Reconnect on error with mongoose.

reconnect.js

db.on('error', function(error) {
 console.error('Error in MongoDb connection: %j', error);
 mongoose.disconnect();
});

db.on('disconnected', function() {
 console.log('MongoDB disconnected!');
 mongoose.connect(config.mongo.uri, config.mongo.options);
});

//
// Ensure that `options` has `server: { auto_reconnect: true }`
//
mongoose.connect(config.mongo.uri, config.mongo.options);