Docker the Hard Way with WordPress

Orchestrating WordPress-MySQL containers w. Docker command

5 min readMay 22, 2019

Recently I was helping a friend get rapidly up to speed in Docker, and developed this small lab, which I am sharing in hopes this might be helpful in your Docker learning activities.

For this lab challenge, you will run a WordPress and MySQL containers, and then use your web browser to point to the container.

Why WordPress

You might ask, why WordPress?

Simply, WordPress is a class multi-tier monolithic web application with dependency to a database. As WordPress is widely used and well known, it has become the gestalt to demonstrate automation, especially for change configuration. This makes it great as a teaching tool to demonstrate docker.

About the Tools Required

Docker consists of many components, but for this lab we mainly focus on the docker client tool, simply called docker. The docker client will communicate to a docker service running on a Linux server.

Getting Docker on macOS (aka Mac OS X)

You can set all of this up with either Docker Desktop or Docker Machine (or both). If you have Homebrew installed, you can get the components with these commands:

Docker Desktop: brew cask install docker
Docker Toolbox (for Docker Machine): brew cask install docker-toolbox

Getting Docker on Windows 10

You can set all of this up with either Docker Desktop or Docker Machine. If you have Chocolatey installed, you can install either of these tools with:

Docker Desktop: choco install docker-desktop
Docker Toolbox (for Docker Machine): choco install docker-toolbox

Getting Docker on Linux

On Linux, you can follow instructions for Docker CE (Community Edition).

The Lab Challenge

The goal of this exercise is to create a shell script (or whatever you would like to use for automating command lines) to automate using the docker command and do the following below, divided into basic and advanced features.

Once completed, you will have a self executing script (docker_run.sh, docker_run.py, docker_run.rb, or other language, or simply docker_run) that will run the docker commands to do this.

The script will do this solution completely using the docker command. You will only need four docker commands to complete this solution.

Basic Features

For the basics, we simply want to launch the containers:

For the basic features, we’ll do the following:

Launch MySQL (mysql:5.7) with restart policy of always, container name of db, and pass environment variables to the container that will trigger the container’s internal self-configuring automation.
Launch WordPress (wordpress:latest) with restart policy of always, container name of wordpress, and map the container port 80 to a host port of 8080, and pass environment variables to the container that will trigger the container’s internal self-configuring automation.

Advanced Features

For these features, we want to use a private network, have a persistent volume for the database, and allow the user to specify the host port using an environment variable WORDPRESS_PORT.

For the advanced features, we’ll need to do the following:

Create a private network wordpress_net, and configure the containers to use the private network.
Create a volume called db_data, and mount the volume as /var/lib/mysql in the MySQL db container.
For the wordpress container, set the host port to the environment variable WORDPRESS_PORT, and if this is not set, then default it to port 8080.

Further Notes

For this exercise, you do not need to craft any Dockerfile for either WordPress or MySQL containers. Use the official Docker images mysql:5.7 and wordpress:latest.

When the script is completed, test the script, by running these tests:

No port set, test by navigating your web browser to localhost:8080, or if Docker Machine is used, use the IP addressed specified by docker-machine ip.
Clean Up the running containers (see clean up below).
Run the script again, but this time with the environment WORDPRESS_PORT set to another value, e.g. 8888, and then navigate your web browser to the same address (in step 1) with this port, e.g. localhost:8888.

Clean Up

To stop and remove the containers, you can the following:

docker ps -f name=wordpress -q | xargs docker stop && \
  docker ps -f name=wordpress -aq | xargs docker rmdocker ps -f name=db -q | xargs docker stop && \
  docker ps -f name=db -aq | xargs docker rm

If you would like to remove the volume and network, you can run:

docker volume rm db_data
docker network rm wordpress_net

Verifying Solution

If you have the tool Inspec installed, you can use this test case to validate the environment and practice systems level TDD.

Then with the containers running, run:

# run your solution
./docker_run # verify your solution
inspec exec container_test.rb

If you use specified a custom host port with WORDPRESS_PORT, you can do this:

# run your solution
export WORDPRESS_PORT=8888
./docker_run# verify your solution
echo "port: $WORDPRESS_PORT" > attributes.yml
inspec exec container_test.rb --attrs=attributes.yml

After, you should see something like this:

**Inspec Test Results of Successful Solution**

Until Next Time…

That’s the the lab, and if you are unfamiliar with Docker, this will require some research and tinkering. For those familiar with Docker, this may be a good lab to review commands, and also to compare and contrast to something like Docker Compose, that is easier to use than raw docker commands.

In the next article, I will follow up with a solution, and introduce doing a similar lab with Docker Compose and Ansible as alternatives to interact with Docker service and orchestrate containers.