style(tsdb): extract some methods

pkg/tsdb/graphite/graphite.go

@@ -36,7 +36,7 @@ func init() {
 func (e *GraphiteExecutor) Execute(queries tsdb.QuerySlice, context *tsdb.QueryContext) *tsdb.BatchResult {
 	result := &tsdb.BatchResult{}
 
-	params := url.Values{
+	formData := url.Values{
 		"from":          []string{"-" + formatTimeRange(context.TimeRange.From)},
 		"until":         []string{formatTimeRange(context.TimeRange.To)},
 		"format":        []string{"json"},
@@ -44,63 +44,79 @@ func (e *GraphiteExecutor) Execute(queries tsdb.QuerySlice, context *tsdb.QueryC
 	}
 
 	for _, query := range queries {
-		params["target"] = []string{query.Query}
+		formData["target"] = []string{query.Query}
 	}
 
-	u, _ := url.Parse(e.Url)
-	u.Path = path.Join(u.Path, "render")
-	glog.Info("Graphite request body", "formdata", params.Encode())
+	glog.Info("Graphite request body", "formdata", formData.Encode())
 
-	req, err := http.NewRequest(http.MethodPost, u.String(), strings.NewReader(params.Encode()))
+	req, err := e.createRequest(formData)
 	if err != nil {
-		glog.Info("Failed to create request", "error", err)
-		result.Error = fmt.Errorf("Failed to create request. error: %v", err)
+		result.Error = err
 		return result
 	}
-
-	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-	if e.BasicAuth {
-		req.SetBasicAuth(e.BasicAuthUser, e.BasicAuthPassword)
+	res, err := HttpClient.Do(req)
+	if err != nil {
+		result.Error = err
+		return result
 	}
 
-	res, err := HttpClient.Do(req)
+	data, err := e.parseResponse(res)
 	if err != nil {
 		result.Error = err
 		return result
 	}
 
+	result.QueryResults = make(map[string]*tsdb.QueryResult)
+	queryRes := &tsdb.QueryResult{}
+	for _, series := range data {
+		queryRes.Series = append(queryRes.Series, &tsdb.TimeSeries{
+			Name:   series.Target,
+			Points: series.DataPoints,
+		})
+	}
+
+	result.QueryResults["A"] = queryRes
+	return result
+}
+
+func (e *GraphiteExecutor) parseResponse(res *http.Response) ([]TargetResponseDTO, error) {
 	body, err := ioutil.ReadAll(res.Body)
 	defer res.Body.Close()
 	if err != nil {
-		result.Error = err
-		return result
+		return nil, err
 	}
 
 	if res.StatusCode == http.StatusUnauthorized {
 		glog.Info("Request is Unauthorized", "status", res.Status, "body", string(body))
-		result.Error = fmt.Errorf("Request is Unauthorized status: %v body: %s", res.Status, string(body))
-		return result
+		return nil, fmt.Errorf("Request is Unauthorized status: %v body: %s", res.Status, string(body))
 	}
 
 	var data []TargetResponseDTO
 	err = json.Unmarshal(body, &data)
 	if err != nil {
 		glog.Info("Failed to unmarshal graphite response", "error", err, "status", res.Status, "body", string(body))
-		result.Error = err
-		return result
+		return nil, err
 	}
 
-	result.QueryResults = make(map[string]*tsdb.QueryResult)
-	queryRes := &tsdb.QueryResult{}
-	for _, series := range data {
-		queryRes.Series = append(queryRes.Series, &tsdb.TimeSeries{
-			Name:   series.Target,
-			Points: series.DataPoints,
-		})
+	return data, nil
+}
+
+func (e *GraphiteExecutor) createRequest(data url.Values) (*http.Request, error) {
+	u, _ := url.Parse(e.Url)
+	u.Path = path.Join(u.Path, "render")
+
+	req, err := http.NewRequest(http.MethodPost, u.String(), strings.NewReader(data.Encode()))
+	if err != nil {
+		glog.Info("Failed to create request", "error", err)
+		return nil, fmt.Errorf("Failed to create request. error: %v", err)
 	}
 
-	result.QueryResults["A"] = queryRes
-	return result
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	if e.BasicAuth {
+		req.SetBasicAuth(e.BasicAuthUser, e.BasicAuthPassword)
+	}
+
+	return req, err
 }
 
 func formatTimeRange(input string) string {