Can you define optional docker-compose services?

Question

Is there a way to define a Docker Compose service such that it is only brought up when you explicitly request it?

That is to say:

docker-compose up 

would not start it, but

docker-compose up optional_service 

would.

Answer 1

One way to achieve that is to define your optional service in a different compose file. Then to start the optional service, run:

$ docker-compose -f docker-compose.yml -f optional-service.yaml up 

For example, if I have a docker-compose.yml file that looks like:

version: '2.1' services:   lb:     image: nginx:1.13              db:     image: redis:3.2.9 

I can extend it with an optional-service.yml that looks like:

version: '2.1' services:   busy:     image: busybox 

Notice that both compose files must use the same Compose file version.

You can read more about it in the Compose documentation.

Answer 2

Docker compose now supports profiles, which allow you to a) disable one or more services by default, and b) enable them when docker compose is ran with the corresponding --profile argument.

This is done by adding a profiles key to your service in the docker-compose.yml file. Services that have don't have this key are always started by docker-compose (for all profiles).

For example, with the following docker-compose.yml file

version: '3.9' services   app_service:     # ...   test_service:     profiles:       - testing     # ... 

Running docker-compose up will only start the app_service, and running docker-compose --profile testing up will start both the app_service and the test_service.

Multiple profiles can be specified by passing multiple --profile flags.

More info can be found here: https://docs.docker.com/compose/profiles/

Edit: I had to update to docker engine v20.10.5 for this to work.