServer() so that it will get defined again. After this I don't have to call connectToServer() in the app.js which makes my code clean.
let getDb = async() => {
if(_db) {
return _db
} else {
_db = await connectToServer()
return _db
}
}
And then, I simply call getDb() everywhere. Also, What I observed, It takes about 64ms on first call. After first call it takes about, 2-6ms everytime.
I answered here because i have less reputation to comment.
all after long effort my working by this operational method:
Please follow this link this is also good solution:
https://mrvautin.com/re-use-mongodb-database-connection-in-routes/
Folks, in 2022 there is no need for reconnection logic, the Node.js MongoDB driver handles this all for you (v4+).
You can simply connect as described in the official docs. Put this in a db.js file, then you can import client or db anywhere in your app:
import { MongoClient, ServerApiVersion } from 'mongodb'
const uri = `mongodb+srv://...`;
// Create a new MongoClient
export const client = new MongoClient(uri, { useNewUrlParser: true, useUnifiedTopology: true, serverApi: ServerApiVersion.v1 });
export const db = client.db('your_db');
When making queries, use try/catch to capture potential connection errors.
try {
const res = await db.collection("testdata").insertOne({test: Math.random()});
console.log('Inserted', res);
} catch(e) {
console.error('MONGO ERROR', e);
}
AFAIK, the Mongo driver will keep retrying forever if the connection is lost.
Try it yourself: put the above code in a setInterval and turn off your internet connection for a while then turn it back on, Mongo will automatically reconnect, even after hours of downtime. It will even submit some queries that were made while the connection was down.
Updated for 2023
MongoDB Connection
const { MongoClient, ServerApiVersion } = require('mongodb');
const dbconfig = require('./config');
module.exports = {
client: client = new MongoClient(dbconfig.uri, { useNewUrlParser: true, useUnifiedTopology: true, serverApi: ServerApiVersion.v1 }),
connectToDB: async () => {
try {
await client.connect()
console.log('connected!')
} catch (err) {
console.log('Err', err)
}
}
}
In your controller
const db = require('../config/mongodb.connection')
const hha_data = db.client.db('hha-sit').collection('hnh-data')
exports.addNewCustomer = async (req, res) => {
try {
await db.connectToDB()
let result = await hha_data.findOne({}, { account_id: 'MDB829001337' })
console.log('result', result)
} catch (err) {
console.error('Connection Error !', err)
} finally {
await db.client.close()
}
res.send('Hi')
}
Please feel free to revise it if you have any suggestions. :)
This approach is correct, and it can be improved in the following ways:
1.Wrap the MongoClient connect function inside a module and export it as a singleton object to be used across your application. This way, you can make sure only one connection is established to the MongoDB server and is reused across your modules.
2.Add error handling to your code to handle potential issues like a connection failure.
3.Use the MongoDB native driver's connection pooling feature instead of maintaining a single connection throughout the application's lifetime, as this can lead to resource exhaustion and poor performance.
This is an example of a improved implementation:
const MongoClient = require('mongodb').MongoClient;
let _db;
const connectToDb = async (url) => {
if (db) return db;
let client;
try {
client = await MongoClient.connect(url, {
useNewUrlParser: true,
useUnifiedTopology: true
});
_db = client.db();
} catch (err) {
console.error('Error connecting to MongoDB: ', err);
process.exit(1);
}
return _db;
};
module.exports = connectToDb;
const connectToDb = require('./db');
const userModule = async (app) => {
const db = await connectToDb('mongodb://localhost:27017/marankings');
return {
addUser: () => console.log('add user'),
getAll: () => 'all users'
};
};
module.exports = userModule;
const userModule = require('./userModule');
(async () => {
const users = await userModule();
console.log(users.getAll());
})();
I have an API endpoint in my Node/Express app. The endpoint is responsible to upload files. There are several stages involved in the upload process. like image conversion, sending images to another third party API, etc. I am using socket.io to tell the client about the current stage of upload.
The problem is, The socket connection works fine in the first call, but in my second call to the endpoint, the socket connection runs twice and retains the data which I sent in the previous call.
Here's my code:
server.js
import ClientsRouter from './api/routes/clients';
import express from 'express';
import http from 'http';
import io from 'socket.io';
const port = process.env.PORT || 3000;
const app = express();
const server = http.Server(app);
const socket = io(server);
app.set('socket', socket);
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());
app.set('view engine', 'ejs');
app.use(express.static('dist'))
app.use('/uploads', express.static('uploads'));
app.use('/api/clients', ClientsRouter);
server.listen(port, () => console.log(`Server Listening on ${process.env.URL}`));
api/routes/clients.js
import express from 'express';
import ClientsController from '../controllers/clients';
ClientsRouter.post('/uploadClientData/', clientDataUpload.array('client_data'), ClientsController.uploadClientData);
controllers/clients.js
const uploadClientData = async (req, res) => {
try {
const files = req.files
const clientFolder = req.body.client_folder
const { dbxUser } = req;
const team_member_id = req.body.team_member_id;
const data = req.files.map( i => ({team_member_id, destination: i.destination.substring(1), filename: i.filename, status: 1 } ))
const io = req.app.get("socket");
console.log("Outside Socket", data); //This contains my currently passed data
io.on('connection', async socket => {
console.log("Socket Connection established");
console.log("Inside Socket", data); //But This contains my current data aling with the data that I passed in previous call
await uploadQueue.collection.insertMany(data)
socket.emit('upload stage', { upload_stage: 2, progress: 33 })
await helpers.convertImagesToWebResolution(team_member_id, req.body.dpi, req.body.resolution);
socket.emit('upload stage', { upload_stage: 3, progress: 66 })
await helpers.uploadImagesToDropbox(team_member_id, dbxUser, clientFolder)
socket.emit('upload stage', { upload_stage: 4, progress: 100 })
})
res.status(200).json({message: "Uploaded"});
} catch (error) {
console.log(error)
res.status(500).json({
error
});
}
}
And in my front-end react component
componentDidMount(){
const { currentFolder } = this.props;
this.setState({ client_folder: currentFolder }, () => this.afterFileSelect())
}
componentDidUpdate(prevProps){
const { selectedFiles } = this.props;
if(prevProps.selectedFiles !== selectedFiles){
this.afterFileSelect()
}
}
afterFileSelect = async () => {
const { selectedFiles, setSelectedFiles, currentFolder, user, uploadSettings} = this.props;
let formData = new FormData()
formData.append('client_folder', currentFolder)
formData.append('team_member_id', user.team_member_id)
formData.append('resolution', uploadSettings.resolution.split("x")[0])
formData.append('dpi', uploadSettings.dpi)
for(let selectedFile of selectedFiles){
formData.append('client_data', selectedFile)
}
let uploadResp = uploadSettings.convert_web_res ? await uploadClientData(formData) : await dropboxDirectUpload(formData)
const endpoint = uploadResp.config.url;
const host = endpoint.substring(0, endpoint.indexOf("api"));
const socket = socketIOClient(host);
socket.on("upload stage", data => {
this.setState({upload_stage: data.upload_stage, progress: data.progress})
data.upload_stage === 4 && this.setState({client_folder: ""})
})
}
Also I want to know if this is the correct way to to track upload progress?