Express Application Development using Bitnami Docker Images

We increasingly see developers adopting two strategies for development. Using a so called “micro services” architecture and using containers for development. At Bitnami, we have developed tools and assets that dramatically lowers the overhead for developing with this approach.

If you’ve never tried to start a project with containers before, or you have tried it and found the advice, tools, and documentation to be chaotic, out of date, or wrong, then this tutorial may be for you.

In this tutorial we walk you through using the Bitnami docker images during the development lifecycle of a Express application.

Why Docker?

We think developers are adopting containers for development because they offer many of the same advantages as developing in VMs, but with lower overhead in terms of developer effort and development machine resources. With Docker, you can create a development environment for your code, and teammates can pull the whole development environment, install it, and quickly get started writing code or fixing bugs.

Docker development environments are more likely to be reproducible than VMs because the definition of each container and how to build it is captured in a Dockerfile.

Docker also has a well known and standard API so tools and cloud services are readily available for docker containers.

The Bitnami Approach

When we designed and built our development containers, we kept the following guiding principles in mind:

1. Infrastructure should be effort free. By this, we mean, there are certain services in an application that are merely configured. For example, databases and web servers are essential parts of an application, but developers should depend on them like plumbing. They should be there ready to use, but developers should not be forced to waste time and effort creating the plumbing.

2. Production deployment is a late bound decision. Containers are great for development. Sometimes they are great for production, sometimes they are not. If you choose to get started with Bitnami containers for development, it is an easy matter to decide later between monolithic and services architectures, between VMs and Containers, between Cloud and bare metal deployment. This is because Bitnami builds containers specifically with flexibility of production deployment in mind. We ensure that a service running in an immutable and well tested container will behave precisely the same as the same service running in a VM or bare metal.

Assumptions

First, we assume that you have the following components properly setup:

• Docker Engine
• Docker Compose
• Docker Machine

The Docker documentation walks you through installing each of these components.

We also assume that you have some beginner-level experience using these tools.

Note:

If your host OS is Linux you may skip setting up Docker Machine since you'll be able to launch the containers directly in the host OS environment.

Further, we also assume that your application will be using a database. In fact, we assume that it will be using MongoDB. Of course, for a real project you may be using a different database, or, in fact, no database. But, this is a common set up and will help you learn the development approach.

Download the Bitnami Orchestration File for Express development

We assume that you're starting the development of the Express application from scratch. So lets begin by creating a directory for the application source where we'll be bootstrapping a Express application:

$ mkdir ~/workdir/myapp
$ cd ~/workdir/myapp

Next, download our Docker Compose orchestration file for Express development:

$ curl -L "https://raw.githubusercontent.com/bitnami/bitnami-docker-express/master/docker-compose.yml" > docker-compose.yml

We encourage you to take a look at the contents of the orchestration file to get an idea of the services that will be started for Express development.

Run

Lets put the orchestration file to the test:

$ docker-compose up

This command reads the contents of the orchestration file and begins downloading the Docker images required to launch each of the services listed therein. Depending on the network speeds this can take anywhere from a few seconds to a couple minutes.

After the images have been downloaded, each of the services listed in the orchestration file is started, which in this case are the mongodb and myapp services.

As mentioned earlier, the mongodb service provides a database backend which can be used for the development of a data-driven Express application. The service is setup using the bitnami/mongodb docker image and is configured with the default credentials.

The second service thats started is named myapp and uses the Bitnami Express development image. The service mounts the current working directory (~/workdir/myapp) at the /app location in the container and provides all the necessary infrastucture to get you started developing a data-driven Express application.

Once the Node HTTP server has been started, visit port 3000 of the Docker Machine in your favourite web browser and you'll be greeted by the Express welcome page.

Lets inspect the contents of the ~/workdir/myapp directory:

~/workdir/myapp # ls
app.js  config              node_modules  public  views
bin     docker-compose.yml  package.json  routes

You can see that we have a new Express application bootstrapped in the ~/workdir/myapp directory of the host and is being served by the Node HTTP server running inside the Bitnami Express development container.

Since the application source resides on the host, you can use your favourite IDE for developing the application. Only the execution of the application occurs inside the isolated container environment.

That’s all there is to it. Without actually installing a single Express component on the host you have a completely isolated and highly reproducible Express development environment which can be shared with the rest of the team to get them started building the next big feature without worrying about the plumbing involved in setting up the development environment. Let Bitnami do that for you.

In the next sections we take a look at some of the common tasks that are involved during the development of a Express application and how we go about executing those tasks.

Executing commands

You may recall that we've not installed a single Node.js or Express component on the host and that the entire development environment is running inside the myapp service container. This means that if we wanted to execute NPM or any other Node command, we'd have to execute it inside the container.

This may sound like a complex task to achieve. But don't worry, Docker Compose makes it very simple to execute tasks inside a service container using the exec command. The general form of the command looks something like the following:

$ docker-compose exec <service> <command>

This instructs Docker Compose to execute the command specified by <command> inside the service container specified by <service>. The return value of the docker-compose command will reflect that of the specified command.

With this information lets load the Node.js REPL in the myapp container:

$ docker-compose exec myapp node

To list all the NPM modules currently installed:

$ docker-compose exec myapp npm ls

How about installing the Bootstramp NPM module:

$ docker-compose exec myapp npm install bootstrap --save

To inspect that the module was installed:

$ docker-compose exec myapp npm ls bootstrap

You get the idea..

With the bootstrap NPM module installed, lets modify our Express application and use it to change the look and feel of the UI.

Add a static route for serving the Bootstrap CSS by appending the following after the line app.use(express.static(path.join(__dirname, 'public'))); in app.js.

app.use('/stylesheets', express.static(path.join(__dirname, 'node_modules/bootstrap/dist/css')));

Next in views/layout.jade, import the bootstrap.min.css style sheet by appending the following at the same indentation level after the line link(rel='stylesheet', href='/stylesheets/style.css') and at the same indentation level.

link(rel='stylesheet', href='/stylesheets/bootstrap.min.css')

Lastly, modify views/index.jade of our application to use the Bootstrap classes so that it looks like:

extends layout

block content
  .container
    .jumbotron
      h1= title
      p My awesome #{title} website using Bootstrap CSS

The Node server should be restarted for the changes to take effect:

$ docker-compose restart myapp

Thats it! refresh your browser window and you'll see that the changes have taken effect.

Connecting to Database

Express by default does not require a database connection to work but we provide a running and configured MongoDB service and an example file config/mongodb.js with some insights for how to connect to it.

You can use Mongoose ODM in your application to model your application data.