From d858f18787fe3ef437d803a1548a0296f4eca14d Mon Sep 17 00:00:00 2001
From: Joe Betz <jpbetz@google.com>
Date: Thu, 14 Mar 2019 13:26:19 -0700
Subject: [PATCH] Paginate List call performed by Reflector's ListAndWatch call

Kubernetes-commit: 84723c2d3ef5ff5d30aadd1ad72068bf2254358c
---
 tools/cache/reflector.go      | 15 +++++++++++-
 tools/cache/reflector_test.go | 45 ++++++++++++++++++++++++++++++++++-
 2 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/tools/cache/reflector.go b/tools/cache/reflector.go
index a629fd4e..21bba3ae 100644
--- a/tools/cache/reflector.go
+++ b/tools/cache/reflector.go
@@ -17,6 +17,7 @@ limitations under the License.
 package cache
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -38,6 +39,7 @@ import (
 	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
 	"k8s.io/apimachinery/pkg/util/wait"
 	"k8s.io/apimachinery/pkg/watch"
+	"k8s.io/client-go/tools/pager"
 	"k8s.io/klog"
 	"k8s.io/utils/trace"
 )
@@ -68,6 +70,9 @@ type Reflector struct {
 	lastSyncResourceVersion string
 	// lastSyncResourceVersionMutex guards read/write access to lastSyncResourceVersion
 	lastSyncResourceVersionMutex sync.RWMutex
+	// WatchListPageSize is the requested chunk size of initial and resync watch lists.
+	// Defaults to pager.PageSize.
+	WatchListPageSize int64
 }
 
 var (
@@ -179,7 +184,15 @@ func (r *Reflector) ListAndWatch(stopCh <-chan struct{}) error {
 					panicCh <- r
 				}
 			}()
-			list, err = r.listerWatcher.List(options)
+			// Attempt to gather list in chunks, if supported by listerWatcher, if not, the first
+			// list request will return the full response.
+			pager := pager.New(pager.SimplePageFunc(func(opts metav1.ListOptions) (runtime.Object, error) {
+				return r.listerWatcher.List(opts)
+			}))
+			if r.WatchListPageSize != 0 {
+				pager.PageSize = r.WatchListPageSize
+			}
+			list, err = pager.List(context.Background(), options)
 			close(listCh)
 		}()
 		select {
diff --git a/tools/cache/reflector_test.go b/tools/cache/reflector_test.go
index bb06059f..caa07232 100644
--- a/tools/cache/reflector_test.go
+++ b/tools/cache/reflector_test.go
@@ -24,7 +24,7 @@ import (
 	"testing"
 	"time"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/util/wait"
@@ -387,3 +387,46 @@ func TestReflectorResync(t *testing.T) {
 		t.Errorf("exactly 2 iterations were expected, got: %v", iteration)
 	}
 }
+
+func TestReflectorWatchListPageSize(t *testing.T) {
+	stopCh := make(chan struct{})
+	s := NewStore(MetaNamespaceKeyFunc)
+
+	lw := &testLW{
+		WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
+			// Stop once the reflector begins watching since we're only interested in the list.
+			close(stopCh)
+			fw := watch.NewFake()
+			return fw, nil
+		},
+		ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
+			if options.Limit != 4 {
+				t.Fatalf("Expected list Limit of 4 but got %d", options.Limit)
+			}
+			pods := make([]v1.Pod, 10)
+			for i := 0; i < 10; i++ {
+				pods[i] = v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: fmt.Sprintf("pod-%d", i), ResourceVersion: fmt.Sprintf("%d", i)}}
+			}
+			switch options.Continue {
+			case "":
+				return &v1.PodList{ListMeta: metav1.ListMeta{ResourceVersion: "10", Continue: "C1"}, Items: pods[0:4]}, nil
+			case "C1":
+				return &v1.PodList{ListMeta: metav1.ListMeta{ResourceVersion: "10", Continue: "C2"}, Items: pods[4:8]}, nil
+			case "C2":
+				return &v1.PodList{ListMeta: metav1.ListMeta{ResourceVersion: "10"}, Items: pods[8:10]}, nil
+			default:
+				t.Fatalf("Unrecognized continue: %s", options.Continue)
+			}
+			return nil, nil
+		},
+	}
+	r := NewReflector(lw, &v1.Pod{}, s, 0)
+	// Set the reflector to paginate the list request in 4 item chunks.
+	r.WatchListPageSize = 4
+	r.ListAndWatch(stopCh)
+
+	results := s.List()
+	if len(results) != 10 {
+		t.Errorf("Expected 10 results, got %d", len(results))
+	}
+}