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Hello,
From the description, I understand that you have performed RDS Blue/Green deployment manually and need clarification on how to reflect the same in CloudFormation (CFT).
I would like to inform you that by design, CloudFormation does not support RDS Blue/Green deployment. You can find the Open GitHub issue[1] to track the feature request.
Therefore, if you perform a Blue/Green deployment for RDS resources created by CloudFormation, it would lead to Drift. You can verify the current drift of the CFT stack using the steps in doc and proceed to fix the same.
For example, if the stack contains the following RDS resources for Aurora MySQL, I suspect that the drifted state would display changes in "DBClusterParameterGroupName" and "EngineVersion" properties for the "AWS::RDS::DBCluster" and "DBParameterGroupName" property for the "AWS::RDS::DBInstance" resources respectively.
AWS::RDS::DBCluster
AWS::RDS::DBClusterParameterGroup
AWS::RDS::DBInstance
AWS::RDS::DBParameterGroup
In the above scenario, you would have the below options to fix the drift and get back to normal stack operations:
- In general, we perform an IMPORT operation to resolve the drift as mentioned in doc. You can check the considerations for performing the same in doc. However, this approach is more useful for severe drifts observed for properties that mention as "Update requires: Replacement".
- If the only change in drift is for the ParameterGroup then you can perform a normal update the stack to add the "DbInstanceParameterGroup" and "DbClusterParameterGroup" resources with the Green MySQL 8.0 properties. However, you would have to monitor the RDS console to check if the DB goes into "Modifying" state/reboots as a change to these properties would have "Update requires: Some interruptions".
However, in case you are unable to perform the above tests and wish to get recommendation specific to your stack, you can reachout to AWS Support via Support case with the "CloudFormation" team.
