I've been trying to connect my application to my database, but it has not been possible. I've tried this below, and it still did not recognize my models
const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
// Connection URL
const url = process.env.MONGODB_URL;
// Database Name
const dbName = 'KaydeeAcedemy';
// Use connect method to connect to the server
MongoClient.connect(url, { useNewUrlParser: true, useUnifiedTopology: true }, function(err, client) {
assert.equal(null, err);
console.log("Connected successfully to server");
const db = client.db(dbName);
client.close();
});
I've also tried using this connection string, yet no headway.
const { MongoClient } = require('mongodb');
const uri = process.env.MONGODB_URL;
const client = new MongoClient(uri, { useNewUrlParser: true, useUnifiedTopology: true });
client.connect(err => {
const collection = client.db("test").collection("devices");
// perform actions on the collection object
client.close();
});
when I try to add a new user from my application, i get this error as a result of the database.
Operation `users.findOne()` buffering timed out after 10000ms
the mongodb url looks like this:
MONGODB_URL = mongodb+srv://Kaydeeacademy:**************#cluster0.ehclf.mongodb.net/KaydeeAcademy?retryWrites=true&w=majority
I don't know if I missed something in the connection string or somewhere.
Can you test/compare out some of my code (working)
// have you called in the dot.env file?
require('dotenv').config()
const express = require('express')
const mongoose = require('mongoose')
// don't include the "useNewUrlParser: true, useUnifiedTopology: true" see answer below:
// https://stackoverflow.com/questions/68915722/option-usefindandmodify-is-not-supported
// make sure there are no spaces in the dot.env file
mongoose.connect(process.env.MONGO_URI)
.then(() => console.log("db connected!"))
.catch(err => console.error("db connection failed ", err))
Im trying to connect mongodb in node.js and take the link to client to the outer variable.
I need to create a module that would return a result of .find() method. How can i do this?
const MongoClient = require('mongodb').MongoClient
let client
mongoClient = new MongoClient('mongodb://localhost:27017/', {useUnifiedTopology: true, useNewUrlParser: true})
mongoClient.connect((err, db) => {
if (err) {
return console.log(err)
}
client = db
})
const database = client.db('db')
const collection = database.collection('collection')
client.close()
And the error
const database = client.db('db')
^
TypeError: Cannot read property 'db' of undefined
As the comment suggests, you can use async/await to wait for the connection to be established, and do the error handling with a try/catch statement:
try {
const client = await mongoClient.connect()
const database = client.db('db')
const collection = database.collection('collection')
} catch(e) {
console.log(e)
}
Don't forget to use it in an async function.
Update
An async function example, you may want to return the collection:
const getData = async () => {
try {
mongoClient = new MongoClient('mongodb://localhost:27017/', {useUnifiedTopology: true, useNewUrlParser: true})
const client = await mongoClient.connect()
const database = client.db('db')
const collection = database.collection('collection')
client.close()
return collection
} catch(e) {
console.log(e)
}
}
after uri you must define db name
mongoClient = new MongoClient('mongodb://localhost:27017/', {useUnifiedTopology: true, useNewUrlParser: true})
like this
mongoClient = new MongoClient('mongodb://localhost:27017/shop', {useUnifiedTopology: true, useNewUrlParser: true})
I'm new to MongoDB and Node. I have connected to Mongo using below
const mongoose = require("mongoose")
mongoose.connect('mongodb://localhost/testaroo', {
useNewUrlParser: true
})
mongoose.connection.once('open', function() {
console.log("Connection has been made ..")
}).on('error', function(error) {
console.log("Connection error", error)
});
And I created the below model
const mongoose = require('mongoose')
const schema = mongoose.Schema;
const marioCharSchema = new schema({
name: String, // Optional
weight: Number // Optional
})
const marioCharModel = mongoose.model('mariochar', marioCharSchema);
module.exports = marioCharModel;
EDIT
Inserting Data
const assert = require('assert');
const mariochar = require('../test/models/mariochar')
// Describe tests
describe('Saving records', function () {
//Create tests
it("Saving records to database", function (done) {
const char = new mariochar({
name = "Test",
weight: 45
});
char.save().then(
function () {
assert(char.isNew === false)
done();
}
)
})
})
And I tried to save a new record to this model and I tested it using mocha and it saved successfully. Now I want to view my database and my records using Mongo compass.
I tried to connect to mongodb://localhost/testaroo on port 27017
but I couldn't see my database. So what I'm missing here?
FIXED
For future viewers I fixed it by passing this option useUnifiedTopology: true to the to the MongoClient constructor
mongoose.connect('mongodb://localhost/Mydb', { useNewUrlParser: true, useUnifiedTopology: true })
Use mongo shell to insert and retrieve documents from the database, verify this works.
Use compass to view documents you inserted via the shell, verify this works.
Insert documents in your application and retrieve them via the shell, verify this works.
At this point whatever issue you have between your application and compass should be resolved.
[nodemon] starting node server.js
C:\Users\Abhay\Desktop\todo-app\node_modules\mongodb\lib\utils.js:725
throw error;
^
TypeError: Cannot read property 'db' of undefined
at C:\Users\Abhay\Desktop\todo-app\server.js:8:17
at C:\Users\Abhay\Desktop\todo-app\node_modules\mongodb\lib\utils.js:722:9
at C:\Users\Abhay\Desktop\todo-app\node_modules\mongodb\lib\mongo_client.js:223:23
at C:\Users\Abhay\Desktop\todo-app\node_modules\mongodb\lib\operations\connect.js:279:21
at QueryReqWrap.callback (C:\Users\Abhay\Desktop\todo-app\node_modules\mongodb\lib\core\uri_parser.js:56:21)
at QueryReqWrap.onresolve [as oncomplete] (dns.js:202:10)
[nodemon] app crashed - waiting for file changes before starting...
let express = require('express')
let mongodb = require('mongodb')
let app = express()
let db
let connectionString = 'mongodb+srv://todoAppUser:kTL7PYesKzfB6FMz#cluster0.fif5n.mongodb.net/TodoApp?retryWrites=true&w=majority'
mongodb.connect(connectionString, {useNewUrlParser: true, useUnifiedTopology: true}, function(err, client) {
db = client.db()
app.listen(3000)
})
It seems you're trying to use the static connect method of MongoClient to make a connection to your db, but you are not using the MongoClient class itself.
To connect to any db, you will need a connected instance of MongoClient. Using the static connect method, you can achieve it in the following way:
const mongodb = require("mongodb");
const connectionURL = "mongodb+srv://your-connection-srv-here"
const dbName = "your_db_name"
//get MongoClient
const MongoClient = mongodb.MongoClient;
let db = null;
MongoClient.connect(connectionURL,{
useNewUrlParser: true,
useUnifiedTopology: true
},(err,connectedClient) => {
if(err){
throw err;
}
//connectedClient will be the connected instance of MongoClient
db = connectedClient.db(dbName);
//now you can write queries
db.collection("your_collection").find({}).toArray()
.then(r => {
console.log(r);
}).catch(e => {
console.error(`ERROR:`,e);
})
})
However, using callbacks will be quite cumbersome. As per the docs linked above, most functions in the MongoDb driver for Node.js will return a promise if a callback function is not passed, which is very convenient. Using this, you can write a function which return a promise that resolves a connected instance to your db.
const MongoClient = require('mongodb').MongoClient;
/*
we draw the connection srv and the db name from the config to return just one instance of that db.
Now this function call be called wherever a connection is needed
*/
const getDbInstance = (config) => new Promise((resolve,reject) => {
const client = new MongoClient(config.dbUrl, {
useNewUrlParser: true,
useUnifiedTopology: true
});
client.connect((error) => {
if(error){
console.error(error);
reject(error);
}
let db = client.db(config.dbName);
resolve(db);
})
})
const doSomeDbOperations = async() => {
//hardcoding it here, but this config will probably come from environment variables in your project
const config = {
dbUrl: "mongodb+srv://your-connection-srv-here",
dbName: "your_db_name"
};
try{
const db = await getDbInstance(config);
//do whatever querying you wish here
}catch(e){
console.error(`ERROR: `,e);
}
}
doSomeDbOperations();
I'm using the node-mongodb-native driver with MongoDB to write a website.
I have some questions about how to manage connections:
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?
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?
Should I use a global connection pool? I hear the driver has a native connection pool. Is it a good choice?
If I use a connection pool, how many connections should be used?
Are there other things I should notice?
The primary committer to node-mongodb-native says:
You open do MongoClient.connect once when your app boots up and reuse
the db object. It's not a singleton connection pool each .connect
creates a new connection pool.
So, to answer your question directly, reuse the db object that results from MongoClient.connect(). This gives you pooling, and will provide a noticeable speed increase as compared with opening/closing connections on each db action.
Open a new connection when the Node.js application starts, and reuse the existing db connection object:
/server.js
import express from 'express';
import Promise from 'bluebird';
import logger from 'winston';
import { MongoClient } from 'mongodb';
import config from './config';
import usersRestApi from './api/users';
const app = express();
app.use('/api/users', usersRestApi);
app.get('/', (req, res) => {
res.send('Hello World');
});
// Create a MongoDB connection pool and start the application
// after the database connection is ready
MongoClient.connect(config.database.url, { promiseLibrary: Promise }, (err, db) => {
if (err) {
logger.warn(`Failed to connect to the database. ${err.stack}`);
}
app.locals.db = db;
app.listen(config.port, () => {
logger.info(`Node.js app is listening at http://localhost:${config.port}`);
});
});
/api/users.js
import { Router } from 'express';
import { ObjectID } from 'mongodb';
const router = new Router();
router.get('/:id', async (req, res, next) => {
try {
const db = req.app.locals.db;
const id = new ObjectID(req.params.id);
const user = await db.collection('user').findOne({ _id: id }, {
email: 1,
firstName: 1,
lastName: 1
});
if (user) {
user.id = req.params.id;
res.send(user);
} else {
res.sendStatus(404);
}
} catch (err) {
next(err);
}
});
export default router;
Source: How to Open Database Connections in a Node.js/Express App
Here is some code that will manage your MongoDB connections.
var MongoClient = require('mongodb').MongoClient;
var url = require("../config.json")["MongoDBURL"]
var option = {
db:{
numberOfRetries : 5
},
server: {
auto_reconnect: true,
poolSize : 40,
socketOptions: {
connectTimeoutMS: 500
}
},
replSet: {},
mongos: {}
};
function MongoPool(){}
var p_db;
function initPool(cb){
MongoClient.connect(url, option, function(err, db) {
if (err) throw err;
p_db = db;
if(cb && typeof(cb) == 'function')
cb(p_db);
});
return MongoPool;
}
MongoPool.initPool = initPool;
function getInstance(cb){
if(!p_db){
initPool(cb)
}
else{
if(cb && typeof(cb) == 'function')
cb(p_db);
}
}
MongoPool.getInstance = getInstance;
module.exports = MongoPool;
When you start the server, call initPool
require("mongo-pool").initPool();
Then in any other module you can do the following:
var MongoPool = require("mongo-pool");
MongoPool.getInstance(function (db){
// Query your MongoDB database.
});
This is based on MongoDB documentation. Take a look at it.
Manage mongo connection pools in a single self contained module. This approach provides two benefits. Firstly it keeps your code modular and easier to test. Secondly your not forced to mix your database connection up in your request object which is NOT the place for a database connection object. (Given the nature of JavaScript I would consider it highly dangerous to mix in anything to an object constructed by library code). So with that you only need to Consider a module that exports two methods. connect = () => Promise and get = () => dbConnectionObject.
With such a module you can firstly connect to the database
// runs in boot.js or what ever file your application starts with
const db = require('./myAwesomeDbModule');
db.connect()
.then(() => console.log('database connected'))
.then(() => bootMyApplication())
.catch((e) => {
console.error(e);
// Always hard exit on a database connection error
process.exit(1);
});
When in flight your app can simply call get() when it needs a DB connection.
const db = require('./myAwesomeDbModule');
db.get().find(...)... // I have excluded code here to keep the example simple
If you set up your db module in the same way as the following not only will you have a way to ensure that your application will not boot unless you have a database connection you also have a global way of accessing your database connection pool that will error if you have not got a connection.
// myAwesomeDbModule.js
let connection = null;
module.exports.connect = () => new Promise((resolve, reject) => {
MongoClient.connect(url, option, function(err, db) {
if (err) { reject(err); return; };
resolve(db);
connection = db;
});
});
module.exports.get = () => {
if(!connection) {
throw new Error('Call connect first!');
}
return connection;
}
If you have Express.js, you can use express-mongo-db for caching and sharing the MongoDB connection between requests without a pool (since the accepted answer says it is the right way to share the connection).
If not - you can look at its source code and use it in another framework.
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
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
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");
});
If using express there is another more straightforward method, which is to utilise Express's built in feature to share data between routes and modules within your app. There is an object called app.locals. We can attach properties to it and access it from inside our routes. To use it, 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, or indeed any other data you wish to share around the modules of you app can now be accessed within your routes with req.app.locals 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 creation of any additional modules.
Best approach to implement connection pooling is you should create one global array variable which hold db name with connection object returned by MongoClient and then reuse that connection whenever you need to contact Database.
In your Server.js define var global.dbconnections = [];
Create a Service naming connectionService.js. It will have 2 methods getConnection and createConnection.
So when user will call getConnection(), it will find detail in global connection variable and return connection details if already exists else it will call createConnection() and return connection Details.
Call this service using <db_name> and it will return connection object if it already have else it will create new connection and return it to you.
Hope it helps :)
Here is the connectionService.js code:
var mongo = require('mongoskin');
var mongodb = require('mongodb');
var Q = require('q');
var service = {};
service.getConnection = getConnection ;
module.exports = service;
function getConnection(appDB){
var deferred = Q.defer();
var connectionDetails=global.dbconnections.find(item=>item.appDB==appDB)
if(connectionDetails){deferred.resolve(connectionDetails.connection);
}else{createConnection(appDB).then(function(connectionDetails){
deferred.resolve(connectionDetails);})
}
return deferred.promise;
}
function createConnection(appDB){
var deferred = Q.defer();
mongodb.MongoClient.connect(connectionServer + appDB, (err,database)=>
{
if(err) deferred.reject(err.name + ': ' + err.message);
global.dbconnections.push({appDB: appDB, connection: database});
deferred.resolve(database);
})
return deferred.promise;
}
In case anyone wants something that works in 2021 with Typescript, here's what I'm using:
import { MongoClient, Collection } from "mongodb";
const FILE_DB_HOST = process.env.FILE_DB_HOST as string;
const FILE_DB_DATABASE = process.env.FILE_DB_DATABASE as string;
const FILES_COLLECTION = process.env.FILES_COLLECTION as string;
if (!FILE_DB_HOST || !FILE_DB_DATABASE || !FILES_COLLECTION) {
throw "Missing FILE_DB_HOST, FILE_DB_DATABASE, or FILES_COLLECTION environment variables.";
}
const client = new MongoClient(FILE_DB_HOST, {
useNewUrlParser: true,
useUnifiedTopology: true,
});
class Mongoose {
static FilesCollection: Collection;
static async init() {
const connection = await client.connect();
const FileDB = connection.db(FILE_DB_DATABASE);
Mongoose.FilesCollection = FileDB.collection(FILES_COLLECTION);
}
}
Mongoose.init();
export default Mongoose;
I believe if a request occurs too soon (before Mongo.init() has time to finish), an error will be thrown, since Mongoose.FilesCollection will be undefined.
import { Request, Response, NextFunction } from "express";
import Mongoose from "../../mongoose";
export default async function GetFile(req: Request, res: Response, next: NextFunction) {
const files = Mongoose.FilesCollection;
const file = await files.findOne({ fileName: "hello" });
res.send(file);
}
For example, if you call files.findOne({ ... }) and Mongoose.FilesCollection is undefined, then you will get an error.
npm i express mongoose
mongodb.js
const express = require('express');
const mongoose =require('mongoose')
const app = express();
mongoose.set('strictQuery', true);
mongoose.connect('mongodb://localhost:27017/db_name', {
useNewUrlParser: true,
useUnifiedTopology: true
})
.then(() => console.log('MongoDB Connected...'))
.catch((err) => console.log(err))
app.listen(3000,()=>{ console.log("Started on port 3000 !!!") })
node mongodb.js
Using below method you can easily manage as many as possible connection
var mongoose = require('mongoose');
//Set up default mongoose connection
const bankDB = ()=>{
return mongoose.createConnection('mongodb+srv://<username>:<passwprd>#mydemo.jk4nr.mongodb.net/<database>?retryWrites=true&w=majority',options);
}
bankDB().then(()=>console.log('Connected to mongoDB-Atlas bankApp...'))
.catch((err)=>console.error('Could not connected to mongoDB',err));
//Set up second mongoose connection
const myDB = ()=>{
return mongoose.createConnection('mongodb+srv://<username>:<password>#mydemo.jk4nr.mongodb.net/<database>?retryWrites=true&w=majority',options);
}
myDB().then(()=>console.log('Connected to mongoDB-Atlas connection 2...'))
.catch((err)=>console.error('Could not connected to mongoDB',err));
module.exports = { bankDB(), myDB() };