Update go dependencies

vendor/k8s.io/client-go/tools/leaderelection/metrics.go

@@ -0,0 +1,109 @@
+/*
+Copyright 2018 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 leaderelection
+
+import (
+	"sync"
+)
+
+// This file provides abstractions for setting the provider (e.g., prometheus)
+// of metrics.
+
+type leaderMetricsAdapter interface {
+	leaderOn(name string)
+	leaderOff(name string)
+}
+
+// GaugeMetric represents a single numerical value that can arbitrarily go up
+// and down.
+type SwitchMetric interface {
+	On(name string)
+	Off(name string)
+}
+
+type noopMetric struct{}
+
+func (noopMetric) On(name string)  {}
+func (noopMetric) Off(name string) {}
+
+// defaultLeaderMetrics expects the caller to lock before setting any metrics.
+type defaultLeaderMetrics struct {
+	// leader's value indicates if the current process is the owner of name lease
+	leader SwitchMetric
+}
+
+func (m *defaultLeaderMetrics) leaderOn(name string) {
+	if m == nil {
+		return
+	}
+	m.leader.On(name)
+}
+
+func (m *defaultLeaderMetrics) leaderOff(name string) {
+	if m == nil {
+		return
+	}
+	m.leader.Off(name)
+}
+
+type noMetrics struct{}
+
+func (noMetrics) leaderOn(name string)  {}
+func (noMetrics) leaderOff(name string) {}
+
+// MetricsProvider generates various metrics used by the leader election.
+type MetricsProvider interface {
+	NewLeaderMetric() SwitchMetric
+}
+
+type noopMetricsProvider struct{}
+
+func (_ noopMetricsProvider) NewLeaderMetric() SwitchMetric {
+	return noopMetric{}
+}
+
+var globalMetricsFactory = leaderMetricsFactory{
+	metricsProvider: noopMetricsProvider{},
+}
+
+type leaderMetricsFactory struct {
+	metricsProvider MetricsProvider
+
+	onlyOnce sync.Once
+}
+
+func (f *leaderMetricsFactory) setProvider(mp MetricsProvider) {
+	f.onlyOnce.Do(func() {
+		f.metricsProvider = mp
+	})
+}
+
+func (f *leaderMetricsFactory) newLeaderMetrics() leaderMetricsAdapter {
+	mp := f.metricsProvider
+	if mp == (noopMetricsProvider{}) {
+		return noMetrics{}
+	}
+	return &defaultLeaderMetrics{
+		leader: mp.NewLeaderMetric(),
+	}
+}
+
+// SetProvider sets the metrics provider for all subsequently created work
+// queues. Only the first call has an effect.
+func SetProvider(metricsProvider MetricsProvider) {
+	globalMetricsFactory.setProvider(metricsProvider)
+}