after_res_hooks.js

## after_res_hooks.js
var db = mongoose.connect('mongodb://localhost:27017/DB');

// In middleware
app.use(function (req, res, next) {

  // action after response
  var afterResponse = function() {
   logger.info({req: req}, "End request");

    // any other clean ups
    mongoose.connection.close(function () {
      console.log('Mongoose connection disconnected');
    });
  }

  // hooks to execute after response
  res.on('finish', afterResponse);
  res.on('close', afterResponse);

  // do more stuff

  next();
}

## connect-mongo_session_store.js
var express = require('express');
var MongoStore = require('connect-mongo')(express);

app.use(express.session({
  secret: settings.cookie_secret,
  store: new MongoStore({
    "db": "dbName",
    "host": "localhost",
    "port": "27017",
    "collection": "mysessions",
    "clear_interval": 3600,
    "auto_reconnect": true
  })
}));

## connect-mongo_use_mongoose_conn1.js
new MongoStore({
  db: mongoose.connection.db
})

## connect-mongo_use_mongoose_conn2.js
new MongoStore({
  mongoose_connection : mongoose.connections[0],
})

## mocha_tests.js
var mongoose = require('mongoose');

describe('My test', function() {
  before(function(done) {
    //Another possibility is to check if mongoose.connection.readyState equals 1
    if (mongoose.connection.db) return done();
    mongoose.connect('mongodb://localhost/puan_test', done);
  });
});

// You can put one ‘after()’ statement above all else that will run when all tests are finished
after(function(done){
  db.connection.db.dropDatabase(function(){
    db.connection.close(function(){
      done();
    });
  });
});

## model_close_conn.js
var db = mongoose.connect('mongodb://localhost:27017/DB');
Model.findOne({}, function () {

  // do your stuff

  // For any weird reason you want to close connection everytime
  db.disconnect();
});

## mongoose_connet.js
var mongoose   = require('mongoose');
var express    = require('express');

var config     = require('./config/config');

var db_server  = process.env.DB_ENV || 'primary';

mongoose.connection.on("connected", function(ref) {
  console.log("Connected to " + db_server + " DB!");

  var app = express();

  // add your middleware set-up
  // add your routes

  port = process.env.port || 3000;
  ip = process.env.ip;

  app.listen(port, ip, function() {
  console.log('listening on port ' + port);
  });
});

// If the connection throws an error
mongoose.connection.on("error", function(err) {
  console.error('Failed to connect to DB ' + db_server + ' on startup ', err);
});

// When the connection is disconnected
mongoose.connection.on('disconnected', function () {
  console.log('Mongoose default connection to DB :' + db_server + ' disconnected');
});

var gracefulExit = function() {
  mongoose.connection.close(function () {
    console.log('Mongoose default connection with DB :' + db_server + ' is disconnected through app termination');
    process.exit(0);
  });
}

// If the Node process ends, close the Mongoose connection
process.on('SIGINT', gracefulExit).on('SIGTERM', gracefulExit);

try {
  options.server.socketOptions = options.replset.socketOptions = { keepAlive: 1 };
  mongoose.connect(config.getDBURL(db_server));
  console.log("Trying to connect to DB " + db_server);
} catch (err) {
  console.log("Sever initialization failed " , err.message);
}

## mongostore_conn.js
mongoose.connect(config.db, {auto_reconnect: true, native_parser: true}, function(err) {
    var MongoStore = require("connect-mongodb");

    var app = express();
    app.use(express.session({
        cookie: {maxAge: 60000 * 20},
        secret: "secret",
        store: new MongoStore({db: mongoose.connection.db})
    }));
});