9.6 Docker Compose Best Practices

Keeping Compose Files Simple and Readable

A good docker-compose.yml is easy to read and easy to change. Treat it like code that others will maintain after you.

Use clear, descriptive service names that reflect their role instead of internal hostnames. For example, prefer web, api, or db instead of service1 or containerA. Group related settings visually with consistent indentation and ordering. Many teams follow a simple order for keys inside a service such as image, build, ports, environment, volumes, depends_on, and then anything more advanced.

Avoid mixing everything into a single huge file when the project grows. You will see in larger setups that teams often split configuration by environment or concern so local development, testing, and production do not all live in one gigantic docker-compose.yml.

Write comments to explain non obvious decisions, especially when you add unusual networking, volume mappings, or entrypoint customizations. Comments help future you understand why a particular setting was added.

Finally, keep the version of your Compose file consistent across the project and update it deliberately. Even though newer Compose specifications often remove the need for a version field, if you use it, do not mix different styles in one repository.

Separating Build and Runtime Configuration

Compose can both build images and run them. It is tempting to cram all build settings and runtime settings into one place, but separating these concerns keeps the setup easier to manage.

Use the build section only for image building details such as context, dockerfile, and build arguments. Do not hide runtime configuration like passwords or environment specific URLs as build arguments. These should be provided as environment variables or configuration files at runtime.

When possible, prefer using pre built images from a registry for production and use build primarily for local development. This keeps the deployment more predictable and avoids surprising rebuilds when you deploy.

You can also define a base compose file that describes the core services, then have a separate override file that adds the build sections for local development. That way, all environments share the same layout, but only developers build locally.

Managing Environment Variables and Secrets

Compose makes it very convenient to pass environment variables to containers. This convenience can lead to bad habits if you are not deliberate about it.

Use .env files to centralize environment values used by Compose, especially values that change between machines like port numbers or hostnames. Keep these files out of version control when they contain anything sensitive. Many teams commit a .env.example which contains placeholders, then each developer creates their own real .env file locally.

Whenever you define credentials, API keys, or tokens, do not hard code them in docker-compose.yml. They should come from environment variables, separate configuration files, or a dedicated secrets mechanism.

For local development, you can sometimes use dummy values in the compose file itself, but treat this as a conscious choice and clearly label them as non production values.

Using Volumes Wisely

Volumes are powerful, but misuse can cause confusing bugs or performance issues. Compose makes it very easy to define and reuse volumes, so good habits matter.

Use named volumes for persistent data that containers should not overwrite on rebuilds. For example, a database service can use a named volume to hold its data directory. This keeps your data safe even if you remove and recreate the container.

Use bind mounts mainly for source code in development so you can hot reload or edit files on your host machine. Be careful not to mount over important paths inside the container by accident. A bind mount on a directory will hide whatever was in that directory in the image.

Declare volumes at the bottom of the compose file in the volumes section. This makes it easy to see all persistent storage used by your project in one place.

Try to avoid using anonymous volumes unless you know exactly why you need them. Anonymous volumes are created automatically without a name, which can make cleanup and debugging harder.

Networking and Service Communication

Compose sets up a default network so services can talk to each other by service name. Rely on this behavior instead of hard coding IP addresses. Have your web service connect to db:5432 or similar, not to an IP value. This keeps your setup portable and less fragile.

Use port mappings only when you want to expose a service to the host. For example, your database usually does not need to be reachable from outside the Compose network for simple local setups. Exposing fewer ports reduces risk and potential confusion.

If you need to separate traffic or apply different network rules, define additional custom networks and attach services to the appropriate ones. This helps when your project grows and you need more control over which services can communicate.

When mapping ports, avoid relying on privileged or conflicting host ports unless necessary. Instead of binding directly to a port already used by other software on your machine, choose an alternative host port when possible.

Dependencies and Start Up Order

Compose lets you define basic dependencies between services. Use depends_on only to describe that one service should start before another, not as a full health check or readiness tool.

Your application should handle the fact that a dependency might be up but not ready. For example, a web app should retry its database connection if the database is still starting. Compose is not a replacement for proper retry logic inside your application.

Avoid deeply nested or circular dependency chains in your compose file. They can make the startup process slow and hard to reason about. Keep dependency relationships simple and obvious.

If a specific service must be healthy before others can work, consider using health checks at the container level and let your application react to them rather than relying exclusively on Compose start order.

Structuring Multiple Environments

Projects often need separate setups for development, testing, and production. Compose supports this by letting you combine multiple files.

A common pattern is to keep a base docker-compose.yml that describes the core services in a generic way. Then you create environment specific files such as docker-compose.override.yml or docker-compose.prod.yml which adjust configuration for that environment.

Use overrides for values that change between environments such as published ports, resource limits, volume mounts for source code, and environment variables. This keeps common structure in one place while environment differences stay explicit and controlled.

When using multiple files, be consistent about how you run Compose. Use the same file combinations in your commands and in any scripts or CI pipelines so everyone gets the same behavior.

Handling Logs and Debugging

Compose collects logs from all services and can show them together. Use docker compose logs to review what is happening across the stack. For longer running projects, you might want to limit log size or configure log drivers on the individual services.

Design your compose setup to make debugging easy. Expose the minimum necessary ports, but include enough to connect debuggers or tools you rely on. Allow attaching to containers with shells or debugging processes without needing to rebuild images.

Keep your log related settings outside of production encrypted secrets so you can adjust them easily. This includes log levels set through environment variables and any volume mounts used for log files.

Controlling Resources and Limits

As projects grow, you may run many services at once. Without resource limits, a single misbehaving service can affect your whole system.

Use Compose to define reasonable CPU and memory limits for services where it makes sense. This is especially useful for local development so your workstation remains responsive while multiple containers run.

Be mindful that aggressive limits can cause services to restart frequently or behave strangely. Start with modest constraints and adjust based on real behavior you observe.

In some environments, like certain desktop operating systems, you might also configure overall Docker resource limits. Make sure your compose resource limits fit within these global settings.

Keeping Images and Dependencies Clean

Compose makes it easy to spin up many services, but each service uses images and potentially large dependencies. Over time, unused images, volumes, and networks can accumulate.

Regularly clean up unused resources with appropriate commands so your development environment stays lean. Do this deliberately to avoid losing data you still need from named volumes or running containers.

When updating images in your compose file, be explicit about tags. Relying on latest can lead to surprises when a new image is published that behaves differently. Instead, specify a tag that you know works for your project and update it intentionally.

Compose itself should be updated at times as well. When you update Compose or Docker versions, test your project carefully since behavior and defaults can change.

Using Compose in Teams and Automation

Compose is often part of a team workflow, not just a single developer’s tool. Design your files so any teammate can clone the repository, run a simple docker compose up, and get a working environment with minimal extra steps.

Document any prerequisites that must be installed before running Compose, and keep any custom scripts used to manage the project in the repository as well. This reduces surprises for new team members.

In automation, such as continuous integration, use Compose files that are close to what you run locally. This reduces the risk of “it works on my machine” problems. If you need special test only settings, keep them in a dedicated override file so the relationship to your regular compose setup remains clear.

Finally, treat docker-compose.yml as a core part of your application. Review changes to it carefully, just like you would review application code, because those changes control how your entire stack behaves.