I'm just starting to use Mongodb without mongoose (to get away from the schemas), and wanted to create a simple module with various exported functions to use in the rest of my app. I've pasted the code below.
The problem I'm having is that the databasesList.databases comes back as undefined, and I'm not sure why. There should be 2 databases on my cluster, and one collection in each database.
As a tangential question, I thought maybe I would check the collections instead (now commented out), but though I found this page (https://docs.mongodb.com/manual/reference/method/db.getCollectionNames/) the function getCollectionNames seems not to exist. Now I'm wondering if I'm using the wrong documentation and that is why my databases are coming back undefined.
const client = new MongoClient(uri)
const connection = client.connect( function (err, database) {
if (err) throw err;
else if (!database) console.log('Unknown error connecting to database');
else {
console.log('Connected to MongoDB database server');
}
});
module.exports = {
getDatabaseList: function() {
console.log('start ' + client);
databasesList = client.db().admin().listDatabases();
//collectionList = client.db().getCollectionNames();
//console.log("Collections: " + collectionList);
console.log("Databases: " + databasesList.databases);
//databasesList.databases.forEach(db => console.log(` - ${db.name}`));
}
}```
your code is correct Just need to change few things.
module.exports = {
getDatabaseList: async function() {
console.log('start ' + client);
databasesList = await client.db().admin().listDatabases();
//collectionList = await client.db().getCollectionNames();
//console.log("Collections: " + collectionList);
console.log("Databases: " + databasesList.databases);
databasesList.databases.forEach(db => console.log(` - ${db.name}`));
}
}
You have to declare async function and use await also.
The async and await keywords enable asynchronous, promise-based behaviour to be written in a cleaner style, avoiding the need to explicitly configure promise chains.
You can use this modular approach to build your database access code:
index.js: Run your database application code, like list database names, collection names and read from a collection.
const connect = require('./database');
const dbFunctions = require('./dbFunctions');
const start = async function() {
const connection = await connect();
console.log('Connected...');
const dbNames = await dbFunctions.getDbNames(connection);
console.log(await dbNames.databases.map(e => e.name));
const colls = await dbFunctions.getCollNames(connection, 'test');
console.log(await colls.map(e => e.name));
console.log(await dbFunctions.getDocs(connection, 'test', 'test'));
};
start();
database.js:: Create a connection object. This connection is used for all your database access code. In general, a single connection creates a connection pool and this can be used throughout a small application
const { MongoClient } = require('mongodb');
const url = 'mongodb://localhost:27017/';
const opts = { useUnifiedTopology: true };
async function connect() {
console.log('Connecting to db server...');
return await MongoClient.connect(url, opts );
}
module.exports = connect;
dbFunctions.js:: Various functions to access database details, collection details and query a specific collection.
module.exports = {
// return list of database names
getDbNames: async function(conn) {
return await conn.db().admin().listDatabases( { nameOnly: true } );
},
// return collections list as an array for a given database
getCollNames: async function(conn, db) {
return await conn.db(db).listCollections().toArray();
},
// return documents as an array for a given database and collection
getDocs: async function(conn, db, coll) {
return await conn.db(db).collection(coll).find().toArray();
}
}
I'm using shortid package to shorten my URLs.
Currently, user have this kind of url: https://bucard.co.il/digitalCard/5edd4112eb6ba017d8a4595c (the long string is the _id),
and I want to make it like this: https://bucard.co.il/digitalCard/Y2i1_53Vc
So, I added ShortID field, and as in the documantion, I did this in models/VisitCard.js:
const mongoose = require('mongoose');
const shortid = require('shortid');
const VisitCardsSchema = mongoose.Schema({
ShortID: {
type: String,
default: shortid.generate
},
....
});
module.exports = mongoose.model('VisitCards', VisitCardsSchema);
And my get request in routes/VisitCard.js:
// Get a specific visit card
router.get('/:visitCardId', async (req, res) => {
try {
let cardShortId = req.params.visitCardId;
let allVisitCards = await VisitCard.find({}); // That's how I saw that all the values changed after every get request.
let visitCard = await VisitCard.findOne({ ShortID: cardShortId }); // Never found the card by the short id - even after coping the short id from above, after the next try it changes.
if (!visitCard) {
return res.status(404).json({
message: 'Not existing card.'
});
} else {
return res.status(200).json(visitCard);
}
} catch (error) {
console.log(error);
return res.status(404).json({
message: 'Some server issue accured...'
});
}
});
Now, the proplem is where after every refresh of the browser or another get request, all the ShortID's of all cards are changing (generated again). I want instead that the short url will not be refreshes after every restart of the server, and it will be stored in the Database.
How can I do that after each card gets it's shortID (by default) it will directlly be stored in the DB ?
By the way, I could just have that after every submits of visit card to put some random string to be stored with the other paramters, but I already have visit cards of users in my service.
THANK YOU !!!
Tried reproducing your issue:
const mongoose = require("mongoose");
const shortid = require("shortid");
mongoose.connect("mongodb://localhost/test9999", {
useNewUrlParser: true
});
const db = mongoose.connection;
db.on("error", console.error.bind(console, "connection error:"));
db.once("open", async function() {
await mongoose.connection.db.dropDatabase();
// we're connected!
console.log("Connected");
const VisitCardsSchema = mongoose.Schema({
name: String,
ShortID: {
type: String,
default: shortid.generate
}
});
const VisitCard = mongoose.model("VisitCard", VisitCardsSchema);
const v1 = new VisitCard({name: "abc"});
const v2 = new VisitCard({name: "cde"});
await v1.save();
await v2.save();
await VisitCard.find(function(err, vcs) {
if (err) return console.error(err);
console.log(vcs);
});
console.log("VCS second call:");
await VisitCard.find(function(err, vcs) {
if (err) return console.error(err);
console.log(vcs);
});
});
Apparently, it works perfectly fine. I even commented part with dropping db for a moment and values are persisted correctly.
The problem must be somewhere else - you sure you do not drop the db or the collection with each GET request somewhere else in the code?
This one: await mongoose.connection.db.dropDatabase(); drops entire db, mongooseconnection.connection.db.dropCollection drops a collection. Check if you can find such lines somewhere in your code.
I couldn't find an answer pertaining to my problem.
Here's my db.js
// for mongoDB connection
const mongoose = require("mongoose");
// require the directory
const config = require("config");
// get all contents of JSON file
const db = config.get("mongoURI");
const connectDb = async () => {
try {
// outputs correct string with correct credentials, as seen in Mongodb
console.log(db);
// hangs here
await mongoose.connect(db, {
useNewUrlParser: true,
useCreateIndex: true,
useFindAndModify: false
});
// never reached
console.log("Mongo DB connected");
} catch (err) {
// never reached either, no error is thrown
console.log(err.message);
//exit if failure
process.exit(1);
}
};
module.exports = connectDb;
I've added allow access from anywhere as a whitelist option for IPs on Atlas MongoDB.
I've created new clusters to verify that nothing was corrupted somehow on MongoDB.
It was working literally just two days ago, now it just simply isn't.
All packages are up to date, as well as Node and npm itself
MongoDB connected is never printed.
I've tested on different networks.
Not sure where to go from here.
I´m developing a rest full api with node and exrpess, my database is postgresql, I need to use the postgres package pg-promise.
I know that I need to connect my app with the database in the app.js file, but my question is, How I should use this connection in my endpoints.
I have routes and I am using controllers.
For example
app.js
//in this file, suppously I have to to the connection
const db = pgp('postgres://john:pass123#localhost:5432/products');
app.use('/products', productsRoute);
products.js (route)
router.get('/', ProductsController.get_all_products);
products.js (controller)
exports.get_all_products = (req, res, next ) => {
// Here i want to use de database connection to do the query to find all
//products in the database
}
How do I get access to the connection to do something like
db.any('SELECT * FROM products WHERE active = $1', [true])
.then(function(data) {
// success;
})
.catch(function(error) {
// error;
});
From the controller.
Update
Ok, I´m using now node-prostgres, pg. I saw is better, Thanks for the advice people.
I want to create one time de db instance, and call it anywhere, in specific in the controllers
Could I use app.local to save my client?, connect, do a query and then close it. Do this anywhere
I haven't used pg-promise.
If it helps, you can use PostgreSQL client for Node.js. You can also use async/await with it.
Instead of a router, you can use Express middle-ware straightaway as follows.
//app.js:
const express = require('express')
const bodyParser = require('body-parser')
const app = express()
const port = 1234
const db = require('./dbconnector')
//...omitted for brevity`
// 'db' is exported from a file such as
// dbconnector.js.
app.get('/products', db.getProducts)
//In dbconnector.js:
const Pool = require('pg').Pool
const pool = new Pool({
user: 'postgres',
host: 'localhost',
database: 'mydb',
password: 'mypwd',
port: 5432,
})
const getProducts = (request, response) => {
pool.query('SELECT * FROM products ORDER BY id
ASC', (error, results) => {
if (error) {
throw error
}
response.status(200).json(results.rows)
})
}
// ...omitted for brevity
module.exports = {
getProducts
}
For modular design, please use a separate file (not app.js/index.js/server.js) for db connections as best practice and require that in your main app.js.
Here is help on pg module.
Here's an example how to use it:
// mydb.js
async function someDbQuery() {
let result;
try {
result = db.any('SELECT * FROM products WHERE active = $1', [true])
} catch (e) {
throw e
}
return result;
}
module.exports = someDbQuery;
// in your controller after importing
const { someDbQuery } = require('./mydb.js')
exports.get_all_products = async (req, res, next ) => {
// Here i want to use de database connection to do the query to find all
//products in the database
try {
const result = await someDbQuery();
// use result here
} catch (e) {
// handle error
console.error(e)
}
}
Side note:
From the docs pg-promise
Built on top of node-postgres
node-postgres now supports promise too.
You do not need to do anything, pg-promise manages connections automatically. It will be allocated for the query and released right after. See examples.
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() };