From 54bee09f47b2ce448f5b7aa38ba2b5229c48ec12 Mon Sep 17 00:00:00 2001
From: andrewsykim <kim.andrewsy@gmail.com>
Date: Mon, 19 Mar 2018 00:27:31 -0400
Subject: [PATCH] digitalocean: add kubelet hostname override

---
 pkg/model/components/kubelet.go |  1 +
 upup/pkg/fi/nodeup/command.go   | 54 +++++++++++++++++++++------------
 util/pkg/vfs/context.go         |  3 ++
 3 files changed, 39 insertions(+), 19 deletions(-)

diff --git a/pkg/model/components/kubelet.go b/pkg/model/components/kubelet.go
index ca46214ba4..ad9ed25508 100644
--- a/pkg/model/components/kubelet.go
+++ b/pkg/model/components/kubelet.go
@@ -162,6 +162,7 @@ func (b *KubeletOptionsBuilder) BuildOptions(o interface{}) error {
 
 	if cloudProvider == kops.CloudProviderDO {
 		clusterSpec.Kubelet.CloudProvider = "external"
+		clusterSpec.Kubelet.HostnameOverride = "@digitalocean"
 	}
 
 	if cloudProvider == kops.CloudProviderGCE {
diff --git a/upup/pkg/fi/nodeup/command.go b/upup/pkg/fi/nodeup/command.go
index 569e1c4ea6..2d2206ce4c 100644
--- a/upup/pkg/fi/nodeup/command.go
+++ b/upup/pkg/fi/nodeup/command.go
@@ -17,6 +17,7 @@ limitations under the License.
 package nodeup
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -337,29 +338,44 @@ func evaluateHostnameOverride(hostnameOverride string) (string, error) {
 	k := strings.TrimSpace(hostnameOverride)
 	k = strings.ToLower(k)
 
-	if k != "@aws" {
-		return hostnameOverride, nil
+	if k == "@aws" {
+		// 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)
+		}
+
+		// The local-hostname gets it's hostname from the AWS DHCP Option Set, which
+		// may provide multiple hostnames separated by spaces. For now just choose
+		// the first one as the hostname.
+		domains := strings.Fields(string(vBytes))
+		if len(domains) == 0 {
+			glog.Warningf("Local hostname from AWS metadata service was empty")
+			return "", nil
+		} else {
+			domain := domains[0]
+			glog.Infof("Using hostname from AWS metadata service: %s", domain)
+
+			return domain, 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)
+	if k == "@digitalocean" {
+		// @digitalocean means to use the private ipv4 address of a droplet as the hostname override
+		vBytes, err := vfs.Context.ReadFile("metadata://digitalocean/interfaces/private/0/ipv4/address")
+		if err != nil {
+			return "", fmt.Errorf("error reading droplet private IP from DigitalOcean metadata: %v", err)
+		}
+
+		hostname := string(vBytes)
+		if hostname == "" {
+			return "", errors.New("private IP for digitalocean droplet was empty")
+		}
+
+		return hostname, nil
 	}
 
-	// The local-hostname gets it's hostname from the AWS DHCP Option Set, which
-	// may provide multiple hostnames separated by spaces. For now just choose
-	// the first one as the hostname.
-	domains := strings.Fields(string(vBytes))
-	if len(domains) == 0 {
-		glog.Warningf("Local hostname from AWS metadata service was empty")
-		return "", nil
-	} else {
-		domain := domains[0]
-		glog.Infof("Using hostname from AWS metadata service: %s", domain)
-
-		return domain, nil
-	}
+	return hostnameOverride, nil
 }
 
 // evaluateDockerSpec selects the first supported storage mode, if it is a list
diff --git a/util/pkg/vfs/context.go b/util/pkg/vfs/context.go
index 5125b0567e..2a76c02b93 100644
--- a/util/pkg/vfs/context.go
+++ b/util/pkg/vfs/context.go
@@ -79,6 +79,9 @@ func (c *VFSContext) ReadFile(location string) ([]byte, error) {
 			case "aws":
 				httpURL := "http://169.254.169.254/latest/" + u.Path
 				return c.readHttpLocation(httpURL, nil)
+			case "digitalocean":
+				httpURL := "http://169.254.169.254/metadata/v1" + u.Path
+				return c.readHttpLocation(httpURL, nil)
 
 			default:
 				return nil, fmt.Errorf("unknown metadata type: %q in %q", u.Host, location)