如何在CircleCI中关闭PR时触发构建及删除K8s预览环境？

Hey there! Let's break down your two CircleCI questions with practical, actionable steps:

CircleCI lets you target specific GitHub events (like PR closures) using workflow conditionals. Here's how to set it up in your .circleci/config.yml:

• Define a workflow that only runs when a PR is closed:

  workflows:
    pr-closed-trigger:
      jobs:
        - your-cleanup-job-name  # Replace this with the job you want to run
      when:
        and:
          - equal: [ github.event_name, pull_request ]
          - equal: [ github.event.action, closed ]
  

• If you need to filter further (e.g., only trigger for PRs targeting your main branch), add an extra condition:

  when:
    and:
      - equal: [ github.event_name, pull_request ]
      - equal: [ github.event.action, closed ]
      - equal: [ github.event.pull_request.base.ref, main ]
  

Absolutely! You can tie this cleanup directly to the PR closure trigger we just set up. Here's how to make it work:

Step 1: Grant CircleCI Access to Your Kubernetes Cluster #

First, ensure CircleCI can authenticate with your K8s cluster:

• Create a Context in the CircleCI dashboard, and add your Kubernetes credentials (e.g., a KUBECONFIG file content, or cluster API keys/certificates).
• Reference this context in your cleanup job to grant it cluster access.

Step 2: Write the Cleanup Job #

Define a job that runs kubectl commands to delete your preview environment. Most teams tag preview resources with the PR number (e.g., pr-id: ${CIRCLE_PR_NUMBER}) for easy targeting:

jobs:
  cleanup-preview-environment:
    docker:
      - image: cimg/base:stable
    context:
      - your-k8s-context-name  # Replace with your CircleCI context name
    steps:
      - run:
          name: Install kubectl
          command: |
            curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
            chmod +x kubectl
            sudo mv kubectl /usr/local/bin/
      - run:
          name: Authenticate to Kubernetes
          command: |
            # Load your kubeconfig (adjust this to match your auth method)
            echo "$KUBECONFIG_CONTENT" > ~/.kube/config
      - run:
          name: Delete Preview Environment Resources
          command: |
            # Delete all resources tagged with the PR number
            kubectl delete all -l pr-id=${CIRCLE_PR_NUMBER}
            # Or delete the entire namespace if you created one for the PR
            # kubectl delete namespace preview-pr-${CIRCLE_PR_NUMBER}

Step 3: Link the Job to the PR Closure Workflow #

Update your workflow to use this cleanup job, just like in the first example:

workflows:
  pr-closed-trigger:
    jobs:
      - cleanup-preview-environment
    when:
      and:
        - equal: [ github.event_name, pull_request ]
        - equal: [ github.event.action, closed ]

内容的提问来源于stack exchange，提问作者joseph