CI/CD Overview

Continuous Integration (CI) and Continuous Deployment (CD) automate the software delivery process, enabling teams to release code changes frequently and reliably.

CI/CD Pipeline Stages

Code → Build → Test → Deploy → Monitor

Stage Breakdown

Stage	Purpose	Typical Tools
Source	Version control	Git, GitHub, GitLab
Build	Compile & package	Docker, Maven, npm
Test	Validate changes	Jest, PyTest, Selenium
Deploy	Release to environment	Kubernetes, Docker, AWS
Monitor	Track performance	Prometheus, Grafana

CI/CD Patterns

Git-Based CI

Triggers on every push or pull request. Runs tests and builds automatically.

Best For: Open source, team collaboration, code review workflows

Branch-Based Deployment

Different branches deploy to different environments.

Branch	Environment	Purpose
main	Production	Stable releases
staging	Staging	Pre-production testing
develop	Development	Feature integration
feature/*	Feature environments	Individual feature testing

GitOps

Git is the single source of truth for infrastructure and deployments.

Principles:

• Entire system described in Git
• Desired state declared in Git
• Approved changes automatically applied
• Drift detection and correction

Best For: Kubernetes deployments, infrastructure as code

Tool Selection Guide

Tool	Type	When to Use	Strengths	Weaknesses
GitHub Actions	SaaS CI/CD	GitHub-hosted projects	Deep GitHub integration, free for public repos	Limited to GitHub
GitLab CI	Integrated CI/CD	GitLab-based projects	All-in-one, extensive features	Requires GitLab
Jenkins	Self-hosted	On-premise, complex pipelines	Highly customizable, plugin ecosystem	Requires maintenance
ArgoCD	GitOps	Kubernetes deployments	Declarative, K8s-native	Limited to Kubernetes

Deployment Strategies

Rolling Deployment

Gradually replace instances with new version, keeping application available.

Pros: Zero downtime, gradual rollout Cons: Slower deployment, can have multiple versions running simultaneously

Blue-Green Deployment

Maintain two identical production environments. Switch traffic between them.

Pros: Instant rollback, clean testing Cons: Double infrastructure cost, complex state management

Canary Deployment

Roll out to small percentage of users before full deployment.

Pros: Safe testing with real users, gradual rollout Cons: Requires sophisticated traffic routing, longer deployment window

Feature Flags

Release features behind configuration flags without deploying new code.

Pros: Instant enable/disable, no rollback needed Cons: Technical debt accumulation, testing complexity

Common CI/CD Scenarios

Scenario: Simple Web Application

Tools: GitHub Actions, Docker Pipeline:

1. Push to main branch triggers pipeline
2. Build Docker image
3. Run unit tests
4. Deploy to server
5. Run smoke tests

Scenario: Microservices Architecture

Tools: Jenkins, Kubernetes, ArgoCD Pipeline:

1. Each service has its own pipeline
2. Independent testing and deployment
3. ArgoCD syncs manifests from Git
4. Rollback with Git revert

Scenario: Enterprise Application

Tools: GitLab CI, multiple environments, feature flags Pipeline:

1. Multi-stage pipeline (build, test, deploy)
2. Promotions between environments
3. Manual approvals for production
4. Feature flags control feature rollout

Best Practices

Testing Pyramid

• Unit Tests: Fast, many tests, isolated code
• Integration Tests: Slower, fewer tests, component interaction
• End-to-End Tests: Slowest, fewest tests, full user flows

Pipeline Optimization

• Parallelize independent tests
• Cache dependencies between builds
• Use incremental builds
• Separate fast feedback from slow verification

Security Integration

• Scan dependencies for vulnerabilities (Snyk, Dependabot)
• Static analysis (SonarQube, ESLint)
• Container image scanning (Trivy, Clair)
• Infrastructure security checks (Terraform sec)

Monitoring and Alerting

• Track deployment frequency and lead time
• Monitor failure rate and recovery time
• Alert on pipeline failures
• Collect deployment metrics

Getting Started Guides

• GitHub Actions - Build, test, and deploy with GitHub
• GitLab CI - Integrated CI/CD in GitLab
• Jenkins - Self-hosted automation server
• CircleCI - Hosted CI/CD platform
• ArgoCD - GitOps for Kubernetes
• CI/CD Concepts - Deep dive into CI/CD patterns