mirror of https://github.com/k3s-io/k3s
123 lines
2.7 KiB
Go
123 lines
2.7 KiB
Go
/*
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Copyright 2014 Google Inc. All rights reserved.
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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 registry
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import (
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"sync"
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"sync/atomic"
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"time"
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)
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type Clock interface {
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Now() time.Time
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}
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type SystemClock struct{}
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func (SystemClock) Now() time.Time {
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return time.Now()
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}
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type CachingMinionRegistry struct {
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delegate MinionRegistry
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ttl time.Duration
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minions []string
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lastUpdate int64
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lock sync.RWMutex
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clock Clock
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}
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func NewCachingMinionRegistry(delegate MinionRegistry, ttl time.Duration) (MinionRegistry, error) {
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list, err := delegate.List()
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if err != nil {
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return nil, err
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}
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return &CachingMinionRegistry{
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delegate: delegate,
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ttl: ttl,
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minions: list,
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lastUpdate: time.Now().Unix(),
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clock: SystemClock{},
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}, nil
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}
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func (c *CachingMinionRegistry) List() ([]string, error) {
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if c.expired() {
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err := c.refresh(false)
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if err != nil {
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return c.minions, err
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}
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}
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return c.minions, nil
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}
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func (c *CachingMinionRegistry) Insert(minion string) error {
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err := c.delegate.Insert(minion)
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if err != nil {
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return err
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}
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return c.refresh(true)
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}
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func (c *CachingMinionRegistry) Delete(minion string) error {
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err := c.delegate.Delete(minion)
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if err != nil {
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return err
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}
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return c.refresh(true)
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}
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func (c *CachingMinionRegistry) Contains(minion string) (bool, error) {
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if c.expired() {
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err := c.refresh(false)
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if err != nil {
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return false, err
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}
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}
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// block updates in the middle of a contains.
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c.lock.RLock()
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defer c.lock.RUnlock()
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for _, name := range c.minions {
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if name == minion {
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return true, nil
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}
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}
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return false, nil
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}
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// refresh updates the current store. It double checks expired under lock with the assumption
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// of optimistic concurrency with the other functions.
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func (c *CachingMinionRegistry) refresh(force bool) error {
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c.lock.Lock()
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defer c.lock.Unlock()
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if force || c.expired() {
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var err error
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c.minions, err = c.delegate.List()
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time := c.clock.Now()
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atomic.SwapInt64(&c.lastUpdate, time.Unix())
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return err
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}
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return nil
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}
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func (c *CachingMinionRegistry) expired() bool {
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var unix int64
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atomic.SwapInt64(&unix, c.lastUpdate)
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return c.clock.Now().Sub(time.Unix(c.lastUpdate, 0)) > c.ttl
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}
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