 Resources from Joel Lord in 2024

While "It works on my computer" might give you an excuse to close a bug ticket in the backlog, it doesn't really work when you're working on a team.

You need to ensure that your application can run regardless of what hardware your teammates are running or libraries they have installed.

Docker solves this problem by collecting everything your application needs to run into a container.

Containers aren't just for source code. They can hold configuration, scripts, and even their own filesystem. It's similar to a Virtual Machine, without having to bring a full operating system along for the ride.

Because containers run in isolation, there is some configuration involved to allow for files to be saved and containers to communicate with one another.

One of the most useful ways to get your head around Docker is to see it in action.

Follow along with Joel Lord as he works through the process of preparing an application to run in separate containers for the frontend and backend of an application that searches for gifs and re-encodes them with a caption supplied by the user.

You'll see how to configure the separate containers to communicate with one another, work with environment variables, and persist data to your local machine. Along the way, you'll pick up some tips on useful commands and bash scripting. Finally, you'll learn how to use Docker Compose to make it easy to run multiple containers simultaneously.


Docker containers wrap a piece of software in a complete filesystem that contains everything needed to run: code, runtime, system tools, system libraries – anything that can be installed on a server. This guarantees that the software will always run the same, regardless of its environment.

docker

Containerize Full-Stack JavaScript Applications with Docker

In this lesson, you will learn how to start basic containers and how to use them in your day to day developer life. You will also learn how to start a database container that can be used with the demo application for this course.

Running Your First Container

You will learn how to create your own images that will include all the source code of your application, along with a specific version of Node.js and all the dependencies that are needed. Once you are done, you will be able to share this image with other people and this will ensure that everyone is running the same environment. It will event let people that don’t have Node.js run this server. This will also have the added benefit of cleaning up everything once you close the application.

You'll notice that we will run into the same error stating we can't connect to the database. This is expected and we'll fix this in [Allow Container to Communicate through Docker Networks](https://egghead.io/lessons/docker-allow-container-to-communicate-through-docker-networks)

Create a Custom Image with a Dockerfile running Node.js

In the previous lesson, [Containerize the Front End of an Application with a Multi-Step Docker Build](https://egghead.io/lessons/egghead-containerize-the-front-end-with-a-multi-step-build?pl=introduction-to-docker-afaf), we managed to put all of our front-end in a container and we can now distribute this container to the rest of our team. This will work well with stand-alone websites but as soon as you need to connect to an API, this could become an issue. 

You will need to specify the base URL of your server and this would need to be done as an environment variable. The problem here is that since our application lives in a browser, it can’t read the environment variables from the server.

In the last lesson, you’ve seen that all requests were made to `http://localhost:3000`. This means that this value was hard-coded somewhere in the front end source code. The first thing you will want to do is to find out where this was coded and make sure that it is only defined in one place.

The fix here will be to create a bash script that updates the hardcoded `localhost:3000` URL to a BASE_URL environment variable and update the instances that are used within the frontend app to your environment variable. This script will be called in the projects Dockerfile and override the original entry point.

Access Environment Variables in a Dockerfile to Build a Front-End Container

This lesson uses some advanced concepts and some bash scripting to build a better Dockerfile. By using the concepts showed here, you will be able to build more future-proof and production-ready containers. If you prefer to focus on the content about containers, feel free to ignore this lesson and come back to it later on if needed.

Currently, we use `sed` to overwrite the hard-coded path to the API. This works well when there is a single value to replace. Now if one of your team members replaced the value of localhost:3000, your build will break.

We'll use `jq` to fix this issue. Jq is a command-line tool that makes it easy to change values in a JSON file. The base image that we used for building the application does not contain this tool, but that is not an issue. To install `jq`, you will need to download the [binary](https://github.com/stedolan/jq/releases/download/jq-${JQ_VERSION}/jq-linux64.), we'll need that to execute `jq` commands in our Dockerfile. This will allow us to update specific properties i

Modify a JSON Configuration File with jq

The containers you built in the previous lessons are running as root for a few reasons. First of all, we read and write files from the file system in order to install tools like jq or to change some configuration files. And second, we are running servers on ports that are restricted to the root user (such as port 80).

While the risks are very limited in your own environment, you will need to have security in mind when you are deploying those containers to a production server. Some hosts will prevent any container where the user is root to be running at all.

From the Dockerfile, we will specify the use that builds the container will be the `node` user that the node image gives us. To do this we will need to set permissions for the node user to add and modify specific files.

Create a Node.js Non-root Image

Now that you have three containers ready to be used, you will learn how to create a docker-compose.yaml file. By using Docker Compose, you will be able to share a single YAML file and anyone will be able to run your application.

Docker-compose is part of the Docker tools suite and is an application that will take a YAML file to start all of your containers with one single command. 

Using Compose is basically a three-step process:

1. Define your app’s environment with a `Dockerfile` so it can be reproduced anywhere.
2. Define the services that make up your app in `docker-compose.yml` so they can be run together in an isolated environment.
3. Run `docker-compose up` and Compose starts and runs your applications. 

Compose works in all environments: production, staging, development, and testing.

Use Docker Compose To Share An Entire Application

Running MySQL in a Docker Container is great for being able to emulate various environments. The more advanced containers will include a bunch of executables and runtimes that will allow you to do run more intricate commands. These commands can be very useful for sharing with other teams for testing purposes. It doesn't matter what runtimes they have on their end, by using the `docker` command, you'll be able to specify what runtimes to use to execute your code. 

Run MySQL in Docker Container

Starting up our server and running the curl command `curl localhost:3000/health`, we find that we get an error. Our server is complaining about us not having a database. Since this is a fresh install, we have no data at all. SQL comes with a file called `init.sql` inside of your `db` folder that will create a database, add the necessary tables for our application, and prepopulate the table with a single entry. We just have to put it in the folder that MySQL will use to populate the database!

Integrate a MySQL Docker Container Into an Application

Running our server as a Non-Root user is very important for testing things such as quality assurance. Many things can get missed when using a privileged account such as your root user account. Here we need to set up and change the Nginx configuration to run as a Non-Root user. 

This container uses two steps. The first step uses a container to build the production version of your VueJs application. This container won’t be deployed on a server, its purpose is to create the necessary files for the second step. It's fine to leave this container running as root. 

In the next step of the build, the Nginx server is the one that will need to run as a non-root user because it is actually run on servers you want to deploy to. To do so, you will first need to change the Nginx configuration to run the build using the Nginx user with files modified for that user to access them.

Run an Nginx Image as Non-Root Within a Multi-Step Docker Build Process

Docker containers that are running on your local machine can't communicate with each other. In this mini talk, the instructor explains why and shows a demonstration of Docker networks.

Mini talk - Allow Containers to Communicate through Docker Networks

In this small talk, the instructor explains why you need to use a multi-step build to prepare your front-end container.

Mini talk - Containerize the Front End of an Application with a Multi-Step Docker Build

First, we'll see how you can have different run-times installed in a docker container that isn't dependent on your system's current installs. You don't need anything but docker to run these containers! We will demonstrate this by installing the latest version of Node.js in a docker container and compare that to the version of Node.js I'm running on my machine.

Next, you'll see how to pass environment variables to containers. This is important because you will use these variables for API calls as well as configuring databases, and more!

Use Environment Variables for Docker Containers

Introduction for the lesson on using environment variables in a front-end container

Mini talk - Access Environment Variables in a Dockerfile to Build a Front-End Container

The end is nigh. Your application is almost ready, and you will need to deploy it. And with the deployment, the endless tweaking to get everything running on your production servers. 

If only there were a way to test everything first. That is where containers will come in to save the day. With containers, you not only run your code in an environment similar to the production server, but you also run your code in precisely the same environment. 

In this talk, the attendees will learn about how to create container friendly applications and how to use containers to share their code with their team.

Containers for Software Developers

JavaScript® (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB. It is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles.

javascript

First, we'll get a tour of the application and what it does then we will start configuring a fresh project. 

The application UI is simple. It asks for a keyword and will search and display a random GIF from Giphy. Once you are satisfied with the image, you will be able to add a caption to it. The server will deconstruct the GIF frames, add the caption and re-create the GIF for you. Everything is then saved to a database so that all the users can benefit from your creations.

The tech involved to do this is a Vue frontend, Node.js backend, and MySQL database. I'll walk you through cloning, installing dependencies, configuring the giphy API key that we use, and starting the application. You'll notice at the end we'll need to configure the database. We'll get an error but this is expected!

Configure and Run a Node.js API Powered by a Vue Application

In the last lesson [Create a Custom Image with a Dockerfile running Node.js](https://egghead.io/lessons/docker-create-a-custom-image-with-a-dockerfile-running-node-js?pl=introduction-to-docker-afaf), our backend stopped working again because it couldn’t find the database.

One of the advantages of running containers is that they run in isolation. As far as the container is concerned, nothing exists outside of it. It behaves as if it was its own operating system. This is why the backend can’t find the database on "localhost". The two containers are running on the same host but as far as the backend is concerned, there is no database. The same goes for the database. It can’t see anything outside of what is running in its container therefore it can’t see the backend application running.

When you need a way for multiple containers to talk to each other, Docker has a tool called networks to help you. We'll use a network to allow our backend to successfully connect to the database.

Allow Containers to Communicate through Docker Networks

For your front end, a VueJs application has been created from the CLI. VueJS, just like React and Angular applications have a development mode as well as a production mode.

Once you are ready to deploy this application, you won’t want to use the same code as you do when you develop. In fact, you will need to run another script to build a production application. This script will take all of your JavaScript files and merge everything into a single minified JavaScript file. It will do the same for your CSS. By doing so, you will end up with a minimal set of files that can be served over any static file webserver. In this case, you will be using an Nginx server to serve those files. Nginx is an open-source, high-performance HTTP server that will be able to handle many requests to your front end.

We'll do this with a multi-step build in a Dockerfile that will discard the first container that we use to build the source code and run it in a container that's built on top of the nginx image.

Containerize the Front End of an Application with a Multi-Step Docker Build

This course will take you through the process of preparing an application that's configured for development to deployed on a Kubernetes cluster.

First, you will need to tweak your application so that it can run in containers. Then, you will see how you can use containers to complement your application and run a database without even installing the actual software. Eventually, you will create a whole environment with your containers that will enable you to start all the applications with a single command. This can be useful to share the application with your colleagues.

We'll make sure you have the correct software installed on your machine to get started.

You will need a few software installed:

- [Node.js](http://nodejs.org)
- [Docker](http://docker.com/) or [Podman](http://podman.io/)
- [git](http://git-scm.com/)

As well as an [API key from giphy](http://developers.giphy.com/)

Course Intro: Containerize Full-Stack JavaScript Applications with Docker

Now that all three tiers of your application are available in containers, you'll need to push those images to container registries. Registries are the container equivalent to repositories for your code. Registries can be public or private. 

In this lesson, we'll use Docker Hub to push our images. Docker Hub repositories allow you share container images with your team, customers, or the Docker community at large.

Docker images are pushed to Docker Hub through the `[docker push](https://docs.docker.com/engine/reference/commandline/push/)` command. A single Docker Hub repository can hold many Docker images (stored as **tags**).

Images pushed to a public registry can be downloaded by using the `docker pull` command. Once they have the image downloaded, they can use Docker run to start each container just like you did in the previous steps.

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Joel Lord