circleci

name: circleci description: "[Applies to: **/*] This guide provides opinionated, actionable best practices for writing maintainable, secure, and performant CircleCI configurations and orbs." source: "cursor_mdc"

circleci Best Practices

CircleCI is the backbone of our CI/CD. Adhere to these guidelines to ensure our pipelines are efficient, secure, and maintainable.

1. Code Organization & Reusability

1.1. Author and Consume Orbs for Reusability

Encapsulate common logic into orbs. This promotes DRY principles and consistent patterns across projects.

• Descriptive Naming: Use clear namespace/orb-name slugs. ❌ BAD: myorg/plugin, myorg/ci-tool ✅ GOOD: myorg/docker-publish, myorg/aws-deploy

• Semantic Versioning: Lock to specific orb versions. ❌ BAD: myorg/aws-deploy@volatile ✅ GOOD: myorg/aws-deploy@1.2.3

• Comprehensive Descriptions: Every orb component (commands, jobs, executors, parameters) must have a clear description.

  # .circleci/orb.yml
  commands:
    my-command:
      description: "Utilize this command to echo Hello to a step in the UI."
      steps:
        - run: echo "Hello"
  

1.2. Reuse Commands, Executors, and Jobs

Within your config.yml or orbs, define reusable components to avoid duplication.

❌ BAD:

jobs:
  build-and-test:
    docker:
      - image: cimg/node:18.17.1
    steps:
      - checkout
      - run: npm install
      - run: npm test
  another-job:
    docker:
      - image: cimg/node:18.17.1
    steps:
      - checkout
      - run: npm install # Duplication
      - run: npm run build

✅ GOOD:

# .circleci/config.yml
version: 2.1
commands:
  install_deps:
    description: "Install Node.js dependencies."
    steps:
      - run: npm install

jobs:
  build-and-test:
    docker:
      - image: cimg/node:18.17.1
    steps:
      - checkout
      - install_deps
      - run: npm test
  build-app:
    docker:
      - image: cimg/node:18.17.1
    steps:
      - checkout
      - install_deps
      - run: npm run build

1.3. Use Pass-Through Parameters in Jobs

When a job uses a command or executor that accepts parameters, expose those parameters at the job level for flexibility.

# .circleci/orb.yml (partial)
executors:
  default:
    docker:
      - image: 'cimg/node:<<parameters.tag>>'
    parameters:
      tag:
        type: string
        default: '18.17'

jobs:
  test:
    description: "Simple job to test Node.js application."
    parameters:
      version: # Pass-through parameter for the executor's tag
        type: string
        default: '18.17'
    executor:
      name: default
      tag: << parameters.version >> # Pass parameter to executor
    steps:
      - checkout
      - run: npm test

2. Security & Configuration Management

2.1. Store Secrets in Contexts

Never hard-code secrets or expose them directly in config.yml. Use CircleCI Contexts for sensitive environment variables.

❌ BAD:

jobs:
  deploy:
    steps:
      - run: echo "Deploying with API_KEY=$MY_API_KEY" # MY_API_KEY defined directly in config or as unmanaged env var

✅ GOOD:

# In CircleCI UI, define a Context named 'my-app-secrets' with MY_API_KEY
jobs:
  deploy:
    docker:
      - image: cimg/base:stable
    steps:
      - run: echo "Deploying with API_KEY=$MY_API_KEY" # MY_API_KEY is loaded from 'my-app-secrets' context
workflows:
  build-and-deploy:
    jobs:
      - deploy:
          context: my-app-secrets # Apply the context to the job

3. Performance Optimization

3.1. Leverage Caching for Dependencies

Cache dependencies and build artifacts to significantly speed up pipeline execution.

❌ BAD:

jobs:
  build:
    docker:
      - image: cimg/node:18.17.1
    steps:
      - checkout
      - run: npm install # Downloads dependencies every time
      - run: npm test

✅ GOOD:

jobs:
  build:
    docker:
      - image: cimg/node:18.17.1
    steps:
      - checkout
      - restore_cache: # Restore cache based on package-lock.json
          keys:
            - v1-dependencies-{{ checksum "package-lock.json" }}
            - v1-dependencies- # Fallback to latest cache
      - run: npm install
      - save_cache: # Save cache if dependencies changed
          paths:
            - node_modules
          key: v1-dependencies-{{ checksum "package-lock.json" }}
      - run: npm test

3.2. Parallelize Jobs and Tests

Distribute work across multiple containers to reduce overall build time, especially for large test suites.

jobs:
  run-tests:
    docker:
      - image: cimg/node:18.17.1
    parallelism: 4 # Run 4 containers concurrently
    steps:
      - checkout
      - run:
          name: Run parallel tests
          command: |
            # Example: split tests using a tool like 'circleci tests split'
            npx jest --json --outputFile=test-results.json --coverage --testResultsProcessor="jest-junit" \
              $(circleci tests glob "src/**/*.test.js" | circleci tests split --split-by=timings)
      - store_test_results:
          path: test-results.json

3.3. Consolidate run Steps

Minimize UI noise and improve readability by combining related shell commands into a single run step.

❌ BAD:

steps:
  - run: pip install example
  - run: example login $MY_TOKEN
  - run: example deploy my-app

✅ GOOD:

steps:
  - run:
      name: Deploy application
      command: |
        pip install example
        example login $MY_TOKEN
        example deploy my-app

4. Robust Testing & Quality Gates

4.1. Implement Comprehensive Testing

Automate unit, integration, and security (SAST/DAST) tests. Enforce these tests as gatekeepers before deployment.

workflows:
  build-test-deploy:
    jobs:
      - unit-test
      - integration-test:
          requires: [unit-test]
      - security-scan:
          requires: [integration-test]
      - deploy-staging:
          requires: [security-scan]
      - hold-for-prod:
          type: approval
          requires: [deploy-staging]
      - deploy-production:
          requires: [hold-for-prod]

4.2. Serverless CI/CD Considerations

For serverless applications, include specific steps for packaging, Infrastructure as Code (IaC) validation, and canary deployments.

jobs:
  serverless-deploy:
    docker:
      - image: cimg/python:3.9
    steps:
      - checkout
      - run: pip install serverless # Install Serverless Framework
      - run: serverless deploy --stage dev # Deploy to dev
      - run: serverless deploy --stage prod --type canary # Canary deployment

5. Common Pitfalls & Best Practices

5.1. Conditionally Use sudo

Check if the user is already root before adding sudo to commands.

❌ BAD:

steps:
  - run: sudo apt-get update

✅ GOOD:

steps:
  - run:
      name: Update apt packages
      command: |
        if [[ $EUID == 0 ]]; then export SUDO=""; else export SUDO="sudo"; fi
        $SUDO apt-get update

5.2. Pin Docker Image Tags

Always use specific, stable Docker image tags, not latest.

❌ BAD: cimg/node:latest ✅ GOOD: cimg/node:18.17.1

5.3. Use Admonitions in Documentation

For orb descriptions or comments in config.yml, use CircleCI's admonition syntax for emphasis.

# NOTE: This command requires AWS credentials configured in a context.
# CAUTION: Deploying to production will trigger a canary release.