Fix unnecessary HPA updates when Resource based Trigger is used (#1541)

Signed-off-by: Zbynek Roubalik <zroubali@redhat.com>

CHANGELOG.md

@@ -63,6 +63,7 @@
 - Serve OpenAPI spec from KEDA Metrics Apiserver ([#1512](https://github.com/kedacore/keda/pull/1512))
 - Support metrics with multiple dimensions and configurable metricValues on AWS Cloudwatch Scaler ([#1230](https://github.com/kedacore/keda/issues/1230))
 - Show `MIN/MAX` replica counts when using `kubectl get scaledobject/scaledjob` ([#1534](https://github.com/kedacore/keda/pull/1534))
+- Fix unnecessary HPA updates when Resource based Trigger is used ([#1541](https://github.com/kedacore/keda/pull/1541))
 
 ### Breaking Changes
 

controllers/hpa.go

@@ -3,6 +3,7 @@ package controllers
 import (
 	"context"
 	"fmt"
+	"sort"
 
 	"github.com/go-logr/logr"
 	version "github.com/kedacore/keda/v2/version"
@@ -161,6 +162,12 @@ func (r *ScaledObjectReconciler) getScaledObjectMetricSpecs(logger logr.Logger,
 		scaler.Close()
 	}
 
+	// sort metrics in ScaledObject, this way we always check the same resource in Reconcile loop and we can prevent unnecessary HPA updates,
+	// see https://github.com/kedacore/keda/issues/1531 for details
+	sort.Slice(scaledObjectMetricSpecs, func(i, j int) bool {
+		return scaledObjectMetricSpecs[i].Type < scaledObjectMetricSpecs[j].Type
+	})
+
 	// store External.MetricNames,Resource.MetricsNames used by scalers defined in the ScaledObject
 	status := scaledObject.Status.DeepCopy()
 	status.ExternalMetricNames = externalMetricNames