Inject kubectl-compatible config file into the CI job

Release notes

Until now users of the Kubernetes Agent CI tunnel had to inject a corresponding kubeconfig file into the CI manually. Creating this kubeconfig required the editing of the CI pipeline definition, the knowledge of the Agent ID and the understanding of how a kubeconfig is structured, and introduced boilerplate code into the CI pipeline definition. GitLab now ships with an automatically injected kubeconfig file that contains all the available agent connections for the given project, and the user has to simply choose just the right kubecontext to use.

The injected kubeconfig contains contexts for every available agent in the form of group/agent-config-project/slug:agent-name. Users can easily select the agent connection they want to use by providing just the context name following this pattern.

Proposal

The context name should use the format <config project path>:<agent name>:

$ kubectl config set-context group/config/project:agent-name
$ kubectl config get-contexts | grep "group/config/project"

Going that route will also make it easier/more robust to select a default current-context via future .gitlab-ci.yaml syntactic sugar, see environment.kubernetes.context below:

deploy:
  stage: deploy
  variables:
    AGENT_CONFIG_PROJECT: group/config/project
  parallel:
    matrix:
    - AGENT: us-west1
    - AGENT: us-east1
    - AGENT: us-central1
  environment:
    name: production
    kubernetes:
      context: $AGENT_CONFIG_PROJECT:$AGENT # easy to construct + maps 1:1 with context name
  script:
  - kubectl config current-context # -> "group/config/project:us-..."
  - make deploy-app

Scope

• [ ] inject the kubecontext

Not in scope

• the CI extension of environment.kubernetes.context