aws cdk publish lambda version alias

3 min read 08-12-2024

Publishing AWS Lambda Version and Alias with AWS CDK

The AWS Cloud Development Kit (CDK) simplifies infrastructure as code (IaC), allowing you to define and manage your AWS resources using familiar programming languages. This article focuses on how to use the CDK to publish a new version of your Lambda function and create or update an alias pointing to that version. This is crucial for managing deployments and ensuring smooth rollbacks if needed.

Understanding Lambda Versions and Aliases

Before diving into the CDK implementation, let's clarify the concepts:

Lambda Function: Your core Lambda code.
Lambda Version: An immutable snapshot of your Lambda function code and configuration at a specific point in time. Publishing a new version creates a new, distinct version.
Lambda Alias: A logical pointer to a specific Lambda version. This allows you to update your function's version without changing the invocation endpoint. This is crucial for maintaining stability and enabling rollbacks.

CDK Implementation: Publishing a Lambda Version and Alias

Here's how to achieve this using the AWS CDK in TypeScript. Adapt the code to your preferred language (Python, Java, etc.) as needed.

import * as cdk from 'aws-cdk-lib';
import * as lambda from 'aws-cdk-lib/aws-lambda';
import { Construct } from 'constructs';

export class MyStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    // Define your Lambda function
    const myLambda = new lambda.Function(this, 'MyLambdaFunction', {
      runtime: lambda.Runtime.NODEJS_16_X, // Choose your runtime
      handler: 'index.handler',
      code: lambda.Code.fromAsset('lambda'), // Path to your Lambda code
    });

    // Publish a new version
    const newVersion = new lambda.Version(this, 'MyLambdaVersion', {
      lambda: myLambda,
      removalPolicy: cdk.RemovalPolicy.RETAIN, // Important: Avoid accidental deletion of versions
    });

    // Create or update an alias pointing to the new version
    const myAlias = new lambda.Alias(this, 'MyLambdaAlias', {
      aliasName: 'prod', // Choose your alias name (e.g., 'prod', 'dev', 'staging')
      version: newVersion,
    });


    //Optional: Add a description for better understanding.
    myAlias.addMetadata('Description', 'Production alias for MyLambdaFunction');
  }
}

Explanation:

lambda.Function: Defines your Lambda function. Replace placeholders like runtime, handler, and code with your specific settings.
lambda.Version: This creates a new version of your Lambda function. The removalPolicy: cdk.RemovalPolicy.RETAIN is crucial. This prevents accidental deletion of older versions, which are essential for rollbacks.
lambda.Alias: This creates or updates an alias named 'prod' (you can change this). It points to the newly created version. If an alias with the same name already exists, it will be updated to point to the new version.

Deploying with the CDK

After defining your stack, deploy it using the CDK CLI:

cdk deploy

This will create or update your Lambda function, publish a new version, and create/update the alias. Future invocations using the alias name (prod in this example) will always target the latest published version.

Handling Rollbacks

In case of issues with the new version, you can easily rollback by updating the alias to point to a previous version. You can achieve this by manually updating the alias in the AWS console or by modifying your CDK code to point to a different version and redeploying.

Best Practices

Versioning: Always publish new versions. This allows for easy rollbacks and avoids directly modifying the live function.
Alias Naming: Use meaningful alias names (e.g., prod, staging, dev) to clearly identify different deployment stages.
Removal Policy: Never delete Lambda versions unless you are absolutely certain you no longer need them.
Monitoring: Monitor your Lambda function's performance and logs after deploying new versions.

This comprehensive guide provides a solid foundation for managing Lambda deployments efficiently using the AWS CDK. Remember to adapt the code snippets to match your specific project requirements and always prioritize best practices for robust and maintainable infrastructure.