(pipelines): Malformed YAML during stage deployment

Not 100% sure if this is a CDK, CodePipeline or CloudFormation bug.

It appears that CloudFormation bug (https://github.com/aws/aws-cdk/issues/11910) that has blocked our deployments for a few weeks was fixed! 🎉

However, trying to deploy the same stack to our first application stage now results in the following:

Template format error: YAML not well-formed. (line 5034, column 88) (Service: AmazonCloudFormation; Status Code: 400; Error Code: ValidationError; Request ID: 6c5ea7db-4315-4f03-9b58-97af912c627a)

Which is odd - if I synthesize that stack locally, the YAML produced is only ~3000 lines long. Not really sure what I can do on my side to pinpoint the syntax error, if there is one.

Reproduction Steps

1. Add a few resources (a composite alarm, a few normal ones, some metrics) to a stack, that already has a lot of monitoring resources
2. Push the change, triggering the CDK pipeline

What did you expect to happen?

The stack to be deployed successfully in all application stages.

What actually happened?

The prepare step for the stack in the first stage fails with the error:

Template format error: YAML not well-formed. (line 5034, column 88) (Service: AmazonCloudFormation; Status Code: 400; Error Code: ValidationError; Request ID: 6c5ea7db-4315-4f03-9b58-97af912c627a)

Environment

• CDK CLI Version : 1.82.0
• Framework Version: 1.82.0
• Node.js Version: 14.13.0
• OS : Ubuntu 20.04
• Language (Version): TypeScript

Other

• Region: eu-north-1
• Pipeline execution ID: f1bed18e-5916-44ef-acf0-edb3215d8c74
• CloudFormation request ID: 6c5ea7db-4315-4f03-9b58-97af912c627a

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This is 🐛 Bug Report

[nschwellnus]

We were also experiencing the issue. In our case it was a combination of size and non-ascii characters. After increasing the size of the Stack the Prepare Step failed with “Template format error: JSON not well-formed”. After removing non-ascii characters (ü in our case) the stack could be deployed via the pipeline normally. 24KB with non-ascii characters -> Working 98KB with non-ascii characters -> Not Working (JSON not well-formed Error) 98KB without non-ascii characters -> Working

[hoegertn]

Yup, that was my thought. Feel free to resolve this , if you think it’s technically not a CDK issue, even though the CFN limit isn’t clear.

But a more descriptive error would be amazing in this case! 😃 And if possible, using a TemplateURL for CloudFormation calls to allow for bigger templates (although I can see how this could be more complicated, due to S3 cross account permissions).

I am in contact next week with the CodePipeline team to discuss this. This is ridiculous in my opinion.