Docker link to previously started containers

Question

I'd like to carry out a one shot docker-compose run that will run against some previously started containers. My docker-compose.yml file will look like this:

one_shot_service:
 ...
  links:
    - long_running_service:docker
long_running_service:
  ...

My workflow is:

1. Start the long running service docker-compose up long_running_service
2. Run the one shot service multiple times. docker-compose run --no-deps one_shot_service

When I do this the /etc/hosts file on the one_shot_service does not contain an entry for docker. When I run without --no-deps it's fine. The reason I don't want to run without no-deps is beause the long_running_service takes a long time to start up.

So long story short, how can I link to existing containers?

Answer 1

You can use the external_links directive.

Example:

external_links:
    - long_running_service:your_alias