Merge pull request #680 from jnummelin/controller-counter

Use true leader elector for controller counting

cmd/server.go

@@ -180,6 +180,14 @@ func startServer(token string) error {
 		LogLevel:      logging["kube-apiserver"],
 		Storage:       storageBackend,
 	})
+
+	if clusterConfig.Spec.API.ExternalAddress != "" {
+		componentManager.Add(&server.ControllerLease{
+			ClusterConfig:     clusterConfig,
+			KubeClientFactory: adminClientFactory,
+		})
+	}
+
 	componentManager.Add(&server.Konnectivity{
 		ClusterConfig:     clusterConfig,
 		LogLevel:          logging["konnectivity-server"],

pkg/component/server/controllerlease.go

@@ -0,0 +1,87 @@
+package server
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/sirupsen/logrus"
+
+	config "github.com/k0sproject/k0s/pkg/apis/v1beta1"
+	kubeutil "github.com/k0sproject/k0s/pkg/kubernetes"
+	"github.com/k0sproject/k0s/pkg/leaderelection"
+)
+
+// ControllerLease implements a component that manages a lease per controller.
+// The per-controller leases are used to determine the amount of currently running controllers
+type ControllerLease struct {
+	ClusterConfig     *config.ClusterConfig
+	KubeClientFactory kubeutil.ClientFactory
+
+	cancelCtx   context.Context
+	cancelFunc  context.CancelFunc
+	leaseCancel context.CancelFunc
+}
+
+// Init initializes the component needs
+func (c *ControllerLease) Init() error {
+	return nil
+}
+
+// Run runs the leader elector to keep the lease object up-to-date.
+func (c *ControllerLease) Run() error {
+	c.cancelCtx, c.cancelFunc = context.WithCancel(context.Background())
+	log := logrus.WithFields(logrus.Fields{"component": "controllerlease"})
+	client, err := c.KubeClientFactory.GetClient()
+	if err != nil {
+		return fmt.Errorf("can't create kubernetes rest client for lease pool: %v", err)
+	}
+
+	// hostname used to make the lease names be clear to which controller they belong to
+	holderIdentity, err := os.Hostname()
+	if err != nil {
+		return nil
+	}
+	leaseID := fmt.Sprintf("k0s-ctrl-%s", holderIdentity)
+
+	leasePool, err := leaderelection.NewLeasePool(client, leaseID, leaderelection.WithLogger(log))
+
+	if err != nil {
+		return err
+	}
+	events, cancel, err := leasePool.Watch()
+	if err != nil {
+		return err
+	}
+
+	c.leaseCancel = cancel
+
+	go func() {
+		for {
+			select {
+			case <-events.AcquiredLease:
+				log.Info("acquired leader lease")
+			case <-events.LostLease:
+				log.Error("lost leader lease, this should not really happen!?!?!?")
+			case <-c.cancelCtx.Done():
+				return
+			}
+		}
+	}()
+	return nil
+}
+
+// Stop stops the component
+func (c *ControllerLease) Stop() error {
+	if c.leaseCancel != nil {
+		c.leaseCancel()
+	}
+
+	if c.cancelFunc != nil {
+		c.cancelFunc()
+	}
+	return nil
+}
+
+// Healthy is a no-op healchcheck
+func (c *ControllerLease) Healthy() error { return nil }