Add new compose Kind

[vista-]

Users should be able to use Docker Compose projects in their Containerlab labs.

Motivation

At the moment, it requires some finesse and ext-container usage to be able to inject a project created via Docker Compose to a given container lab. Many of the more complex network applications require spinning up multiple containers for their dependencies, such as akvorado, and are made available as a Docker compose project.

To ease the creation of labs that include such applications, a new type of Kind, compose, could be introduced.

New compose kind

The compose kind should be very easy to use, like docker compose is. Specify a Docker Compose project (a YAML file), and you should have your Compose project running and connected into the lab's management network.

topology:
  nodes:
    composed_app:
      kind: compose
      project: app.yaml

Implementation

The Docker API used in the docker runtime implementation already includes Docker Compose functionality. The first, initial implementation of this feature should be able to load a given YAML file containing a Docker Compose project. The project's network, subnet and gateway config should be adjusted to match the lab's own, before passing it to the API's equivalent of docker compose up -d.

For tearing down the lab, one can just use the docker compose down API equivalent -- since Docker's Compose functionality does not require storing state, it can just re-use the specified compose project file.

The tricky parts are: data plane links to the composed application's containers, and of course, overriding regular single-container behaviour that default nodes exhibit.

The latter can be done by looking at ext-container's code and doing a similar approach (e.g. override GetContainers to return multiple containers associated with the Compose Project).

Limitations

There are some projects where a Docker Compose project is made out of multiple files, or to use overrides/envvars for templating. Data-plane links is also a hard problem to solve. The initial implementation should not be required to support these.