feat(renderer): add timeout for the renderer api

closes #4325

pkg/api/render.go

@@ -31,6 +31,7 @@ func RenderToPng(c *middleware.Context) {
 		Width:     queryReader.Get("width", "800"),
 		Height:    queryReader.Get("height", "400"),
 		SessionId: c.Session.ID(),
+		Timeout:   queryReader.Get("timeout", "15"),
 	}
 
 	renderOpts.Url = setting.ToAbsUrl(renderOpts.Url)

pkg/components/renderer/renderer.go

@@ -11,6 +11,7 @@ import (
 	"github.com/grafana/grafana/pkg/log"
 	"github.com/grafana/grafana/pkg/setting"
 	"github.com/grafana/grafana/pkg/util"
+	"strconv"
 )
 
 type RenderOpts struct {
@@ -18,6 +19,7 @@ type RenderOpts struct {
 	Width     string
 	Height    string
 	SessionId string
+	Timeout   string
 }
 
 func RenderToPng(params *RenderOpts) (string, error) {
@@ -60,8 +62,13 @@ func RenderToPng(params *RenderOpts) (string, error) {
 		close(done)
 	}()
 
+	timeout, err := strconv.Atoi(params.Timeout)
+	if err != nil {
+		timeout = 15
+	}
+
 	select {
-	case <-time.After(15 * time.Second):
+	case <-time.After(time.Duration(timeout) * time.Second):
 		if err := cmd.Process.Kill(); err != nil {
 			log.Error(4, "failed to kill: %v", err)
 		}