Add some event traps for MongoDB

* Gracefully disconnect from MongoDB during restarts
* Add some console messages in for tracking
* Remove the `bind` on error trap

Applies to OpenUserJS#845, OpenUserJS#851, Automattic/mongoose#3588 and loosely christkv/mongodb-core#66

Author: Martii

app.js

@@ -86,14 +86,38 @@ app.set('securePort', process.env.SECURE_PORT || null);
 
 // Connect to the database
 mongoose.connect(connectStr, dbOptions);
-db.on('error', console.error.bind(console, 'connection error:'));
+
+// Trap a few events for MongoDB
+db.on('error', function () {
+  console.error(chalk.red('MongoDB connection error'));
+});
+
 db.once('open', function () {
+  console.log(chalk.green('MongoDB connection is opened'));
+});
+
+db.on('connected', function () {
   var admin = new mongoose.mongo.Admin(mongoose.connection.db);
   admin.buildInfo(function (aErr, aInfo) {
     console.log(chalk.green('Connected to MongoDB v' + aInfo.version));
   });
 });
 
+db.on('disconnected', function () {
+  console.error(chalk.yellow('\nMongoDB connection is disconnected'));
+});
+
+db.on('reconnected', function () {
+  console.error(chalk.yellow('MongoDB connection is reconnected'));
+});
+
+process.on('SIGINT', function () {
+  db.close(function () {
+    console.log(chalk.green('MongoDB connection disconnected gracefully with app termination'));
+    process.exit(0);
+  });
+});
+
 var sessionStore = new MongoStore({ mongooseConnection: db });
 
 // Force HTTPS