feat: Implemented leaderelection.LeaseHijacker (#99)

Author: ellistarn

leaderelection/leasehijacker.go

@@ -0,0 +1,39 @@
+package leaderelection
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/samber/lo"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/uuid"
+	coordinationv1client "k8s.io/client-go/kubernetes/typed/coordination/v1"
+	corev1client "k8s.io/client-go/kubernetes/typed/core/v1"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/tools/leaderelection/resourcelock"
+	"sigs.k8s.io/controller-runtime/pkg/log"
+)
+
+// LeaseHijacker implements lease stealing to accelerate development workflows
+// TODO: migrate to https://kubernetes.io/docs/concepts/cluster-administration/coordinated-leader-election/ when it's past alpha.
+func LeaseHijacker(ctx context.Context, config *rest.Config, namespace string, name string) resourcelock.Interface {
+	if os.Getenv("HIJACK_LEASE") != "true" {
+		return nil // If not set, fallback to other controller-runtime lease settings
+	}
+	id := fmt.Sprintf("%s_%s", lo.Must(os.Hostname()), uuid.NewUUID())
+	log.FromContext(ctx).Info("hijacking lease", "namespace", namespace, "name", name)
+	kubeClient := coordinationv1client.NewForConfigOrDie(config)
+	lease := lo.Must(kubeClient.Leases(namespace).Get(ctx, name, metav1.GetOptions{}))
+	lease.Spec.HolderIdentity = lo.ToPtr(id)
+	lease.Spec.AcquireTime = lo.ToPtr(metav1.NowMicro())
+	lo.Must(kubeClient.Leases(namespace).Update(ctx, lease, metav1.UpdateOptions{}))
+	return lo.Must(resourcelock.New(
+		resourcelock.LeasesResourceLock,
+		namespace,
+		name,
+		corev1client.NewForConfigOrDie(config),
+		coordinationv1client.NewForConfigOrDie(config),
+		resourcelock.ResourceLockConfig{Identity: id},
+	))
+}