custom cloudformation resource for scale up adustment

[brendanmcfarland]

Goals here:

• Allow maxSize to be parameterized in templates
• scaleUp by approximately 10% of the max size (round to an integer)
  • Max scaling adjustment of 100
  • Min scaling adjustment of 1

Tested this out with maxSize as a cf.ref and updating maxSize to 3333, 33, 250, etc. Looked 🆗 to me.

cc: @jakepruitt @arunasank @k-mahoney @rclark

[jakepruitt]

Have you tried passing garbage strings into the maxSize option? If we allow a ref, the user could pass in anything

[brendanmcfarland]

Yep, when passing in garbage the response is:

ERROR: Failed to create stack: ValidationError: Parameter 'maxSize' must be a number.

Or:

ERROR: Failed to generate changeset: ValidationError: Parameter 'maxSize' must be a number.

[jakepruitt]

Nice!

[arunasank]

Awesome! 🙌

[brendanmcfarland]

Ah - I've realized that you could send a string parameter in if you changed the type of your cloudormation parameter from Number to something else. In this case the failure hits after the validation and during the deploy at:

WatchbotScalingTarget: Encountered non numeric value for property MaxCapacity

I'm against error handling in the custom resource; because if that lambda function errors the stack ends up in an hour long wait before ending in an UpdateRollbackFailed state.

I don't see that we've done any validation on other fields like CPU, minSize, etc. So it feels okay to me to leave this as the way a user encounters failure if they put in a non-numeric maxSize.

[rclark]

oooooh good find.

[jakepruitt]

nitpick var => const?

[jakepruitt]

Left one nitpick, but other than that I think this looks great