aws-cloudformationaws-cdk

Hash in the Logical Id of the resources in CDK/Cloudformation

Whenever I generate cloudformation template from CDK, I see that in logical ids, it adds some kind of Hash. What does that Hash mean? Eg.

Test4FCEEF4A

How does this Hash 4FCEEF4A gets generated?

Solution

  • The logical IDs for resources are set using the allocateLogicalId method which you can find here. It calls the makeUniqueId method which you can find here. In the makeUniqueId method, it creates a hash component of the logical ID and a human-readable component of the logical ID. It uses the crypto library to create an md5 hash using path, which it gets from the IDs of the nodes of the CfnElement and returns a hex value. So the Hash 4FCEEF4A you see is the hash component that is created in the makeUniqueId method.