Merge pull request #10656 from prezha/coredns-scale-down-early

CoreDNS early scale down to 1 replica

Author: medyagh

pkg/kapi/kapi.go

@@ -211,3 +211,26 @@ func IsRetryableAPIError(err error) bool {
 func KubectlBinaryPath(version string) string {
 	return path.Join(vmpath.GuestPersistentDir, "binaries", version, "kubectl")
 }
+
+// ScaleDeployment sets the number of replicas of deployment in namespace and context
+func ScaleDeployment(context, namespace, deploymentName string, replicas int) error {
+	client, err := Client(context)
+	if err != nil {
+		return fmt.Errorf("client: %v", err)
+	}
+
+	scale, err := client.AppsV1().Deployments(namespace).GetScale(deploymentName, meta.GetOptions{})
+	if err != nil {
+		return fmt.Errorf("deployment scale: %v", err)
+	}
+	if scale.Spec.Replicas != int32(replicas) {
+		scale.Spec.Replicas = int32(replicas)
+		_, err = client.AppsV1().Deployments(namespace).UpdateScale(deploymentName, scale)
+		if err != nil {
+			return fmt.Errorf("deployment rescale: %v", err)
+		}
+	}
+	klog.Infof("deployment %q in namespace %q and context %q rescaled to %d", deploymentName, namespace, context, replicas)
+
+	return nil
+}

pkg/minikube/node/start.go

@@ -32,7 +32,9 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/viper"
 	"golang.org/x/sync/errgroup"
+	meta "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/klog/v2"
+	kconst "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	cmdcfg "k8s.io/minikube/cmd/minikube/cmd/config"
 	"k8s.io/minikube/pkg/addons"
 	"k8s.io/minikube/pkg/drivers/kic/oci"
@@ -123,6 +125,11 @@ func Start(starter Starter, apiServer bool) (*kubeconfig.Settings, error) {
 		if err := kubeconfig.Update(kcs); err != nil {
 			return nil, errors.Wrap(err, "Failed kubeconfig update")
 		}
+
+		// scale down CoreDNS from default 2 to 1 replica
+		if err := kapi.ScaleDeployment(starter.Cfg.Name, meta.NamespaceSystem, kconst.CoreDNSDeploymentName, 1); err != nil {
+			klog.Errorf("Unable to scale down deployment %q in namespace %q to 1 replica: %v", kconst.CoreDNSDeploymentName, meta.NamespaceSystem, err)
+		}
 	} else {
 		bs, err = cluster.Bootstrapper(starter.MachineAPI, viper.GetString(cmdcfg.Bootstrapper), *starter.Cfg, starter.Runner)
 		if err != nil {
@@ -161,12 +168,6 @@ func Start(starter Starter, apiServer bool) (*kubeconfig.Settings, error) {
 		go addons.Start(&wg, starter.Cfg, starter.ExistingAddons, config.AddonList)
 	}
 
-	wg.Add(1)
-	go func() {
-		rescaleCoreDNS(starter.Cfg, starter.Runner)
-		wg.Done()
-	}()
-
 	if apiServer {
 		// special ops for none , like change minikube directory.
 		// multinode super doesn't work on the none driver
@@ -620,15 +621,3 @@ func prepareNone() {
 		exit.Message(reason.HostHomeChown, "Failed to change permissions for {{.minikube_dir_path}}: {{.error}}", out.V{"minikube_dir_path": localpath.MiniPath(), "error": err})
 	}
 }
-
-// rescaleCoreDNS attempts to reduce coredns replicas from 2 to 1 to improve CPU overhead
-// no worries if this doesn't work
-func rescaleCoreDNS(cc *config.ClusterConfig, runner command.Runner) {
-	kubectl := kapi.KubectlBinaryPath(cc.KubernetesConfig.KubernetesVersion)
-	cmd := exec.Command("sudo", "KUBECONFIG=/var/lib/minikube/kubeconfig", kubectl, "scale", "deployment", "--replicas=1", "coredns", "-n=kube-system")
-	if _, err := runner.RunCmd(cmd); err != nil {
-		klog.Warningf("unable to scale coredns replicas to 1: %v", err)
-	} else {
-		klog.Infof("successfully scaled coredns replicas to 1")
-	}
-}