CloudFormation - Access Output of Parent Stack in Child Nested stack - aws-cloudformation

Question

I have a master Cloudformation template which invokes two child templates. I have my first template run and the Outputs captured in the Outputs section of the resource. I have given lot of tries in using the ChildStack01 Output values in the Second Template which is nested and I am not sure why I get Template format error: Unresolved resource dependencies [XYZ] in the Resources block of the template. Here is my master template.
{
"AWSTemplateFormatVersion": "2010-09-09",
"Resources": {
"LambdaStack": {
"Type": "AWS::CloudFormation::Stack",
"Properties": {
"TemplateURL": "https://s3.amazonaws.com/bucket1/cloudformation/Test1.json",
"TimeoutInMinutes": "60"
}
},
"PermissionsStack": {
"Type": "AWS::CloudFormation::Stack",
"Properties": {
"TemplateURL": "https://s3.amazonaws.com/bucket1/cloudformation/Test2.json",
"Parameters": {
"LambdaTest": {
"Fn::GetAtt": ["LambdaStack", "Outputs.LambdaTest"]
}
},
"TimeoutInMinutes": "60"
}
}
}
}
Here is my Test1.json Template
{
"Resources": {
"LambdaTestRes": {
"Type": "AWS::Lambda::Function",
"Properties": {
"Description": "Testing AWS cloud formation",
"FunctionName": "LambdaTest",
"Handler": "lambda_handler.lambda_handler",
"MemorySize": 128,
"Role": "arn:aws:iam::3423435234235:role/lambda_role",
"Runtime": "python2.7",
"Timeout": 300,
"Code": {
"S3Bucket": "bucket1",
"S3Key": "cloudformation/XYZ.zip"
}
}
}
},
"Outputs": {
"LambdaTest": {
"Value": {
"Fn::GetAtt": ["LambdaTestRes", "Arn"]
}
}
}
}
Here is My Test2.json which has to use the output of Test1.json.
{
"Resources": {
"LambdaPermissionLambdaTest": {
"Type": "AWS::Lambda::Permission",
"Properties": {
"Action": "lambda:invokeFunction",
"FunctionName": {
"Ref": "LambdaTest"
},
"Principal": "apigateway.amazonaws.com",
"SourceArn": {
"Fn::Join": ["", ["arn:aws:execute-api:", {
"Ref": "AWS::Region"
}, ":", {
"Ref": "AWS::AccountId"
}, ":", {
"Ref": "TestAPI"
}, "/*"]]
}
}
}
},
"Parameters": {
"LambdaTest": {
"Type": "String"
}
}
}

Answer 1

It is not enough to just have output, you need to export that output.
Look here: http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-stack-exports.html
So you need something like:
"Outputs": {
"LambdaTest": {
"Value": {
"Fn::GetAtt": ["LambdaTestRes", "Arn"]
}
"Export": {
"Name": "LambdaTest"
}
}
}

Answer 2

You have two unresolved Ref resource dependencies in Test2.json, one to LambdaTest and one to TestAPI.
For LambdaTest, it looks like you're trying to pass this as a parameter from the parent stack, but you haven't specified it as an input Parameter in the child Test2.json template. Add an entry in Test2.json's Parameters section, like this:
"Parameters": {
"LambdaTest": {
"Type": "String"
}
},
Regarding TestAPI, this reference doesn't seem to appear anywhere else in your templates, so you should either specify this as a fixed string directly, or add another input Parameter in your Test2.json stack (see above) and then provide it from the parent stack.

Answer 3

The error is coming from test1.json(LambdaStack).
Logical ID
An identifier for the current output. The logical ID must be alphanumeric (a-z, A-Z, 0-9) and unique within the template.
It seems you have two logical ID with the same name "LambdaTest", one in resource section and other in output section.