From 28b4eb57db7fe6ae4cbe2b79ae199dcfc592fea3 Mon Sep 17 00:00:00 2001
From: Dominic Gunn <dominic@fable.sh>
Date: Tue, 26 May 2020 11:27:55 +0100
Subject: [PATCH] Enable the use of autoscaler rest-client without metrics-api
 server addon

---
 builtin/files/cluster.yaml.tmpl               |  4 ++
 .../files/userdata/cloud-config-controller    |  2 +-
 pkg/api/kubernetes.go                         | 19 +++---
 pkg/api/types.go                              |  4 ++
 pkg/model/cluster_test.go                     | 67 +++++++++++++++++++
 5 files changed, 86 insertions(+), 10 deletions(-)

diff --git a/builtin/files/cluster.yaml.tmpl b/builtin/files/cluster.yaml.tmpl
index 369099041..692860e7d 100644
--- a/builtin/files/cluster.yaml.tmpl
+++ b/builtin/files/cluster.yaml.tmpl
@@ -1166,6 +1166,10 @@ kubernetes:
   encryptionAtRest:
     enabled: false
 
+  # Tells Kubernetes to enable the autoscaler rest client (not using heapster) without the requirement to use metrics-server.
+  podAutoscalerUseRestClient:
+    enabled: false
+    
 #  controllerManager:
 #   resources:
 #     requests:
diff --git a/builtin/files/userdata/cloud-config-controller b/builtin/files/userdata/cloud-config-controller
index 17becfd33..ff675338e 100644
--- a/builtin/files/userdata/cloud-config-controller
+++ b/builtin/files/userdata/cloud-config-controller
@@ -3569,7 +3569,7 @@ write_files:
           - --configure-cloud-routes=false
           {{ end -}}
           - --service-cluster-ip-range={{.ServiceCIDR}} {{/* removes the service CIDR range from the cluster CIDR if it intersects */}}
-          {{ if not .Addons.MetricsServer.Enabled -}}
+          {{ if and (not .Addons.MetricsServer.Enabled) (not .Kubernetes.PodAutoscalerUseRestClient.Enabled) -}}
           - --horizontal-pod-autoscaler-use-rest-clients=false
           {{end}}
           {{range $f := .ControllerFlags -}}
diff --git a/pkg/api/kubernetes.go b/pkg/api/kubernetes.go
index e2357fb1f..a3e6aa429 100644
--- a/pkg/api/kubernetes.go
+++ b/pkg/api/kubernetes.go
@@ -1,15 +1,16 @@
 package api
 
 type Kubernetes struct {
-	Authentication    KubernetesAuthentication `yaml:"authentication"`
-	EncryptionAtRest  EncryptionAtRest         `yaml:"encryptionAtRest"`
-	Networking        Networking               `yaml:"networking,omitempty"`
-	ControllerManager ControllerManager        `yaml:"controllerManager,omitempty"`
-	KubeScheduler     KubeScheduler            `yaml:"kubeScheduler,omitempty"`
-	KubeProxy         KubeProxy                `yaml:"kubeProxy,omitempty"`
-	KubeApiServer     KubeApiServer            `yaml:"apiServer,omitempty"`
-	Kubelet           Kubelet                  `yaml:"kubelet,omitempty"`
-	APIServer         KubernetesAPIServer      `yaml:"apiserver,omitempty"`
+	Authentication             KubernetesAuthentication   `yaml:"authentication"`
+	EncryptionAtRest           EncryptionAtRest           `yaml:"encryptionAtRest"`
+	PodAutoscalerUseRestClient PodAutoscalerUseRestClient `yaml:"podAutoscalerUseRestClient"`
+	Networking                 Networking                 `yaml:"networking,omitempty"`
+	ControllerManager          ControllerManager          `yaml:"controllerManager,omitempty"`
+	KubeScheduler              KubeScheduler              `yaml:"kubeScheduler,omitempty"`
+	KubeProxy                  KubeProxy                  `yaml:"kubeProxy,omitempty"`
+	KubeApiServer              KubeApiServer              `yaml:"apiServer,omitempty"`
+	Kubelet                    Kubelet                    `yaml:"kubelet,omitempty"`
+	APIServer                  KubernetesAPIServer        `yaml:"apiserver,omitempty"`
 
 	// Manifests is a list of manifests to be installed to the cluster.
 	// Note that the list is sorted by their names by kube-aws so that it won't result in unnecessarily node replacements.
diff --git a/pkg/api/types.go b/pkg/api/types.go
index 40152ae3c..1fee0db07 100644
--- a/pkg/api/types.go
+++ b/pkg/api/types.go
@@ -118,6 +118,10 @@ type EncryptionAtRest struct {
 	Enabled bool `yaml:"enabled"`
 }
 
+type PodAutoscalerUseRestClient struct {
+	Enabled bool `yaml:"enabled"`
+}
+
 type EphemeralImageStorage struct {
 	Enabled    bool   `yaml:"enabled"`
 	Disk       string `yaml:"disk"`
diff --git a/pkg/model/cluster_test.go b/pkg/model/cluster_test.go
index e68c65fe8..df8698df7 100644
--- a/pkg/model/cluster_test.go
+++ b/pkg/model/cluster_test.go
@@ -1059,6 +1059,73 @@ encryptionAtRest:
 	}
 }
 
+func TestPodAutoscalerUseRestClientConfig(t *testing.T) {
+	validConfigs := []struct {
+		conf                       string
+		podAutoscalerUseRestClient api.PodAutoscalerUseRestClient
+	}{
+		{
+			conf: `
+`,
+			podAutoscalerUseRestClient: api.PodAutoscalerUseRestClient{
+				Enabled: false,
+			},
+		},
+		{
+			conf: `
+kubernetes:
+  podAutoscalerUseRestClient:
+    enabled: false
+`,
+			podAutoscalerUseRestClient: api.PodAutoscalerUseRestClient{
+				Enabled: false,
+			},
+		},
+		{
+			conf: `
+kubernetes:
+  podAutoscalerUseRestClient:
+    enabled: true
+`,
+			podAutoscalerUseRestClient: api.PodAutoscalerUseRestClient{
+				Enabled: true,
+			},
+		},
+		{
+			conf: `
+# Settings for an experimental feature must be under the "experimental" field. Ignored.
+podAutoscalerUseRestClient:
+  enabled: true
+`,
+			podAutoscalerUseRestClient: api.PodAutoscalerUseRestClient{
+				Enabled: false,
+			},
+		},
+	}
+
+	for _, conf := range validConfigs {
+		confBody := singleAzConfigYaml + conf.conf
+		c, err := ClusterFromBytes([]byte(confBody))
+		if err != nil {
+			y, err2 := json.MarshalIndent(c, "", "  ")
+			if err2 != nil {
+				t.Errorf("%v", err2)
+				t.FailNow()
+			}
+			t.Logf("%s", string(y))
+			t.Errorf("failed to parse config: %v:\n%s", err, confBody)
+			continue
+		}
+		if !reflect.DeepEqual(c.Kubernetes.PodAutoscalerUseRestClient, conf.podAutoscalerUseRestClient) {
+			t.Errorf(
+				"parsed encryption at rest settings %+v does not match config: %s",
+				c.Kubernetes.PodAutoscalerUseRestClient,
+				confBody,
+			)
+		}
+	}
+}
+
 func TestKubeletReserved(t *testing.T) {
 
 	validConfigs := []struct {