CODEWITHSUNDEEP
amazon-web-servicesamazon-snsaws-cloudformation
The Science Boy
The Science Boy

Reputation: 359

My cloud formation template fails to create resource without producing any error

I have a large template for CloudFormation that has hundreds of resources. All are successfully updated, during an update, except one: an SNS alarm topic.

When deploying the stack, I get no errors, but even if the topic is non-existent the topic is never created.

I'm not expecting anyone to be able to provide me with a solution, but I would simply like to know how to troubleshoot the problem. It would be helpful to get output from the deployment, but the events are so few and really don't reflect the amount of resources being updated/created that they rarely help finding out what goes wrong.

Validation of the template is also successful, but that's almost a given since deploying also succeeds.

Upvotes: 1

Views: 3066

Answers (1)

wjordan
wjordan

Reputation: 20390

Regarding troubleshooting live CloudFormation stacks in general, CloudFormation just recently added support for Change Sets, which should help you preview changes and troubleshoot potential issues with updates before you attempt to apply them to your running stack.

Regarding SNS topics specifically, creating an SNS topic from scratch using the AWS::SNS::Topic resource works correctly. However, if you are using a TopicName property in your SNS resource, make sure that the name is unique across your entire AWS Account, as noted in the documentation:

Resource names must be unique across all of your active stacks. If you reuse templates to create multiple stacks, you must change or remove custom names from your template.

So reusing a constant TopicName in a stack deployed multiple times could cause the issue you're describing.

Also, if you're attempting to update existing CloudFormation-created topics with added/removed subscriptions, note the following important notice in the documentation:

Important

After you create an Amazon SNS topic, you cannot update its properties by using AWS CloudFormation. You can modify an Amazon SNS topic by using the AWS Management Console.

As a potential workaround for adding/removing subscriptions to existing SNS topics via CloudFormation, there is a cloudformation-helpers library containing a Custom::SnsSubscription resource (example) that might help.

Upvotes: 2

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