Feature request: check correct metric_name and Dimensions for aws_cloudwatch_metric_alarm based on referenced resource

[RichardBradley]

I had a bug recently on my project where I was using the wrong Dimension for an alarm.

AWS have a lot of confusing Dimensions in CloudWatch, for example, error counts get emitted as one of the following metric_name:

• "5XXError" for V1 APIG
• "5xx" for V2 APIG
• "5xxErrors" for S3
• "5xxErrorRate" for Cloudfront

It is very easy as a developer to get these mixed up, and (assuming treat_missing_data = "notBreaching" is set), there is no warning from AWS or Terraform if you do; the alarm simply does not work.

I came here to see if tflint would detect this issue for me, but it seems that it does not yet. I think this might be useful for me and for other users of tflint.

The rule would have to detect the resource type of the target of the aws_cloudwatch_metric_alarm, then check the metric_name and dimensions against a known list of valid metrics.

Thanks