Compose file

The Compose file is a YAMLopen_in_new file defining:

• Version (Optional)
• Services (Required)
• Networks
• Volumes
• Configs
• Secrets

The default path for a Compose file is compose.yaml (preferred) or compose.yml that is placed in the working directory. Compose also supports docker-compose.yaml and docker-compose.yml for backwards compatibility of earlier versions. If both files exist, Compose prefers the canonical compose.yaml.

You can use fragments and extensions to keep your Compose file efficient and easy to maintain.

Multiple Compose files can be merged together to define the application model. The combination of YAML files are implemented by appending or overriding YAML elements based on the Compose file order you set. Simple attributes and maps get overridden by the highest order Compose file, lists get merged by appending. Relative paths are resolved based on the first Compose file's parent folder, whenever complimentary files being merged are hosted in other folders. As some Compose file elements can both be expressed as single strings or complex objects, merges apply to the expanded form.

If you want to reuse other Compose files, or factor out parts of you application model into separate Compose files, you can also use include. This is useful if your Compose application is dependent on another application which is managed by a different team, or needs to be shared with others.