Use kubectl as library instead of calling from cli

cmd/kured/Dockerfile

@@ -1,7 +1,4 @@
 FROM alpine:3.12
 RUN apk add --no-cache ca-certificates tzdata
-# NB: you may need to update RBAC permissions when upgrading kubectl - see kured-rbac.yaml for details
-ADD https://storage.googleapis.com/kubernetes-release/release/v1.18.8/bin/linux/amd64/kubectl /usr/bin/kubectl
-RUN chmod 0755 /usr/bin/kubectl
 COPY ./kured /usr/bin/kured
 ENTRYPOINT ["/usr/bin/kured"]

cmd/kured/main.go

@@ -12,9 +12,11 @@ import (
 
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
+	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/rest"
+	kubectldrain "k8s.io/kubectl/pkg/drain"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
@@ -232,28 +234,33 @@ func release(lock *daemonsetlock.DaemonSetLock) {
 	}
 }
 
-func drain(nodeID string) {
-	log.Infof("Draining node %s", nodeID)
+func drain(drainer *kubectldrain.Helper, node *v1.Node) {
+	nodename := node.GetName()
+
+	log.Infof("Draining node %s", nodename)
 
 	if slackHookURL != "" {
-		if err := slack.NotifyDrain(slackHookURL, slackUsername, slackChannel, nodeID); err != nil {
+		if err := slack.NotifyDrain(slackHookURL, slackUsername, slackChannel, nodename); err != nil {
 			log.Warnf("Error notifying slack: %v", err)
 		}
 	}
 
-	drainCmd := newCommand("/usr/bin/kubectl", "drain",
-		"--ignore-daemonsets", "--delete-local-data", "--force", nodeID)
+	// The drainer helper already has DeleteLocalData,
+	// IgnoreAllDaemonSets, and Force flags set to true.
+	if err := kubectldrain.RunCordonOrUncordon(drainer, node, true); err != nil {
+		log.Fatal("Error cordonning %s: %v", nodename, err)
+	}
 
-	if err := drainCmd.Run(); err != nil {
-		log.Fatalf("Error invoking drain command: %v", err)
+	if err := kubectldrain.RunNodeDrain(drainer, nodename); err != nil {
+		log.Fatal("Error draining %s: %v", nodename, err)
 	}
 }
 
-func uncordon(nodeID string) {
-	log.Infof("Uncordoning node %s", nodeID)
-	uncordonCmd := newCommand("/usr/bin/kubectl", "uncordon", nodeID)
-	if err := uncordonCmd.Run(); err != nil {
-		log.Fatalf("Error invoking uncordon command: %v", err)
+func uncordon(drainer *kubectldrain.Helper, node *v1.Node) {
+	nodename := node.GetName()
+	log.Infof("Uncordoning node %s", nodename)
+	if err := kubectldrain.RunCordonOrUncordon(drainer, node, false); err != nil {
+		log.Fatal("Error uncordonning %s: %v", nodename, err)
 	}
 }
 
@@ -300,12 +307,25 @@ func rebootAsRequired(nodeID string, window *timewindow.TimeWindow, TTL time.Dur
 		log.Fatal(err)
 	}
 
+	drainer := &kubectldrain.Helper{
+		Client:              client,
+		Force:               true,
+		DeleteLocalData:     true,
+		IgnoreAllDaemonSets: true,
+		ErrOut:              os.Stderr,
+		Out:                 os.Stdout,
+	}
+
 	lock := daemonsetlock.New(client, nodeID, dsNamespace, dsName, lockAnnotation)
 
 	nodeMeta := nodeMeta{}
 	if holding(lock, &nodeMeta) {
 		if !nodeMeta.Unschedulable {
-			uncordon(nodeID)
+			node, err := client.CoreV1().Nodes().Get(context.TODO(), nodeID, metav1.GetOptions{})
+			if err != nil {
+				log.Fatal(err)
+			}
+			uncordon(drainer, node)
 		}
 		release(lock)
 	}
@@ -322,7 +342,7 @@ func rebootAsRequired(nodeID string, window *timewindow.TimeWindow, TTL time.Dur
 
 			if acquire(lock, &nodeMeta, TTL) {
 				if !nodeMeta.Unschedulable {
-					drain(nodeID)
+					drain(drainer, node)
 				}
 				commandReboot(nodeID)
 				for {

go.mod

@@ -12,4 +12,5 @@ require (
 	github.com/spf13/cobra v0.0.0-20181127133106-d2d81d9a96e2
 	k8s.io/apimachinery v0.18.8
 	k8s.io/client-go v0.18.8
+	k8s.io/kubectl v0.18.8
 )