feat: add prometheus summary metrics (#3440)

Co-authored-by: chen quan <chenquan.dev@gmail.com>

core/metric/summary.go

@@ -0,0 +1,65 @@
+package metric
+
+import (
+	prom "github.com/prometheus/client_golang/prometheus"
+	"github.com/zeromicro/go-zero/core/proc"
+	"github.com/zeromicro/go-zero/core/prometheus"
+)
+
+type (
+	// A SummaryVecOpts is a summary vector options
+	SummaryVecOpts struct {
+		VecOpt     VectorOpts
+		Objectives map[float64]float64
+	}
+
+	// A SummaryVec interface represents a summary vector.
+	SummaryVec interface {
+		// Observe adds observation v to labels.
+		Observe(v float64, labels ...string)
+		close() bool
+	}
+
+	promSummaryVec struct {
+		summary *prom.SummaryVec
+	}
+)
+
+// NewSummaryVec return a SummaryVec
+func NewSummaryVec(cfg *SummaryVecOpts) SummaryVec {
+	if cfg == nil {
+		return nil
+	}
+
+	vec := prom.NewSummaryVec(
+		prom.SummaryOpts{
+			Namespace:  cfg.VecOpt.Namespace,
+			Subsystem:  cfg.VecOpt.Subsystem,
+			Name:       cfg.VecOpt.Name,
+			Help:       cfg.VecOpt.Help,
+			Objectives: cfg.Objectives,
+		},
+		cfg.VecOpt.Labels,
+	)
+	prom.MustRegister(vec)
+	sv := &promSummaryVec{
+		summary: vec,
+	}
+	proc.AddShutdownListener(func() {
+		sv.close()
+	})
+
+	return sv
+}
+
+func (sv *promSummaryVec) Observe(v float64, labels ...string) {
+	if !prometheus.Enabled() {
+		return
+	}
+
+	sv.summary.WithLabelValues(labels...).Observe(v)
+}
+
+func (sv *promSummaryVec) close() bool {
+	return prom.Unregister(sv.summary)
+}