Add shard_ordinal label

Facilitates many otherwise impossible promql queries

internal/store/builder.go

@@ -20,6 +20,7 @@ import (
 	"context"
 	"reflect"
 	"sort"
+	"strconv"
 	"strings"
 
 	"github.com/pkg/errors"
@@ -104,7 +105,9 @@ func (b *Builder) WithNamespaces(n options.NamespaceList) {
 // WithSharding sets the shard and totalShards property of a Builder.
 func (b *Builder) WithSharding(shard int32, totalShards int) {
 	b.shard = shard
-	b.shardingMetrics.Ordinal.Set(float64(shard))
+	labels := map[string]string{sharding.LabelOrdinal: strconv.Itoa(int(shard))}
+	b.shardingMetrics.Ordinal.Reset()
+	b.shardingMetrics.Ordinal.With(labels).Set(float64(shard))
 	b.totalShards = totalShards
 	b.shardingMetrics.Total.Set(float64(totalShards))
 }

main_test.go

@@ -388,7 +388,7 @@ kube_pod_status_reason{namespace="default",pod="pod0",uid="abc-0",reason="Unexpe
 # HELP kube_state_metrics_total_shards Number of total shards this instance is aware of
 # TYPE kube_state_metrics_shard_ordinal gauge
 # TYPE kube_state_metrics_total_shards gauge
-kube_state_metrics_shard_ordinal 0
+kube_state_metrics_shard_ordinal{shard_ordinal="0"} 0
 kube_state_metrics_total_shards 1
 `
 

pkg/sharding/metrics.go

@@ -21,10 +21,15 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
+const (
+	// Name of Prometheus metric label to use in conjunction with kube_state_metrics_shard_ordinal.
+	LabelOrdinal = "shard_ordinal"
+)
+
 // Metrics stores the pointers of kube_state_metrics_shard_ordinal
 // and kube_state_metrics_total_shards metrics.
 type Metrics struct {
-	Ordinal prometheus.Gauge
+	Ordinal *prometheus.GaugeVec
 	Total   prometheus.Gauge
 }
 
@@ -32,11 +37,11 @@ type Metrics struct {
 // and registers sharding configuration metrics. It returns those registered metrics.
 func NewShardingMetrics(r prometheus.Registerer) *Metrics {
 	return &Metrics{
-		Ordinal: promauto.With(r).NewGauge(
+		Ordinal: promauto.With(r).NewGaugeVec(
 			prometheus.GaugeOpts{
 				Name: "kube_state_metrics_shard_ordinal",
 				Help: "Current sharding ordinal/index of this instance",
-			},
+			}, []string{LabelOrdinal},
 		),
 		Total: promauto.With(r).NewGauge(
 			prometheus.GaugeOpts{