Our next troubleshooting method is going to be CPU profiling. This will let us know what functions are the most CPU intensive. For this, we will use webkit-devtools-agent. The setup for this tool is a little more difficult than the last.

The first thing we need to do is add a reference to the module. Open up app.js and add this line to the top, as highlighted in the following code:

var agent = require('webkit-devtools-agent');
var express = require('express');
var app = express();

Technically, this is all we need to add to our code. If this was a production codebase, we could check whether we were in development or not and load this module. We can start the node at this time.

The next step is to send a USR2 signal to the process-running node. Signals are a way to notify a process. A common signal is TERM that tells the process to start shutting down and to terminate. USR2 is a user-defined signal. This means that developers can decide what to do when the signal...