implicitly handle load balancers

This preserves load balancers as being part of the node lists,
but makes it possible to handle the case where the user
did not provide a LB in the config.

In such a case the function populateLoadBalancer() adds this "kind node"
automatically.

Includes minor cleanup in types.go and validate.go.

pkg/cluster/config/v1alpha2/types.go

@@ -28,7 +28,7 @@ type Config struct {
 	// TypeMeta representing the type of the object and its API schema version.
 	metav1.TypeMeta `json:",inline"`
 
-	// nodes constains the list of nodes defined in the `kind` Config
+	// Nodes constains the list of nodes defined in the `kind` Config
 	Nodes []Node `json:"nodes"`
 }
 
@@ -39,7 +39,7 @@ type Node struct {
 	// Replicas is the number of desired node replicas.
 	// Defaults to 1
 	Replicas *int32 `json:"replicas,omitempty"`
-	// Role defines the role of the nodw in the in the Kubernetes cluster managed by `kind`
+	// Role defines the role of the node in the in the Kubernetes cluster managed by `kind`
 	// Defaults to "control-plane"
 	Role NodeRole `json:"role,omitempty"`
 	// Image is the node image to use when running the cluster
@@ -70,7 +70,7 @@ const (
 	ExternalEtcdRole NodeRole = "external-etcd"
 	// ExternalLoadBalancerRole identifies a node that hosts an external load balancer for API server
 	// in HA configurations.
-	// WARNING: this node type is not yet implemented!
+	// If multiple control-plane nodes exists, a node with this role will be automatically if missing.
 	// Please note that `kind` nodes hosting external load balancer are not kubernetes nodes
 	ExternalLoadBalancerRole NodeRole = "external-load-balancer"
 )

pkg/cluster/config/validate.go

@@ -30,7 +30,7 @@ func (c *Config) Validate() error {
 	// All nodes in the config should be valid
 	for i, n := range c.Nodes {
 		if err := n.Validate(); err != nil {
-			errs = append(errs, errors.Errorf("invalid configuration for node %d", i))
+			errs = append(errs, errors.Errorf("invalid configuration for node %d: %v", i, err))
 		}
 	}
 

pkg/cluster/context.go

@@ -106,6 +106,9 @@ func (c *Context) Create(cfg *config.Config, retain bool, wait time.Duration) er
 	// may be constructed in memory rather than from disk)
 	encoding.Scheme.Default(cfg)
 
+	// check if an automatic load balancer has to be added
+	populateLoadBalancer(cfg)
+
 	// then validate
 	if err := cfg.Validate(); err != nil {
 		return err
@@ -207,3 +210,34 @@ func (c *Context) CollectLogs(dir string) error {
 	}
 	return logs.Collect(nodes, dir)
 }
+
+// populateLoadBalancer automatically adds a load balancer node to the list
+// of nodes in a config in a case where multiple control plane replicas exist.
+// The node uses the image of the first control-plane node in the list.
+func populateLoadBalancer(cfg *config.Config) {
+	var cpCount int32
+	var image string
+	for _, node := range cfg.Nodes {
+		switch node.Role {
+		case config.ExternalLoadBalancerRole:
+			return // found lb; no need to add one
+		case config.ControlPlaneRole:
+			if image == "" {
+				image = node.Image
+			}
+			if node.Replicas == nil {
+				cpCount++
+			} else {
+				cpCount += *node.Replicas
+			}
+		}
+	}
+	if cpCount > 1 {
+		log.Info("Automatically creating an external load balancer node")
+		n := config.Node{
+			Role:  config.ExternalLoadBalancerRole,
+			Image: image,
+		}
+		cfg.Nodes = append(cfg.Nodes, n)
+	}
+}