Docker Compose for Database Containers: Best Practices

Docker Compose is a nice way to easily handle any multi-container Docker application. Best practices of containers for databases are necessary to ensure reliability, security, and performance. This article covers key strategies for managing database containers using Docker Compose and therefore is a strong foundation for deploying and maintaining databases in an environment with containers.

Primary Terminologies

• Docker Compose: It is a tool that allows defining and running multi-container Docker applications. It provides users with an ability to manage the whole application lifecycle by just a single command, employing a YAML file for configuring services, networks, and volumes.
• Database Container: This is a database engine that is encapsulated in a Docker container instance, be it MySQL, PostgreSQL, or MongoDB, these containers execute the isolated instance of databases, making it easy to deploy, scale, and administrate.
• Volumes: Docker volumes are used to persist the data that is created with and consumed by Docker containers. For database containers, that helps in ensuring the data remains intact even when the container is restarted or removed.
• Networking: In Docker Compose, it is configuring the way communication is organized between containers. For database containers, this refers to the manner in which the database container communicates with other application services.
• Environment Variables: Key-value pairs defined in the Docker Compose file that configure container settings, for example, passwords for databases, user credentials, and connection details

Step-by-Step Process: Setting Up and Managing a Database Container with Docker Compose

Step 1: Install docker

Install docker

sudo yum -y install docker

Now start and enable docker daemon

sudo systemctl start docker
sudo systemctl enable docker
sudo systemctl status docker

Step 2: Install docker compose

Install docker compose

sudo curl -L https://github.com/docker/compose/releases/download/1.22.0/docker-compose-$(uname -s)-$(uname -m) -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose

Step 3: Define Environment Variables Securely

Environment variables, such as database credentials, should be managed securely. Instead of hardcoding sensitive information directly in the docker-compose.yml file, consider using a .env file:

Create a .env file in the project directory:

touch .env

• Add the environment variables to the .env file:

MYSQL_ROOT_PASSWORD=example_root_password

MYSQL_DATABASE=example_db

MYSQL_USER=example_user

MYSQL_PASSWORD=example_password

Step 4: Create a docker-compose.yml File

• In the docker-compose.yml file, define the database service. This example sets up a MySQL database

version: '3.3'

services:

db:

image: mysql:latest

container_name: my_database

env_file:

- .env

volumes:

- db_data:/var/lib/mysql

networks:

- app_network

ports:

- "3306:3306"

restart: unless-stopped

healthcheck:

test: ["CMD-SHELL", "mysqladmin ping -h localhost"]

interval: 30s

timeout: 10s

retries: 5

volumes:

db_data:

driver: local

networks:

app_network:

driver: bridge

Step 5: Start the Services with Docker Compose

• With your docker-compose.yml configured, start the services using Docker Compose:

docker-compose up -d

Step 6: Verify the Database Container

To ensure that the database container is running correctly, you can use the following command

docker ps 

Step 7: Connect to the Database

Before going to connect install MySQL by using following command

sudo yum install mysql -y

You can connect to the MySQL database container using the MySQL command-line client from another container in the same network or directly from your host machine.

Access MySQL inside the Docker container:

docker exec -it my_database mysql -u root -p

Show Databases

To list all databases:

Select a Database

• To switch to a specific database:

USE your_database_name;

Replace your_database_name with the name of the database you want to use

Insert Data

• To insert data into a table:

INSERT INTO example_table (name) VALUES ('Sample Data');

Show Tables

• To list all tables in the currently selected database:

SHOW TABLES;

Exit MySQL

• To exit the MySQL monitor:

EXIT;

Step 8: Stop the MySQL Container

docker-compose down

Best Practices for Managing Database Containers

• Data Persistence: Always use Docker volumes to persist your database data this will keep the data safe even if the containers are stopped or removed.
• Secure Configuration: Make use of environment variables, and .env files, for handling sensitive information like passwords and API keys, never hardcode these types of values directly in the docker-compose.yml file.
• Networking Configuration: Keep your database container on a private network, which is open only to trusted services. Make database ports public if, and only if, necessary.
• Backups: Regularly back up the data in your database with scheduled jobs that dump the content of your database and store it outside of your container environment.
• Monitoring and Logging: Monitor and log activities in and around your database containers for performance metrics, error logs, and access patterns

Conclusion

In this article, we have covered the best practices for managing MySQL databases with Docker Compose. We configured a docker-compose.yml file to set up a MySQL container with environment variables to manage credentials securely, map ports for external access, and health checks for reliability. We handled connection issues by showing how to use host IP and resolve issues about authentication plugin errors. We also connected to MySQL from within Docker and from outside systems, and we covered basic SQL commands used for database management. Some troubleshooting tips were also detailed in the document, which might come in handy in resolving common problems such as client upgrades or changing authentication methods, by doing this, you will now be able to handle your MySQL databases within Docker in a more secure, scalable, and usable way. The MySQL and Docker documentation will help you with more assistance