feat(extra/redisprometheus): prometheus.Collector implementation for redis clients

Signed-off-by: Knut Zuidema <me@knutzuidema.de>

extra/redisprometheus/collector.go

@@ -0,0 +1,117 @@
+package redisprometheus
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+
+	"github.com/go-redis/redis/v9"
+)
+
+// StatGetter provides a method to get pool statistics.
+type StatGetter interface {
+	PoolStats() *redis.PoolStats
+}
+
+// Collector collects statistics from a redis client.
+// It implements the prometheus.Collector interface.
+type Collector struct {
+	getter      StatGetter
+	hitDesc     *prometheus.Desc
+	missDesc    *prometheus.Desc
+	timeoutDesc *prometheus.Desc
+	totalDesc   *prometheus.Desc
+	idleDesc    *prometheus.Desc
+	staleDesc   *prometheus.Desc
+}
+
+var _ prometheus.Collector = (*Collector)(nil)
+
+// NewCollector returns a new Collector based on the provided StatGetter.
+// The given namespace and subsystem are used to build the fully qualified metric name,
+// i.e. "{namespace}_{subsystem}_{metric}".
+// The provided metrics are:
+//   * pool_hit_total
+//   * pool_miss_total
+//   * pool_timeout_total
+//   * pool_conn_total_current
+//   * pool_conn_idle_current
+//   * pool_conn_stale_total
+func NewCollector(namespace, subsystem string, getter StatGetter) *Collector {
+	return &Collector{
+		getter: getter,
+		hitDesc: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, subsystem, "pool_hit_total"),
+			"Number of times a connection was found in the pool",
+			nil, nil,
+		),
+		missDesc: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, subsystem, "pool_miss_total"),
+			"Number of times a connection was not found in the pool",
+			nil, nil,
+		),
+		timeoutDesc: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, subsystem, "pool_timeout_total"),
+			"Number of times a timeout occurred when looking for a connection in the pool",
+			nil, nil,
+		),
+		totalDesc: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, subsystem, "pool_conn_total_current"),
+			"Current number of connections in the pool",
+			nil, nil,
+		),
+		idleDesc: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, subsystem, "pool_conn_idle_current"),
+			"Current number of idle connections in the pool",
+			nil, nil,
+		),
+		staleDesc: prometheus.NewDesc(
+			prometheus.BuildFQName(namespace, subsystem, "pool_conn_stale_total"),
+			"Number of times a connection was removed from the pool because it was stale",
+			nil, nil,
+		),
+	}
+}
+
+// Describe implements the prometheus.Collector interface.
+func (s *Collector) Describe(descs chan<- *prometheus.Desc) {
+	descs <- s.hitDesc
+	descs <- s.missDesc
+	descs <- s.timeoutDesc
+	descs <- s.totalDesc
+	descs <- s.idleDesc
+	descs <- s.staleDesc
+}
+
+// Collect implements the prometheus.Collector interface.
+func (s *Collector) Collect(metrics chan<- prometheus.Metric) {
+	stats := s.getter.PoolStats()
+	metrics <- prometheus.MustNewConstMetric(
+		s.hitDesc,
+		prometheus.CounterValue,
+		float64(stats.Hits),
+	)
+	metrics <- prometheus.MustNewConstMetric(
+		s.missDesc,
+		prometheus.CounterValue,
+		float64(stats.Misses),
+	)
+	metrics <- prometheus.MustNewConstMetric(
+		s.timeoutDesc,
+		prometheus.CounterValue,
+		float64(stats.Timeouts),
+	)
+	metrics <- prometheus.MustNewConstMetric(
+		s.totalDesc,
+		prometheus.GaugeValue,
+		float64(stats.TotalConns),
+	)
+	metrics <- prometheus.MustNewConstMetric(
+		s.idleDesc,
+		prometheus.GaugeValue,
+		float64(stats.IdleConns),
+	)
+	metrics <- prometheus.MustNewConstMetric(
+		s.staleDesc,
+		prometheus.CounterValue,
+		float64(stats.StaleConns),
+	)
+}