Deploying new version of lambda function

❓ General Issue

The Question

I’m attempting to setup a CodeDeploy deployment group for a Lambda function. The CDK documentation for the Version class states:

If you want to deploy through CloudFormation and use aliases, you need to add a new version (with a new name) to your Lambda every time you want to deploy an update. An alias can then refer to the newly created Version.

This suggests that if I want to make a new CodeDeploy deployment, I should change the version name. For this end, I’m naming the versions using the sha1 of the latest Git commit that affects the Lambda’s code or configuration. However, if I commit code that makes cosmetic changes to the configuration (i.e., to CDK code pertaining to the lambda), that will produce no differences in the CloudFormation template, and I will get the error A version for this Lambda function exists ( 1 ). Modify the function to create a new version.

This suggests that for a new version to be deployed I need to change the code or make semantic changes to the configuration. If this is the case, why require the version name to be unique between versions?

Code:

const lambdaName = basename(__dirname)

async function getRevision(dir: string): Promise<string> {
    const root = basename((await run("git rev-parse --show-toplevel")).line())
    const p = dir.substring(dir.lastIndexOf(root) + root.length + 1, dir.length)
    return (await run(`git rev-list --abbrev-commit -1 HEAD -- ${p}`)).line()
}

export async function myLambda(stack: Stack): Promise<Alias> {
    const f = new Function(stack, lambdaName, {
        runtime: Runtime.GO_1_X,
        handler: "main",
        code: Code.asset(join(__dirname, "lambda.zip")),
    })

    const alias = new Alias(stack, lambdaName + "-alias", {
        aliasName: "live",
        version: f.addVersion(await getRevision(__dirname)),
    })

    new LambdaDeploymentGroup(stack, lambdaName + "-deployment", {
        alias: alias,
        deploymentConfig: LambdaDeploymentConfig.LINEAR_10PERCENT_EVERY_10MINUTES,
    })

    return alias
}

Environment

• **CDK CLI Version: 1.18.0
• **Module Version: 1.18.0
• **OS: macOS Catalina
• **Language: Typescript

Other information

[skinny85]

Actually, I figured out a workaround 😃 changing the description of the Function is enough to make the Version creation succeed, so this works:

        const func = new lambda.Function(this, 'lambdaName', {
            // whatever properties you need...
            description: `Generated on: ${new Date().toISOString()}`,
        });

        const version = func.addVersion(new Date().toISOString());

        const alias = new lambda.Alias(this, 'lambdaName-alias', {
            aliasName: 'live',
            version: version,
        });

        new codedeploy.LambdaDeploymentGroup(this, 'lambdaName-deployment', {
            alias: alias,
            deploymentConfig: codedeploy.LambdaDeploymentConfig.LINEAR_10PERCENT_EVERY_1MINUTE,
        });

[aripalo]

Yeah it would be nice if one could do something in the manner of:

const fn = new lambda.VersionedFunction(this, "MyFunc", { /*...*/});

… which would calculate a combined hash of the source code and of the AWS::Lambda::Function.

Then it would also create a new version if the hash has changed.

Not sure if this is doable, but just thinking out loud.