feat(CLI): Support context

[gaocegege]

Description

context is used to switch between the backends (e.g. docker, kubernetes)

[gaocegege]

cc @FogDong

[knight42]

It seems we could save the contexts into the config file, something like:

$ cat config.yaml
current-context: foo
contexts:
- name: foo
  docker:
    config-path: /path/to/config.json (Defaults to ~/.docker/config.json)
- name: bar
  kubernetes:
    config-path: /path/to/kubeconfig (Defaults to ~/.kube/config)

We could add a new subcommand, say context, to manage contexts in the config.

[knight42]

BTW this issue reminds me that docker cli supports context now: https://docs.docker.com/engine/context/working-with-contexts/

[gaocegege]

It seems we could save the contexts into the config file, something like:

$ cat config.yaml
current-context: foo
contexts:
- name: foo
  docker:
    config-path: /path/to/config.json (Defaults to ~/.docker/config.json)
- name: bar
  kubernetes:
    config-path: /path/to/kubeconfig (Defaults to ~/.kube/config)

We could add a new subcommand, say context, to manage contexts in the config.

Yeah, the design LGTM although envd does not support k8s now. We can support different docker contexts currently.

[gaocegege]

We may need to support two different context types: build and run.

The context for the build is to determine what buildkit will be used in envd. For example, buildkit container in the docker daemon docker-container://envd_buildkitd can be used. Or kube-pod://<pod-name-for-buildkit> also can be used if there is a buildkitd running on the Kubernetes.

Users may expect to use the buildkit on Kubernetes for CI. Ref #510

The context for the run will be used when running envd up. The container or pod will be created after the image is built successfully with buildkitd. We can use Docker or Kubernetes to run it. Thus we also need to support context here.

[gaocegege]

The user experience for the build may look like this:

envd context create --name docker-buildkit --builder docker-container://envd_buildkitd
envd context create --name kubernetes-buildkit --builder kube-pod://envd-buildkitd
envd context use --name kubernetes-buildkit
envd build 

The user experience for the run may look like this:

envd context create --name docker --docker /var/run/docker.sock
envd context create --name kubernetes --kubernetes <kubeconfig-path>
envd context use kubernetes 
envd up

The default builder should be docker-container://envd_buildkitd, the default runner should be --docker /var/run/docker.sock (Maybe different in macOS)

[gaocegege]

@rudeigerc Hi are you still interested in the issue? Users expect it in the next release to support #510

[rudeigerc]

@gaocegege I am a little bit running out of time recently. Please feel free to unassign me if other ones are interested in this issue.