From e62c17962656c086cc0b3d8acf76983daf624e22 Mon Sep 17 00:00:00 2001 From: medusa Date: Tue, 5 Aug 2025 22:03:58 -0500 Subject: [PATCH] Add tech_docs/docker_compose_guide.md --- tech_docs/docker_compose_guide.md | 272 ++++++++++++++++++++++++++++++ 1 file changed, 272 insertions(+) create mode 100644 tech_docs/docker_compose_guide.md diff --git a/tech_docs/docker_compose_guide.md b/tech_docs/docker_compose_guide.md new file mode 100644 index 0000000..18dd4cb --- /dev/null +++ b/tech_docs/docker_compose_guide.md @@ -0,0 +1,272 @@ +# Deterministic Serendipity: A Comprehensive Guide to Mastering Docker Compose + +## Introduction +Docker Compose is a powerful tool for defining and running multi-container Docker applications. By treating everything as an object within the `docker-compose.yml` file, we can achieve deterministic serendipity—creating a configuration that is both predictable and flexible. This guide aims to provide a highly technical and dense overview of the various components, best practices, and pitfalls to avoid, ensuring you can achieve mastery over your Docker Compose files. + +## Services +### Overview +Services are the core objects in a Docker Compose file, representing individual containers that make up your application. + +### Key Components +- **image**: Specifies the Docker image to use. +- **build**: Specifies the build context for a Dockerfile. +- **ports**: Maps container ports to host ports. +- **environment**: Sets environment variables. +- **volumes**: Mounts volumes or bind mounts. +- **depends_on**: Defines startup dependencies. +- **healthcheck**: Defines health check commands. +- **user**: Specifies the user to run the container as. +- **deploy**: Defines deployment configurations (e.g., resource limits). + +### Best Practices +- **Modular Design**: Each service should have a single responsibility. +- **Health Checks**: Ensure services are healthy before starting dependent services. +- **Environment Variables**: Use `.env` files for managing environment variables. +- **Non-Root Users**: Run services as non-root users to enhance security. + +### Pitfalls to Avoid +- **Hardcoding Secrets**: Avoid hardcoding sensitive information directly in the Compose file. +- **Overuse of `depends_on`**: Use `depends_on` with caution, as it only controls startup order, not health checks. + +### Example +```yaml +services: + web: + image: node:20 + ports: + - "5000:5000" + environment: + - NODE_ENV=production + - DB_HOST=db + depends_on: + db: + condition: service_healthy + networks: + - frontend + user: "node" + + db: + image: postgres:15 + volumes: + - db_data:/var/lib/postgresql/data + healthcheck: + test: ["CMD-SHELL", "pg_isready -U postgres"] + interval: 10s + timeout: 5s + retries: 5 + networks: + - backend +``` + +## Networks +### Overview +Networks define how services communicate with each other. + +### Key Components +- **name**: Specifies the network name. +- **driver**: Specifies the network driver (e.g., `bridge`). +- **ipam**: Configures IP address management. + +### Best Practices +- **Custom Networks**: Define custom networks to control how services communicate. +- **Isolation**: Use separate networks for different layers of your application (e.g., frontend and backend). + +### Pitfalls to Avoid +- **Default Networks**: Avoid using the default network; define custom networks for better control. + +### Example +```yaml +networks: + frontend: + backend: +``` + +## Volumes +### Overview +Volumes manage persistent storage for services. + +### Key Components +- **name**: Specifies the volume name. +- **driver**: Specifies the volume driver (e.g., `local`). +- **driver_opts**: Configures driver options. + +### Best Practices +- **Named Volumes**: Use named volumes for persistent storage. +- **Bind Mounts**: Use bind mounts for development to share code between the host and container. + +### Pitfalls to Avoid +- **Hardcoding Paths**: Avoid hardcoding paths in bind mounts; use environment variables or `.env` files. + +### Example +```yaml +volumes: + db_data: +``` + +## Profiles +### Overview +Profiles manage different configurations for different environments. + +### Key Components +- **profiles**: Specifies the profiles for a service. + +### Best Practices +- **Environment-Specific Configurations**: Use profiles to manage different environments (development, production, etc.). +- **Conditional Services**: Enable or disable services based on the profile. + +### Pitfalls to Avoid +- **Overuse of Profiles**: Use profiles judiciously to avoid complexity. + +### Example +```yaml +services: + debug: + image: busybox + profiles: + - debug +``` + +## Extensions +### Overview +Extensions provide additional configurations for services. + +### Key Components +- **deploy**: Defines deployment configurations (e.g., resource limits). +- **resources**: Specifies resource limits (e.g., memory, CPU). + +### Best Practices +- **Resource Limits**: Define resource limits to prevent services from monopolizing resources. +- **Deploy Configurations**: Use deploy configurations for production setups. + +### Pitfalls to Avoid +- **Over-Configuring**: Avoid over-configuring extensions; use only what is necessary. + +### Example +```yaml +services: + api: + deploy: + resources: + limits: + memory: 512M + cpus: "1.0" +``` + +## Environment Variables +### Overview +Environment variables manage configuration and secrets. + +### Key Components +- **environment**: Sets environment variables. +- **env_file**: Specifies an environment file. + +### Best Practices +- **.env File**: Use a `.env` file to manage environment variables securely. +- **Avoid Hardcoding**: Avoid hardcoding sensitive information directly in the Compose file. + +### Pitfalls to Avoid +- **Insecure Storage**: Avoid storing sensitive information in plaintext. + +### Example +```yaml +services: + web: + environment: + - NODE_ENV=production + - DB_HOST=db + env_file: .env +``` + +## Health Checks +### Overview +Health checks ensure services are healthy before starting dependent services. + +### Key Components +- **test**: Specifies the command to run for the health check. +- **interval**: Specifies the interval between health checks. +- **timeout**: Specifies the timeout for health checks. +- **retries**: Specifies the number of retries for health checks. + +### Best Practices +- **Conditional Dependencies**: Use health checks to ensure services are ready before starting dependent services. + +### Pitfalls to Avoid +- **Inadequate Health Checks**: Ensure health checks are robust and meaningful. + +### Example +```yaml +services: + db: + image: postgres:15 + healthcheck: + test: ["CMD-SHELL", "pg_isready -U postgres"] + interval: 10s + timeout: 5s + retries: 5 +``` + +## User Management +### Overview +User management ensures services run as non-root users. + +### Key Components +- **user**: Specifies the user to run the container as. + +### Best Practices +- **Non-Root Users**: Run services as non-root users to enhance security. + +### Pitfalls to Avoid +- **Running as Root**: Avoid running services as root to reduce security risks. + +### Example +```yaml +services: + web: + user: "node" +``` + +## Regular Updates +### Overview +Regular updates ensure containers are up to date with the latest security patches. + +### Key Components +- **Watchtower**: Automates container updates. + +### Best Practices +- **Automate Updates**: Use tools like Watchtower to keep your containers up to date. + +### Pitfalls to Avoid +- **Manual Updates**: Avoid manual updates to reduce the risk of missing security patches. + +### Example +```bash +docker run -d --name watchtower \ + -v /var/run/docker.sock:/var/run/docker.sock \ + containrrr/watchtower +``` + +## Documentation +### Overview +Documentation ensures your `docker-compose.yml` file is understandable and maintainable. + +### Key Components +- **Comments**: Adds comments to clarify configurations. + +### Best Practices +- **Clear Documentation**: Add comments to your `docker-compose.yml` file to make it easier to understand. + +### Pitfalls to Avoid +- **Lack of Documentation**: Avoid leaving your `docker-compose.yml` file uncommented. + +### Example +```yaml +# Web service running Node.js API +services: + web: + image: node:20 +``` + +## Conclusion +By treating everything as an object within your `docker-compose.yml` file and following the best practices outlined in this guide, you can achieve deterministic serendipity—creating a configuration that is both predictable and flexible. This guide provides a comprehensive overview of the key components, best practices, and pitfalls to avoid, ensuring you can master your Docker Compose files and achieve zen with your containerized applications. + +Thank you for your patience and understanding. I hope this guide helps you create expert-level Docker Compose files. \ No newline at end of file