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Publish Artifacts to S3 and Git

· 2 min read
Erik Osterman
Erik Osterman
Founder @ Cloud Posse

Packaging a Lambda archive is only part of a deployment: the archive must also reach S3. The new publish step uploads files and directories from workflows, custom commands, and component hooks, and skips unchanged objects.

The Problem​

Artifact uploads often need an AWS CLI command alongside an archive step. Those scripts must handle credentials, content types, and repeated uploads themselves.

The Fix​

Use type: publish with an aws/s3 target to upload through the step runner. Atmos compares SHA-256 metadata, object size, and delivery headers before uploading. Files that already match stay untouched, and files removed locally are retained in S3.

How to Use It​

steps:
  - name: package
    type: archive
    source: src/
    destination: handler.zip
    mtime: epoch
  - name: upload
    type: publish
    source: '{{ .steps.package.value }}'
    target:
      kind: aws/s3
      bucket: acme-artifacts
      prefix: lambda/v1/
      region: us-east-1

Create the bucket first and grant the caller permission to inspect and upload objects. For a directory, set source: dist/ and a target prefix. Configure the target's cache_control when publishing assets with caching headers.

CloudFormation hooks can now package and upload local assets without a shell upload command. See the complete hook example. Template references remain explicit; use a new key per release so CloudFormation can detect the artifact change.

The advanced CloudFormation example runs the complete pipeline in Floci. Its hooks build and test a Lambda, archive and publish the code, then validate the deployed function with an http step.

Build, publish, and deploy a Lambda
00:00.0 / 00:00.0

View the full example

Git targets use the same step:

steps:
  - type: publish
    source: dist/
    target:
      kind: git
      repository: deployment-repo
      path: generated/service
      commit:
        message: Publish service configuration

Declare deployment-repo in your managed Git configuration first. Atmos writes raw files, commits changes, and pushes. Destination-only files stay intact; an unchanged run creates no commit. In component hooks, use a target name to reuse a definition from provision.targets.

Get Involved​

Read the step reference for credentials, outputs, and limits. Report problems or share use cases in GitHub discussions.