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+:title: Running a Node.js app on CentOS
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+:description: Installing and running a Node.js app on CentOS
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+:keywords: docker, example, package installation, node, centos
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+
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+.. _nodejs_web_app:
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+
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+Node.js Web App
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+===============
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+
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+.. include:: example_header.inc
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+
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+The goal of this example is to show you how you can build your own docker images
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+from a parent image using a ``Dockerfile`` . We will do that by making a simple
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+Node.js hello world web application running on CentOS. You can get the full
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+source code at https://github.com/gasi/docker-node-hello.
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+
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+Create Node.js app
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+++++++++++++++++++
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+
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+First, create a ``package.json`` file that describes your app and its
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+dependencies:
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+
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+.. code-block:: json
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+
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+ {
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+ "name": "docker-centos-hello",
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+ "private": true,
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+ "version": "0.0.1",
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+ "description": "Node.js Hello World app on CentOS using docker",
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+ "author": "Daniel Gasienica <daniel@gasienica.ch>",
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+ "dependencies": {
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+ "express": "3.2.4"
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+ }
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+ }
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+
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+Then, create an ``index.js`` file that defines a web app using the
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+`Express.js <http://expressjs.com/>`_ framework:
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+
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+.. code-block:: javascript
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+
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+ var express = require('express');
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+
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+ // Constants
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+ var PORT = 8080;
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+
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+ // App
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+ var app = express();
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+ app.get('/', function (req, res) {
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+ res.send('Hello World\n');
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+ });
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+
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+ app.listen(PORT)
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+ console.log('Running on http://localhost:' + PORT);
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+
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+
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+In the next steps, we’ll look at how you can run this app inside a CentOS
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+container using docker. First, you’ll need to build a docker image of your app.
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+
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+Creating a ``Dockerfile``
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++++++++++++++++++++++++++
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+
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+Create an empty file called ``Dockerfile``:
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+
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+.. code-block:: bash
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+
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+ touch Dockerfile
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+
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+Open the ``Dockerfile`` in your favorite text editor and add the following line
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+that defines the version of docker the image requires to build
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+(this example uses docker 0.3.4):
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+
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+.. code-block:: bash
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+
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+ # DOCKER-VERSION 0.3.4
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+
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+Next, define the parent image you want to use to build your own image on top of.
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+Here, we’ll use `CentOS <https://index.docker.io/_/centos/>`_ (tag: ``6.4``)
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+available on the `docker index`_:
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+
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+.. code-block:: bash
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+
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+ FROM centos:6.4
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+
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+Since we’re building a Node.js app, you’ll have to install Node.js as well as
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+npm on your CentOS image. Node.js is required to run your app and npm to install
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+your app’s dependencies defined in ``package.json``.
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+To install the right package for CentOS, we’ll use the instructions from the
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+`Node.js wiki`_:
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+
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+.. code-block:: bash
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+
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+ # Enable EPEL for Node.js
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+ RUN rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
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+ # Install Node.js and npm
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+ RUN yum install -y npm-1.2.17-5.el6
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+
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+To bundle your app’s source code inside the docker image, use the ``ADD``
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+command:
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+
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+.. code-block:: bash
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+
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+ # Bundle app source
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+ ADD . /src
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+
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+Install your app dependencies using npm:
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+
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+.. code-block:: bash
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+
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+ # Install app dependencies
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+ RUN cd /src; npm install
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+
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+Your app binds to port ``8080`` so you’ll use the ``EXPOSE`` command to have it
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+mapped by the docker daemon:
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+
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+.. code-block:: bash
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+
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+ EXPOSE 8080
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+
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+Last but not least, define the command to run your app using ``CMD`` which
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+defines your runtime, i.e. ``node``, and the path to our app, i.e.
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+``src/index.js`` (see the step where we added the source to the container):
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+
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+.. code-block:: bash
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+
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+ CMD ["node", "/src/index.js"]
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+
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+Your ``Dockerfile`` should now look like this:
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+
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+.. code-block:: bash
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+
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+
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+ # DOCKER-VERSION 0.3.4
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+ FROM centos:6.4
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+
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+ # Enable EPEL for Node.js
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+ RUN rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
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+ # Install Node.js and npm
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+ RUN yum install -y npm-1.2.17-5.el6
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+
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+ # Bundle app source
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+ ADD . /src
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+ # Install app dependencies
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+ RUN cd /src; npm install
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+
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+ EXPOSE 8080
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+ CMD ["node", "/src/index.js"]
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+
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+
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+Building your image
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++++++++++++++++++++
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+
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+Go to the directory that has your ``Dockerfile`` and run the following command
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+to build a docker image. The ``-t`` flag let’s you tag your image so it’s easier
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+to find later using the ``docker images`` command:
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+
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+.. code-block:: bash
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+
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+ docker build -t <your username>/centos-node-hello .
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+
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+Your image will now be listed by docker:
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+
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+.. code-block:: bash
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+
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+ docker images
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+
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+ > # Example
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+ > REPOSITORY TAG ID CREATED
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+ > centos 6.4 539c0211cd76 8 weeks ago
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+ > gasi/centos-node-hello latest d64d3505b0d2 2 hours ago
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+
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+
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+Run the image
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++++++++++++++
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+
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+Running your image with ``-d`` runs the container in detached mode, leaving the
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+container running in the background. Run the image you previously built:
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+
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+.. code-block:: bash
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+
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+ docker run -d <your username>/centos-node-hello
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+
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+Print the output of your app:
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+
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+.. code-block:: bash
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+
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+ # Get container ID
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+ docker ps
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+
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+ # Print app output
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+ docker logs <container id>
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+
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+ > # Example
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+ > Running on http://localhost:8080
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+
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+
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+Test
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+++++
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+
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+To test your app, get the the port of your app that docker mapped:
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+
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+.. code-block:: bash
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+
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+ docker ps
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+
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+ > # Example
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+ > ID IMAGE COMMAND ... PORTS
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+ > ecce33b30ebf gasi/centos-node-hello:latest node /src/index.js 49160->8080
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+
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+In the example above, docker mapped the ``8080`` port of the container to
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+``49160``.
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+
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+Now you can call your app using ``curl`` (install if needed via:
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+``sudo apt-get install curl``):
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+
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+.. code-block:: bash
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+
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+ curl -i localhost:49160
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+
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+ > HTTP/1.1 200 OK
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+ > X-Powered-By: Express
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+ > Content-Type: text/html; charset=utf-8
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+ > Content-Length: 12
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+ > Date: Sun, 02 Jun 2013 03:53:22 GMT
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+ > Connection: keep-alive
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+ >
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+ > Hello World
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+
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+We hope this tutorial helped you get up and running with Node.js and CentOS on
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+docker. You can get the full source code at
|
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+https://github.com/gasi/docker-node-hello.
|
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+
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+Continue to :ref:`running_redis_service`.
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+
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+
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+.. _Node.js wiki: https://github.com/joyent/node/wiki/Installing-Node.js-via-package-manager#rhelcentosscientific-linux-6
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+.. _docker index: https://index.docker.io/
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Solomon Hykes