Graphite: Convert tag values returned as numbers to strings (#37882)

* Convert tag values returned as numbers to string

This is a bug in Graphite <= 1.1.7. Since 1.1.8 all values are converted to strings.

* Simplify type conversions

* Fix linting errors

pkg/tsdb/graphite/graphite.go

@@ -10,6 +10,7 @@ import (
 	"net/url"
 	"path"
 	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
@@ -248,15 +249,25 @@ func (s *Service) toDataFrames(response *http.Response) (frames data.Frames, err
 			values = append(values, value)
 		}
 
+		tags := make(map[string]string)
+		for name, value := range series.Tags {
+			switch value := value.(type) {
+			case string:
+				tags[name] = value
+			case float64:
+				tags[name] = strconv.FormatFloat(value, 'f', -1, 64)
+			}
+		}
+
 		frames = append(frames, data.NewFrame(name,
 			data.NewField("time", nil, timeVector),
-			data.NewField("value", series.Tags, values).SetConfig(&data.FieldConfig{DisplayNameFromDS: name})))
+			data.NewField("value", tags, values).SetConfig(&data.FieldConfig{DisplayNameFromDS: name})))
 
 		if setting.Env == setting.Dev {
 			s.logger.Debug("Graphite response", "target", series.Target, "datapoints", len(series.DataPoints))
 		}
 	}
-	return
+	return frames, nil
 }
 
 func (s *Service) createRequest(dsInfo *datasourceInfo, data url.Values) (*http.Request, error) {