WIP

pkg/constants/constants.go

@@ -34,4 +34,6 @@ const (
 	// that do not specify any priority class and there is no priority class
 	// marked as default.
 	DefaultPriority = 0
+
+	PreemptionAdmissionCheckName = "kueue-preemption"
 )

pkg/controller/admissionchecks/preemption/preemption.go

@@ -0,0 +1,123 @@
+package preemption
+
+import (
+	"context"
+	"time"
+
+	"github.com/go-logr/logr"
+	apimeta "k8s.io/apimachinery/pkg/api/meta"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/tools/record"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/manager"
+	"sigs.k8s.io/controller-runtime/pkg/reconcile"
+
+	kueue "sigs.k8s.io/kueue/apis/kueue/v1beta1"
+	"sigs.k8s.io/kueue/pkg/cache"
+	"sigs.k8s.io/kueue/pkg/constants"
+	"sigs.k8s.io/kueue/pkg/workload"
+)
+
+const (
+	controllerName  = "PreemptionController"
+	throttleTimeout = 500 * time.Millisecond
+)
+
+type Controller struct {
+	log      logr.Logger
+	cache    *cache.Cache
+	client   client.Client
+	recorder record.EventRecorder
+	// preemptor
+
+	triggerChan chan struct{}
+}
+
+func NewContriller(cache *cache.Cache) *Controller {
+	return &Controller{
+		log:         ctrl.Log.WithName(controllerName),
+		cache:       cache,
+		triggerChan: make(chan struct{}),
+	}
+}
+
+func (c *Controller) SetupWithManager(mgr ctrl.Manager) error {
+	c.client = mgr.GetClient()
+	c.recorder = mgr.GetEventRecorderFor(controllerName)
+	if err := mgr.Add(c); err != nil {
+		return err
+	}
+	return ctrl.NewControllerManagedBy(mgr).
+		//TODO: filter the events
+		For(&kueue.Workload{}).
+		Complete(c)
+}
+
+var _ manager.Runnable = (*Controller)(nil)
+var _ reconcile.Reconciler = (*Controller)(nil)
+
+func (c *Controller) Start(ctx context.Context) error {
+	c.log.V(5).Info("Staring main loop")
+	ticker := time.NewTicker(throttleTimeout)
+	trigger := false
+	timeout := false
+	for {
+		select {
+		case <-c.triggerChan:
+			trigger = true
+		case <-ticker.C:
+			timeout = true
+		case <-ctx.Done():
+			c.log.V(5).Info("End main loop")
+			return nil
+		}
+
+		if trigger && timeout {
+			c.run()
+			trigger = false
+			timeout = false
+		}
+	}
+}
+
+func (c *Controller) Reconcile(_ context.Context, _ ctrl.Request) (ctrl.Result, error) {
+	select {
+	case c.triggerChan <- struct{}{}:
+		c.log.V(6).Info("Triggered")
+	default:
+	}
+	return ctrl.Result{}, nil
+}
+
+func (c *Controller) run() {
+	snapsot := c.cache.Snapshot()
+	workloads := filterWorkloads(&snapsot)
+	for _, wl := range workloads {
+		//1. remove it from Snapshot
+		snapsot.RemoveWorkload(wl)
+		//2. check if preemption is needed
+
+		// 2.1 - issue eviction
+
+		// 2.2 - set the check to true
+
+		// 3 add it back to the Snapshot
+		snapsot.AddWorkload(wl)
+	}
+}
+
+func filterWorkloads(snapsot *cache.Snapshot) []*workload.Info {
+	ret := []*workload.Info{}
+
+	for _, cq := range snapsot.ClusterQueues {
+		for _, wl := range cq.Workloads {
+			// if the workload has the preemption check set to unknown
+			if apimeta.IsStatusConditionPresentAndEqual(wl.Obj.Status.AdmissionChecks, constants.PreemptionAdmissionCheckName, metav1.ConditionUnknown) {
+				ret = append(ret, wl)
+				//TODO: check if it should be taken into account based on admission check policy
+			}
+		}
+	}
+	return ret
+}