How to package AWS CDK into Lambda layer?

Question

What is the best way to bundle up the AWS CDK as a Lambda layer please?

I need to call the CDK from a Java process, so wish to use the Java 11 runtime and then install N

Answer 1

I ended up using a Docker container to install the aws-cdk module into a specific path, then zip up the container and copying it to a bind-mounted directory so that it is available on the underlying host.

I built the project using Gradle and the gradle-docker-plugin by Ben Muschko. I have not spent time trying to use a smaller Node image to speed up builds.

task createCdkDockerfile(type: Dockerfile) {
    from 'node:latest'
    defaultCommand('/bin/bash', '-c', "apt-get update && apt-get install -y zip && mkdir -p /nodejs && npm config set prefix /nodejs/bin && npm install -g aws-cdk && pushd /nodejs/bin && zip -r --symlinks /opt/aws-cdk.zip *")
}

task buildCdkImage(type:DockerBuildImage) {
    dependsOn createCdkDockerfile
    images.add('my-aws-cdk:latest')
}

ext.maybeConvertWindowsPath = { path ->
    if (Os.isFamily(Os.FAMILY_WINDOWS)) {
        path = "/${path.replace("\\", "/").replace(":", "")}"
    }
    return path
}

task createCdkContainer(type: DockerCreateContainer) {
    def dockerBindDir = new File(buildDir, "docker")
    dockerBindDir.mkdirs()
    dependsOn buildCdkImage
    targetImageId buildCdkImage.getImageId()
    hostConfig.autoRemove = true
    hostConfig.binds = ["${maybeConvertWindowsPath(buildDir.toString())}/docker" : "/opt"]
}

task startCdkContainer(type: DockerStartContainer) {
    dependsOn createCdkContainer
    targetContainerId createCdkContainer.getContainerId()
}

task waitCdkContainer(type: DockerWaitContainer) {
    dependsOn startCdkContainer
    targetContainerId createCdkContainer.getContainerId()
}

The zip file is available at ${buildDir}/docker/aws-cdk.zip.

Adding the CDK as a layer is as per the Nodejs example in my question, so something like this:

LayerVersion nodeLayer = LayerVersion.Builder.create(this, "aws-cdk-layer")
        .description("Layer containing AWS CDK")
        .code(
                Code.fromAsset(somePathTo-aws-cdk.zip)
        )
        .build();

Points to watch out for:

• if building on Windows, zipping up on Windows then unzipping on Linux will give issues with files that should be executable no longer being executable, i.e. cdk itself.
• bind mounting directories seems to have issues when on Windows, hence the need to sanitize the filename.
• when zipping, it's important to use the --symlinks option, otherwise the cdk executable will not be able to find the cdk.js file.

I would have preferred using tar to zip the file up, but fromAsset() won't accept tar files.