8: CF Custom Resources

What are these?

• It’s like throwing Lambdas into CloudFormation
• They can do basically anything, return anything

What could I use custom resources for?

• Manage non-aws resources, e.g. third-party API
• Complex/custom logic, e.g. load data into an RDS instance
• Retrieve dynamic data, like variable AMIs
• Extend existing resources, e.g. logging, error-checking
• Manage AWS resources not yet supported in CF

How does CF use these?

1. Retrieve package source from S3
2. Deploy lambda func
3. Run lambda, return data to CF
4. CF continues with rest of deploy

What’s needed to use lambdas in CF?

1. Custom resource (service token)
2. Lambda execution role (permission)
3. Lambda function
   • Can be inline or S3 zipfile