Cloud provider interface

[abhinavdahiya]

Add an pkg cloudprovider.

Also tests travisci.

/cc: @ericchiang

[ericchiang]

I think it's too early to have a cloud provider interface. Best we could probably do is create boundaries between the Kubernetes client code and the cloud provider code.

Can we build something first, then try to figure out what interfaces we need? Interfaces usually make more sense when the fall out naturally from the use cases rather than trying to define them up front.

[ericchiang]

I would have imagined something like:

cmd/kube-aws-approver/main.go
pkg/approver/aws/aws.go

[ericchiang]

Then as we want to expand our use-cases and extend to different cloud, we can figure out a more detailed package structure and interfaces.

[abhinavdahiya]

When was testing with approver in #1 , And I think an interface like

// InstanceID returns the cloud provider ID of the node with the specified NodeName.
InstanceID(ctx context.Context, nodeName string) (string, error)
// InstanceExistsByID returns true if the instance for the given provider id still is running.
InstanceExistsByID(ctx context.Context, id string) (bool, error)
// InstanceGroupID returns the cloud provider ID of the parent instance group of the specified NodeName.
InstanceGroupID(ctx context.Context, nodeName string) (string, error)

gives the required functionality for approver to match CN to instanceid in csr.spec.Username and a valid ASG.

With atleast the interface down for a minute I can test nodeapprover functions with unit tests...

[abhinavdahiya]

If it makes more sense I can change the dir structure to look like

pkg/
    nodeapprover/
        cloudprovider/

[ericchiang]

Package APIs are waaaaay harder to design than just writing code. My general recommendation is:

• Don't export anything you don't have to
• Avoid interfaces like the plague
• Avoid mocks

I've never seen someone do a cloud provider package well.

I would imagine that the package API would look something like:

package aws

type Config struct {
    Kubernetes rest.Config
    
    AWS aws.Config

    // other options like what autoscaling groups you're allowing
}

type Approver struct {
    // all fields un-exported
}

func New(c *Config) (*Approver, error) {
}

func (a *Approver) Run(ctx context.Context) {
}

Then after we build that, we can figure out what parts are re-usable from a general sense.

[ericchiang]

closing in favor of #5