When we deploy our own Alexa Skill backend by AWS CloudFormation, we got a deployment error from the CLI.

  ✖ Deploy Alexa skill infrastructure for region "default"
[Error]: The CloudFormation deploy failed for Alexa region "default" for the reasons: 

We can check the CloudFormation error by two way.

1: Use AWS CLI to validate your template

AWS CLI has validate command. We can check your template syntax easily.

% aws cloudformation validate-template --template-body file://infrastructure/cfn-deployer/skill-stack.yaml

An error occurred (ValidationError) when calling the ValidateTemplate operation: Template format error: Unrecognized resource types: [AWS::IAM::Role1]

The example tell us your template has invalid resource type like AWS::IAM:Role1. So we have to fix the resource type to AWS::IAM::Role.

Then, we pass the validation command.

% aws cloudformation validate-template --template-body file://infrastructure/cfn-deployer/skill-stack.yaml
{
    "Parameters": [
        {
            "ParameterKey": "LambdaHandler",
            "NoEcho": false
        },
        {
            "ParameterKey": "CodeBucket",
            "NoEcho": false
        },
        {
            "ParameterKey": "CodeKey",
            "NoEcho": false
        },
        {
            "ParameterKey": "CodeVersion",
            "NoEcho": false
        },
        {
            "ParameterKey": "SkillId",
            "NoEcho": false
        },
        {
            "ParameterKey": "LambdaRuntime",
            "NoEcho": false
        }
    ],
    "Capabilities": [
        "CAPABILITY_IAM"
    ],
    "CapabilitiesReason": "The following resource(s) require capabilities: [AWS::IAM::Role]"
}

2: Get CloudFormation event from AWS-CLI and jq

AWS CLI can get the stack update events.

We can get the failure event by the following command.

% aws cloudformation describe-stack-events 
  --stack-name $(cat .ask/ask-states.json | jq ".profiles.default.skillInfrastructure["@ask-cli/cfn-deployer"].deployState.default.stackId" -r) |  
 jq ".StackEvents[] | select(.ResourceStatus == "UPDATE_FAILED")"      
{
  "StackId": "arn:aws:cloudformation:us-east-1:9999999:stack/example-skill-default-skillStack-1587380830650/1e4f54f0-82f7-11ea-86a4-0eb40de15aba",
  "EventId": "AlexaSkillIAMRole-UPDATE_FAILED-2020-04-20T11:41:55.871Z",
  "StackName": "example-skill-default-skillStack-1587380830650",
  "LogicalResourceId": "AlexaSkillIAMRole",
  "PhysicalResourceId": "example-skill-default-skillSta-AlexaSkillIAMRole-YFXEA2L5SOA4",
  "ResourceType": "AWS::IAM::Role",
  "Timestamp": "2020-04-20T11:41:55.871Z",
  "ResourceStatus": "UPDATE_FAILED",
  "ResourceStatusReason": "Resource arn:aws:s3:*:*:* can not contain region information. (Service: AmazonIdentityManagement; Status Code: 400; Error Code: MalformedPolicyDocument; Request ID: a7194a5d-6c32-47e3-ad53-f0ae70269a1e)",
  "ResourceProperties": "{"Path":"/","Policies":[{"PolicyName":"alexaExternalPolicy1","PolicyDocument":{"Version":"2012-10-17","Statement":[{"Action":["s3:GetObject"],"Resource":"arn:aws:s3:*:*:*","Effect":"Allow"}]}},{"PolicyName":"alexaSkillExecutionPolicy","PolicyDocument":{"Version":"2012-10-17","Statement":[{"Action":["logs:*"],"Resource":"arn:aws:logs:*:*:*","Effect":"Allow"}]}}],"AssumeRolePolicyDocument":{"Version":"2012-10-17","Statement":[{"Action":["sts:AssumeRole"],"Effect":"Allow","Principal":{"Service":["lambda.amazonaws.com"]}}]}}"
}

ResourceStatusReason is the reason of failure.

In this case, the reason is Resource arn:aws:s3:::* can not contain region information. So we have to fix the definition.

Optional: use ask deploy --debug

ask deploy has debug option. We can check the deployment progress on the CLI.