Add cidrset to support multiple CIDRs

Add a new cidrset named `multicidrset` which extends the current
cidrset mechanism to track allocatable Pod and Service CIDRs.
multicidrset stores the info about allocated CIDRs in a Map as opposed
to the current cidrset implementation where it is stored in a bitmap.

pkg/controller/nodeipam/ipam/multicidrset/metrics.go

@@ -0,0 +1,78 @@
+/*
+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 multicidrset
+
+import (
+	"sync"
+
+	"k8s.io/component-base/metrics"
+	"k8s.io/component-base/metrics/legacyregistry"
+)
+
+const nodeIpamSubsystem = "node_ipam_controller"
+
+var (
+	cidrSetAllocations = metrics.NewCounterVec(
+		&metrics.CounterOpts{
+			Subsystem:      nodeIpamSubsystem,
+			Name:           "multicidrset_cidrs_allocations_total",
+			Help:           "Counter measuring total number of CIDR allocations.",
+			StabilityLevel: metrics.ALPHA,
+		},
+		[]string{"clusterCIDR"},
+	)
+	cidrSetReleases = metrics.NewCounterVec(
+		&metrics.CounterOpts{
+			Subsystem:      nodeIpamSubsystem,
+			Name:           "multicidrset_cidrs_releases_total",
+			Help:           "Counter measuring total number of CIDR releases.",
+			StabilityLevel: metrics.ALPHA,
+		},
+		[]string{"clusterCIDR"},
+	)
+	cidrSetUsage = metrics.NewGaugeVec(
+		&metrics.GaugeOpts{
+			Subsystem:      nodeIpamSubsystem,
+			Name:           "multicidrset_usage_cidrs",
+			Help:           "Gauge measuring percentage of allocated CIDRs.",
+			StabilityLevel: metrics.ALPHA,
+		},
+		[]string{"clusterCIDR"},
+	)
+	cidrSetAllocationTriesPerRequest = metrics.NewHistogramVec(
+		&metrics.HistogramOpts{
+			Subsystem:      nodeIpamSubsystem,
+			Name:           "multicidrset_allocation_tries_per_request",
+			Help:           "Histogram measuring CIDR allocation tries per request.",
+			StabilityLevel: metrics.ALPHA,
+			Buckets:        metrics.ExponentialBuckets(1, 5, 5),
+		},
+		[]string{"clusterCIDR"},
+	)
+)
+
+var registerMetrics sync.Once
+
+// registerCidrsetMetrics the metrics that are to be monitored.
+func registerCidrsetMetrics() {
+	registerMetrics.Do(func() {
+		legacyregistry.MustRegister(cidrSetAllocations)
+		legacyregistry.MustRegister(cidrSetReleases)
+		legacyregistry.MustRegister(cidrSetUsage)
+		legacyregistry.MustRegister(cidrSetAllocationTriesPerRequest)
+	})
+}