mirror of
https://github.com/prometheus/prometheus.git
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118 lines
3.7 KiB
Go
118 lines
3.7 KiB
Go
/*
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Copyright 2017 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package pager
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import (
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"context"
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"fmt"
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"k8s.io/apimachinery/pkg/api/errors"
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"k8s.io/apimachinery/pkg/api/meta"
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metainternalversion "k8s.io/apimachinery/pkg/apis/meta/internalversion"
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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"k8s.io/apimachinery/pkg/runtime"
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)
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const defaultPageSize = 500
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// ListPageFunc returns a list object for the given list options.
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type ListPageFunc func(ctx context.Context, opts metav1.ListOptions) (runtime.Object, error)
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// SimplePageFunc adapts a context-less list function into one that accepts a context.
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func SimplePageFunc(fn func(opts metav1.ListOptions) (runtime.Object, error)) ListPageFunc {
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return func(ctx context.Context, opts metav1.ListOptions) (runtime.Object, error) {
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return fn(opts)
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}
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}
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// ListPager assists client code in breaking large list queries into multiple
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// smaller chunks of PageSize or smaller. PageFn is expected to accept a
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// metav1.ListOptions that supports paging and return a list. The pager does
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// not alter the field or label selectors on the initial options list.
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type ListPager struct {
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PageSize int64
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PageFn ListPageFunc
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FullListIfExpired bool
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}
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// New creates a new pager from the provided pager function using the default
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// options. It will fall back to a full list if an expiration error is encountered
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// as a last resort.
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func New(fn ListPageFunc) *ListPager {
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return &ListPager{
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PageSize: defaultPageSize,
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PageFn: fn,
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FullListIfExpired: true,
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}
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}
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// TODO: introduce other types of paging functions - such as those that retrieve from a list
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// of namespaces.
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// List returns a single list object, but attempts to retrieve smaller chunks from the
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// server to reduce the impact on the server. If the chunk attempt fails, it will load
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// the full list instead. The Limit field on options, if unset, will default to the page size.
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func (p *ListPager) List(ctx context.Context, options metav1.ListOptions) (runtime.Object, error) {
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if options.Limit == 0 {
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options.Limit = p.PageSize
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}
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var list *metainternalversion.List
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for {
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obj, err := p.PageFn(ctx, options)
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if err != nil {
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if !errors.IsResourceExpired(err) || !p.FullListIfExpired {
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return nil, err
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}
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// the list expired while we were processing, fall back to a full list
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options.Limit = 0
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options.Continue = ""
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return p.PageFn(ctx, options)
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}
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m, err := meta.ListAccessor(obj)
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if err != nil {
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return nil, fmt.Errorf("returned object must be a list: %v", err)
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}
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// exit early and return the object we got if we haven't processed any pages
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if len(m.GetContinue()) == 0 && list == nil {
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return obj, nil
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}
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// initialize the list and fill its contents
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if list == nil {
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list = &metainternalversion.List{Items: make([]runtime.Object, 0, options.Limit+1)}
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list.ResourceVersion = m.GetResourceVersion()
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list.SelfLink = m.GetSelfLink()
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}
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if err := meta.EachListItem(obj, func(obj runtime.Object) error {
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list.Items = append(list.Items, obj)
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return nil
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}); err != nil {
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return nil, err
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}
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// if we have no more items, return the list
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if len(m.GetContinue()) == 0 {
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return list, nil
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}
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// set the next loop up
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options.Continue = m.GetContinue()
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}
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}
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