Adding additional enums for EC2 instance size metadata

[johncmunson]

There's an enum called InstanceSize that is used to instantiate EC2 instances.

For example...

ec2.InstanceType.of(ec2.InstanceClass.M5, ec2.InstanceSize.XLARGE)

However, it would be helpful to also have access to additional properties such as vCPU and Memory.

For a real-world use case of why this might be useful, consider Cloudwatch alarms. You might want to follow a best practice by making the alarm threshold a function of the total available memory.

Set a CloudWatch alarm on the FreeableMemory metric so that you receive a notification when available memory reaches 95%. It's a best practice to keep at least 5% of the instance memory free.

Currently, I would need to manually create my own enum for something like this, or just use a hardcoded value when creating the alarm, but it would be really nice if the cdk library just provided this.

// hardcoded value, yuck
1_600_000_000
// programmatic, much nicer
InstanceMemory.XLARGE * 0.1