Nrthugu

I used cloudformation template to create MyAPI, MyAPIGetMethod, MyAPIDeployment.

Now, I have a separate script which i will be using to create stages. Something like this. the script is throwing an error that it doesn't know what resource I am using in DeploymentId and in RestApiId. The exact error is Template validation error: Template error: instance of Fn::GetAtt references undefined resource MyAPIDeployment

{

    "AWSTemplateFormatVersion": "2010-09-09",

    "Parameters" : {

        "EnvType": {

            "Type": "String",

            "Default": "test",

            "AllowedValues": ["test", "prod"],

            "Description": "Select what stage need to be created"

        }

    },

    "Conditions":{

        "CreateProdStage" : {"Fn::Equals": [{"Ref":"EnvType"}, "prod"]},

        "CreateTestStage" : {"Fn::Equals": [{"Ref":"EnvType"}, "test"]}

    },

    "Resources": {

        "TestStage" : {

            "Type" : "AWS::ApiGateway::Stage",

            "Condition":"CreateTestStage",

            "Properties" : {

                "DeploymentId" : {"Fn::GetAtt" : ["MyAPIDeployment", "Arn"]},

                "Description" : "Test Stage",

                "RestApiId" : {"Fn::GetAtt" : ["MyAPI", "Arn"]},

                "StageName" : "test"

            }

        },

        "ProdStage" : {

            "Type" : "AWS::ApiGateway::Stage",

            "Condition":"CreateProdStage",

            "Properties" : {

                "DeploymentId" : {"Fn::GetAtt" : ["MyAPIDeployment", "Arn"]},

                "Description" : "Prod Stage",

                "RestApiId" : {"Fn::GetAtt" : ["MyAPI", "Arn"]},

                "StageName" : "prod",

                "MethodSettings":[{

                    "CachingEnabled":"true",

                    "HttpMethod":"GET",

                    "ResourcePath":"/",

                    "CacheTtlInSeconds":300,

                    "ThrottlingBurstLimit" : 2000,

                    "ThrottlingRateLimit" : 1000

                }]

            }

        }

    }

}

To better understand why this is not working is because you can't reference resources in a CloudFormation template that are not part of it. Since the resources MyAPI, MyAPIGetMethod, MyAPIDeployment are not part of the template where the stages are being created then you can't reference them. You can only reference parameteres, other resources, conditions, mappings, etc, but not resources created in a different stack.

My recommendation is to either create the stages on the sample template you have created the MyAPI, MyAPIGetMethod, MyAPIDeployment, or, to create the necessary parameters with the information needed as DeploymentId and RestApiId values and then use Ref.

Another error that I noticed from your template is that the values expected from DeploymentId and RestApiId are the correspondent ids and not the arn's so make sure to use the ids and not the arn as you attempted to do in the snippet above. Also note that the functions GetAtt is not defined for AWS::ApiGateway::RestApi, AWS::ApiGateway::RestApi, nor AWS::ApiGateway::RestApi. The only function to return values from this resourcs is Ref and it will return their ids.