[v11.4.x] Azure/GCM: Improve error display (#97594)

* Azure/GCM: Improve error display (#96921)

Improve handling of errors

(cherry picked from commit 9f75a448d4)

* Update var name and import

---------

Co-authored-by: Andreas Christou <andreas.christou@grafana.com>

pkg/tsdb/azuremonitor/azuremonitor-resource-handler.go

@@ -1,6 +1,7 @@
 package azuremonitor
 
 import (
+	"encoding/json"
 	"fmt"
 	"io"
 	"net/http"
@@ -82,9 +83,13 @@ func (s *Service) getDataSourceFromHTTPReq(req *http.Request) (types.DatasourceI
 	return ds, nil
 }
 
-func writeResponse(rw http.ResponseWriter, code int, msg string) {
+func writeErrorResponse(rw http.ResponseWriter, code int, msg string) {
 	rw.WriteHeader(http.StatusBadRequest)
-	_, err := rw.Write([]byte(msg))
+	errorBody := map[string]string{
+		"error": msg,
+	}
+	jsonRes, _ := json.Marshal(errorBody)
+	_, err := rw.Write(jsonRes)
 	if err != nil {
 		backend.Logger.Error("Unable to write HTTP response", "error", err)
 	}
@@ -96,20 +101,20 @@ func (s *Service) handleResourceReq(subDataSource string) func(rw http.ResponseW
 
 		newPath, err := getTarget(req.URL.Path)
 		if err != nil {
-			writeResponse(rw, http.StatusBadRequest, err.Error())
+			writeErrorResponse(rw, http.StatusBadRequest, err.Error())
 			return
 		}
 
 		dsInfo, err := s.getDataSourceFromHTTPReq(req)
 		if err != nil {
-			writeResponse(rw, http.StatusInternalServerError, fmt.Sprintf("unexpected error %v", err))
+			writeErrorResponse(rw, http.StatusInternalServerError, fmt.Sprintf("unexpected error %v", err))
 			return
 		}
 
 		service := dsInfo.Services[subDataSource]
 		serviceURL, err := url.Parse(service.URL)
 		if err != nil {
-			writeResponse(rw, http.StatusInternalServerError, fmt.Sprintf("unexpected error %v", err))
+			writeErrorResponse(rw, http.StatusInternalServerError, fmt.Sprintf("unexpected error %v", err))
 			return
 		}
 		req.URL.Path = newPath
@@ -118,7 +123,7 @@ func (s *Service) handleResourceReq(subDataSource string) func(rw http.ResponseW
 
 		rw, err = s.executors[subDataSource].ResourceRequest(rw, req, service.HTTPClient)
 		if err != nil {
-			writeResponse(rw, http.StatusInternalServerError, fmt.Sprintf("unexpected error %v", err))
+			writeErrorResponse(rw, http.StatusInternalServerError, fmt.Sprintf("unexpected error %v", err))
 			return
 		}
 	}

pkg/tsdb/cloud-monitoring/resource_handler.go

@@ -38,13 +38,13 @@ func (s *Service) newResourceMux() *http.ServeMux {
 func (s *Service) getGCEDefaultProject(rw http.ResponseWriter, req *http.Request) {
 	project, err := s.gceDefaultProjectGetter(req.Context(), resourceManagerScope)
 	if err != nil {
-		writeResponse(rw, http.StatusBadRequest, fmt.Sprintf("unexpected error %v", err))
+		writeErrorResponse(rw, http.StatusBadRequest, fmt.Sprintf("unexpected error %v", err))
 		return
 	}
 
 	encoded, err := json.Marshal(project)
 	if err != nil {
-		writeResponse(rw, http.StatusBadRequest, fmt.Sprintf("error retrieving default project %v", err))
+		writeErrorResponse(rw, http.StatusBadRequest, fmt.Sprintf("error retrieving default project %v", err))
 		return
 	}
 	writeResponseBytes(rw, http.StatusOK, encoded)
@@ -54,7 +54,7 @@ func (s *Service) handleResourceReq(subDataSource string, responseFn processResp
 	return func(rw http.ResponseWriter, req *http.Request) {
 		client, code, err := s.setRequestVariables(req, subDataSource)
 		if err != nil {
-			writeResponse(rw, code, fmt.Sprintf("unexpected error %v", err))
+			writeErrorResponse(rw, code, fmt.Sprintf("unexpected error %v", err))
 			return
 		}
 		getResources(rw, req, client, responseFn)
@@ -63,19 +63,19 @@ func (s *Service) handleResourceReq(subDataSource string, responseFn processResp
 
 func getResources(rw http.ResponseWriter, req *http.Request, cli *http.Client, responseFn processResponse) http.ResponseWriter {
 	if responseFn == nil {
-		writeResponse(rw, http.StatusInternalServerError, "responseFn should not be nil")
+		writeErrorResponse(rw, http.StatusInternalServerError, "responseFn should not be nil")
 		return rw
 	}
 
 	responses, headers, encoding, code, err := getResponses(req, cli, responseFn)
 	if err != nil {
-		writeResponse(rw, code, fmt.Sprintf("unexpected error %v", err))
+		writeErrorResponse(rw, code, fmt.Sprintf("unexpected error %v", err))
 		return rw
 	}
 
 	body, err := buildResponse(responses, encoding)
 	if err != nil {
-		writeResponse(rw, http.StatusInternalServerError, fmt.Sprintf("error formatting responose %v", err))
+		writeErrorResponse(rw, http.StatusInternalServerError, fmt.Sprintf("error formatting responose %v", err))
 		return rw
 	}
 	writeResponseBytes(rw, code, body)
@@ -390,8 +390,12 @@ func writeResponseBytes(rw http.ResponseWriter, code int, msg []byte) {
 	}
 }
 
-func writeResponse(rw http.ResponseWriter, code int, msg string) {
-	writeResponseBytes(rw, code, []byte(msg))
+func writeErrorResponse(rw http.ResponseWriter, code int, msg string) {
+	errorBody := map[string]string{
+		"error": msg,
+	}
+	json, _ := json.Marshal(errorBody)
+	writeResponseBytes(rw, code, json)
 }
 
 func (s *Service) getDataSourceFromHTTPReq(req *http.Request) (*datasourceInfo, error) {