From 2ceb595dc365b57325efd6b94fb20e6a98529ab8 Mon Sep 17 00:00:00 2001
From: Dries De Peuter <dries@stenic.io>
Date: Thu, 1 Jun 2023 12:40:19 +0200
Subject: [PATCH] feat: Only write on changes

---
 go.mod         |  1 +
 go.sum         |  2 ++
 server/main.go | 14 ++++++++++++--
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/go.mod b/go.mod
index e65c2ac..7f2cf07 100644
--- a/go.mod
+++ b/go.mod
@@ -19,6 +19,7 @@ require (
 require (
 	github.com/bep/debounce v1.2.1
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/davegardnerisme/deephash v0.0.0-20210406090112-6d072427d830
 	github.com/emicklei/go-restful/v3 v3.9.0 // indirect
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-openapi/jsonpointer v0.19.5 // indirect
diff --git a/go.sum b/go.sum
index a4e905f..f8dd32f 100644
--- a/go.sum
+++ b/go.sum
@@ -45,6 +45,8 @@ github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ3
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davegardnerisme/deephash v0.0.0-20210406090112-6d072427d830 h1:gn7TsPBQ3HoEUaa8oBLbMalIBPf3eeQb7W/8kK3gERk=
+github.com/davegardnerisme/deephash v0.0.0-20210406090112-6d072427d830/go.mod h1:ToGe2SdaElKXzEmYLttAgFHy0exxh0wyq9zG7ZjjjYM=
 github.com/docopt/docopt-go v0.0.0-20180111231733-ee0de3bc6815/go.mod h1:WwZ+bS3ebgob9U8Nd0kOddGdZWjyMGR8Wziv+TBNwSE=
 github.com/emicklei/go-restful/v3 v3.9.0 h1:XwGDlfxEnQZzuopoqxwSEllNcCOM9DhhFyhFIIGKwxE=
 github.com/emicklei/go-restful/v3 v3.9.0/go.mod h1:6n3XBCmQQb25CM2LCACGz8ukIrRry+4bhvbpWn3mrbc=
diff --git a/server/main.go b/server/main.go
index c1e49e6..b5e7d12 100644
--- a/server/main.go
+++ b/server/main.go
@@ -23,6 +23,8 @@ import (
 
 	"github.com/bep/debounce"
 	"k8s.io/client-go/tools/clientcmd"
+
+	"github.com/davegardnerisme/deephash"
 )
 
 var kubeconfig string
@@ -32,6 +34,7 @@ var id string
 var leaseLockName string
 
 func main() {
+	klog.InitFlags(nil)
 	if home := homedir.HomeDir(); home != "" {
 		flag.StringVar(&kubeconfig, "kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
 	} else {
@@ -41,7 +44,6 @@ func main() {
 	flag.StringVar(&cmName, "configmap", "well-known-generated", "")
 	flag.StringVar(&id, "id", os.Getenv("POD_NAME"), "the holder identity name")
 	flag.StringVar(&leaseLockName, "lease-lock-name", "well-known", "the lease lock resource name")
-
 	flag.Parse()
 
 	// creates the in-cluster config
@@ -138,13 +140,14 @@ func loop(ctx context.Context, clientset *kubernetes.Clientset) {
 	}
 
 	debounced := debounce.New(500 * time.Millisecond)
+	hash := []byte{}
 
 	for event := range watch.ResultChan() {
 		svc, ok := event.Object.(*v1.Service)
 		if !ok {
 			continue
 		}
-		klog.Infof("Change detected on %s", svc.GetName())
+		klog.V(1).Infof("Change detected on %s", svc.GetName())
 
 		debounced(func() {
 			reg, err := discoverData(clientset, namespace)
@@ -153,6 +156,13 @@ func loop(ctx context.Context, clientset *kubernetes.Clientset) {
 				return
 			}
 
+			newHash := deephash.Hash(reg)
+			if string(hash) == string(newHash) {
+				klog.V(1).Info("No changes detected")
+				return
+			}
+			hash = newHash
+
 			klog.Info("Writing configmap")
 			if err := updateConfigMap(ctx, clientset, reg); err != nil {
 				klog.Error(err)