From f2d9cfb8c84be89826a55782c904908e7783d004 Mon Sep 17 00:00:00 2001
From: David Eads <deads@redhat.com>
Date: Fri, 10 Jan 2025 16:23:23 -0500
Subject: [PATCH] switch to using the real FIFO

Kubernetes-commit: a9aab298b4738f4ea9111131cdf193a3b1ba14e5
---
 features/known_features.go     |  7 +++++++
 tools/cache/controller.go      | 17 ++++++++++++-----
 tools/cache/controller_test.go |  7 ++-----
 tools/cache/shared_informer.go | 15 ++++++++++-----
 4 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/features/known_features.go b/features/known_features.go
index a74f6a833..344d2ebb7 100644
--- a/features/known_features.go
+++ b/features/known_features.go
@@ -53,6 +53,12 @@ const (
 	// alpha: v1.30
 	InformerResourceVersion Feature = "InformerResourceVersion"
 
+	// owner: @deads2k
+	// beta: v1.33
+	//
+	// Refactor informers to deliver watch stream events in order instead of out of order.
+	InOrderInformers Feature = "InOrderInformers"
+
 	// owner: @p0lyn0mial
 	// beta: v1.30
 	//
@@ -73,5 +79,6 @@ var defaultKubernetesFeatureGates = map[Feature]FeatureSpec{
 	ClientsAllowCBOR:        {Default: false, PreRelease: Alpha},
 	ClientsPreferCBOR:       {Default: false, PreRelease: Alpha},
 	InformerResourceVersion: {Default: false, PreRelease: Alpha},
+	InOrderInformers:        {Default: true, PreRelease: Beta},
 	WatchListClient:         {Default: false, PreRelease: Beta},
 }
diff --git a/tools/cache/controller.go b/tools/cache/controller.go
index 9ea1f494a..1497700d8 100644
--- a/tools/cache/controller.go
+++ b/tools/cache/controller.go
@@ -19,6 +19,7 @@ package cache
 import (
 	"context"
 	"errors"
+	clientgofeaturegate "k8s.io/client-go/features"
 	"sync"
 	"time"
 
@@ -592,11 +593,17 @@ func newInformer(clientState Store, options InformerOptions) Controller {
 	// This will hold incoming changes. Note how we pass clientState in as a
 	// KeyLister, that way resync operations will result in the correct set
 	// of update/delete deltas.
-	fifo := NewDeltaFIFOWithOptions(DeltaFIFOOptions{
-		KnownObjects:          clientState,
-		EmitDeltaTypeReplaced: true,
-		Transformer:           options.Transform,
-	})
+
+	var fifo Queue
+	if clientgofeaturegate.FeatureGates().Enabled(clientgofeaturegate.InOrderInformers) {
+		fifo = NewRealFIFO(MetaNamespaceKeyFunc, clientState, options.Transform)
+	} else {
+		fifo = NewDeltaFIFOWithOptions(DeltaFIFOOptions{
+			KnownObjects:          clientState,
+			EmitDeltaTypeReplaced: true,
+			Transformer:           options.Transform,
+		})
+	}
 
 	cfg := &Config{
 		Queue:            fifo,
diff --git a/tools/cache/controller_test.go b/tools/cache/controller_test.go
index edc1c24a4..054257920 100644
--- a/tools/cache/controller_test.go
+++ b/tools/cache/controller_test.go
@@ -49,10 +49,7 @@ func Example() {
 	// This will hold incoming changes. Note how we pass downstream in as a
 	// KeyLister, that way resync operations will result in the correct set
 	// of update/delete deltas.
-	fifo := NewDeltaFIFOWithOptions(DeltaFIFOOptions{
-		KeyFunction:  MetaNamespaceKeyFunc,
-		KnownObjects: downstream,
-	})
+	fifo := NewRealFIFO(MetaNamespaceKeyFunc, downstream, nil)
 
 	// Let's do threadsafe output to get predictable test results.
 	deletionCounter := make(chan string, 1000)
@@ -87,7 +84,7 @@ func Example() {
 
 				// fifo's KeyOf is easiest, because it handles
 				// DeletedFinalStateUnknown markers.
-				key, err := fifo.KeyOf(newest.Object)
+				key, err := fifo.keyOf(newest.Object)
 				if err != nil {
 					return err
 				}
diff --git a/tools/cache/shared_informer.go b/tools/cache/shared_informer.go
index c511a0ceb..a8156a286 100644
--- a/tools/cache/shared_informer.go
+++ b/tools/cache/shared_informer.go
@@ -540,11 +540,16 @@ func (s *sharedIndexInformer) RunWithContext(ctx context.Context) {
 		s.startedLock.Lock()
 		defer s.startedLock.Unlock()
 
-		fifo := NewDeltaFIFOWithOptions(DeltaFIFOOptions{
-			KnownObjects:          s.indexer,
-			EmitDeltaTypeReplaced: true,
-			Transformer:           s.transform,
-		})
+		var fifo Queue
+		if clientgofeaturegate.FeatureGates().Enabled(clientgofeaturegate.InOrderInformers) {
+			fifo = NewRealFIFO(MetaNamespaceKeyFunc, s.indexer, s.transform)
+		} else {
+			fifo = NewDeltaFIFOWithOptions(DeltaFIFOOptions{
+				KnownObjects:          s.indexer,
+				EmitDeltaTypeReplaced: true,
+				Transformer:           s.transform,
+			})
+		}
 
 		cfg := &Config{
 			Queue:             fifo,