fix: RunnerDeployment should clean up old RunnerReplicaSets ASAP

Since the initial implementation of RunnerDeployment and until this change, any update to a runner deployment has been leaving old runner replicasets until the next resync interval. This fixes that, by continusouly retrying the reconcilation 10 seconds later to see if there are any old runner replicasets that can be removed.

In addition to that, the cleanup of old runner replicasets has been improved to be deferred until all the runners of the newest replica set to be available. This gives you hopefully zero or at less downtime updates of runner deployments.

Fixes #24

controllers/runnerdeployment_controller.go

@@ -20,7 +20,9 @@ import (
 	"context"
 	"fmt"
 	"hash/fnv"
+	"k8s.io/apimachinery/pkg/types"
 	"sort"
+	"time"
 
 	"github.com/davecgh/go-spew/spew"
 	"github.com/go-logr/logr"
@@ -58,7 +60,7 @@ type RunnerDeploymentReconciler struct {
 
 func (r *RunnerDeploymentReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) {
 	ctx := context.Background()
-	log := r.Log.WithValues("runnerreplicaset", req.NamespacedName)
+	log := r.Log.WithValues("runnerdeployment", req.NamespacedName)
 
 	var rd v1alpha1.RunnerDeployment
 	if err := r.Get(ctx, req.NamespacedName, &rd); err != nil {
@@ -130,38 +132,69 @@ func (r *RunnerDeploymentReconciler) Reconcile(req ctrl.Request) (ctrl.Result, e
 			return ctrl.Result{}, err
 		}
 
-		return ctrl.Result{}, nil
+		// We requeue in order to clean up old runner replica sets later.
+		// Otherwise, they aren't cleaned up until the next re-sync interval.
+		return ctrl.Result{RequeueAfter: 5 * time.Second}, nil
 	}
 
+	const defaultReplicas = 1
+
+	currentDesiredReplicas := getIntOrDefault(newestSet.Spec.Replicas, defaultReplicas)
+	newDesiredReplicas := getIntOrDefault(desiredRS.Spec.Replicas, defaultReplicas)
+
 	// Please add more conditions that we can in-place update the newest runnerreplicaset without disruption
-	if newestSet.Spec.Replicas != desiredRS.Spec.Replicas {
-		newestSet.Spec.Replicas = desiredRS.Spec.Replicas
+	if currentDesiredReplicas != newDesiredReplicas {
+		newestSet.Spec.Replicas = &newDesiredReplicas
 
 		if err := r.Client.Update(ctx, newestSet); err != nil {
 			log.Error(err, "Failed to update runnerreplicaset resource")
 
 			return ctrl.Result{}, err
 		}
 
-		return ctrl.Result{}, nil
+		return ctrl.Result{}, err
 	}
 
-	for i := range oldSets {
-		rs := oldSets[i]
+	// Do we old runner replica sets that should eventually deleted?
+	if len(oldSets) > 0 {
+		readyReplicas := newestSet.Status.ReadyReplicas
 
-		if err := r.Client.Delete(ctx, &rs); err != nil {
-			log.Error(err, "Failed to delete runner resource")
+		if readyReplicas < currentDesiredReplicas {
+			log.WithValues("runnerreplicaset", types.NamespacedName{
+				Namespace: newestSet.Namespace,
+				Name:      newestSet.Name,
+			}).
+				Info("Waiting until the newest runner replica set to be 100% available")
 
-			return ctrl.Result{}, err
+			return ctrl.Result{RequeueAfter: 10 * time.Second}, nil
 		}
 
-		r.Recorder.Event(&rd, corev1.EventTypeNormal, "RunnerReplicaSetDeleted", fmt.Sprintf("Deleted runnerreplicaset '%s'", rs.Name))
-		log.Info("Deleted runnerreplicaset", "runnerdeployment", rd.ObjectMeta.Name, "runnerreplicaset", rs.Name)
+		for i := range oldSets {
+			rs := oldSets[i]
+
+			if err := r.Client.Delete(ctx, &rs); err != nil {
+				log.Error(err, "Failed to delete runner resource")
+
+				return ctrl.Result{}, err
+			}
+
+			r.Recorder.Event(&rd, corev1.EventTypeNormal, "RunnerReplicaSetDeleted", fmt.Sprintf("Deleted runnerreplicaset '%s'", rs.Name))
+
+			log.Info("Deleted runnerreplicaset", "runnerdeployment", rd.ObjectMeta.Name, "runnerreplicaset", rs.Name)
+		}
 	}
 
 	return ctrl.Result{}, nil
 }
 
+func getIntOrDefault(p *int, d int) int {
+	if p == nil {
+		return d
+	}
+
+	return *p
+}
+
 func getTemplateHash(rs *v1alpha1.RunnerReplicaSet) (string, bool) {
 	hash, ok := rs.Labels[LabelKeyRunnerTemplateHash]