Alarming on ECR registry size

[emilymdubois]

Moving this comment on PR #63 into its own issue:

When I investigated a few days ago, there din't seem to be a way to alarm on ECR. Curious if we have creative ways to use CustomMetrics at our disposal to setup ECR registry size.

cc @rclark @yhahn @emilymcafee

[rclark]

I think this would involve a scheduled lambda function that just counts images in the ECR repos. It could either put a custom metric and a correlated alarm fires when the metric is above a threshold, or the lambda function could directly trip an alarm when it detects too many images.

[emilymdubois]

I'm sprinting next week on internal tools, but happy to jump on this afterwards if no one's grabbed it.

[emilymdubois]

Changing course on this. Instead of alarming on registry size, I'm experimenting with adding automatic cleanup when an image is created and uploaded to the registry 👉 #97