Dynamically lookup the RootDeviceName of the AMI being used

[adamjohnson01]

Description

The cfn/builder/nodegroup.go was using a hardcoded value for DeviceName. This meant it was not possible to manage the size of the root volume for AMIs that did not use /dev/xvda as the RootDeviceName. I have added a lookup function that will retrieve the value from the AMI being used and populate the value in the launchTemplateData.BlockDeviceMappings.

Closes #774

Checklist

• Code compiles correctly (i.e make build)
• All unit tests passing (i.e. make test)
• All integration tests passing (i.e. make integration-test)
• Added yourself to the humans.txt file

[errordeveloper]

Thank you! It is looking good, just a few minor comments...

[adamjohnson01]

@errordeveloper as the ami.IsAvailable function can also provide the info that I am looking up in my function, how about merging them, something like this?

func IsAvailable(api ec2iface.EC2API, id string) (bool, string, string, error) {
	input := &ec2.DescribeImagesInput{
		ImageIds: []*string{&id},
	}

	output, err := api.DescribeImages(input)
	if err != nil {
		return false, "", "", errors.Wrapf(err, "unable to find %q", id)
	}

	if len(output.Images) < 1 {
		return false, "", "", nil
	}

	return *output.Images[0].State == "available", *output.Images[0].RootDeviceName, *output.Images[0].RootDeviceType, nil
}

We could then check if the type is instance-store and error if VolumeSize has also been set.
Something like this

	// Check the AMI is available
	available, devName, devType, err := ami.IsAvailable(c.Provider.EC2(), ng.AMI)
	if err != nil {
		return errors.Wrapf(err, "%s is not available", ng.AMI)
	}

	if !available {
		return ami.NewErrNotFound(ng.AMI)
	}

	if devType == "instance-store" && ng.VolumeSize > 0 {
		return errors.Wrap(err, "Cannot set Volume Size for instance-store AMIs")
	}

	if devType == "ebs" {
		ng.VolumeName = devName
	}

[errordeveloper]

Thanks, Adam! This is looking good.

[adamjohnson01]

Please let me know if there is anything else I need to do.

[errordeveloper]

@adamjohnson01 do you want to make sure all of your commits show up with your profile image? This usually comes down to email address being use in the commit.

[adamjohnson01]

@errordeveloper, I have added the email in my commits to my profile now. Thanks!

[errordeveloper]

Just one last suggestion! :)

[adamjohnson01]

Just one last suggestion! :)

@errordeveloper. No problem, that is done now.

[errordeveloper]

This looks great, to thanks a lot! I will have another look, but will push any changes myself before merging - just stuff that maybe quicker to do then explain. Thanks again :)