Plugins: Update client to use SDK resource contract (#42888)

* client uses sdk resource handler

* apply pr feedback

pkg/api/plugins.go

@@ -5,12 +5,15 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"net/http"
+	"net/url"
 	"os"
 	"path/filepath"
 	"sort"
 	"strings"
+	"sync"
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
 	"github.com/grafana/grafana/pkg/api/dtos"
@@ -22,6 +25,8 @@ import (
 	"github.com/grafana/grafana/pkg/plugins/backendplugin"
 	"github.com/grafana/grafana/pkg/plugins/manager/installer"
 	"github.com/grafana/grafana/pkg/setting"
+	"github.com/grafana/grafana/pkg/util/errutil"
+	"github.com/grafana/grafana/pkg/util/proxyutil"
 	"github.com/grafana/grafana/pkg/web"
 )
 
@@ -390,18 +395,7 @@ func (hs *HTTPServer) CheckHealth(c *models.ReqContext) response.Response {
 //
 // /api/plugins/:pluginId/resources/*
 func (hs *HTTPServer) CallResource(c *models.ReqContext) {
-	pluginID := web.Params(c.Req)[":pluginId"]
-
-	pCtx, found, err := hs.PluginContextProvider.Get(c.Req.Context(), pluginID, "", c.SignedInUser, false)
-	if err != nil {
-		c.JsonApiErr(500, "Failed to get plugin settings", err)
-		return
-	}
-	if !found {
-		c.JsonApiErr(404, "Plugin not found", nil)
-		return
-	}
-	hs.pluginClient.CallResource(pCtx, c, web.Params(c.Req)["*"])
+	hs.callPluginResource(c, web.Params(c.Req)[":pluginId"], "")
 }
 
 func (hs *HTTPServer) GetPluginErrorsList(_ *models.ReqContext) response.Response {
@@ -522,3 +516,218 @@ func (hs *HTTPServer) pluginMarkdown(ctx context.Context, pluginId string, name
 func mdFilepath(mdFilename string) string {
 	return filepath.Clean(filepath.Join("/", fmt.Sprintf("%s.md", mdFilename)))
 }
+
+func (hs *HTTPServer) callPluginResource(c *models.ReqContext, pluginID, dsUID string) {
+	pCtx, found, err := hs.PluginContextProvider.Get(c.Req.Context(), pluginID, dsUID, c.SignedInUser, false)
+	if err != nil {
+		c.JsonApiErr(500, "Failed to get plugin settings", err)
+		return
+	}
+	if !found {
+		c.JsonApiErr(404, "Plugin not found", nil)
+		return
+	}
+
+	var dsURL string
+	if pCtx.DataSourceInstanceSettings != nil {
+		dsURL = pCtx.DataSourceInstanceSettings.URL
+	}
+
+	err = hs.PluginRequestValidator.Validate(dsURL, c.Req)
+	if err != nil {
+		c.JsonApiErr(http.StatusForbidden, "Access denied", err)
+		return
+	}
+
+	clonedReq := c.Req.Clone(c.Req.Context())
+	rawURL := web.Params(c.Req)["*"]
+	if clonedReq.URL.RawQuery != "" {
+		rawURL += "?" + clonedReq.URL.RawQuery
+	}
+	urlPath, err := url.Parse(rawURL)
+	if err != nil {
+		handleCallResourceError(err, c)
+		return
+	}
+	clonedReq.URL = urlPath
+
+	if err = hs.makePluginResourceRequest(c.Resp, clonedReq, pCtx); err != nil {
+		handleCallResourceError(err, c)
+	}
+}
+
+func (hs *HTTPServer) makePluginResourceRequest(w http.ResponseWriter, req *http.Request, pCtx backend.PluginContext) error {
+	keepCookieModel := struct {
+		KeepCookies []string `json:"keepCookies"`
+	}{}
+	if dis := pCtx.DataSourceInstanceSettings; dis != nil {
+		err := json.Unmarshal(dis.JSONData, &keepCookieModel)
+		if err != nil {
+			hs.log.Warn("failed to to unpack JSONData in datasource instance settings", "err", err)
+		}
+	}
+	proxyutil.ClearCookieHeader(req, keepCookieModel.KeepCookies)
+	proxyutil.PrepareProxyRequest(req)
+
+	body, err := ioutil.ReadAll(req.Body)
+	if err != nil {
+		return fmt.Errorf("failed to read request body: %w", err)
+	}
+
+	crReq := &backend.CallResourceRequest{
+		PluginContext: pCtx,
+		Path:          req.URL.Path,
+		Method:        req.Method,
+		URL:           req.URL.String(),
+		Headers:       req.Header,
+		Body:          body,
+	}
+
+	childCtx, cancel := context.WithCancel(req.Context())
+	defer cancel()
+	stream := newCallResourceResponseStream(childCtx)
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+
+	defer func() {
+		if err := stream.Close(); err != nil {
+			hs.log.Warn("Failed to close plugin resource stream", "err", err)
+		}
+		wg.Wait()
+	}()
+
+	var flushStreamErr error
+	go func() {
+		flushStreamErr = hs.flushStream(stream, w)
+		wg.Done()
+	}()
+
+	if err := hs.pluginClient.CallResource(req.Context(), crReq, stream); err != nil {
+		return err
+	}
+
+	return flushStreamErr
+}
+
+func (hs *HTTPServer) flushStream(stream callResourceClientResponseStream, w http.ResponseWriter) error {
+	processedStreams := 0
+
+	for {
+		resp, err := stream.Recv()
+		if errors.Is(err, io.EOF) {
+			if processedStreams == 0 {
+				return errors.New("received empty resource response")
+			}
+			return nil
+		}
+		if err != nil {
+			if processedStreams == 0 {
+				return errutil.Wrap("failed to receive response from resource call", err)
+			}
+
+			hs.log.Error("Failed to receive response from resource call", "err", err)
+			return stream.Close()
+		}
+
+		// Expected that headers and status are only part of first stream
+		if processedStreams == 0 && resp.Headers != nil {
+			// Make sure a content type always is returned in response
+			if _, exists := resp.Headers["Content-Type"]; !exists {
+				resp.Headers["Content-Type"] = []string{"application/json"}
+			}
+
+			for k, values := range resp.Headers {
+				// Due to security reasons we don't want to forward
+				// cookies from a backend plugin to clients/browsers.
+				if k == "Set-Cookie" {
+					continue
+				}
+
+				for _, v := range values {
+					// TODO: Figure out if we should use Set here instead
+					// nolint:gocritic
+					w.Header().Add(k, v)
+				}
+			}
+			w.WriteHeader(resp.Status)
+		}
+
+		if _, err := w.Write(resp.Body); err != nil {
+			hs.log.Error("Failed to write resource response", "err", err)
+		}
+
+		if flusher, ok := w.(http.Flusher); ok {
+			flusher.Flush()
+		}
+		processedStreams++
+	}
+}
+
+func handleCallResourceError(err error, reqCtx *models.ReqContext) {
+	if errors.Is(err, backendplugin.ErrPluginUnavailable) {
+		reqCtx.JsonApiErr(503, "Plugin unavailable", err)
+		return
+	}
+
+	if errors.Is(err, backendplugin.ErrMethodNotImplemented) {
+		reqCtx.JsonApiErr(404, "Not found", err)
+		return
+	}
+
+	reqCtx.JsonApiErr(500, "Failed to call resource", err)
+}
+
+// callResourceClientResponseStream is used for receiving resource call responses.
+type callResourceClientResponseStream interface {
+	Recv() (*backend.CallResourceResponse, error)
+	Close() error
+}
+
+type callResourceResponseStream struct {
+	ctx    context.Context
+	stream chan *backend.CallResourceResponse
+	closed bool
+}
+
+func newCallResourceResponseStream(ctx context.Context) *callResourceResponseStream {
+	return &callResourceResponseStream{
+		ctx:    ctx,
+		stream: make(chan *backend.CallResourceResponse),
+	}
+}
+
+func (s *callResourceResponseStream) Send(res *backend.CallResourceResponse) error {
+	if s.closed {
+		return errors.New("cannot send to a closed stream")
+	}
+
+	select {
+	case <-s.ctx.Done():
+		return errors.New("cancelled")
+	case s.stream <- res:
+		return nil
+	}
+}
+
+func (s *callResourceResponseStream) Recv() (*backend.CallResourceResponse, error) {
+	select {
+	case <-s.ctx.Done():
+		return nil, s.ctx.Err()
+	case res, ok := <-s.stream:
+		if !ok {
+			return nil, io.EOF
+		}
+		return res, nil
+	}
+}
+
+func (s *callResourceResponseStream) Close() error {
+	if s.closed {
+		return errors.New("cannot close a closed stream")
+	}
+
+	close(s.stream)
+	s.closed = true
+	return nil
+}