Reuse of connections in Nodejs + Mongoose

Question

I’m starting now with Node and used Mongoose to make my connections to the database in Mongodb. I put 1 log in my application, for every time I open the connection it print in this log.

What happens to you: Every time someone calls my 1 URL, my Node application opens a connection to Mongodb, is that normal and correct? That is, if 1,000 access my site, will there be 1,000 open connections? Is there any way to improve that and avoid problems, or is that normal for this environment?

For each model of mine, I have 1 code of this type:

var mongoose = require('mongoose');
var database = require('../config/database');
var mongoOptions = { db: { safe: true }};
mongoOptions.user = database.user;
mongoOptions.pass = database.pass;

console.log('Running mongoose version %s', mongoose.version);

mongoose.connect(database.url, mongoOptions, function (err, res) {
  if (err) { 
    console.log ('ERROR connecting to: ' + database.url + '. ' + err);
  } else {
    console.log ('Successfully connected to: ' + database.url);
  }
});

var Schema = mongoose.Schema;
var citySchema = new Schema({
    name: String,
    url: String,
    uf: String,
    dtRequest: Date,
    active: Boolean,
    loc: {
        type: [Number],
        index: '2dsphere'
    }
});

module.exports = mongoose.model('City', citySchema);

var db = mongoose.connection;
db.on('error', console.error);

process.on('SIGINT', function() {
  db.close(function () {
    console.log('Mongoose default connection disconnected through app termination');
    process.exit(0);
  });
});

Answer 1

The connection to the database should be in the main project file, the one that Node will run, so the connection will only be made once.

For example, the code below is your main file, the app.js, responsible for the project’s routes and settings:

const express = require('express');
const database = require('../config/database');
const mongoose = require('mongoose');

const app = express();

const mongoOptions = { 
    db: { safe: true },
    user: database.user,
    pass: database.pass
};

mongoose.connect(database.url, mongoOptions, function (err, res) {
    if (err) { 
        console.log ('ERROR connecting to: ' + database.url + '. ' + err);
    } else {
        console.log ('Successfully connected to: ' + database.url);
    }
});

app.listen(8080);

The code below is your model:

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const citySchema = new Schema({
    name: String,
    url: String,
    uf: String,
    dtRequest: Date,
    active: Boolean,
    loc: {
        type: [Number],
        index: '2dsphere'
    }
});

module.exports = mongoose.model('City', citySchema);

When you run a Node app.js the connection will be started only once, and will remain so until the process is completed or an error occurs.