[ECS] [Service Discovery]: Service discovery is failing when you run Cloudformation template to perform blue green deployment

I am Performing ECS blue/green deployments through CodeDeploy using AWS CloudFormation . Please refer this link for sample CF template _https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/blue-green.html._ I have included Service Discovery in the template . While deploying first time i dont see any issue . But when I have a code update and trying to deploy Green task set i am getting an error saying Service Discover service already exist and cannot be created .

Here are my Questions :
1. Why is CF trying to recreate the Service Discovery service when it already exits in the template .
2. I am calling the ServiceRegisteries in Bluetask set . So when Green task set is created is it trying to Create a New Service in the Service discovery ? If so why cant it just reference to the existing one ?
3. Is Service Discover supported in CF for Blue Green Deployments ?

Start with the AWS CloudFormation blue/green deployment sample linked in the issue and reproduce the first deployment followed by a code update that creates the Green task set. Inspect the ECS ServiceRegistries configuration and deployment events to determine whether the Service Discovery service is recreated; done means establishing the supported behavior and documenting the required configuration or limitation.

Written by the indexing model from the issue text.