feat: add prometheus summary metrics (#3440)

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

core/metric/summary_test.go

@@ -0,0 +1,68 @@
+package metric
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus/testutil"
+	"github.com/stretchr/testify/assert"
+	"github.com/zeromicro/go-zero/core/proc"
+)
+
+func TestNewSummaryVec(t *testing.T) {
+	summaryVec := NewSummaryVec(&SummaryVecOpts{
+		VecOpt: VectorOpts{
+			Namespace: "http_server",
+			Subsystem: "requests",
+			Name:      "duration_quantiles",
+			Help:      "rpc client requests duration(ms) φ quantiles ",
+			Labels:    []string{"method"},
+		},
+		Objectives: map[float64]float64{
+			0.5: 0.01,
+			0.9: 0.01,
+		},
+	})
+	defer summaryVec.close()
+	summaryVecNil := NewSummaryVec(nil)
+	assert.NotNil(t, summaryVec)
+	assert.Nil(t, summaryVecNil)
+}
+
+func TestSummaryObserve(t *testing.T) {
+	startAgent()
+	summaryVec := NewSummaryVec(&SummaryVecOpts{
+		VecOpt: VectorOpts{
+			Namespace: "http_server",
+			Subsystem: "requests",
+			Name:      "duration_quantiles",
+			Help:      "rpc client requests duration(ms) φ quantiles ",
+			Labels:    []string{"method"},
+		},
+		Objectives: map[float64]float64{
+			0.3: 0.01,
+			0.6: 0.01,
+			1:   0.01,
+		},
+	})
+	defer summaryVec.close()
+	sv := summaryVec.(*promSummaryVec)
+	sv.Observe(100, "GET")
+	sv.Observe(200, "GET")
+	sv.Observe(300, "GET")
+	metadata := `
+		# HELP http_server_requests_duration_quantiles rpc client requests duration(ms) φ quantiles 
+		# TYPE http_server_requests_duration_quantiles summary
+`
+	val := `
+		http_server_requests_duration_quantiles{method="GET",quantile="0.3"} 100
+		http_server_requests_duration_quantiles{method="GET",quantile="0.6"} 200
+		http_server_requests_duration_quantiles{method="GET",quantile="1"} 300
+		http_server_requests_duration_quantiles_sum{method="GET"} 600
+		http_server_requests_duration_quantiles_count{method="GET"} 3
+`
+
+	err := testutil.CollectAndCompare(sv.summary, strings.NewReader(metadata+val))
+	assert.Nil(t, err)
+	proc.Shutdown()
+}