A company is using AWS CodePipeline to deploy a serverless application. The pipeline includes stages for Source, Build, and Deploy. In the Deploy stage, they are using an AWS CloudFormation action to update the serverless stack. They have noticed that sometimes, during a deployment, new Lambda function versions are created, but the API Gateway stage is not immediately updated to point to the latest Lambda version, causing inconsistencies. How can they ensure that the API Gateway stage always points to the latest deployed Lambda function version automatically?
- AManually update the API Gateway stage configuration after each CodePipeline execution.
- BEmbed the Lambda function version ARN directly into the API Gateway definition in the CloudFormation template.
- CRecreate the entire API Gateway and Lambda function for every deployment.
- DUse an AWS Lambda alias for the function and configure the API Gateway stage to point to that alias, updating the alias to the new function version within the CodePipeline.
Show answer & explanationAnswer & explanation
Correct answer: D. Use an AWS Lambda alias for the function and configure the API Gateway stage to point to that alias, updating the alias to the new function version within the CodePipeline.
The best practice for managing Lambda function versions with API Gateway is to use Lambda aliases. The API Gateway stage should be configured to point to a specific alias (e.g., 'prod'). In the CodePipeline, after a new Lambda function version is deployed, an action can update this alias to point to the newly deployed function version. This ensures API Gateway always references the latest stable version without downtime and allows for easy rollbacks by simply reverting the alias.
Why the other options are wrong
- A. Manual updates defeat automation and are prone to human error, especially for critical applications.
- B. Embedding a specific function version ARN directly ties the API Gateway to a static version. When a new version is deployed, the ARN changes, requiring a full API Gateway update, which can be disruptive. Aliases provide a stable reference that can be updated without changing the API Gateway configuration itself.
- C. Recreating resources for every deployment is inefficient, causes downtime, and is not a scalable solution.
Lambda Aliases with API Gateway
Lambda aliases provide a stable endpoint to invoke a specific Lambda function version. API Gateway stages can be configured to point to these aliases, allowing seamless updates to the underlying Lambda function version without changing the API Gateway configuration.
- Aliases provide a mutable pointer to an immutable function version.
- API Gateway points to the alias, not the version ARN.
- Updating the alias shifts traffic to a new version.
- Enables blue/green deployments and easy rollbacks for serverless.
Memory trick: Alias points the way, so API Gateway doesn't sway.