Prometheus: Implement Streaming JSON Parser (#48477)

use `prometheusStreamingJSONParser` feature toggle to enable

pkg/tsdb/prometheus/querydata/response.go

@@ -0,0 +1,111 @@
+package querydata
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"sort"
+	"strings"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana-plugin-sdk-go/data"
+	"github.com/grafana/grafana/pkg/tsdb/prometheus/models"
+	"github.com/grafana/grafana/pkg/util/converter"
+	jsoniter "github.com/json-iterator/go"
+)
+
+func (s *QueryData) parseResponse(ctx context.Context, q *models.Query, res *http.Response) (*backend.DataResponse, error) {
+	defer func() {
+		if err := res.Body.Close(); err != nil {
+			s.log.Error("Failed to close response body", "err", err)
+		}
+	}()
+
+	iter := jsoniter.Parse(jsoniter.ConfigDefault, res.Body, 1024)
+	r := converter.ReadPrometheusStyleResult(iter)
+	if r == nil {
+		return nil, fmt.Errorf("received empty response from prometheus")
+	}
+
+	// The ExecutedQueryString can be viewed in QueryInspector in UI
+	for _, frame := range r.Frames {
+		addMetadataToFrame(q, frame)
+	}
+
+	return r, nil
+}
+
+func addMetadataToFrame(q *models.Query, frame *data.Frame) {
+	if frame.Meta == nil {
+		frame.Meta = &data.FrameMeta{}
+	}
+	frame.Meta.ExecutedQueryString = executedQueryString(q)
+	if len(frame.Fields) < 2 {
+		return
+	}
+	frame.Name = getName(q, frame)
+	frame.Fields[0].Config = &data.FieldConfig{Interval: float64(q.Step.Milliseconds())}
+	if frame.Name != "" {
+		frame.Fields[1].Config = &data.FieldConfig{DisplayNameFromDS: frame.Name}
+	}
+}
+
+// this is based on the logic from the String() function in github.com/prometheus/common/model.go
+func metricNameFromLabels(f *data.Frame) string {
+	labels := f.Fields[1].Labels
+	metricName, hasName := labels["__name__"]
+	numLabels := len(labels) - 1
+	if !hasName {
+		numLabels = len(labels)
+	}
+	labelStrings := make([]string, 0, numLabels)
+	for label, value := range labels {
+		if label != "__name__" {
+			labelStrings = append(labelStrings, fmt.Sprintf("%s=%q", label, value))
+		}
+	}
+
+	switch numLabels {
+	case 0:
+		if hasName {
+			return metricName
+		}
+		return "{}"
+	default:
+		sort.Strings(labelStrings)
+		return fmt.Sprintf("%s{%s}", metricName, strings.Join(labelStrings, ", "))
+	}
+}
+
+func executedQueryString(q *models.Query) string {
+	return "Expr: " + q.Expr + "\n" + "Step: " + q.Step.String()
+}
+
+func getName(q *models.Query, frame *data.Frame) string {
+	labels := frame.Fields[1].Labels
+	legend := metricNameFromLabels(frame)
+
+	if q.LegendFormat == legendFormatAuto && len(labels) > 0 {
+		return ""
+	}
+
+	if q.LegendFormat != "" {
+		result := legendFormatRegexp.ReplaceAllFunc([]byte(q.LegendFormat), func(in []byte) []byte {
+			labelName := strings.Replace(string(in), "{{", "", 1)
+			labelName = strings.Replace(labelName, "}}", "", 1)
+			labelName = strings.TrimSpace(labelName)
+			if val, exists := labels[labelName]; exists {
+				return []byte(val)
+			}
+			return []byte{}
+		})
+		legend = string(result)
+	}
+
+	// If legend is empty brackets, use query expression
+	if legend == "{}" {
+		return q.Expr
+	}
+
+	return legend
+}