CodeBuild

Learning objectives#

• Write a buildspec.yml
• Use environment variables and secrets
• Build and push Docker images
• Speed up builds with caching

Explanation#

A build project defines the source, the build environment (image, compute size) and the service role.

buildspec.yml has phases: install, pre_build, build and post_build, plus artifacts and reports.

Environment variables can come from Parameter Store or Secrets Manager. Docker builds require privileged mode.

You pay per build minute; caching dependencies cuts both time and cost.

Code example: Test, build and push a Node.js image#

1version: 0.2
2env:
3  variables: { REPO: 123456789012.dkr.ecr.ap-south-1.amazonaws.com/shop-api }
4phases:
5  install:
6    runtime-versions: { nodejs: 22 }
7  pre_build:
8    commands:
9      - npm ci
10      - npm test
11      - aws ecr get-login-password | docker login --username AWS --password-stdin ${REPO%%/*}
12      - TAG=${CODEBUILD_RESOLVED_SOURCE_VERSION:0:7}
13  build:
14    commands:
15      - docker build -t $REPO:$TAG .
16  post_build:
17    commands:
18      - docker push $REPO:$TAG
19      - printf '[{"name":"api","imageUri":"%s"}]' "$REPO:$TAG" > imagedefinitions.json
20artifacts:
21  files: [imagedefinitions.json]
22cache:
23  paths: ['/root/.npm/**/*']

[Container] Phase complete: PRE_BUILD State: SUCCEEDED
[Container] Running command docker push .../shop-api:3f2a9c1
[Container] Phase complete: POST_BUILD State: SUCCEEDED

This example is illustrative. Copy or download it and run it in your own environment; the expected output is shown above.

Step-by-step explanation#

1. Node.js 22 is installed in the install phase.
2. Tests run before any image is built — a failure stops the build.
3. The image is tagged with the short commit SHA.
4. imagedefinitions.json is produced for the ECS deploy stage.

Real-world use case#

Common mistakes#

Best practices#

• Run tests before building images
• Tag images with commit SHAs
• Cache dependencies
• Give the service role only what the build needs

Remember this#

Practice exercise#

1env:
2  secrets-manager:
3    NPM_TOKEN: ci/npm:token

Mini quiz#

Want more? Practise all AWS MCQs · AWS interview questions

Related topics#

My notes#

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