1. docker
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Add Node.js web app example using CentOS

Daniel Gasienica authored on 2013/06/02 13:53:22
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docs/sources/examples/index.rst
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 :title: Docker Examples
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 :description: Examples on how to use Docker
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-:keywords: docker, hello world, python, couch, couchdb, redis, ssh, sshd, examples
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+:keywords: docker, hello world, node, nodejs, python, couch, couchdb, redis, ssh, sshd, examples
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@@ -16,6 +16,7 @@ Contents:
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    hello_world
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    hello_world_daemon
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    python_web_app
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+   nodejs_web_app
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    running_redis_service
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    running_ssh_service
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    couchdb_data_volumes
docs/sources/examples/nodejs_web_app.rst
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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.
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+
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+Create Node.js app
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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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+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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+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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+    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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+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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+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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+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/