From 537085d94c92ed60c5a98428937912b39b5b111f Mon Sep 17 00:00:00 2001
From: Justin Santa Barbara <justin@fathomdb.com>
Date: Sun, 8 Jan 2017 14:48:58 -0500
Subject: [PATCH] dns-controller: don't make spurious updates in buffer

These will be caught later anyway, but we can save a false invalidation
and a spurious log message.
---
 dns-controller/cmd/dns-controller/main.go |  4 ++--
 dns-controller/pkg/dns/dnscontroller.go   | 29 +++++++++++++++++++++--
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/dns-controller/cmd/dns-controller/main.go b/dns-controller/cmd/dns-controller/main.go
index dd9bd48840..7001766cb5 100644
--- a/dns-controller/cmd/dns-controller/main.go
+++ b/dns-controller/cmd/dns-controller/main.go
@@ -23,8 +23,8 @@ import (
 	"k8s.io/kops/dns-controller/pkg/dns"
 	"k8s.io/kops/dns-controller/pkg/watchers"
 	"k8s.io/kubernetes/federation/pkg/dnsprovider"
-	client "k8s.io/kubernetes/pkg/client/clientset_generated/release_1_5/typed/core/v1"
-	client_extensions "k8s.io/kubernetes/pkg/client/clientset_generated/release_1_5/typed/extensions/v1beta1"
+	client "k8s.io/kubernetes/pkg/client/clientset_generated/clientset/typed/core/v1"
+	client_extensions "k8s.io/kubernetes/pkg/client/clientset_generated/clientset/typed/extensions/v1beta1"
 	kubectl_util "k8s.io/kubernetes/pkg/kubectl/cmd/util"
 	"os"
 
diff --git a/dns-controller/pkg/dns/dnscontroller.go b/dns-controller/pkg/dns/dnscontroller.go
index d4d6097c73..0ea4bba8cb 100644
--- a/dns-controller/pkg/dns/dnscontroller.go
+++ b/dns-controller/pkg/dns/dnscontroller.go
@@ -480,19 +480,44 @@ func (s *DNSControllerScope) MarkReady() {
 }
 
 func (s *DNSControllerScope) Replace(recordName string, records []Record) {
-	glog.V(2).Infof("Update %s/%s: %v", s.ScopeName, recordName, records)
-
 	s.mutex.Lock()
 	defer s.mutex.Unlock()
 
+	existing, exists := s.Records[recordName]
+
 	if len(records) == 0 {
+		if !exists {
+			glog.V(6).Infof("skipping spurious removal of record %s/%s", s.ScopeName, recordName)
+			return
+		}
+
 		delete(s.Records, recordName)
 	} else {
+		if recordsSliceEquals(existing, records) {
+			glog.V(6).Infof("skipping spurious update of record %s/%s=%s", s.ScopeName, recordName, records)
+			return
+		}
+
 		s.Records[recordName] = records
 	}
+
+	glog.V(2).Infof("Update %s/%s: %v", s.ScopeName, recordName, records)
 	s.parent.recordChange()
 }
 
+// recordsSliceEquals compares two []Record
+func recordsSliceEquals(l, r []Record) bool {
+	if len(l) != len(r) {
+		return false
+	}
+	for i := range l {
+		if l[i] != r[i] {
+			return false
+		}
+	}
+	return true
+}
+
 // CreateScope creates a scope object.
 func (c *DNSController) CreateScope(scopeName string) (Scope, error) {
 	c.mutex.Lock()