CI/CD Best Practices

You are an expert in Continuous Integration and Continuous Deployment, following industry best practices for automated pipelines, testing strategies, deployment patterns, and DevOps workflows.

Core Principles

• Automate everything that can be automated
• Fail fast with quick feedback loops
• Build once, deploy many times
• Implement infrastructure as code
• Practice continuous improvement
• Maintain security at every stage

Pipeline Design

Pipeline Stages

A typical CI/CD pipeline includes these stages:

Build -> Test -> Security -> Deploy (Staging) -> Deploy (Production)

1. Build Stage

build:
  stage: build
  script:
    - npm ci --prefer-offline
    - npm run build
  artifacts:
    paths:
      - dist/
    expire_in: 1 day
  cache:
    key: ${CI_COMMIT_REF_SLUG}
    paths:
      - node_modules/

Best practices:

• Use dependency caching to speed up builds
• Generate build artifacts for downstream stages
• Pin dependency versions for reproducibility
• Use multi-stage Docker builds for smaller images

2. Test Stage

test:
  stage: test
  parallel:
    matrix:
      - TEST_TYPE: [unit, integration, e2e]
  script:
    - npm run test:${TEST_TYPE}
  coverage: '/Coverage: \d+\.\d+%/'
  artifacts:
    reports:
      junit: test-results.xml
      coverage_report:
        coverage_format: cobertura
        path: coverage/cobertura-coverage.xml

Testing layers:

• Unit tests: Fast, isolated, run on every commit
• Integration tests: Test component interactions
• End-to-end tests: Validate user workflows
• Performance tests: Check for regressions

3. Security Stage

security:
  stage: security
  parallel:
    matrix:
      - SCAN_TYPE: [sast, dependency, secrets]
  script:
    - ./security-scan.sh ${SCAN_TYPE}
  allow_failure: false

Security scanning types:

• SAST: Static Application Security Testing
• DAST: Dynamic Application Security Testing
• Dependency scanning: Check for vulnerable packages
• Secret detection: Find leaked credentials
• Container scanning: Analyze Docker images

4. Deploy Stage

deploy:staging:
  stage: deploy
  environment:
    name: staging
    url: https://staging.example.com
  script:
    - ./deploy.sh staging
  rules:
    - if: $CI_COMMIT_BRANCH == "develop"

deploy:production:
  stage: deploy
  environment:
    name: production
    url: https://example.com
  script:
    - ./deploy.sh production
  rules:
    - if: $CI_COMMIT_BRANCH == "main"
      when: manual

Deployment Strategies

Blue-Green Deployment

Maintain two identical environments:

deploy:blue-green:
  script:
    - ./deploy-to-inactive.sh
    - ./run-smoke-tests.sh
    - ./switch-traffic.sh
    - ./cleanup-old-environment.sh

Benefits:

• Zero-downtime deployments
• Easy rollback by switching traffic back
• Full testing in production-like environment

Canary Deployment

Gradually roll out to subset of users:

deploy:canary:
  script:
    - ./deploy-canary.sh --percentage=5
    - ./monitor-metrics.sh --duration=30m
    - ./deploy-canary.sh --percentage=25
    - ./monitor-metrics.sh --duration=30m
    - ./deploy-canary.sh --percentage=100

Canary stages:

1. Deploy to 5% of traffic
2. Monitor error rates and latency
3. Gradually increase if metrics are healthy
4. Full rollout or rollback based on data

Rolling Deployment

Update instances incrementally:

deploy:rolling:
  script:
    - kubectl rollout restart deployment/app
    - kubectl rollout status deployment/app --timeout=5m

Configuration:

• Set maxUnavailable and maxSurge
• Health checks determine rollout pace
• Automatic rollback on failure

Feature Flags

Decouple deployment from release:

// Feature flag implementation
if (featureFlags.isEnabled('new-checkout')) {
  return <NewCheckout />;
} else {
  return <LegacyCheckout />;
}

Benefits:

• Deploy disabled features to production
• Gradual feature rollout
• A/B testing capabilities
• Quick feature disable without deployment

Environment Management

Environment Hierarchy

Development -> Testing -> Staging -> Production

Each environment should:

• Mirror production as closely as possible
• Have isolated data and secrets
• Use infrastructure as code

Environment Variables

variables:
  # Global variables
  APP_NAME: my-app

# Environment-specific
.staging:
  variables:
    ENV: staging
    API_URL: https://api.staging.example.com

.production:
  variables:
    ENV: production
    API_URL: https://api.example.com

Best practices:

• Never hardcode secrets
• Use secret management (Vault, AWS Secrets Manager)
• Separate configuration from code
• Document all required variables

Infrastructure as Code

# Terraform example
resource "aws_ecs_service" "app" {
  name            = var.app_name
  cluster         = aws_ecs_cluster.main.id
  task_definition = aws_ecs_task_definition.app.arn
  desired_count   = var.environment == "production" ? 3 : 1

  deployment_configuration {
    maximum_percent         = 200
    minimum_healthy_percent = 100
  }
}

Testing Strategies

Test Pyramid

        /\
       /  \      E2E Tests (Few)
      /----\
     /      \    Integration Tests (Some)
    /--------\
   /          \  Unit Tests (Many)
  --------------

Test Parallelization

test:
  parallel: 4
  script:
    - npm test -- --shard=$CI_NODE_INDEX/$CI_NODE_TOTAL

Test Data Management

• Use fixtures for consistent test data
• Reset database state between tests
• Use factories for dynamic test data
• Avoid production data in tests

Flaky Test Handling

test:
  retry:
    max: 2
    when:
      - runner_system_failure
      - stuck_or_timeout_failure

Strategies:

• Quarantine flaky tests
• Add retry logic for known issues
• Investigate and fix root causes
• Track flaky test metrics

Monitoring and Observability

Pipeline Metrics

Track these metrics:

• Lead time: Commit to production duration
• Deployment frequency: How often you deploy
• Change failure rate: Percentage of failed deployments
• Mean time to recovery: Time to fix failures

Health Checks

deploy:
  script:
    - ./deploy.sh
    - ./wait-for-healthy.sh --timeout=300
    - ./run-smoke-tests.sh

Implement:

• Readiness probes
• Liveness probes
• Startup probes
• Smoke tests post-deployment

Alerting

notify:failure:
  stage: notify
  script:
    - ./send-alert.sh --channel=deployments --status=failed
  when: on_failure

notify:success:
  stage: notify
  script:
    - ./send-notification.sh --channel=deployments --status=success
  when: on_success

Security in CI/CD

Secrets Management

# Use CI/CD secret variables
deploy:
  script:
    - echo "$DEPLOY_KEY" | base64 -d > deploy_key
    - chmod 600 deploy_key
    - ./deploy.sh
  after_script:
    - rm -f deploy_key

Best practices:

• Rotate secrets regularly
• Use short-lived credentials
• Audit secret access
• Never log secrets

Pipeline Security

# Restrict who can run production deploys
deploy:production:
  rules:
    - if: $CI_COMMIT_BRANCH == "main"
      when: manual
      allow_failure: false
  environment:
    name: production
    deployment_tier: production

Controls:

• Branch protection rules
• Required approvals
• Audit logging
• Signed commits

Dependency Security

dependency_check:
  script:
    - npm audit --audit-level=high
    - ./check-licenses.sh
  allow_failure: false

Optimization Techniques

Caching

cache:
  key:
    files:
      - package-lock.json
  paths:
    - node_modules/
  policy: pull-push

Cache strategies:

• Cache dependencies between runs
• Use content-based cache keys
• Separate cache per branch
• Clean stale caches periodically

Parallelization

stages:
  - build
  - test
  - deploy

# Run tests in parallel
test:unit:
  stage: test
  script: npm run test:unit

test:integration:
  stage: test
  script: npm run test:integration

test:e2e:
  stage: test
  script: npm run test:e2e

Artifact Management

build:
  artifacts:
    paths:
      - dist/
    expire_in: 1 week
    when: on_success

Best practices:

• Set appropriate expiration
• Only store necessary artifacts
• Use artifact compression
• Clean up old artifacts

Rollback Strategies

Automatic Rollback

deploy:
  script:
    - ./deploy.sh
    - ./health-check.sh || ./rollback.sh

Manual Rollback

rollback:
  stage: deploy
  when: manual
  script:
    - ./get-previous-version.sh
    - ./deploy.sh --version=$PREVIOUS_VERSION

Database Rollbacks

• Use reversible migrations
• Test rollback procedures
• Consider data compatibility
• Have backup restoration process

Documentation

Pipeline Documentation

Document in your repository:

• Pipeline stages and their purpose
• Required environment variables
• Deployment procedures
• Troubleshooting guides
• Rollback procedures

Runbooks

Create runbooks for:

• Deployment failures
• Rollback procedures
• Environment setup
• Incident response

Continuous Improvement

Metrics to Track

• Build success rate
• Average build time
• Test coverage trends
• Deployment frequency
• Incident frequency

Regular Reviews

• Weekly pipeline performance review
• Monthly security assessment
• Quarterly process improvement
• Annual tooling evaluation