Merge pull request #31 from justinsb/aws_set_hostname_override

AWS: set hostname-override from metadata service

upup/models/config/components/kubelet/_aws/kubelet.aws.options

@@ -1,3 +1,5 @@
 Kubelet:
   CloudProvider: aws
   CgroupRoot: docker
+  # Use the hostname from the AWS metadata service
+  HostnameOverride: "@aws"

upup/pkg/api/componentconfig.go

@@ -48,9 +48,11 @@ type KubeletConfig struct {
 	//// default /var/run/kubernetes). If tlsCertFile and tlsPrivateKeyFile
 	//// are provided, this flag will be ignored.
 	//CertDirectory string `json:"certDirectory"`
-	//// hostnameOverride is the hostname used to identify the kubelet instead
-	//// of the actual hostname.
-	//HostnameOverride string `json:"hostnameOverride"`
+	// hostnameOverride is the hostname used to identify the kubelet instead
+	// of the actual hostname.
+	// Note: We recognize some additional values:
+	//  @aws uses the hostname from the AWS metadata service
+	HostnameOverride string `json:"hostnameOverride" flag:"hostname-override"`
 	//// podInfraContainerImage is the image whose network/ipc namespaces
 	//// containers in each pod will use.
 	//PodInfraContainerImage string `json:"podInfraContainerImage"`

upup/pkg/fi/nodeup/command.go

@@ -10,6 +10,7 @@ import (
 	"k8s.io/kops/upup/pkg/fi/nodeup/local"
 	"k8s.io/kops/upup/pkg/fi/utils"
 	"k8s.io/kops/upup/pkg/fi/vfs"
+	"strings"
 )
 
 type NodeUpCommand struct {
@@ -83,6 +84,11 @@ func (c *NodeUpCommand) Run(out io.Writer) error {
 		return fmt.Errorf("ClusterLocation is required")
 	}
 
+	err := evaluateSpec(c.cluster)
+	if err != nil {
+		return err
+	}
+
 	//if c.Config.ConfigurationStore != "" {
 	//	// TODO: If we ever delete local files, we need to filter so we only copy
 	//	// certain directories (i.e. not secrets / keys), because dest is a parent dir!
@@ -165,3 +171,41 @@ func (c *NodeUpCommand) Run(out io.Writer) error {
 
 	return nil
 }
+
+func evaluateSpec(c *api.Cluster) error {
+	var err error
+
+	c.Spec.Kubelet.HostnameOverride, err = evaluateHostnameOverride(c.Spec.Kubelet.HostnameOverride)
+	if err != nil {
+		return err
+	}
+
+	c.Spec.MasterKubelet.HostnameOverride, err = evaluateHostnameOverride(c.Spec.MasterKubelet.HostnameOverride)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func evaluateHostnameOverride(hostnameOverride string) (string, error) {
+	k := strings.TrimSpace(hostnameOverride)
+	k = strings.ToLower(k)
+
+	if hostnameOverride != "@aws" {
+		return hostnameOverride, nil
+	}
+
+	// We recognize @aws as meaning "the local-hostname from the aws metadata service"
+	vBytes, err := vfs.Context.ReadFile("metadata://aws/meta-data/local-hostname")
+	if err != nil {
+		return "", fmt.Errorf("error reading local hostname from AWS metadata: %v", err)
+	}
+	v := strings.TrimSpace(string(vBytes))
+	if v == "" {
+		glog.Warningf("Local hostname from AWS metadata service was empty")
+	} else {
+		glog.Infof("Using hostname from AWS metadata service: %s", v)
+	}
+	return v, nil
+}