From c4bec1585fe9c31303c928c11ac45e380d2eaf77 Mon Sep 17 00:00:00 2001
From: Clayton Coleman <ccoleman@redhat.com>
Date: Mon, 23 May 2016 12:35:36 -0400
Subject: [PATCH] Delay flush if the watch queue has pending items

Simple deferral of flush can reduce Syscalls when watch queues build up.
---
 pkg/apiserver/watch.go | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/pkg/apiserver/watch.go b/pkg/apiserver/watch.go
index 8094ac9c00..9f3d393bb9 100644
--- a/pkg/apiserver/watch.go
+++ b/pkg/apiserver/watch.go
@@ -168,13 +168,14 @@ func (s *WatchServer) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	flusher.Flush()
 
 	buf := &bytes.Buffer{}
+	ch := s.watching.ResultChan()
 	for {
 		select {
 		case <-cn.CloseNotify():
 			return
 		case <-timeoutCh:
 			return
-		case event, ok := <-s.watching.ResultChan():
+		case event, ok := <-ch:
 			if !ok {
 				// End of results.
 				return
@@ -196,7 +197,9 @@ func (s *WatchServer) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 				// client disconnect.
 				return
 			}
-			flusher.Flush()
+			if len(ch) == 0 {
+				flusher.Flush()
+			}
 
 			buf.Reset()
 		}