Compose Files

Compose uses YAML files to define multi-service applications. YAML is a subset of JSON, so you can also use JSON. However, all the examples in this chapter will be YAML.

The default name for a Compose YAML file is docker-compose.yml. However, you can use the -f flag to specify custom filenames.

Sample YAML file

The following example shows a very simple Compose file that defines a small Flask app with two microservices (web-fe and redis). The app is a simple web server that counts the number of visits to a web page and stores the value in Redis. We’ll call the app counter-app and use it as the example application for the rest of the chapter.