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Add a cache for what resource types are scalable so not every reconcile has to do a GET to the /scale endpoint #1453

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merged 2 commits into from
Jan 4, 2021
Merged

Add a cache for what resource types are scalable so not every reconcile has to do a GET to the /scale endpoint #1453

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f056fe5
Add a cache so not every reconcile has to do a GET to the /scale endp…
coderanger Dec 26, 2020
521b038
Add statefulsets to the prefill list too.
coderanger Dec 28, 2020
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@
- Mask password in postgres scaler auto generated metricName. ([PR #1381](https://github.com/kedacore/keda/pull/1381))
- Bug fix for pending jobs in ScaledJob's accurateScalingStrategy . ([#1323](https://github.com/kedacore/keda/issues/1323))
- Fix memory leak because of unclosed scalers. ([#1413](https://github.com/kedacore/keda/issues/1413))
- Reduce unnecessary /scale requests from ScaledObject controller ([#1453](https://github.com/kedacore/keda/pull/1453))

### Breaking Changes

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52 changes: 38 additions & 14 deletions controllers/scaledobject_controller.go
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Expand Up @@ -7,6 +7,7 @@ import (
"time"

"github.com/go-logr/logr"
autoscalingv1 "k8s.io/api/autoscaling/v1"
autoscalingv2beta2 "k8s.io/api/autoscaling/v2beta2"
"k8s.io/apimachinery/pkg/api/errors"
"k8s.io/apimachinery/pkg/api/meta"
Expand Down Expand Up @@ -53,6 +54,17 @@ type ScaledObjectReconciler struct {
globalHTTPTimeout time.Duration
}

// A cache mapping "resource.group" to true or false if we know if this resource is scalable.
var isScalableCache map[string]bool

func init() {
// Prefill the cache with some known values for core resources in case of future parallelism to avoid stampeding herd on startup.
isScalableCache = map[string]bool{
"deployments.apps": true,
"statefusets.apps": true,
}
}

// SetupWithManager initializes the ScaledObjectReconciler instance and starts a new controller managed by the passed Manager instance.
func (r *ScaledObjectReconciler) SetupWithManager(mgr ctrl.Manager) error {
// create Discovery clientset
Expand Down Expand Up @@ -231,26 +243,38 @@ func (r *ScaledObjectReconciler) checkTargetResourceIsScalable(logger logr.Logge
gvkString := gvkr.GVKString()
logger.V(1).Info("Parsed Group, Version, Kind, Resource", "GVK", gvkString, "Resource", gvkr.Resource)

// let's try to detect /scale subresource
scale, errScale := (*r.scaleClient).Scales(scaledObject.Namespace).Get(context.TODO(), gvkr.GroupResource(), scaledObject.Spec.ScaleTargetRef.Name, metav1.GetOptions{})
if errScale != nil {
// not able to get /scale subresource -> let's check if the resource even exist in the cluster
unstruct := &unstructured.Unstructured{}
unstruct.SetGroupVersionKind(gvkr.GroupVersionKind())
if err := r.Client.Get(context.TODO(), client.ObjectKey{Namespace: scaledObject.Namespace, Name: scaledObject.Spec.ScaleTargetRef.Name}, unstruct); err != nil {
// resource doesn't exist
logger.Error(err, "Target resource doesn't exist", "resource", gvkString, "name", scaledObject.Spec.ScaleTargetRef.Name)
return gvkr, err
// do we need the scale to update the status later?
wantStatusUpdate := scaledObject.Status.ScaleTargetKind != gvkString || scaledObject.Status.OriginalReplicaCount == nil

// check if we already know.
var scale *autoscalingv1.Scale
gr := gvkr.GroupResource()
isScalable := isScalableCache[gr.String()]
if !isScalable || wantStatusUpdate {
// not cached, let's try to detect /scale subresource
// also rechecks when we need to update the status.
var errScale error
scale, errScale = (*r.scaleClient).Scales(scaledObject.Namespace).Get(context.TODO(), gr, scaledObject.Spec.ScaleTargetRef.Name, metav1.GetOptions{})
if errScale != nil {
// not able to get /scale subresource -> let's check if the resource even exist in the cluster
unstruct := &unstructured.Unstructured{}
unstruct.SetGroupVersionKind(gvkr.GroupVersionKind())
if err := r.Client.Get(context.TODO(), client.ObjectKey{Namespace: scaledObject.Namespace, Name: scaledObject.Spec.ScaleTargetRef.Name}, unstruct); err != nil {
// resource doesn't exist
logger.Error(err, "Target resource doesn't exist", "resource", gvkString, "name", scaledObject.Spec.ScaleTargetRef.Name)
return gvkr, err
}
// resource exist but doesn't expose /scale subresource
logger.Error(errScale, "Target resource doesn't expose /scale subresource", "resource", gvkString, "name", scaledObject.Spec.ScaleTargetRef.Name)
return gvkr, errScale
}
// resource exist but doesn't expose /scale subresource
logger.Error(errScale, "Target resource doesn't expose /scale subresource", "resource", gvkString, "name", scaledObject.Spec.ScaleTargetRef.Name)
return gvkr, errScale
isScalableCache[gr.String()] = true
}

// if it is not already present in ScaledObject Status:
// - store discovered GVK and GVKR
// - store original scaleTarget's replica count (before scaling with KEDA)
if scaledObject.Status.ScaleTargetKind != gvkString || scaledObject.Status.OriginalReplicaCount == nil {
if wantStatusUpdate {
status := scaledObject.Status.DeepCopy()
if scaledObject.Status.ScaleTargetKind != gvkString {
status.ScaleTargetKind = gvkString
Expand Down