Rendering: Add support for rate limiter (#103987)

* Rendering: Add support for rate limiter

* remove unnecessary golint exception

* add lint exception back

pkg/api/render.go

@@ -98,6 +98,11 @@ func (hs *HTTPServer) RenderHandler(c *contextmodel.ReqContext) {
 		Theme:             themeModel,
 	}, nil)
 	if err != nil {
+		if errors.Is(err, rendering.ErrTooManyRequests) {
+			c.JsonApiErr(http.StatusTooManyRequests, "Too many rendering requests", err)
+			return
+		}
+
 		if errors.Is(err, rendering.ErrTimeout) {
 			c.Handle(hs.Cfg, http.StatusInternalServerError, err.Error(), err)
 			return

pkg/services/rendering/http_mode.go

@@ -31,6 +31,7 @@ var netClient = &http.Client{
 }
 
 const authTokenHeader = "X-Auth-Token" //#nosec G101 -- This is a false positive
+const rateLimiterHeader = "X-Tenant-ID"
 
 var (
 	remoteVersionFetchInterval   time.Duration = time.Second * 15
@@ -160,6 +161,7 @@ func (rs *RenderingService) doRequest(ctx context.Context, u *url.URL, headers m
 	}
 
 	req.Header.Set(authTokenHeader, rs.Cfg.RendererAuthToken)
+	req.Header.Set(rateLimiterHeader, rs.domain)
 	req.Header.Set("User-Agent", fmt.Sprintf("Grafana/%s", rs.Cfg.BuildVersion))
 	for k, v := range headers {
 		req.Header[k] = v
@@ -180,6 +182,10 @@ func (rs *RenderingService) doRequest(ctx context.Context, u *url.URL, headers m
 		return nil, fmt.Errorf("failed to send request to remote rendering service: %w", err)
 	}
 
+	if resp.StatusCode == http.StatusTooManyRequests {
+		return nil, ErrTooManyRequests
+	}
+
 	return resp, nil
 }
 

pkg/services/rendering/interface.go

@@ -14,6 +14,7 @@ var ErrTimeout = errors.New("timeout error - you can set timeout in seconds with
 var ErrConcurrentLimitReached = errors.New("rendering concurrent limit reached")
 var ErrRenderUnavailable = errors.New("rendering plugin not available")
 var ErrServerTimeout = errutil.NewBase(errutil.StatusUnknown, "rendering.serverTimeout", errutil.WithPublicMessage("error trying to connect to image-renderer service"))
+var ErrTooManyRequests = errutil.NewBase(errutil.StatusTooManyRequests, "rendering.tooManyRequests", errutil.WithPublicMessage("trying to send too many requests to image-renderer service"))
 
 type RenderType string