3.3.1. AWS CodeDeploy for Application Deployment

💡 First Principle: AWS CodeDeploy automates the deployment of application code to various compute services, ensuring consistent, reliable, and versioned releases with minimal operational overhead.

Scenario: You need to deploy a new version of an application to a fleet of EC2 instances with minimal downtime. The application package is stored in Amazon S3. You want to automate the installation steps and have a clear record of each deployment.

AWS CodeDeploy is a fully managed deployment service that automates application deployments to diverse compute services such as Amazon EC2, AWS Fargate, AWS Lambda, and on-premises servers. It works with application artifacts produced by a build service (e.g., AWS CodeBuild).

Key Features of AWS CodeDeploy:

• Automated Deployment: Automates the process of copying application code and installing it on target resources.
• Compute Target Support: Deploys to EC2 instances, AWS Lambda functions, and Amazon ECS container services.
• Deployment Strategies: Supports various strategies to minimize downtime and risk, including In-place, Rolling, Blue/Green, and Canary deployments.
• appspec.yml File: SysOps Administrators define the deployment lifecycle hooks (e.g., BeforeInstall, ApplicationStart) and specify which files to copy in this file, which is part of the application revision. This file is executed by the CodeDeploy agent on target instances.
• Rollback: Provides automatic or manual rollback options if a deployment fails or issues are detected post-deployment.
• Monitoring: Integrates with CloudWatch for deployment monitoring and alerts.

⚠️ Common Pitfall: Errors in the appspec.yml file, leading to failed deployments or incorrect application configurations.

Key Trade-Offs: Automated deployment (CodeDeploy, consistent, repeatable) versus manual deployment (prone to error, inconsistent).

Practical Implementation: Example appspec.yml for an EC2 deployment:

version: 0.0
os: linux
files:
  - source: /
    destination: /var/www/html
hooks:
  BeforeInstall:
    - location: scripts/install_dependencies.sh
      timeout: 300
      runas: root
  ApplicationStart:
    - location: scripts/start_server.sh
      timeout: 60
      runas: root

Reflection Question: How does AWS CodeDeploy, with its automation capabilities, support for various compute targets, and the use of the appspec.yml file, fundamentally ensure consistent, reliable, and versioned application releases with minimal operational overhead?