lambda: default architecture X86_64 isn't used for cross-platform docker builds

[tabrezm]

Describe the bug

The current documented behavior for the architecture prop on lambda_.DockerImageFunction is:

architecture: The system architectures compatible with this lambda function. Default: Architecture.X86_64

However, I found running cdk deploy on my Mac would not target amd64. This results in the following error message when invoking the deployed Lambda function:

Error: fork/exec /lambda-entrypoint.sh: exec format error Runtime.InvalidEntrypoint

I was able to resolve this by explicitly setting:

lambda_.DockerImageFunction(self, ..., architecture=lambda_.Architecture.X86_64)

Another quirk I found was that specifying --platform in build_args is silently ignored. You can only specify this setting via the platform property.

code=lambda_.DockerImageCode.from_image_asset(
    directory=...,
    build_args={"--platform": "linux/amd64"},  # doesn't work
    platform=ecr_assets.Platform.LINUX_X86_64,  # works
),

Expected Behavior

1. The lambda_.DockerImageFunction() default architecture of lambda_.Architecture.X86_64 is passed to docker build
2. Allow passing --platform in build_args or raise an error

Current Behavior

The default value either seems to not be set correctly, or it's not passed correctly to docker build.

Reproduction Steps

Follow the hello world example here.

lambda_.DockerImageFunction(
            self,
            "HelloWorldLambda",
            code=lambda_.DockerImageCode.from_image_asset(
                directory=...,
                # build_args={"--platform": "linux/amd64"},
                # platform=ecr_assets.DockerPlatform.LINUX_X86_64,
            ),
            # architecture=lambda_.Architecture.X86_64,
        )

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.151.0 (build b8289e2)

Framework Version

No response

Node.js Version

v20.16.0

OS

macOS

Language

Python

Language Version

No response

Other information

No response

[pahud]

Looks like you are trying to build a lambda docker-compatible function of X86_64 architecture from a ARM64 Mac laptop.

The architecture of DockerImageFunction is used for:

1. pass correct architecture for the L1 CfnFunction props, which defaults to X86_64. If your target lambda arch is X86_64, it's fine to leave it undefined.
2. pass additional --platform argument for docker build if specified, especially for cross-platform building(per this PR). Looks like this would be required for cross-platform building.

Can you just specify architecture for DockerImageFunction and let me know if it works for you? I guess we probably need to improve the doc with another PR.

[tabrezm]

Thanks for your reply.

Can you just specify architecture for DockerImageFunction and let me know if it works for you? I guess we probably need to improve the doc with another PR.

Yes, I confirmed this works here (I didn't have any props on from_image_asset specified at the time):

I was able to resolve this by explicitly setting:

lambda_.DockerImageFunction(self, ..., architecture=lambda_.Architecture.X86_64)

Is that what you were asking about?

[pahud]

Yes in your case as I presumed architecture would be the only required option. You don't need to specify --platform because behind the scene according to this PR, it would pass the platform argument all the way to docker build.

I'm glad this works for you. I will cut a tiny PR to improve the doc.

Did I miss anything else?

[tabrezm]

Yes in your case as I presumed architecture would be the only required option. You don't need to specify --platform because behind the scene according to this PR, it would pass the platform argument all the way to docker build.

I'm glad this works for you. I will cut a tiny PR to improve the doc.

Did I miss anything else?

It's more of a nit, but having better fail-fast validation here would've be helpful since there are a few AWS samples still out there that have build_args={"--platform": "linux/amd64"} which seem to be superseded with the newer(?) explicit platform prop:

2. Allow passing --platform in build_args or raise an error

[pahud]

Yes we need to address them with clearer doc. For this issue, I will submit a PR shortly. If you see other similar issues that deserve more clarifying or even a code fix, please raise a new issue for us. Thank you.

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