94 lines
2.5 KiB
Go
94 lines
2.5 KiB
Go
/*
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Copyright 2016 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 expiring
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import (
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"container/list"
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"time"
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"k8s.io/utils/clock"
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)
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type elementWithTimestamp struct {
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value interface{}
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added time.Time
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}
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// List tracks elements along with their creation times.
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// This is essentially a linked list with timestamp on each entry, allowing
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// dropping old entries. This struct is not thread safe.
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// TODO(x13n): Migrate to generics once supported by Go stdlib (container/list
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// in particular).
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type List struct {
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lst list.List
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clock clock.PassiveClock
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}
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// NewList creates a new expiring list.
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func NewList() *List {
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return newListWithClock(clock.RealClock{})
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}
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// Warning: This object doesn't support time travel. Subsequent calls to
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// clock.Now are expected to return non-decreasing time values.
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func newListWithClock(clock clock.PassiveClock) *List {
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return &List{
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clock: clock,
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}
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}
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// ToSlice converts the underlying list of elements into a slice.
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func (e *List) ToSlice() []interface{} {
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p := e.lst.Front()
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ps := make([]interface{}, 0, e.lst.Len())
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for p != nil {
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ps = append(ps, p.Value.(*elementWithTimestamp).value)
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p = p.Next()
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}
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return ps
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}
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// ToSliceWithTimestamp is identical to ToSlice, but additionally returns the
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// timestamp of newest entry (or current time if there are no entries).
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func (e *List) ToSliceWithTimestamp() ([]interface{}, time.Time) {
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if e.lst.Len() == 0 {
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return nil, e.clock.Now()
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}
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return e.ToSlice(), e.lst.Back().Value.(*elementWithTimestamp).added
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}
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// RegisterElement adds new element to the list.
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func (e *List) RegisterElement(elem interface{}) {
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e.lst.PushBack(&elementWithTimestamp{elem, e.clock.Now()})
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}
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// DropNotNewerThan removes all elements of the list that are older or exactly
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// as old as the provided time.
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func (e *List) DropNotNewerThan(expiry time.Time) {
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p := e.lst.Front()
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for p != nil {
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if p.Value.(*elementWithTimestamp).added.After(expiry) {
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// First not-expired element on the list, skip checking
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// the rest.
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return
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}
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d := p
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p = p.Next()
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e.lst.Remove(d)
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}
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}
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