Metrics Server: use gRPC connection to get metrics from Operator

CHANGELOG.md

@@ -38,6 +38,7 @@ To learn more about active deprecations, we recommend checking [GitHub Discussio
 
 ### New
 
+- **General**: Consolidate all exposed Prometheus Metrics in KEDA Operator ([#3919](https://github.com/kedacore/keda/issues/3919))
 - **General**: Disable response compression for k8s restAPI in client-go ([#3863](https://github.com/kedacore/keda/issues/3863)). Kubernetes issue for reference (https://github.com/kubernetes/kubernetes/issues/112296)
 - **General**: Expand Prometheus metric with label "ScalerName" to distinguish different triggers. The scaleName is defined per Trigger.Name ([#3588](https://github.com/kedacore/keda/issues/3588))
 - **General:** Introduce new Loki Scaler ([#3699](https://github.com/kedacore/keda/issues/3699))
@@ -91,6 +92,7 @@ To learn more about active deprecations, we recommend checking [GitHub Discussio
 - **General**: Bump Golang to 1.18.6 ([#3205](https://github.com/kedacore/keda/issues/3205))
 - **General**: Bump `github.com/Azure/azure-event-hubs-go/v3` ([#2986](https://github.com/kedacore/keda/issues/2986))
 - **General**: Migrate from `azure-service-bus-go` to `azservicebus` ([#3394](https://github.com/kedacore/keda/issues/3394))
+- **General**: Metrics Server: use gRPC connection to get metrics from Operator ([#3920](https://github.com/kedacore/keda/issues/3920))
 - **General**: Metrics Server: use OpenAPI definitions served by custom-metrics-apiserver ([#3929](https://github.com/kedacore/keda/issues/3929))
 - **Azure EventHub**: Add e2e tests ([#2792](https://github.com/kedacore/keda/issues/2792))
 

CREATE-NEW-SCALER.md

@@ -40,7 +40,6 @@ KEDA works in conjunction with Kubernetes Horizontal Pod Autoscaler (HPA). When
 
 The return type of this function is `MetricSpec`, but in KEDA's case we will mostly write External metrics. So the property that should be filled is `ExternalMetricSource`, where the:
 - `MetricName`: the name of our metric we are returning in this scaler. The name should be unique, to allow setting multiple (even the same type) Triggers in one ScaledObject, but each function call should return the same name.
-- `MetricSelector`: //TODO
 - `TargetValue`: is the value of the metric we want to reach at all times at all costs. As long as the current metric doesn't match TargetValue, HPA will increase the number of the pods until it reaches the maximum number of pods allowed to scale to.
 - `TargetAverageValue`: the value of the metric for which we require one pod to handle. e.g. if we are have a scaler based on the length of a message queue, and we specificy 10 for `TargetAverageValue`, we are saying that each pod will handle 10 messages. So if the length of the queue becomes 30, we expect that we have 3 pods in our cluster. (`TargetAverage` and `TargetValue` are mutually exclusive)
 

Makefile

@@ -141,6 +141,7 @@ clientset-generate: ## Generate client-go clientset, listers and informers.
 proto-gen: protoc-gen ## Generate Liiklus, ExternalScaler and MetricsService proto
 	PATH="$(LOCALBIN):$(PATH)" protoc -I vendor --proto_path=hack LiiklusService.proto --go_out=pkg/scalers/liiklus --go-grpc_out=pkg/scalers/liiklus
 	PATH="$(LOCALBIN):$(PATH)" protoc -I vendor --proto_path=pkg/scalers/externalscaler externalscaler.proto --go_out=pkg/scalers/externalscaler --go-grpc_out=pkg/scalers/externalscaler
+	PATH="$(LOCALBIN):$(PATH)" protoc -I vendor --proto_path=pkg/metricsservice/api metrics.proto --go_out=pkg/metricsservice/api --go-grpc_out=pkg/metricsservice/api
 
 .PHONY: mockgen-gen
 mockgen-gen: mockgen pkg/mock/mock_scaling/mock_interface.go pkg/mock/mock_scaler/mock_scaler.go pkg/mock/mock_scale/mock_interfaces.go pkg/mock/mock_client/mock_interfaces.go pkg/scalers/liiklus/mocks/mock_liiklus.go

adapter/main.go

@@ -41,7 +41,8 @@ import (
 
 	kedav1alpha1 "github.com/kedacore/keda/v2/apis/keda/v1alpha1"
 	kedacontrollers "github.com/kedacore/keda/v2/controllers/keda"
-	"github.com/kedacore/keda/v2/pkg/prommetrics"
+	"github.com/kedacore/keda/v2/pkg/metricsservice"
+	prommetrics "github.com/kedacore/keda/v2/pkg/prommetrics/adapter"
 	kedaprovider "github.com/kedacore/keda/v2/pkg/provider"
 	"github.com/kedacore/keda/v2/pkg/scaling"
 	kedautil "github.com/kedacore/keda/v2/pkg/util"
@@ -65,6 +66,7 @@ var (
 	adapterClientRequestBurst int
 	metricsAPIServerPort      int
 	disableCompression        bool
+	metricsServiceAddr        string
 )
 
 func (a *Adapter) makeProvider(ctx context.Context, globalHTTPTimeout time.Duration, maxConcurrentReconciles int) (provider.MetricsProvider, <-chan struct{}, error) {
@@ -115,6 +117,12 @@ func (a *Adapter) makeProvider(ctx context.Context, globalHTTPTimeout time.Durat
 		return nil, nil, fmt.Errorf("invalid KEDA_METRICS_LEADER_ELECTION_RETRY_PERIOD (%s)", err)
 	}
 
+	useMetricsServiceGrpc, err := kedautil.ResolveOsEnvBool("KEDA_USE_METRICS_SERVICE_GRPC", true)
+	if err != nil {
+		logger.Error(err, "Invalid KEDA_USE_METRICS_SERVICE_GRPC")
+		return nil, nil, fmt.Errorf("invalid KEDA_USE_METRICS_SERVICE_GRPC (%s)", err)
+	}
+
 	metricsBindAddress := fmt.Sprintf(":%v", metricsAPIServerPort)
 	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
 		MetricsBindAddress: metricsBindAddress,
@@ -137,13 +145,19 @@ func (a *Adapter) makeProvider(ctx context.Context, globalHTTPTimeout time.Durat
 
 	prometheusServer := &prommetrics.PrometheusMetricServer{}
 	go func() { prometheusServer.NewServer(fmt.Sprintf(":%v", prometheusMetricsPort), prometheusMetricsPath) }()
-	stopCh := make(chan struct{})
 
-	if err := runScaledObjectController(ctx, mgr, handler, logger, externalMetricsInfo, externalMetricsInfoLock, maxConcurrentReconciles, stopCh); err != nil {
+	logger.Info("Connecting Metrics Service gRPC client to the server", "address", metricsServiceAddr)
+	grpcClient, err := metricsservice.NewGrpcClient(metricsServiceAddr)
+	if err != nil {
+		logger.Error(err, "error connecting Metrics Service gRPC client to the server", "address", metricsServiceAddr)
 		return nil, nil, err
 	}
 
-	return kedaprovider.NewProvider(ctx, logger, handler, mgr.GetClient(), namespace, externalMetricsInfo, externalMetricsInfoLock), stopCh, nil
+	stopCh := make(chan struct{})
+	if err := runScaledObjectController(ctx, mgr, handler, logger, externalMetricsInfo, externalMetricsInfoLock, maxConcurrentReconciles, stopCh); err != nil {
+		return nil, nil, err
+	}
+	return kedaprovider.NewProvider(ctx, logger, handler, mgr.GetClient(), *grpcClient, useMetricsServiceGrpc, namespace, externalMetricsInfo, externalMetricsInfoLock), stopCh, nil
 }
 
 func runScaledObjectController(ctx context.Context, mgr manager.Manager, scaleHandler scaling.ScaleHandler, logger logr.Logger, externalMetricsInfo *[]provider.ExternalMetricInfo, externalMetricsInfoLock *sync.RWMutex, maxConcurrentReconciles int, stopCh chan<- struct{}) error {
@@ -167,6 +181,19 @@ func runScaledObjectController(ctx context.Context, mgr manager.Manager, scaleHa
 	return nil
 }
 
+// generateDefaultMetricsServiceAddr generates default Metrics Service gRPC Server address based on the current Namespace.
+// By default the Metrics Service gRPC Server runs in the same namespace on the keda-operator pod.
+func generateDefaultMetricsServiceAddr() string {
+	const defaultNamespace = "keda"
+	podNamespace := os.Getenv("POD_NAMESPACE")
+
+	if podNamespace == "" {
+		podNamespace = defaultNamespace
+	}
+
+	return fmt.Sprintf("keda-operator.%s.svc.cluster.local:9666", podNamespace)
+}
+
 func printVersion() {
 	logger.Info(fmt.Sprintf("KEDA Version: %s", version.Version))
 	logger.Info(fmt.Sprintf("KEDA Commit: %s", version.GitCommit))
@@ -204,6 +231,7 @@ func main() {
 	cmd.Flags().IntVar(&metricsAPIServerPort, "port", 8080, "Set the port for the metrics API server")
 	cmd.Flags().IntVar(&prometheusMetricsPort, "metrics-port", 9022, "Set the port to expose prometheus metrics")
 	cmd.Flags().StringVar(&prometheusMetricsPath, "metrics-path", "/metrics", "Set the path for the prometheus metrics endpoint")
+	cmd.Flags().StringVar(&metricsServiceAddr, "metrics-service-address", generateDefaultMetricsServiceAddr(), "The address of the gRPRC Metrics Service Server.")
 	cmd.Flags().Float32Var(&adapterClientRequestQPS, "kube-api-qps", 20.0, "Set the QPS rate for throttling requests sent to the apiserver")
 	cmd.Flags().IntVar(&adapterClientRequestBurst, "kube-api-burst", 30, "Set the burst for throttling requests sent to the apiserver")
 	cmd.Flags().BoolVar(&disableCompression, "disable-compression", true, "Disable response compression for k8s restAPI in client-go. ")

apis/keda/v1alpha1/indentifier.go

@@ -0,0 +1,27 @@
+/*
+Copyright 2022 The KEDA Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package v1alpha1
+
+import (
+	"fmt"
+	"strings"
+)
+
+// GenerateIdentifier returns identifier for the object in form "kind.namespace.name" (lowercase)
+func GenerateIdentifier(kind, namespace, name string) string {
+	return strings.ToLower(fmt.Sprintf("%s.%s.%s", kind, namespace, name))
+}

apis/keda/v1alpha1/withtriggers_types.go

@@ -17,8 +17,6 @@ limitations under the License.
 package v1alpha1
 
 import (
-	"fmt"
-	"strings"
 	"time"
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -89,7 +87,7 @@ func (t *WithTriggers) GetPollingInterval() time.Duration {
 	return time.Second * time.Duration(defaultPollingInterval)
 }
 
-// GenerateIdenitifier returns identifier for the object in for "kind.namespace.name"
-func (t *WithTriggers) GenerateIdenitifier() string {
-	return strings.ToLower(fmt.Sprintf("%s.%s.%s", t.Kind, t.Namespace, t.Name))
+// GenerateIdentifier returns identifier for the object in for "kind.namespace.name"
+func (t *WithTriggers) GenerateIdentifier() string {
+	return GenerateIdentifier(t.Kind, t.Namespace, t.Name)
 }