From 9c02c39487d9b408e5c8b139b3b701ef96bc9f9b Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@victoriametrics.com>
Date: Thu, 20 Oct 2022 08:42:41 +0300
Subject: [PATCH] lib/workingsetcache: randomize interval for swapping curr and
 prev caches

This should make CPU usage smoother over time, since different caches
will be swapped at different times.
---
 lib/workingsetcache/cache.go | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/lib/workingsetcache/cache.go b/lib/workingsetcache/cache.go
index 8c4c220b0..1045db821 100644
--- a/lib/workingsetcache/cache.go
+++ b/lib/workingsetcache/cache.go
@@ -129,7 +129,8 @@ func (c *Cache) runWatchers(expireDuration time.Duration) {
 }
 
 func (c *Cache) expirationWatcher(expireDuration time.Duration) {
-	t := time.NewTicker(expireDuration / 2)
+	expireDuration += timeJitter(expireDuration / 10)
+	t := time.NewTicker(expireDuration)
 	for {
 		select {
 		case <-c.stopCh:
@@ -155,7 +156,9 @@ func (c *Cache) expirationWatcher(expireDuration time.Duration) {
 }
 
 func (c *Cache) cacheSizeWatcher() {
-	t := time.NewTicker(1500 * time.Millisecond)
+	checkInterval := 1500 * time.Millisecond
+	checkInterval += timeJitter(checkInterval / 10)
+	t := time.NewTicker(checkInterval)
 	defer t.Stop()
 
 	var maxBytesSize uint64
@@ -375,3 +378,8 @@ func (c *Cache) SetBig(key, value []byte) {
 	curr := c.curr.Load().(*fastcache.Cache)
 	curr.SetBig(key, value)
 }
+
+func timeJitter(d time.Duration) time.Duration {
+	n := float64(time.Now().UnixNano()%1e9) / 1e9
+	return time.Duration(float64(d) * n)
+}