aws-ecr-assets: TarballImageAsset hardcodes container runtime.

[commiterate]

Describe the bug

aws-ecr-assets.TarballImageAsset currently hardcodes the container runtime for the image load command.

https://github.com/aws/aws-cdk/blob/v2.155.0/packages/aws-cdk-lib/aws-ecr-assets/lib/tarball-asset.ts#L80

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Version

None.

Expected Behavior

aws-ecr-assets.TarballImageAsset should use the undocumented (#25657) CDK_DOCKER environment variable introduced by #23855.

Alternatively, use the proposed container runtime configuration in cdk.json (#31319).

Current Behavior

aws-ecr-assets.TarballImageAsset hardcodes docker.

Reproduction Steps

Using aws-ecr-assets.TarballImageAsset as documented produces the following {stack}.assets.json:

{
  // ...
  "dockerImages": {
    "{asset hash}": {
      "source": {
        "executable": [
          "sh",
          "-c",
          "docker load -i asset.{asset hash}.tar.gz | tail -n 1 | sed \"s/Loaded image: //g\""
        ]
      },
      // ...
    }
  }
}

CDK CLI Version

2.155.0

Framework Version

2.155.0

Node.js Version

20.16.0

OS

macOS 14 (Sonoma)

Language

TypeScript

Language Version

5.5.4

[ashishdhingra]

The PR #23855 added support for CDK_DOCKER for using alternative container implementations for docker. Taking example from PR,

CDK_DOCKER=finch ./scripts/foreach.sh "yarn build"
CDK_DOCKER=finch ./scripts/foreach.sh "yarn test"

Finch is one of the docker alternatives.

CDK_DOCKER is an undocumented feature.

Looking at aws-s3-assets, it appears to support CDK_DOCKER environment variable. Perhaps we need to support similar behavior for aws-ecr-assets.

Needs discussion with the team.