title: Mongoose.connection('once') what does it mean
body: <p>I am newbie on MongoDb. What is the use of db.connect('once', function(){});</p>
  
  <p>This will create the connection once per request??</p>
  
  <p>This will by default close the connection when this job is done??</p>
  
  <pre><code>    mongoose.connect(uri, options);
      var db = mongoose.connection;
      db.on('error', console.error.bind(console, 'connection error:'));
      db.once('open', function(err, resp){
        console.log(resp);
      });
  </code></pre>
  
  <p>Any help is Appreciated. </p>