Merge pull request #128430 from richabanker/kubelet-metrics-slis-fix

do not install handler for '/metrics/slis' endpoint using sync.Once

Kubernetes-commit: e7bcf571713ce09c268b0e27e27c74eb03ab6314

metrics/prometheus/slis/routes.go

@@ -38,8 +38,8 @@ type SLIMetrics struct{}
 func (s SLIMetrics) Install(m mux) {
 	installOnce.Do(func() {
 		Register(Registry)
-		m.Handle("/metrics/slis", metrics.HandlerFor(Registry, metrics.HandlerOpts{}))
 	})
+	m.Handle("/metrics/slis", metrics.HandlerFor(Registry, metrics.HandlerOpts{}))
 }
 
 type SLIMetricsWithReset struct{}
@@ -48,6 +48,6 @@ type SLIMetricsWithReset struct{}
 func (s SLIMetricsWithReset) Install(m mux) {
 	installWithResetOnce.Do(func() {
 		Register(Registry)
-		m.Handle("/metrics/slis", metrics.HandlerWithReset(Registry, metrics.HandlerOpts{}))
 	})
+	m.Handle("/metrics/slis", metrics.HandlerWithReset(Registry, metrics.HandlerOpts{}))
 }

metrics/prometheus/slis/routes_test.go

@@ -0,0 +1,44 @@
+/*
+Copyright 2024 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 slis
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type mockMux struct {
+	handledPaths []string
+}
+
+func (m *mockMux) Handle(path string, handler http.Handler) {
+	m.handledPaths = append(m.handledPaths, path)
+}
+
+func TestSLIMetrics_Install(t *testing.T) {
+	m := &mockMux{}
+	s := SLIMetrics{}
+
+	s.Install(m)
+	assert.Equal(t, []string{"/metrics/slis"}, m.handledPaths)
+
+	s.Install(m)
+	// Assert that the path is registered twice for the 2 calls made to Install().
+	assert.Equal(t, []string{"/metrics/slis", "/metrics/slis"}, m.handledPaths, "Should handle the path twice.")
+}