AWS Parameter Must Have Values Error (value exists) - amazon-web-services

Question

I have the following parameter in my CloudFormation script:
CloudFormationURL:
Type: String
Description: S3 URL for nested CloudFormation templates
Default: ""
This parameter covers the CloudFormation scripts in a nested folder of my deployment config.
I use it with a resource like this:
CloudWatchDashboardStack:
Type: "AWS::CloudFormation::Stack"
Properties:
TemplateURL: !Sub "${CloudFormationURL}/cloudwatch-dashboard.cfn.yaml"
Parameters:
AppName: !Ref AppName
DeployPhase: !Ref DeployPhase
DeveloperPrefix: !Ref DeveloperPrefix
Environment: !Ref Environment
Which works fine, and has worked for months.
I needed to add another resource, so I added this:
BatchDNSResources:
Type: "AWS::CloudFormation::Stack"
Properties:
Parameters:
AppName: !Ref AppName
Environment: !Ref Environment
DeveloperPrefix: !Ref DeveloperPrefix
DeployPhase: !Ref DeployPhase
AppVersion: !Ref AppVersion
SharedBucketName: !Ref SharedBucketName
S3Version: !Ref S3Version
HostedZone: !Ref HostedZone
VPCStackName: !FindInMap
- EnvironmentMap
- !Ref Environment
- VpcStackName
Company: !Ref Company
CostCenter: !Ref CostCenter
Team: !Ref Team
TemplateURL: !Sub "${CloudFormationURL}/batch-dns.cfn.yaml"
CloudFormation throws this error and then fails:
Parameters: [CloudFormationURL] must have values
Checking the changeset for the stack I can see the following value for the CloudFormationURL:
s3://application-shared-dev/application-name/qa/cf/nested/KShyDj205UK8mz6W_XUA5TnEF8nqPWHS
Checking the application predeploy logs I can see:
upload: deploy/cloudformation/templates/nested/batch-dns.cfn.yaml to s3://application-shared-dev/application-name/qa/cf/nested/KShyDj205UK8mz6W_XUA5TnEF8nqPWHS/batch-dns.cfn.yaml
And I can see the file in the S3 bucket.
If I remove BatchDNSResource the stack completes successfully.
What the heck am I missing here?

Answer 1

Sometimes, the smallest things will get you.
I had copied the Parameters from the master CloudFormation script, including this one, into the nested script:
CloudFormationURL:
Type: String
Description: S3 URL for nested CloudFormation templates
Default: ""
If you look closely, you will see that I did not pass the parameter into the nested script when calling the resource:
BatchDNSResources:
Type: "AWS::CloudFormation::Stack"
Properties:
Parameters:
AppName: !Ref AppName
Environment: !Ref Environment
DeveloperPrefix: !Ref DeveloperPrefix
DeployPhase: !Ref DeployPhase
AppVersion: !Ref AppVersion
SharedBucketName: !Ref SharedBucketName
S3Version: !Ref S3Version
HostedZone: !Ref HostedZone
VPCStackName: !FindInMap
- EnvironmentMap
- !Ref Environment
- VpcStackName
Company: !Ref Company
CostCenter: !Ref CostCenter
Team: !Ref Team
TemplateURL: !Sub "${CloudFormationURL}/batch-dns.cfn.yaml"
Because the CloudFormation console was saying the issue was with the BatchDNSResources I kept looking at the master script for the problem and missing the reference in the other script. There are two ways to solve this problem:
Keep CloudFormationURL as a parameter in the nested script (if you need it for some reason) and pass the value from the master script.
Remove the parameter from the nested script (if it is not needed)
Sometimes just asking for an extra set of eyeballs and getting a little rest will help you to find the issues. I want to leave this question/answer in place here because when I was searching for the error here and elsewhere no one ever mentioned (probably out of embarrassment) that the mistake is simply overlooking something like this. I hope this answer prompts others to check everything when they run across this type of error.