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239 lines
6.1 KiB
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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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.. _nodejs_web_app:
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Node.js Web App
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===============
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.. include:: example_header.inc
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The goal of this example is to show you how you can build your own
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Docker images from a parent image using a ``Dockerfile`` . We will do
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that by making a simple Node.js hello world web application running on
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CentOS. You can get the full source code at
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https://github.com/gasi/docker-node-hello.
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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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.. code-block:: json
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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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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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.. code-block:: javascript
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var express = require('express');
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// Constants
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var PORT = 8080;
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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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app.listen(PORT)
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console.log('Running on http://localhost:' + PORT);
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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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Creating a ``Dockerfile``
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+++++++++++++++++++++++++
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Create an empty file called ``Dockerfile``:
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.. code-block:: bash
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touch Dockerfile
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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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.. code-block:: bash
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# DOCKER-VERSION 0.3.4
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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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.. code-block:: bash
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FROM centos:6.4
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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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.. code-block:: bash
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# Enable EPEL for Node.js
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RUN rpm -Uvh http://dl.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
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To bundle your app’s source code inside the Docker image, use the ``ADD``
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instruction:
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.. code-block:: bash
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# Bundle app source
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ADD . /src
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Install your app dependencies using the ``npm`` binary:
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.. code-block:: bash
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# Install app dependencies
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RUN cd /src; npm install
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Your app binds to port ``8080`` so you’ll use the ``EXPOSE`` instruction
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to have it mapped by the ``docker`` daemon:
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.. code-block:: bash
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EXPOSE 8080
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Last but not least, define the command to run your app using ``CMD``
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which defines your runtime, i.e. ``node``, and the path to our app,
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i.e. ``src/index.js`` (see the step where we added the source to the
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container):
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.. code-block:: bash
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CMD ["node", "/src/index.js"]
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Your ``Dockerfile`` should now look like this:
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.. code-block:: bash
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# DOCKER-VERSION 0.3.4
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FROM centos:6.4
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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
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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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EXPOSE 8080
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CMD ["node", "/src/index.js"]
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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
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command to build a Docker image. The ``-t`` flag let’s you tag your
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image so it’s easier to find later using the ``docker images``
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command:
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.. code-block:: bash
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sudo docker build -t <your username>/centos-node-hello .
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Your image will now be listed by Docker:
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.. code-block:: bash
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sudo docker images
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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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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. The ``-p`` flag redirects a public port to a private port in the container. Run the image you previously built:
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.. code-block:: bash
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sudo docker run -p 49160:8080 -d <your username>/centos-node-hello
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Print the output of your app:
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.. code-block:: bash
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# Get container ID
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sudo docker ps
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# Print app output
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sudo docker logs <container id>
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> # Example
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> Running on http://localhost:8080
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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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.. code-block:: bash
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sudo docker ps
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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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In the example above, Docker mapped the ``8080`` port of the container to
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``49160``.
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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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.. code-block:: bash
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curl -i localhost:49160
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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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We hope this tutorial helped you get up and running with Node.js and
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CentOS on Docker. You can get the full source code at
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https://github.com/gasi/docker-node-hello.
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Continue to :ref:`running_redis_service`.
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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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