Best Docker Practices

1. Optimize Image Size

• Use Official Images: Start with trusted and official Docker images as a base.
• Use Minimal Base Images: Lightweight images like alpine are smaller, faster to download, and reduce the attack surface.
• Minimize Layers: Combine commands to minimize the number of layers in your Dockerfile (e.g., use && to chain commands in a single RUN statement).
• Clear Cache: Remove package managers and caches after installation (e.g., apt-get clean for Ubuntu).

2. Secure Images and Containers

• Use Multi-Stage Builds: Separate build dependencies from the runtime environment, making production images leaner.
• Run as Non-Root: Avoid using the root user inside your containers. Use USER in Dockerfile to specify a non-root user.
• Keep Docker Updated: Regularly update Docker itself and any images used.
• Use COPY Instead of ADD: COPY is more straightforward and doesn’t perform automatic decompression like ADD, reducing ambiguity.
• Leverage .dockerignore: To avoid copying unnecessary files to the image, create a .dockerignore file similar to .gitignore.

3. Optimize Dockerfile Instructions

• Order Instructions to Leverage Caching: Place less-frequently changing instructions at the top of your Dockerfile to leverage Docker’s caching mechanism.
• Use Specific Versions: Avoid using latest tags in production environments; pin images to specific versions to ensure stability and reproducibility.

4. Use Docker Compose for Multi-Container Applications

• Separate Concerns by Using Multiple Containers: For complex applications, break down services (e.g., separate databases, web servers, and application layers) into different containers.
• Use Docker Compose for Local Development: It makes handling complex multi-container applications easier and creates a consistent environment.

5. Limit Resource Usage

• Set Memory and CPU Limits: Use Docker’s resource constraints to avoid a single container using excessive resources (--memory, --cpus).
• Use Read-Only Filesystems: Limit filesystem access to read-only whenever possible (--read-only).

6. Logging and Monitoring

• Centralize Logging: Configure Docker to send logs to a centralized logging service (like ELK Stack, Splunk, or AWS CloudWatch).
• Monitor Containers: Use tools like Prometheus or Grafana to monitor performance, memory, and CPU usage.

7. Secure Communication Between Containers

• Use Private Networks: Avoid exposing unnecessary ports and use Docker networks to isolate services.
• Use Secrets Management: For sensitive information like passwords and keys, use Docker Secrets, especially in swarm mode.

8. Optimize Container Health and Lifecycle

• Set Health Checks: Add health checks in your Dockerfile to ensure the container is healthy (HEALTHCHECK directive).
• Clean Up Unused Containers and Images: Regularly clean up unused images, containers, volumes, and networks (docker system prune) to save disk space.

9. Use Multi-Stage Builds

Multi-stage builds allow you to create leaner production images by separating build dependencies from runtime requirements.

• Build Stage: Create a first stage for compiling or building the application. This stage can include all necessary dependencies and tools.
• Final Stage: Copy only the required files from the build stage to a smaller base image. This results in a cleaner, smaller final image.
• Example: We are using Alpine image for laravel

FROM serversideup/php:8.2-cli-v2.2.1 as builder

ARG LARAVEL_ENV_ENCRYPTION_KEY
COPY ./ /var/www
WORKDIR /var/www

RUN <<EOF 
composer install --ignore-platform-reqs --no-interaction --no-dev --prefer-dist --optimize-autoloader

php artisan env:decrypt --force
EOF
# ================================================ #

FROM serversideup/php:8.2-fpm-nginx-v2.2.1

ENV AUTORUN_LARAVEL_MIGRATION=true
ENV SSL_MODE=off
ENV PHP_MEMORY_LIMIT=128M
ENV PHP_MAX_EXECUTION_TIME=30

WORKDIR /var/www/html

COPY --chown=$PUID:$PGID --from=builder /var/www/ /var/www/html

RUN php artisan optimize

HEALTHCHECK CMD curl -s --fail http://localhost/health || exit 1

CMD ["su", "webuser", "-c", "php artisan schedule:work"]

EXPOSE 80

10. Use Build Kit to speed up Docker builds

Docker BuildKit is an opt-in image building engine which offers substantial improvements over the traditional process. BuildKit creates images layers in parallel, accelerating the overall build process.

Although BuildKit is now stable, Docker still doesn't ship with it on by default. Make sure to enable it in your Docker client if you want to use its features. There's an active proposal to make BuildKit the standard build engine but there are still unresolved issues preventing the switch.

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Adhering to these best practices can streamline development, improve security, and make it easier to scale and maintain Docker environments.

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