#node-inspector

[cjus-blog-blog]

Debugging Node apps with Node-Inspector

Lately I've been playing with Cloud9IDE and test driving the development as a service concept (DaaS). While the Cloud9IDE is far from being bulletproof it's showing signs of greatness. As a comparison I figured I should share how I debug my node app before learning about Cloud9IDE.  I should note that this is still my preferred method.

Enter node-inspector, a tool that allows one to remotely debug node applications directly from a webkit enabled browser (safari/chrome). Unlike Cloud9IDE, node-inspector focuses exclusively on debugging. This isn't a huge issue for me as Komodo allows me to remotely edit files whereby sparing me from edit / deploy cycles.

Let's briefly examine what node-inspector offers.

In the upper left panel you can navigate source files. In this example, I've set a breakpoint on line 19 in a file called router.js. In the lower panel is the console view. I've typed "map" in order to view the contents of the map variable. The panel on the right also shows variables which are currently in scope. The upper right panel features the call stack which allows you to switch stack frames.

I still get a kick out of debugging client-side using FireBug and server-side using Node-Inspector. As a side note node-inspector is a good way of learning more about the node.js runtime environment.

Getting started with node-inspector is quick and painless.

Installation

First make sure you have the Node Package Manager (npm) installed.

Next, install node-inspector on the machine where your node.js application will run.

$ npm install -g node-inspector

Using node-inspector

Start node-inspector.

$ node-inspector &

Lastly, start your node.js application in debug mode.

$ node --debug server.js

You can then access the node-inspector via your web browser by accessing your machine via the default port of 8080.  Once the page loads you can select the script you'd like to debug. 

Danny Coates the node-inspector creator and maintainer posted a set of getting started videos on YouTube.

[epiphanymachine]

debugging Node.js App with Chrome dev tools!

Aug 26th 2013 Updates****

the main branch is the most current again as of Aug 20th 2013

there are also updates to the readme that include a lot what I wrote below:

1. install node-inspector

npm install -g node-inspector

2. don't use port 8080 in your node app (this port is used by node-inspector)***

3. start your app using

node --debug-brk app.js

this starts node in debugging mode with a break at line 1

4. start node inspector

node-inspector

this will output a url, open that url in your browser

5. use chrome debugging tools!!

notes:

you can use debugger or breakpoints as normal

no jasmine-node support...

this main app is no longer supported, and I suggest using the fork linked to above

autorestart node-inspector when you hit an error using these commands:

until node-inspector; sleep 1; done

*** if you want to use port 8080 for your node server you can change the port that node-inspector uses

--web-port=[port] port to host the inspector (default 8080)

**** Updated from:

as of july 2013 this fork is the best: strongloop/node-inspector

Thanks to Jake for posting this code in the comments!

[xeektech]

Debugging node.js using node-inspector and Chrome on Mac

Download node-inspector:

Open terminal and type sudo npm install -g node-inspector

Enter the password when prompted

Note: If you encounter this exception: gyp WARN EACCES user “root” does not have permission to access the dev dir then type that command instead:

sudo npm install --unsafe-perm --verbose -g node-inspector

Run your js code with node using the debug-brk param:

node --debug-brk TestWebServer.js

Open a new terminal window and run node inspector:

node-inspector

Copy the URL

Open Chrome and run the already copied URL

There you are, Chrome opens up the javascript code you are looking to debug

Put a breakpoint in the code and issue a request, e.g. http://localhost:3000 and the debugger stops the execution at the breakpoint in the code and you can take it from there