CloudMonitoring: use CallResourceHandler instead of PluginProxy (#41064)

pkg/tsdb/cloudmonitoring/resource_handler.go

@@ -0,0 +1,124 @@
+package cloudmonitoring
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend/resource/httpadapter"
+)
+
+func (s *Service) registerRoutes(mux *http.ServeMux) {
+	mux.HandleFunc("/cloudmonitoring/", s.resourceHandler(cloudMonitor))
+	mux.HandleFunc("/cloudresourcemanager/", s.resourceHandler(resourceManager))
+}
+
+func (s *Service) resourceHandler(subDataSource string) func(rw http.ResponseWriter, req *http.Request) {
+	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))
+			return
+		}
+		doRequest(rw, req, client)
+	}
+}
+
+func (s *Service) setRequestVariables(req *http.Request, subDataSource string) (*http.Client, int, error) {
+	slog.Debug("Received resource call", "url", req.URL.String(), "method", req.Method)
+
+	newPath, err := getTarget(req.URL.Path)
+	if err != nil {
+		return nil, http.StatusBadRequest, err
+	}
+
+	dsInfo, err := s.getDataSourceFromHTTPReq(req)
+	if err != nil {
+		return nil, http.StatusBadRequest, err
+	}
+
+	serviceURL, err := url.Parse(dsInfo.services[subDataSource].url)
+	if err != nil {
+		return nil, http.StatusBadRequest, err
+	}
+	req.URL.Path = newPath
+	req.URL.Host = serviceURL.Host
+	req.URL.Scheme = serviceURL.Scheme
+
+	return dsInfo.services[subDataSource].client, 0, nil
+}
+
+func doRequest(rw http.ResponseWriter, req *http.Request, cli *http.Client) http.ResponseWriter {
+	res, err := cli.Do(req)
+	if err != nil {
+		rw.WriteHeader(http.StatusBadRequest)
+		_, err = rw.Write([]byte(fmt.Sprintf("unexpected error %v", err)))
+		if err != nil {
+			slog.Error("Unable to write HTTP response", "error", err)
+		}
+		return nil
+	}
+	defer func() {
+		if err := res.Body.Close(); err != nil {
+			slog.Warn("Failed to close response body", "err", err)
+		}
+	}()
+
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		rw.WriteHeader(http.StatusInternalServerError)
+		_, err = rw.Write([]byte(fmt.Sprintf("unexpected error %v", err)))
+		if err != nil {
+			slog.Error("Unable to write HTTP response", "error", err)
+		}
+		return nil
+	}
+	rw.WriteHeader(res.StatusCode)
+	_, err = rw.Write(body)
+	if err != nil {
+		slog.Error("Unable to write HTTP response", "error", err)
+	}
+
+	for k, v := range res.Header {
+		rw.Header().Set(k, v[0])
+		for _, v := range v[1:] {
+			rw.Header().Add(k, v)
+		}
+	}
+	// Returning the response write for testing purposes
+	return rw
+}
+
+func getTarget(original string) (target string, err error) {
+	splittedPath := strings.SplitN(original, "/", 3)
+	if len(splittedPath) < 3 {
+		err = fmt.Errorf("the request should contain the service on its path")
+		return
+	}
+	target = fmt.Sprintf("/%s", splittedPath[2])
+	return
+}
+
+func writeResponse(rw http.ResponseWriter, code int, msg string) {
+	rw.WriteHeader(code)
+	_, err := rw.Write([]byte(msg))
+	if err != nil {
+		slog.Error("Unable to write HTTP response", "error", err)
+	}
+}
+
+func (s *Service) getDataSourceFromHTTPReq(req *http.Request) (*datasourceInfo, error) {
+	ctx := req.Context()
+	pluginContext := httpadapter.PluginConfigFromContext(ctx)
+	i, err := s.im.Get(pluginContext)
+	if err != nil {
+		return nil, nil
+	}
+	ds, ok := i.(*datasourceInfo)
+	if !ok {
+		return nil, fmt.Errorf("unable to convert datasource from service instance")
+	}
+	return ds, nil
+}