Getting Started with Nitrogen

• How do I create a new Nitrogen application?
• How do I start and stop my application?
• How do I change configuration settings?
• Where is the code for my website?
• How do I compile my code?
• How do I create new pages, custom elements, or custom actions?
• How do I upgrade to a new version of Nitrogen?

Yes! You can view the slides from Rusty's Nitrogen Tutorial at the Erlang User Conference 2010 here.

First, check the Downloads page to see if a pre-built package exists for your OS/architecture. If it does, then just download the package, unzip, and you are ready to start coding. (You don't even need to have Erlang installed, the Nitrogen binaries come with it pre-packaged.)

If you don't see a package that will run on your computer, or you want to try running from the latest code in source control, then follow the steps below:

Pull the latest source code from GitHub and run:

make rel_inets

This creates a completely self-contained starter application under ./rel/nitrogen that runs on Inets, Erlang's built in HTTP server. "Self-contained" here means that the ./rel/nitrogen directory contains everything you need to develop and run nitrogen, including the Erlang VM. To create a .tar.gz version of this code, exactly like you would find on the Downloads page, run:

make package_inets

You can also run Nitrogen on Mochiweb or Yaws. Run one of the scripts provided in the ./deps/ directory to download the Mochiweb or Yaws code.

# For Mochiweb...
./deps/get_mochiweb.sh

# For Yaws...
./deps/get_yaws.sh

Then, create the release or the binary package (example below is for Mochiweb):

# Build a release in ./rel/nitrogen
make rel_mochiweb

# Build a binary package in ./builds
make package_mochiweb

Nitrogen 2.0 uses Dave "Dizzy" Smith's Rebar (source code) to build OTP-compliant releases and packages. Check it out, it is awesome.

Once you have a build of Nitrogen that will run on your application, the next step is to start the application. Nitrogen includes a handy script inside your release, under ./bin/nitrogen, that will let you bring your Nitrogen application up or down:

# Start the app in the background...
./bin/nitrogen start

# Connect to the app in the background. Control-D to disconnect.
./bin/nitrogen attach

# Stop the app...
./bin/nitrogen stop

# Start the app in "console" mode...
./bin/nitrogen console

# Ping the app to see if it is running...
./bin/nitrogen ping

Once you have started your application, open http://localhost:8000. You should see a basic welcome page.x

All configuration files for your application can be found under the ./etc directory.

Here, you will see:

• vm.args - This controls the arguments passed in to the VM. Here, you can set the node name, cookie, memory flags, etc.
• app.config - This contains application settings for Nitrogen and sasl (error logging).

Important: Before deploying your app to production, you should change the Erlang cookie (found in ./etc/vm.args) and define a Nitrogen signkey (found in ./etc/app.config).

The Nitrogen project is structured so that all site specific code is contained inside the site directory. It is recommended that you place your entire site directory under source control. This will allow you to move your application to other architectures and configurations easily.

The site directory contains the following sub-directories:

./site/src

Page modules, custom elements, and custom actions for your site.

./site/static

Static files, including Javascript and CSS. These will be served through the web. Place any files you like here, but try not to touch the nitrogen directory, as you will need to overwrite this when you upgrade to a new version of Nitrogen.

./site/templates

Html files used by the #template{} action.

./site/.prototypes

Code used by ./bin/dev to generate a page, element, or action. Feel free to edit these to something more to your liking.

./site/ebin

Compiled .beam files.

There are three different ways to compile code in Nitrogen:

• If you are in the Erlang console then run sync:go().

  This will look at all loaded modules, find their associated Emakefiles, and run make:all([load]). to recompile.

• If Nitrogen is running in the background then run ./bin/dev compile

  This connects to the running Nitrogen application and issues a sync:go(). command.

• If Nitrogen is stopped then run make compile

  This calls erl -make, causing your application to be compiled based on the provided Emakefile.

Nitrogen 2.0 includes a developer tool to help you get started with a bare-bones page, element, or action. This tool uses the files found in ./site/.prototypes as templates. If you wish, you can edit files in this directory to make them more suitable for your application.

• To create a new page at http://localhost/user/login, run:

  ./bin/dev page user_login
  

• To create a new element called #custom_element{}, run:

  ./bin/dev element custom_element
  

• To create a new action called #custom_action{}, run:

  ./bin/dev action custom_action
  

The code is placed under ./site/src, ./site/src/elements, or ./site/src/actions for pages, elements, and actions, respectively.

To upgrade to new versions of Nitrogen 2.0:

• Build or download the new Nitrogen environment for your architecture and preferred web server. Unzip to a new directory.
• Copy your existing ./etc directory to the new build. This retains your configuration settings.
• Copy your existing ./site directory to the new build, except for the files in ./site/static/nitrogen. You will want to use the new version of any files in ./site/static/nitrogen.

This will update the Erlang version, the dependencies files, and all of the Javascript used by Nitrogen.

You will also need to update your code if there are any API level changes.