Handle backend api errors

pkg/resource_handler.go

@@ -25,11 +25,16 @@ func (ds *ZabbixDatasource) zabbixAPIHandler(rw http.ResponseWriter, req *http.R
 	body, err := ioutil.ReadAll(req.Body)
 	defer req.Body.Close()
 	if err != nil || len(body) == 0 {
-		rw.WriteHeader(http.StatusBadRequest)
+		WriteError(rw, http.StatusBadRequest, err)
+		return
 	}
 
 	var reqData ZabbixAPIResourceRequest
 	err = json.Unmarshal(body, &reqData)
+	if err != nil {
+		WriteError(rw, http.StatusInternalServerError, err)
+		return
+	}
 
 	pluginCxt := httpadapter.PluginConfigFromContext(req.Context())
 	ds.logger.Debug("Received Zabbix API call", "ds", pluginCxt.DataSourceInstanceSettings.Name)
@@ -39,11 +44,38 @@ func (ds *ZabbixDatasource) zabbixAPIHandler(rw http.ResponseWriter, req *http.R
 
 	apiReq := &ZabbixAPIRequest{Method: reqData.Method, Params: reqData.Params}
 	result, err := dsInstance.ZabbixAPIQuery(req.Context(), apiReq)
-	resultJson, err := json.Marshal(*result)
-	ds.logger.Debug("Got response", "result", result)
+	if err != nil {
+		WriteError(rw, http.StatusInternalServerError, err)
+		return
+	}
 
-	ds.logger.Debug("Received Zabbix API call", "ds", reqData.DatasourceId, "method", reqData.Method, "params", reqData.Params)
-
-	rw.Write(resultJson)
-	rw.WriteHeader(http.StatusOK)
+	WriteResponse(rw, result)
+}
+
+func WriteResponse(rw http.ResponseWriter, result *interface{}) {
+	resultJson, err := json.Marshal(*result)
+	if err != nil {
+		WriteError(rw, http.StatusInternalServerError, err)
+	}
+
+	rw.Header().Add("Content-Type", "application/json")
+	rw.WriteHeader(http.StatusOK)
+	rw.Write(resultJson)
+}
+
+func WriteError(rw http.ResponseWriter, statusCode int, err error) {
+	data := make(map[string]interface{})
+
+	data["error"] = "Internal Server Error"
+	data["message"] = err.Error()
+
+	var b []byte
+	if b, err = json.Marshal(data); err != nil {
+		rw.WriteHeader(statusCode)
+		return
+	}
+
+	rw.Header().Add("Content-Type", "application/json")
+	rw.WriteHeader(http.StatusInternalServerError)
+	rw.Write(b)
 }