Automating builds with CodeBuild and buildspec.yml

Automating Deployments on AWS

Dunieski Otano

Amazon Web Services Solutions Architect

What CodeBuild does

• CodeBuild is a fully managed build service
• No servers to provision or manage
• Runs your build in a temporary container
• Scales automatically; pay only for build minutes
• Integrates with CodePipeline as the Build stage

 

The buildspec.yml file

• buildspec.yml: YAML file at the root of your source code
• Defines what CodeBuild does during the build
• Four phases execute in order:
  • install: Install dependencies and tools
  • pre_build: Run setup tasks before building
  • build: Compile code, run tests
  • post_build: Package artifacts, clean up

A real buildspec.yml example

• install: pip install -r requirements.txt
• pre_build: [ -z "$DB_URL" ] && exit 1
• build: pytest tests/
• post_build: zip -r app.zip . then echo "Build completed"

Build environment configuration

 

• Compute types: small, medium, large, 2xlarge
  • Choose based on build complexity and speed requirements
• Environment variables: Pass configuration to builds
  • Store secrets in Parameter Store or Secrets Manager
• Dependency caching: Cache downloaded packages between builds
  • Reduces build time significantly for large projects

Artifact outputs and pipeline integration

 

• artifacts section defines what CodeBuild outputs
• files: List of files or patterns; base-directory: root path
• Output artifact stored in S3, passed to next stage automatically
• Wrong artifact paths cause deploy failures even when build succeeds

The full build-test-deploy chain

• Developer pushes code to CodeCommit
• CodePipeline triggers automatically
• CodeBuild: install -> pre_build -> build -> post_build
• Build artifact flows to CodeDeploy
• Application is deployed to the target environment

Let's practice!

Automating Deployments on AWS