From 2298e1746c3d776ea0c987bbe26e675458ec5597 Mon Sep 17 00:00:00 2001
From: Wojciech Tyczynski <wojtekt@google.com>
Date: Thu, 13 Oct 2016 15:20:05 +0200
Subject: [PATCH] Increase buffer sizes in cacher for watchers interested in
 all/many objects.

---
 pkg/storage/cacher.go | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/pkg/storage/cacher.go b/pkg/storage/cacher.go
index 26581972609..2cd9d4483ec 100644
--- a/pkg/storage/cacher.go
+++ b/pkg/storage/cacher.go
@@ -310,10 +310,25 @@ func (c *Cacher) Watch(ctx context.Context, key string, resourceVersion string,
 		triggerValue, triggerSupported = matchValues[0].Value, true
 	}
 
+	// If there is triggerFunc defined, but triggerSupported is false,
+	// we can't narrow the amount of events significantly at this point.
+	//
+	// That said, currently triggerFunc is defined only for Pods and Nodes,
+	// and there is only constant number of watchers for which triggerSupported
+	// is false (excluding those issues explicitly by users).
+	// Thus, to reduce the risk of those watchers blocking all watchers of a
+	// given resource in the system, we increase the sizes of buffers for them.
+	chanSize := 10
+	if c.triggerFunc != nil && !triggerSupported {
+		// TODO: We should tune this value and ideally make it dependent on the
+		// number of objects of a given type and/or their churn.
+		chanSize = 1000
+	}
+
 	c.Lock()
 	defer c.Unlock()
 	forget := forgetWatcher(c, c.watcherIdx, triggerValue, triggerSupported)
-	watcher := newCacheWatcher(watchRV, initEvents, filterFunction(key, c.keyFunc, pred), forget)
+	watcher := newCacheWatcher(watchRV, chanSize, initEvents, filterFunction(key, c.keyFunc, pred), forget)
 
 	c.watchers.addWatcher(watcher, c.watcherIdx, triggerValue, triggerSupported)
 	c.watcherIdx++
@@ -610,10 +625,10 @@ type cacheWatcher struct {
 	forget  func(bool)
 }
 
-func newCacheWatcher(resourceVersion uint64, initEvents []watchCacheEvent, filter FilterFunc, forget func(bool)) *cacheWatcher {
+func newCacheWatcher(resourceVersion uint64, chanSize int, initEvents []watchCacheEvent, filter FilterFunc, forget func(bool)) *cacheWatcher {
 	watcher := &cacheWatcher{
-		input:   make(chan watchCacheEvent, 10),
-		result:  make(chan watch.Event, 10),
+		input:   make(chan watchCacheEvent, chanSize),
+		result:  make(chan watch.Event, chanSize),
 		filter:  filter,
 		stopped: false,
 		forget:  forget,
@@ -728,7 +743,7 @@ func (c *cacheWatcher) process(initEvents []watchCacheEvent, resourceVersion uin
 	// We should understand what is blocking us in those cases (e.g.
 	// is it lack of CPU, network, or sth else) and potentially
 	// consider increase size of result buffer in those cases.
-	const initProcessThreshold = 50 * time.Millisecond
+	const initProcessThreshold = 100 * time.Millisecond
 	startTime := time.Now()
 	for _, event := range initEvents {
 		c.sendWatchCacheEvent(event)
@@ -739,7 +754,7 @@ func (c *cacheWatcher) process(initEvents []watchCacheEvent, resourceVersion uin
 		if len(initEvents) > 0 {
 			objType = reflect.TypeOf(initEvents[0].Object).String()
 		}
-		glog.V(2).Infof("processing %d initEvents of %stook %v", len(initEvents), objType, processingTime)
+		glog.V(2).Infof("processing %d initEvents of %s took %v", len(initEvents), objType, processingTime)
 	}
 
 	defer close(c.result)