add metrics for health checks (for later use in apiserver)

Change-Id: I0dff11cc298c4960ae6620004a071ef6a62ddc9a

staging/src/k8s.io/component-base/metrics/prometheus/health/metrics.go

@@ -0,0 +1,80 @@
+/*
+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 health
+
+import (
+	"context"
+	"errors"
+
+	k8smetrics "k8s.io/component-base/metrics"
+	"k8s.io/component-base/metrics/legacyregistry"
+)
+
+type HealthcheckStatus string
+
+const (
+	SUCCESS HealthcheckStatus = "success"
+	ERROR   HealthcheckStatus = "error"
+	PENDING HealthcheckStatus = "pending"
+)
+
+type HealthcheckType string
+
+const (
+	LIVEZ   HealthcheckType = "livez"
+	READYZ  HealthcheckType = "readyz"
+	HEALTHZ HealthcheckType = "healthz"
+)
+
+var (
+	// healthcheck is a Prometheus Gauge metrics used for recording the results of a k8s healthcheck.
+	healthcheck = k8smetrics.NewGaugeVec(
+		&k8smetrics.GaugeOpts{
+			Name:           "k8s_healthcheck",
+			Help:           "This metric records the result of a single health check.",
+			StabilityLevel: k8smetrics.ALPHA,
+		},
+		[]string{"name", "type", "status"},
+	)
+	statuses  = []HealthcheckStatus{SUCCESS, ERROR, PENDING}
+	statusSet = map[HealthcheckStatus]struct{}{SUCCESS: {}, ERROR: {}, PENDING: {}}
+	checkSet  = map[HealthcheckType]struct{}{LIVEZ: {}, READYZ: {}, HEALTHZ: {}}
+)
+
+func init() {
+	legacyregistry.MustRegister(healthcheck)
+}
+
+func ResetHealthMetrics() {
+	healthcheck.Reset()
+}
+
+func ObserveHealthcheck(ctx context.Context, name string, healthcheckType HealthcheckType, status HealthcheckStatus) error {
+	if _, ok := statusSet[status]; !ok {
+		return errors.New("not a valid healthcheck status")
+	}
+	if _, ok := checkSet[healthcheckType]; !ok {
+		return errors.New("not a valid healthcheck type")
+	}
+	for _, s := range statuses {
+		if status != s {
+			healthcheck.WithContext(ctx).WithLabelValues(name, string(healthcheckType), string(s)).Set(0)
+		}
+	}
+	healthcheck.WithContext(ctx).WithLabelValues(name, string(healthcheckType), string(status)).Set(1)
+	return nil
+}

staging/src/k8s.io/component-base/metrics/prometheus/health/metrics_test.go

@@ -0,0 +1,99 @@
+/*
+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 health
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"k8s.io/component-base/metrics/legacyregistry"
+	"k8s.io/component-base/metrics/testutil"
+)
+
+var (
+	testedMetrics = []string{"k8s_healthcheck"}
+)
+
+func TestObserveHealthcheck(t *testing.T) {
+	defer legacyregistry.Reset()
+	defer ResetHealthMetrics()
+	initialState := ERROR
+	healthcheckName := "healthcheck-a"
+	initialOutput := `
+        # HELP k8s_healthcheck [ALPHA] This metric records the result of a single health check.
+        # TYPE k8s_healthcheck gauge
+        k8s_healthcheck{name="healthcheck-a",status="error",type="healthz"} 1
+        k8s_healthcheck{name="healthcheck-a",status="pending",type="healthz"} 0
+        k8s_healthcheck{name="healthcheck-a",status="success",type="healthz"} 0
+`
+	testCases := []struct {
+		desc     string
+		name     string
+		hcType   HealthcheckType
+		hcStatus HealthcheckStatus
+		want     string
+	}{
+		{
+			desc:     "test pending",
+			name:     healthcheckName,
+			hcType:   HEALTHZ,
+			hcStatus: PENDING,
+			want: `
+        # HELP k8s_healthcheck [ALPHA] This metric records the result of a single health check.
+        # TYPE k8s_healthcheck gauge
+        k8s_healthcheck{name="healthcheck-a",status="error",type="healthz"} 0
+        k8s_healthcheck{name="healthcheck-a",status="pending",type="healthz"} 1
+        k8s_healthcheck{name="healthcheck-a",status="success",type="healthz"} 0
+`,
+		},
+		{
+			desc:     "test success",
+			name:     healthcheckName,
+			hcType:   HEALTHZ,
+			hcStatus: SUCCESS,
+			want: `
+        # HELP k8s_healthcheck [ALPHA] This metric records the result of a single health check.
+        # TYPE k8s_healthcheck gauge
+        k8s_healthcheck{name="healthcheck-a",status="error",type="healthz"} 0
+        k8s_healthcheck{name="healthcheck-a",status="pending",type="healthz"} 0
+        k8s_healthcheck{name="healthcheck-a",status="success",type="healthz"} 1
+`,
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			// let's first record an error as initial state
+			err := ObserveHealthcheck(context.Background(), test.name, test.hcType, initialState)
+			if err != nil {
+				t.Errorf("unexpected err: %v", err)
+			}
+			if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(initialOutput), testedMetrics...); err != nil {
+				t.Fatal(err)
+			}
+			// now record that we successfully purge state
+			err = ObserveHealthcheck(context.Background(), test.name, test.hcType, test.hcStatus)
+			if err != nil {
+				t.Errorf("unexpected err: %v", err)
+			}
+			if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(test.want), testedMetrics...); err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+}