fix: move partition_id into label to make PromQL easier (#14714)

pkg/kafka/partition/metrics.go

@@ -2,6 +2,7 @@ package partition
 
 import (
 	"math"
+	"strconv"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -12,7 +13,7 @@ import (
 )
 
 type readerMetrics struct {
-	partition         prometheus.Gauge
+	partition         *prometheus.GaugeVec
 	phase             *prometheus.GaugeVec
 	receiveDelay      *prometheus.HistogramVec
 	recordsPerFetch   prometheus.Histogram
@@ -26,10 +27,10 @@ type readerMetrics struct {
 // newReaderMetrics initializes and returns a new set of metrics for the PartitionReader.
 func newReaderMetrics(r prometheus.Registerer) readerMetrics {
 	return readerMetrics{
-		partition: promauto.With(r).NewGauge(prometheus.GaugeOpts{
-			Name: "loki_ingest_storage_reader_partition_id",
+		partition: promauto.With(r).NewGaugeVec(prometheus.GaugeOpts{
+			Name: "loki_ingest_storage_reader_partition",
 			Help: "The partition ID assigned to this reader.",
-		}),
+		}, []string{"id"}),
 		phase: promauto.With(r).NewGaugeVec(prometheus.GaugeOpts{
 			Name: "loki_ingest_storage_reader_phase",
 			Help: "The current phase of the consumer.",
@@ -66,13 +67,13 @@ func newReaderMetrics(r prometheus.Registerer) readerMetrics {
 }
 
 func (m *readerMetrics) reportStarting(partitionID int32) {
-	m.partition.Set(float64(partitionID))
+	m.partition.WithLabelValues(strconv.Itoa(int(partitionID))).Set(1)
 	m.phase.WithLabelValues(phaseStarting).Set(1)
 	m.phase.WithLabelValues(phaseRunning).Set(0)
 }
 
 func (m *readerMetrics) reportRunning(partitionID int32) {
-	m.partition.Set(float64(partitionID))
+	m.partition.WithLabelValues(strconv.Itoa(int(partitionID))).Set(1)
 	m.phase.WithLabelValues(phaseStarting).Set(0)
 	m.phase.WithLabelValues(phaseRunning).Set(1)
 }