Complete CI/CD Fundamentals Cheatsheet: From Concepts to Implementation

Introduction: What is CI/CD and Why It Matters

Continuous Integration and Continuous Delivery/Deployment (CI/CD) are software development practices that enable teams to deliver code changes more frequently and reliably. CI/CD automates the building, testing, and deployment processes, reducing manual errors, providing faster feedback, and shortening time-to-market. This approach transforms traditional development cycles into streamlined workflows that can respond quickly to business needs, customer feedback, and security concerns.

CI/CD Defined:

• Continuous Integration (CI): The practice of frequently integrating code changes into a shared repository, followed by automated builds and tests
• Continuous Delivery (CD): The extension of CI that automatically prepares code for release to production, making deployments ready at the click of a button
• Continuous Deployment (CD): The full automation of the deployment process, with every change that passes all stages automatically deployed to production

Core CI/CD Concepts and Principles

Fundamental Principles

1. Automation First: Automate everything that can be automated in the build, test, and deployment processes
2. Fail Fast: Identify and address issues early in the development cycle when they’re easiest to fix
3. Small, Incremental Changes: Make small, frequent updates rather than large, infrequent ones
4. Consistency Across Environments: Ensure development, testing, and production environments are as similar as possible
5. Feedback Loops: Create rapid, clear feedback mechanisms for all stakeholders
6. Infrastructure as Code (IaC): Define infrastructure through code for consistency and version control
7. Shift Left: Move testing, security, and quality checks earlier in the development process
8. Visibility and Traceability: Make the process visible to all stakeholders for alignment and accountability

Key CI/CD Pipeline Components

CI/CD Pipeline: Step-by-Step Flow

1. Code Commit Stage

• Developer writes code locally and runs local tests
• Code is committed to version control
• Commit triggers the CI/CD pipeline
• Pre-commit hooks can enforce code standards

2. Build Stage

• Source code is fetched from repository
• Dependencies are resolved
• Code is compiled if necessary
• Build artifacts are created (binaries, containers, etc.)
• Metadata is attached to build (version, commit hash, timestamp)

3. Test Stage

• Unit Tests: Test individual components in isolation
• Integration Tests: Verify components work together
• Functional Tests: Ensure features work as expected
• Performance Tests: Check system under load
• Security Tests: Identify vulnerabilities
• Test reports are generated and stored

4. Analysis Stage

• Static Code Analysis: Tools like SonarQube check code quality
• Security Scanning: Identify vulnerabilities in code and dependencies
• Compliance Checks: Ensure adherence to standards
• Quality gates determine if pipeline proceeds

5. Artifact Storage

• Built and verified artifacts are stored in a repository
• Artifacts are versioned and properly labeled
• Dependencies are tracked for future reference

6. Deployment Stages

• Development: First deployment environment
• Testing/QA: More comprehensive testing environment
• Staging: Production-like environment for final verification
• Production: Live environment serving real users
• Each environment may have specific verifications and approvals

7. Verification & Monitoring

• Deployment verification tests run
• Health checks confirm system functionality
• Monitoring begins capturing metrics
• Feedback loops inform team of success or issues

Comparison of CI/CD Approaches

Deployment Strategies

CI/CD Tool Categories

Common CI/CD Challenges and Solutions

Challenge: Slow Builds and Tests

Solutions:

• Implement test parallelization
• Use incremental builds
• Optimize test selection to run only affected tests
• Implement build caching
• Scale CI infrastructure horizontally
• Profile and optimize slow tests

Challenge: Environment Inconsistency

Solutions:

• Adopt containerization with Docker
• Implement Infrastructure as Code (IaC)
• Use package managers with locked versions
• Create environment specifications in code
• Automate environment provisioning
• Implement environment validation tests

Challenge: Flaky Tests

Solutions:

• Implement automatic test retries
• Track and tag flaky tests
• Implement quarantine for unreliable tests
• Add more logging and diagnostics
• Improve test isolation
• Eliminate implicit dependencies and race conditions

Challenge: Security Integration

Solutions:

• Implement automated security scanning
• Use pre-approved components and dependencies
• Integrate SAST, DAST, and SCA tools
• Implement policy as code
• Add automated compliance checks
• Create specific security gates for different environments

Challenge: Database Changes

Solutions:

• Implement database migration tools
• Version control database schemas
• Use blue/green for database changes
• Create automated database tests
• Implement backward compatible changes
• Separate code and database deployments

Challenge: Managing Dependencies

Solutions:

• Implement dependency scanning
• Use lockfiles to pin dependency versions
• Create a dependency update pipeline
• Leverage private artifact repositories
• Implement dependency caching
• Automate dependency updates with security validation

CI/CD Implementation By Team Size

Small Teams/Startups

• Pipeline Focus: Simple, minimal approvals, fast feedback
• Tool Recommendations: GitHub Actions, GitLab CI/CD, CircleCI
• Strategy: Start with a simple pipeline, prioritize automation over process
• Key Metrics: Build time, deployment frequency, failure rate

Mid-Size Organizations

• Pipeline Focus: Environment promotion, parallel testing, security checks
• Tool Recommendations: Jenkins, AWS CodePipeline, Azure DevOps
• Strategy: Standardize pipelines, define quality gates, implement IaC
• Key Metrics: Lead time, MTTR, test coverage, security findings

Enterprise

• Pipeline Focus: Compliance, governance, multi-team coordination
• Tool Recommendations: Enterprise Jenkins, GitLab Ultimate, TeamCity
• Strategy: Pipeline templates, approval workflows, audit trails
• Key Metrics: Change failure rate, SLA compliance, security posture

CI/CD Configuration Examples

GitHub Actions Basic CI Workflow (YAML)

name: Basic CI Workflow
on: [push, pull_request]
jobs:
  build-and-test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Set up language runtime
        uses: actions/setup-node@v2
        with:
          node-version: '16'
      - name: Install dependencies
        run: npm ci
      - name: Run linting
        run: npm run lint
      - name: Run tests
        run: npm test
      - name: Build application
        run: npm run build

Jenkins Declarative Pipeline (Jenkinsfile)

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                sh 'mvn clean compile'
            }
        }
        stage('Test') {
            steps {
                sh 'mvn test'
            }
            post {
                always {
                    junit '**/target/surefire-reports/*.xml'
                }
            }
        }
        stage('Package') {
            steps {
                sh 'mvn package'
                archiveArtifacts artifacts: 'target/*.jar', fingerprint: true
            }
        }
        stage('Deploy to Dev') {
            when {
                branch 'develop'
            }
            steps {
                sh './deploy.sh dev'
            }
        }
    }
}

GitLab CI/CD Pipeline (.gitlab-ci.yml)

stages:
  - build
  - test
  - deploy

variables:
  IMAGE_TAG: $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG

build:
  stage: build
  script:
    - docker build -t $IMAGE_TAG .
    - docker push $IMAGE_TAG

test:
  stage: test
  script:
    - docker pull $IMAGE_TAG
    - docker run $IMAGE_TAG npm test

deploy:
  stage: deploy
  script:
    - kubectl set image deployment/app app=$IMAGE_TAG
  environment:
    name: production
  only:
    - main

Best Practices and Tips

CI Best Practices

• Make the main/master branch always deployable
• Run tests locally before committing
• Fix broken builds immediately as highest priority
• Keep the CI pipeline fast (under 10 minutes if possible)
• Make build logs easily accessible and readable
• Use consistent build environments
• Include static analysis as part of the pipeline
• Clean test data between test runs

CD Best Practices

• Ensure every change goes through the pipeline
• Use feature flags to separate deployment from release
• Implement blue/green or canary deployments
• Create automated rollback capabilities
• Make deployment a one-click operation
• Maintain configuration in code
• Test the deployment process itself
• Deploy to a clone of production first

Security Integration Best Practices

• Include security scanning in every pipeline
• Scan both custom code and dependencies
• Fail builds for critical security issues
• Add compliance verification
• Use secrets management solutions (not hardcoded)
• Implement least privilege principle in CI/CD systems
• Scan container images for vulnerabilities

Monitoring Best Practices

• Monitor build health and duration
• Track deployment frequency and success
• Implement automated post-deployment tests
• Set up alerting for pipeline failures
• Track mean time to recovery (MTTR)
• Measure business impact of CI/CD (delivery speed)
• Use dashboards for pipeline visibility

Key CI/CD Pipeline Metrics

Resources for Further Learning

Official Documentation

• Jenkins User Guide
• GitHub Actions Documentation
• GitLab CI/CD Documentation
• Azure DevOps Documentation
• CircleCI Documentation

Books

• “Continuous Delivery” by Jez Humble and David Farley
• “DevOps Handbook” by Gene Kim, Jez Humble, Patrick Debois, and John Willis
• “Accelerate” by Nicole Forsgren, Jez Humble, and Gene Kim
• “Infrastructure as Code” by Kief Morris
• “Site Reliability Engineering” by Google

Online Training

• GitHub Learning Lab
• CircleCI Academy
• Jenkins Guided Tour
• GitLab CI/CD Learning Path
• Docker and Kubernetes Courses on Pluralsight

Communities

• DevOps Stack Exchange
• Jenkins Community
• CircleCI Community
• GitLab Community
• DevOps Subreddit

Remember that implementing CI/CD is a journey rather than a destination. Start small, continuously improve, and adapt your pipeline to your team’s specific needs and workflows. Successful CI/CD implementation requires both technical tools and organizational culture changes to achieve the full benefits of automation, reliability, and speed.