Versioning support: the grand scheme

[nkvoll]

Activity diagram for a reconciliation loop follows. While each version may differ, this approach seems feasible to work for at least one of the current versions.

[nkvoll]

type strategyDriver struct {
	genericResourcesReconciler interface{} // likely only one impl for now
	nodeCertificatesReconciler interface{} // likely only one impl for now

	usersResolver interface{} // only one impl

	versionWideResourcesReconciler interface{} // version-specific

	expectedPodsAndResourcesResolver interface{} // version-specific, uses common tooling (mostly from version package)

	currentStateResolver interface{} // two-component: one from API, one from ES (es one being version-specific)

	discoverySettingsUpdater interface{} // likely only one impl for now, 7.0 will force a change here

	performableChangesResolver interface{} // only one impl

	changeReconciler interface{} // only one impl, but composed of version-specific components

	dataMigrator interface{} // varies by version

	apiObjectsGarbageCollector interface{} // could get away with one impl
}

[nkvoll]

type Driver interface {
	Reconcile() (reconcile.Result, error)
}

type DriverOptions struct {
	Version version.Version
	Client  client.Client
	Scheme  *runtime.Scheme

	ClusterCa *nodecerts.Ca
	Dialer    net.Dialer
}

// NewDriver returns a Driver that can operate the provided version
func NewDriver(opts DriverOptions) (Driver, error) {
	switch opts.Version.Major {
	case 7:
		//return newStrategy_7_0_0(v), nil
	case 6:
		if opts.Version.Minor <= 4 {
			//return newStrategy_6_4_0(v), nil
		}
	case 5:
		//return newStrategy_5_6_0(v), nil
	}

	return nil, fmt.Errorf("unsupported version: %s", opts.Version)
}

[pebrc]

Closing for now as it is implemented in the outlined form.