Register metrics

New metrics:
- build_info: Build info about descheduler, including Go version, Descheduler version, Git SHA, Git branch
- pods_evicted: Number of successfully evicted pods, by the result, by the strategy, by the namespace

metrics/metrics.go

@@ -0,0 +1,72 @@
+/*
+Copyright 2021 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
+
+import (
+	"sync"
+
+	"k8s.io/component-base/metrics"
+	"k8s.io/component-base/metrics/legacyregistry"
+	"sigs.k8s.io/descheduler/pkg/version"
+)
+
+const (
+	// DeschedulerSubsystem - subsystem name used by descheduler
+	DeschedulerSubsystem = "descheduler"
+)
+
+var (
+	PodsEvicted = metrics.NewCounterVec(
+		&metrics.CounterOpts{
+			Subsystem:      DeschedulerSubsystem,
+			Name:           "pods_evicted",
+			Help:           "Number of evicted pods, by the result, by the strategy, by the namespace. 'failed' result means a pod could not be evicted",
+			StabilityLevel: metrics.ALPHA,
+		}, []string{"result", "strategy", "namespace"})
+
+	buildInfo = metrics.NewGauge(
+		&metrics.GaugeOpts{
+			Subsystem:      DeschedulerSubsystem,
+			Name:           "build_info",
+			Help:           "Build info about descheduler, including Go version, Descheduler version, Git SHA, Git branch",
+			ConstLabels:    map[string]string{"GoVersion": version.Get().GoVersion, "DeschedulerVersion": version.Get().GitVersion, "GitBranch": version.Get().GitBranch, "GitSha1": version.Get().GitSha1},
+			StabilityLevel: metrics.ALPHA,
+		},
+	)
+
+	metricsList = []metrics.Registerable{
+		PodsEvicted,
+		buildInfo,
+	}
+)
+
+var registerMetrics sync.Once
+
+// Register all metrics.
+func Register() {
+	// Register the metrics.
+	registerMetrics.Do(func() {
+		RegisterMetrics(metricsList...)
+	})
+}
+
+// RegisterMetrics registers a list of metrics.
+func RegisterMetrics(extraMetrics ...metrics.Registerable) {
+	for _, metric := range extraMetrics {
+		legacyregistry.MustRegister(metric)
+	}
+}