[node-labeler] Introduce workspace count controller

components/node-labeler/cmd/root.go

@@ -32,7 +32,7 @@ var (
 // rootCmd represents the base command when called without any subcommands
 var rootCmd = &cobra.Command{
 	Use:   ServiceName,
-	Short: "node-labeler is in charge of maintining the node labels that workspaces require to run in a node",
+	Short: "node-labeler is in charge of maintaining the node labels that workspaces require to run in a node",
 	PersistentPreRun: func(cmd *cobra.Command, args []string) {
 		log.Init(ServiceName, Version, jsonLog, verbose)
 	},

components/node-labeler/cmd/run.go

@@ -78,7 +78,7 @@ var runCmd = &cobra.Command{
 			LeaderElectionID: "node-labeler.gitpod.io",
 		})
 		if err != nil {
-			log.WithError(err).Fatal("unable to start node-labeber")
+			log.WithError(err).Fatal("unable to start node-labeler")
 		}
 
 		client, err := client.New(ctrl.GetConfigOrDie(), client.Options{})
@@ -123,10 +123,10 @@ var runCmd = &cobra.Command{
 			log.WithError(err).Fatal("unable to set up ready check")
 		}
 
-		log.Info("starting node-labeber")
+		log.Info("starting node-labeler")
 		err = mgr.Start(ctrl.SetupSignalHandler())
 		if err != nil {
-			log.WithError(err).Fatal("problem running node-labeber")
+			log.WithError(err).Fatal("problem running node-labeler")
 		}
 
 		log.Info("Received SIGINT - shutting down")

components/ws-daemon/pkg/controller/workspace_controller.go

@@ -26,6 +26,8 @@ import (
 	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/fields"
+	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/wait"
 	"k8s.io/client-go/tools/record"
@@ -81,6 +83,41 @@ func NewWorkspaceController(c client.Client, recorder record.EventRecorder, node
 	}, nil
 }
 
+type PodCountController struct {
+	client.Client
+	NodeName string
+}
+
+// NewPodCountController creates a controller that tracks workspace pod counts and updates node annotations
+func NewPodCountController(client client.Client, nodeName string) (*PodCountController, error) {
+	return &PodCountController{
+		Client:   client,
+		NodeName: nodeName,
+	}, nil
+}
+
+func (pc *PodCountController) SetupWithManager(mgr ctrl.Manager) error {
+	return ctrl.NewControllerManagedBy(mgr).
+		Named("pod-count").
+		For(&workspacev1.Workspace{}).
+		WithEventFilter(podEventFilter(pc.NodeName)).
+		Complete(pc)
+}
+
+func podEventFilter(nodeName string) predicate.Predicate {
+	return predicate.Funcs{
+		CreateFunc: func(e event.CreateEvent) bool {
+			return workspaceFilter(e.Object, nodeName)
+		},
+		UpdateFunc: func(e event.UpdateEvent) bool {
+			return workspaceFilter(e.ObjectNew, nodeName)
+		},
+		DeleteFunc: func(e event.DeleteEvent) bool {
+			return workspaceFilter(e.Object, nodeName)
+		},
+	}
+}
+
 // SetupWithManager sets up the controller with the Manager.
 func (wsc *WorkspaceController) SetupWithManager(mgr ctrl.Manager) error {
 	return ctrl.NewControllerManagedBy(mgr).
@@ -146,6 +183,45 @@ func (wsc *WorkspaceController) Reconcile(ctx context.Context, req ctrl.Request)
 	return ctrl.Result{}, nil
 }
 
+func (pc *PodCountController) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
+	var podList corev1.PodList
+	err := pc.List(ctx, &podList, &client.ListOptions{
+		FieldSelector: fields.SelectorFromSet(fields.Set{"spec.nodeName": pc.NodeName}),
+		LabelSelector: labels.SelectorFromSet(labels.Set{"component": "workspace"}),
+	})
+	if err != nil {
+		glog.WithError(err).WithField("nodeName", pc.NodeName).Error("failed to list pods")
+		return ctrl.Result{}, err
+	}
+	workspaceCount := len(podList.Items)
+
+	err = retry.RetryOnConflict(retry.DefaultBackoff, func() error {
+		var node corev1.Node
+		err := pc.Get(ctx, types.NamespacedName{Name: pc.NodeName}, &node)
+		if err != nil {
+			return fmt.Errorf("obtaining node %s: %w", pc.NodeName, err)
+		}
+
+		if node.Annotations == nil {
+			node.Annotations = make(map[string]string)
+		}
+
+		if workspaceCount > 0 {
+			node.Annotations["cluster-autoscaler.kubernetes.io/scale-down-disabled"] = "true"
+		} else {
+			delete(node.Annotations, "cluster-autoscaler.kubernetes.io/scale-down-disabled")
+		}
+
+		return pc.Update(ctx, &node)
+	})
+	if err != nil {
+		glog.WithError(err).WithField("nodeName", pc.NodeName).Error("[failed to update node")
+		return ctrl.Result{}, err
+	}
+
+	return ctrl.Result{}, nil
+}
+
 // latestWorkspace checks if the we have the latest generation of the workspace CR. We do this because
 // the cache could be stale and we retrieve a workspace CR that does not have the content init/backup
 // conditions even though we have set them previously. This will lead to us performing these operations

components/ws-daemon/pkg/daemon/daemon.go

@@ -13,6 +13,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/collectors"
 	"golang.org/x/xerrors"
+	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/client-go/kubernetes"
@@ -21,6 +22,7 @@ import (
 	"k8s.io/client-go/tools/clientcmd"
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/cache"
+	"sigs.k8s.io/controller-runtime/pkg/client"
 	"sigs.k8s.io/controller-runtime/pkg/manager"
 	"sigs.k8s.io/controller-runtime/pkg/metrics"
 	metricsserver "sigs.k8s.io/controller-runtime/pkg/metrics/server"
@@ -228,6 +230,26 @@ func NewDaemon(config Config) (*Daemon, error) {
 		return nil, err
 	}
 
+	// the pod count reconciler needs an index on spec.nodeName to be able to list pods by node
+	if err := mgr.GetFieldIndexer().IndexField(
+		context.Background(),
+		&corev1.Pod{},
+		"spec.nodeName",
+		func(o client.Object) []string {
+			pod := o.(*corev1.Pod)
+			return []string{pod.Spec.NodeName}
+		}); err != nil {
+		return nil, err
+	}
+
+	pcc, err := controller.NewPodCountController(mgr.GetClient(), nodename)
+	if err != nil {
+		return nil, err
+	}
+	if err := pcc.SetupWithManager(mgr); err != nil {
+		return nil, err
+	}
+
 	ssctrl := controller.NewSnapshotController(
 		mgr.GetClient(), mgr.GetEventRecorderFor("snapshot"), nodename, config.WorkspaceController.MaxConcurrentReconciles, workspaceOps)
 	err = ssctrl.SetupWithManager(mgr)