description AWS CloudFormation Custom Resources Overview
This advanced feature allows you to embed custom logic (often via Lambda) directly into your CloudFormation templates. For DR, this means you can write a resource type that, when deployed, executes a specific, complex DR actionlike triggering a specific database failover sequence or updating a complex IAM rolethat standard resources cannot handle natively. It bridges the gap between pure IaC and custom automation.
help AWS CloudFormation Custom Resources FAQ
What must a Lambda-backed CloudFormation custom resource return before a DR stack can continue?
CloudFormation sends a request containing RequestType, ResourceProperties, and a presigned ResponseURL; the Lambda handler must return SUCCESS or FAILED to that URL. The ServiceToken is the Lambda ARN, and a missing response leaves the stack waiting until the custom-resource timeout.
Can this custom resource trigger an AWS Elastic Disaster Recovery failover?
It can call AWS APIs from Lambda to coordinate a failover sequence, but CloudFormation Custom Resources do not provide DR safety logic automatically. The function needs least-privilege IAM, idempotency for retries, and a clear rollback or failure path before it touches production recovery state.
How are Create, Update, and Delete handled?
CloudFormation invokes the provider for all three lifecycle events, and a changed PhysicalResourceId can make an update look like a replacement, causing a Delete for the old resource. Use stable physical IDs and treat retries as expected.
When should I use a custom resource instead of a CloudFormation Registry type?
Use a custom resource for an unregistered, one-off action backed by Lambda or SNS inside a template. Use a Registry resource type when you need a reusable third-party resource with Read, Update, Delete, and List operations, rather than only Create, Update, and Delete.
explore Explore More
Similar to AWS CloudFormation Custom Resources
compare_arrows Compare: AWS CloudFormation StackSets See all arrow_forward
Reviews & Comments
Write a Review
Be the first to review
Share your thoughts with the community and help others make better decisions.
