Runtime SDK implement metrics for runtime hook client

go.mod

@@ -114,7 +114,7 @@ require (
 	github.com/pelletier/go-toml v1.9.5 // indirect
 	github.com/peterbourgon/diskv v2.0.1+incompatible // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/prometheus/client_golang v1.12.1 // indirect
+	github.com/prometheus/client_golang v1.12.1
 	github.com/prometheus/client_model v0.2.0 // indirect
 	github.com/prometheus/common v0.32.1 // indirect
 	github.com/prometheus/procfs v0.7.3 // indirect

internal/runtime/client/client.go

@@ -45,6 +45,7 @@ import (
 	runtimev1 "sigs.k8s.io/cluster-api/exp/runtime/api/v1alpha1"
 	runtimecatalog "sigs.k8s.io/cluster-api/exp/runtime/catalog"
 	runtimehooksv1 "sigs.k8s.io/cluster-api/exp/runtime/hooks/api/v1alpha1"
+	runtimemetrics "sigs.k8s.io/cluster-api/internal/runtime/metrics"
 	runtimeregistry "sigs.k8s.io/cluster-api/internal/runtime/registry"
 	"sigs.k8s.io/cluster-api/util"
 )
@@ -377,6 +378,11 @@ func httpCall(ctx context.Context, request, response runtime.Object, opts *httpC
 		return errors.Wrap(err, "http call failed")
 	}
 
+	// Observe request duration metric.
+	start := time.Now()
+	defer func() {
+		runtimemetrics.RequestDuration.Observe(opts.hookGVH, *extensionURL, time.Since(start))
+	}()
 	requireConversion := opts.registrationGVH.Version != opts.hookGVH.Version
 
 	requestLocal := request
@@ -450,6 +456,8 @@ func httpCall(ctx context.Context, request, response runtime.Object, opts *httpC
 	})
 
 	resp, err := client.Do(httpRequest)
+	// Create http request metric.
+	runtimemetrics.RequestsTotal.Observe(httpRequest, resp, opts.hookGVH, err)
 	if err != nil {
 		return errCallingExtensionHandler(
 			errors.Wrapf(err, "http call failed"),

internal/runtime/metrics/metrics.go

@@ -0,0 +1,88 @@
+/*
+Copyright 2022 The Kubernetes 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 metrics provides functions for creating Runtime SDK related metrics.
+package metrics
+
+import (
+	"net/http"
+	"net/url"
+	"strconv"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	ctrlmetrics "sigs.k8s.io/controller-runtime/pkg/metrics"
+
+	runtimecatalog "sigs.k8s.io/cluster-api/exp/runtime/catalog"
+)
+
+func init() {
+	// Register the metrics at the controller-runtime metrics registry.
+	ctrlmetrics.Registry.MustRegister(RequestsTotal.metric)
+	ctrlmetrics.Registry.MustRegister(RequestDuration.metric)
+}
+
+// Metrics subsystem and all of the keys used by the Runtime SDK.
+const (
+	runtimeSDKSubsystem = "capi_runtime_sdk"
+)
+
+var (
+	// RequestsTotal reports request results.
+	RequestsTotal = requestsTotalObserver{
+		prometheus.NewCounterVec(prometheus.CounterOpts{
+			Subsystem: runtimeSDKSubsystem,
+			Name:      "requests_total",
+			Help:      "Number of HTTP requests, partitioned by status code, host and hook.",
+		}, []string{"code", "host", "group", "version", "hook"}),
+	}
+	// RequestDuration reports the request latency in seconds.
+	RequestDuration = requestDurationObserver{
+		prometheus.NewHistogramVec(prometheus.HistogramOpts{
+			Subsystem: runtimeSDKSubsystem,
+			Name:      "request_duration_seconds",
+			Help:      "Request duration in seconds, broken down by hook and host.",
+			Buckets:   prometheus.ExponentialBuckets(0.001, 2, 10),
+		}, []string{"host", "group", "version", "hook"}),
+	}
+)
+
+type requestsTotalObserver struct {
+	metric *prometheus.CounterVec
+}
+
+// Observe observes a http request result and increments the metric for the given
+// error status code, host and gvh.
+func (m *requestsTotalObserver) Observe(req *http.Request, resp *http.Response, gvh runtimecatalog.GroupVersionHook, err error) {
+	host := req.URL.Host
+
+	// Errors can be arbitrary strings. Unbound label cardinality is not suitable for a metric
+	// system so they are reported as `<error>`.
+	code := "<error>"
+	if err == nil {
+		code = strconv.Itoa(resp.StatusCode)
+	}
+	m.metric.WithLabelValues(code, host, gvh.Group, gvh.Version, gvh.Hook).Inc()
+}
+
+type requestDurationObserver struct {
+	metric *prometheus.HistogramVec
+}
+
+// Observe increments the request latency metric for the given host and gvh.
+func (m *requestDurationObserver) Observe(gvh runtimecatalog.GroupVersionHook, u url.URL, latency time.Duration) {
+	m.metric.WithLabelValues(u.Host, gvh.Group, gvh.Version, gvh.Hook).Observe(latency.Seconds())
+}