CodeDeploy::DeploymentGroup Error: The list of target group pairs must have exactly one pair

Question

I am creating a cloudformation nestedDeployment(CodeBuild Project and CodeDeploy Application) with a Blue/Green Deployment, for an ECS (Fargate Managed) Deployment.
The Deployment fails in the creation of the CodeDeployment Group with this error:

"The list of target group pairs must have exactly one pair (Service: AmazonCodeDeploy; Status Code: 400; Error Code: InvalidTargetGroupPairException; Request ID: xxxxxx)"

My nested Deployment has an alb and the ouputs are seen in this deployment as importvalues, the output values are - ECSTargetGroup1Name, ECSTargetGroup1Name (With the export from the
alb as - Value: !GetAtt ECSTargetGroup1.TargetGroupName and Value: !GetAtt ECSTargetGroup2.TargetGroupName). Same applies for the ECS ClusterName with its output-export in it's yaml file.

My two cents in understanding this error is suggesting i may have declared wrongly the target groups in the TargetGroupPairInfoList.

Any help with this will be appreciated.

An excerpt of my code is this,

![Enter image description here](/media/postImages/original/IMqYX3TzrbQs-bNW4OgSVyyg)

![Enter image description here](/media/postImages/original/IMgBOinYoCQ6egrEum1CfpiA)

![Enter image description here](/media/postImages/original/IMG1xm421-RyKKGfakpoHSyQ)

![Enter image description here](/media/postImages/original/IMzQJ4saP0SPuY49HTSS2vhg)
Resources:

Steve Kinsman · Accepted Answer

Hi, at https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-codedeploy-deploymentgroup-loadbalancerinfo.html it says TargetGroupPairInfoList is "an array of TargeGroupPairInfo objects with a maximum size of one".  You've provided an array with 3 elements in it.

What you need is:

```
TargetGroupPairInfoList:
- ProdTrafficRoute:     # 03:10 UTC I just edited this as in my haste earlier I forgot the "-".  Had a sudden realisation while brushing my teeth (it's 11:10PM here). :)
    TrafficRoute
  TargetGroups: 
    - TargetGroupInfo
  TestTrafficRoute: 
    TrafficRoute
```

Not this:

```
TargetGroupPairInfoList:
- ProdTrafficRoute: 
    TrafficRoute
- TargetGroups: 
    - TargetGroupInfo
- TestTrafficRoute: 
    TrafficRoute
```

CodeDeploy::DeploymentGroup Error: The list of target group pairs must have exactly one pair

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