Add a new paging utility for client side ranging

Kubernetes-commit: fb68d1d3a7bfb69f3884db6d360816fb2e7eda1e

tools/pager/BUILD

@@ -0,0 +1,36 @@
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+load(
+    "@io_bazel_rules_go//go:def.bzl",
+    "go_library",
+)
+
+go_library(
+    name = "go_default_library",
+    srcs = ["pager.go"],
+    tags = ["automanaged"],
+    deps = [
+        "//vendor/golang.org/x/net/context:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/api/errors:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/api/meta:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/apis/meta/internalversion:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/runtime:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)

tools/pager/pager.go

@@ -0,0 +1,103 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package pager
+
+import (
+	"fmt"
+
+	"golang.org/x/net/context"
+
+	"k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/api/meta"
+	metainternalversion "k8s.io/apimachinery/pkg/apis/meta/internalversion"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+const defaultPageSize = 500
+
+type ListPageFunc func(ctx context.Context, opts metav1.ListOptions) (runtime.Object, error)
+
+func SimplePageFunc(fn func(opts metav1.ListOptions) (runtime.Object, error)) ListPageFunc {
+	return func(ctx context.Context, opts metav1.ListOptions) (runtime.Object, error) {
+		return fn(opts)
+	}
+}
+
+type ListPager struct {
+	PageSize int64
+	PageFn   ListPageFunc
+
+	FullListIfExpired bool
+}
+
+func New(fn ListPageFunc) *ListPager {
+	return &ListPager{
+		PageSize:          defaultPageSize,
+		PageFn:            fn,
+		FullListIfExpired: true,
+	}
+}
+
+func (p *ListPager) List(ctx context.Context, options metav1.ListOptions) (runtime.Object, error) {
+	if options.Limit == 0 {
+		options.Limit = p.PageSize
+	}
+	var list *metainternalversion.List
+	for {
+		obj, err := p.PageFn(ctx, options)
+		if err != nil {
+			if !errors.IsResourceExpired(err) || !p.FullListIfExpired {
+				return nil, err
+			}
+			// the list expired while we were processing, fall back to a full list
+			options.Limit = 0
+			options.Continue = ""
+			return p.PageFn(ctx, options)
+		}
+		m, err := meta.ListAccessor(obj)
+		if err != nil {
+			return nil, fmt.Errorf("returned object must be a list: %v", err)
+		}
+
+		// exit early and return the object we got if we haven't processed any pages
+		if len(m.GetContinue()) == 0 && list == nil {
+			return obj, nil
+		}
+
+		// initialize the list and fill its contents
+		if list == nil {
+			list = &metainternalversion.List{Items: make([]runtime.Object, 0, options.Limit+1)}
+			list.ResourceVersion = m.GetResourceVersion()
+			list.SelfLink = m.GetSelfLink()
+		}
+		if err := meta.EachListItem(obj, func(obj runtime.Object) error {
+			list.Items = append(list.Items, obj)
+			return nil
+		}); err != nil {
+			return nil, err
+		}
+
+		// if we have no more items, return the list
+		if len(m.GetContinue()) == 0 {
+			return list, nil
+		}
+
+		// set the next loop up
+		options.Continue = m.GetContinue()
+	}
+}