Skill: CI/CD Pipeline

When to Use This Skill

This skill activates when you need to:

• Understand the project's CI/CD setup
• Debug failing CI/CD pipelines
• Fix workflow errors
• Add or modify CI checks
• Understand why checks are failing on your PR

Prerequisites

• Basic understanding of CI/CD concepts
• Access to repository (to view workflow runs)
• Understanding of project's tech stack

Step-by-Step Workflow

Step 1: Identify CI/CD Platform

Check for CI configuration files:

# GitHub Actions
.github/workflows/*.yml

# GitLab CI
.gitlab-ci.yml

# CircleCI
.circleci/config.yml

# Travis CI
.travis.yml

# Jenkins
Jenkinsfile

# Azure Pipelines
azure-pipelines.yml

Step 2: View CI Pipeline Status

GitHub Actions (via CLI):

# Install GitHub CLI if needed
# https://cli.github.com/

# List recent workflow runs
gh run list

# View specific run
gh run view <run-id>

# Watch a running workflow
gh run watch

GitHub Actions (via Web):

1. Go to repository on GitHub
2. Click "Actions" tab
3. Select workflow run
4. View job details and logs

Step 3: Understand Common CI Workflows

Typical CI Pipeline Stages

# .github/workflows/ci.yml example
name: CI
on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Setup
        # Install dependencies
      - name: Lint
        # Run linter
      - name: Test
        # Run tests
      - name: Build
        # Build project

Common stages:

1. Checkout - Clone repository code
2. Setup - Install language/dependencies
3. Lint - Check code style
4. Test - Run test suite
5. Build - Compile/build project
6. Deploy - Deploy to environment (optional)

Step 4: Debug Failing CI Checks

Step 4a: Identify Which Check Failed

Look at PR checks:

• ✅ Green check - Passed
• ❌ Red X - Failed
• 🟡 Yellow dot - Running
• ⚪ Gray circle - Pending

Click on failed check to see:

• Job name
• Failure step
• Error message
• Logs

Step 4b: Common Failure Patterns

Pattern 1: Linting Failures

Error example:

Error: Format check failed
black --check . returned non-zero exit code

Fix:

# Run formatter locally
black .
# or
prettier --write .

# Commit and push
git add .
git commit -m "style: fix formatting"
git push

Pattern 2: Test Failures

Error example:

FAILED tests/test_user.py::test_login - AssertionError

Fix:

# Run tests locally
pytest tests/test_user.py::test_login -v

# Debug and fix
# Re-run all tests
pytest

# Commit fix
git add .
git commit -m "fix: resolve test failure in login"
git push

Pattern 3: Build Failures

Error example:

Error: Module not found: 'missing-package'
npm ERR! code ELIFECYCLE

Fix:

# Add missing dependency
npm install missing-package --save

# Or fix import
# Commit and push
git add package.json package-lock.json
git commit -m "fix: add missing dependency"
git push

Pattern 4: Timeout Errors

Error example:

Error: The job exceeded the maximum execution time

Fix:

# Increase timeout in workflow
jobs:
  test:
    timeout-minutes: 30  # Increase from default 360

Pattern 5: Environment Issues

Error example:

Error: Environment variable DATABASE_URL not set

Fix:

# Add secret/env var in workflow
jobs:
  test:
    env:
      DATABASE_URL: postgresql://localhost/test

Or add in GitHub repository settings:

• Settings → Secrets and variables → Actions
• Add new secret

Step 4c: View Detailed Logs

Download logs:

# GitHub Actions
gh run download <run-id>

# Or via web UI
# Click on failed step → View raw logs → Download

Key things to look for in logs:

• Last successful step before failure
• Exact error message
• Stack trace
• Environment variables
• Dependency versions

Step 5: Fix Common CI Issues

Issue: Tests pass locally but fail in CI

Possible causes:

• Different Python/Node version
• Missing environment variables
• Different OS (Mac vs Linux)
• Cached dependencies
• Timezone differences

Solutions:

# Match local versions in CI
- uses: actions/setup-python@v4
  with:
    python-version: '3.10'  # Match your local version

# Clear cache
- name: Clear pip cache
  run: pip cache purge

# Set environment variables
env:
  TZ: America/New_York
  DATABASE_URL: ${{ secrets.DATABASE_URL }}

Issue: Linter fails in CI but passes locally

Cause: Different linter version or configuration

Solutions:

# Pin linter version
# requirements.txt
black==23.7.0
ruff==0.0.280

# package.json
"devDependencies": {
  "prettier": "3.0.0",
  "eslint": "8.44.0"
}

# Run same command as CI locally
npm run lint
black --check .

Issue: Build succeeds but deploy fails

Cause: Environment-specific issues

Solutions:

• Check deployment credentials
• Verify target environment is accessible
• Check for deployment-specific env vars
• Review deploy step logs carefully

Step 6: Run CI Checks Locally

GitHub Actions with act:

# Install act
brew install act  # macOS
# or download from github.com/nektos/act

# Run workflow locally
act

# Run specific job
act -j test

# Run with secrets
act --secret-file .env.secrets

Pre-commit hooks (mimics CI):

# Install pre-commit
pip install pre-commit

# Install hooks
pre-commit install

# Run all hooks
pre-commit run --all-files

Step 7: Modify CI Workflow

Add a new check:

# .github/workflows/ci.yml
jobs:
  security-scan:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Run security scan
        run: |
          pip install bandit
          bandit -r src/

Add caching:

- name: Cache dependencies
  uses: actions/cache@v3
  with:
    path: ~/.cache/pip
    key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}

Matrix strategy (test multiple versions):

jobs:
  test:
    strategy:
      matrix:
        python-version: ['3.8', '3.9', '3.10', '3.11']
    steps:
      - uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

Common CI/CD Patterns

Pattern 1: PR Checks

name: PR Checks
on: pull_request

jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - run: npm run lint
  
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - run: npm test
  
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - run: npm run build

Pattern 2: Main Branch Deploy

name: Deploy
on:
  push:
    branches: [main]

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Deploy to production
        run: ./deploy.sh
        env:
          DEPLOY_KEY: ${{ secrets.DEPLOY_KEY }}

Pattern 3: Release on Tag

name: Release
on:
  push:
    tags:
      - 'v*'

jobs:
  release:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Build and publish
        run: npm publish

Common Issues and Solutions

Issue: CI is stuck or taking too long

Solutions:

1. Check for infinite loops in tests
2. Verify no blocking operations
3. Increase timeout
4. Use caching for dependencies
5. Cancel and restart workflow

Issue: Secrets not accessible

Solutions:

1. Add secret in repository settings
2. Reference correctly: ${{ secrets.SECRET_NAME }}
3. Check secret is available for forks (if applicable)
4. Verify workflow has correct permissions

Issue: Workflow not triggering

Solutions:

1. Check on: triggers match your action
2. Verify workflow file syntax is valid
3. Check branch name matches filter
4. Look for syntax errors in YAML

Success Criteria

• ✅ Understand why CI checks failed
• ✅ Can reproduce CI failure locally
• ✅ Fixed the issue
• ✅ CI checks pass on re-run
• ✅ Know how to prevent similar failures

Quick Reference

GitHub Actions Commands

# View runs
gh run list
gh run view <run-id>

# Re-run failed jobs
gh run rerun <run-id>

# Download logs
gh run download <run-id>

# Watch live
gh run watch

Common Workflow Triggers

# On push to any branch
on: push

# On pull request
on: pull_request

# On push to specific branch
on:
  push:
    branches: [main, develop]

# On tag
on:
  push:
    tags: ['v*']

# On schedule (cron)
on:
  schedule:
    - cron: '0 0 * * *'

Related Skills

• run-tests - Run tests locally before pushing
• code-formatting - Fix linting issues
• git-workflow - Push changes to fix CI

Documentation References

• GitHub Actions Documentation
• GitHub Actions Syntax
• act - Local GitHub Actions
• pre-commit Documentation