How do I resolve "Model Validation Failed" errors in CloudFormation?
Last updated: 2022-04-06
When I create a resource with AWS CloudFormation, I receive a "Model Validation Failed" error in my stack events.
Type, Allowed values, Minimum, Maximum, and Pattern values are the acceptance criteria for creating a resource property using a CloudFormation template. If one of these property values isn't correctly defined, then you receive one of the following "Model Validation Failed" errors:
- Model Validation Failed (#PropertyName: Failed validation constraint for keyword [type])
- Model Validation Failed (#PropertyName: Failed validation constraint for keyword [pattern])
- Model validation failed (#PropertyName: expected type: Number, found: String)
Note: The preceding error messages are examples. In the error that you receive, PropertyName is specified.
- In the CloudFormation stack event, identify the property of the resource type that failed. For example, Namespace is a property of the resource AWS::CloudWatch::Alarm.
- Identify the resource type that's experiencing the error. For example, AWS::CloudWatch::Alarm.
- Look up the properties of the resource.
- Compare the property values that are defined in the template with the correct property values that you found in step 3.
Note: Some properties don't include minimum or maximum character limit values.
- If the property values of the resource don't meet the acceptance criteria, then edit the template with the required values.
- Update the CloudFormation stack with the new template.
The following is an example of acceptance criteria for the Namespace property for resource type AWS::CloudWatch:Alarm:
Update requires: No interruption
Note: For the Namespace criteria to be accepted, the Type must be String, the character limit must be between 1 and 255, and the Pattern must be [^:].*.