Dockerizing A Project Tutorial + Example

To watch the youtube video explaining this topic, click here.

Introduction

Docker is a tool for containerizing projects so that any required dependencies (libraries) can be installed in isolation within the Docker container and doesn't have to be installed on the host computer.

This is good practice because it:

• Avoid installing unnecessary libraries/CLI tools on your computer.
• Avoids version mismatches. (Your computer has library version 2, but the project uses version 3.)
• Easier to run CI steps like building/testing.
• Easier deployments for backend servers.
• Allows for more complex projects with multiple systems. (One container could have a server, and another has a database. For complex systems, having local copies of services means easier development.)

​​In this blogpost we'll look at Dockerizing a simple project.

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Installing Docker

Your computer must have Docker installed to use it, of course. Docker installation varies depending on your operating system, so google for a guide.

This previous tutorial shows how to install Docker on older versions of Ubuntu linux.

On newer versions, of Ubuntu Linux, you can install docker using the following command:

sudo apt install docker.io

And test it with:

sudo docker run hello-world

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Setting Up A Test Project

The best projects to Dockerize are backend servers, so let's take a very basic Hello World server.

This repository has the bare minimum code required to run a Node.js server.

git clone https://github.com/srcmake/node-bare-minimum-server.git

If you have node/npm installed locally, then you can try running this project locally.

cd node-bare-minimum-server
npm install
node server.js

And go to localhost:3000 in your browser to ensure the server gives a response.

​(If you don't have node/npm installed, then don't worry because we'll be dockerizing the project in the next section to not need to have them installed locally.)

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Dockerizing The Project

To dockerize the project, we must add a Docker file to our project.

touch Dockerfile

There are a few things we need to specify in our Dockerfile:

1. The base Docker image we're going to be copying from. (One with an OS and node/npm already installed would be nice. We can see a list here.) For production projects you can build your own base image. 
2. Specify the folder inside of the Docker image OS that our app code is going to be in.
3. Copy our project files into that folder.
4. Run anything we need to set up the project. (In our case, we need to install our npm libraries. (Note: There are some special caching tricks we could do, but this tutorial will keep it simple.)
5. Since we're running a server, we need to expose a port so connections can go into the Docker container.
6. We specify the command to run to start our server.

Open the Dockerfile and paste the following code inside of it:

Additionally, we're going to specify a Docker Ignore file, which works similarly to a Git Ignore file; it will specify files in our project folder that we don't need copied into the Docker container. (It's good practice to make the Docker container as small as possible.) For example, we don't need to copy our local node_modules folder since we want to rebuild it inside the container, anyway.

​Create the Docker Ignore file:

touch .dockerignore

Open .dockerignore and add the files/folders we don't need copied over into it:

1 2 3 4 5

/.git /node_modules .gitignore LICENSE README

Now our codebase is Dockerized. How do we run the server locally? First we need to build a Docker image for our project, and then we'll run that image.

To build the Docker image:

sudo docker build -t node-min-server .

We can see the image we just built in our list of docker images.

sudo docker images

​To run the Docker image we just built:

sudo docker run -p 8000:3000 -d node-min-server

​Note that the internal Docker container is using port 3000, but we're specifying our local computer to connect to the Docker container on our computer's port 8000. (This is just for clarity, feel free to use the same ports.)

We can now see our server running on port 8000 on our computer, without needing Node or NPM installed. Check at localhost:8000 in your browser.

And that's it. The next steps would be to commit the Dockerfile (and docker ignore file) to our project's repository and update our README for the new deployment steps.

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Conclusion

Dockerization of a project is pretty simple and has many benefits. It's useful when working with multiple people and setting up CI/CD. All it takes to Dockerize a project is creating a Dockerfile and using a few new commands to work locally.

The next blogpost is going to be on using docker compose, which helps create more complex local systems.
We'll also be doing a tutorial on CircleCI, and Docker will help with our CI steps.

​​Like this content and want more? Feel free to look around and find another blog post that interests you. You can also contact me through one of the various social media channels. 

Twitter: @srcmake
Discord: srcmake#3644
Youtube: srcmake
Twitch: www.twitch.tv/srcmake
​Github: srcmake

References
1. ​https://nodejs.org/fr/docs/guides/nodejs-docker-webapp/