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caching_registry.go
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/
caching_registry.go
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/*
Copyright 2014 Google Inc. All rights reserved.
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 minion
import (
"sync"
"sync/atomic"
"time"
"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
)
type Clock interface {
Now() time.Time
}
type SystemClock struct{}
func (SystemClock) Now() time.Time {
return time.Now()
}
type CachingRegistry struct {
delegate Registry
ttl time.Duration
nodes *api.MinionList
lastUpdate int64
lock sync.RWMutex
clock Clock
}
func NewCachingRegistry(delegate Registry, ttl time.Duration) (Registry, error) {
list, err := delegate.ListMinions(nil)
if err != nil {
return nil, err
}
return &CachingRegistry{
delegate: delegate,
ttl: ttl,
nodes: list,
lastUpdate: time.Now().Unix(),
clock: SystemClock{},
}, nil
}
func (r *CachingRegistry) GetMinion(ctx api.Context, nodeID string) (*api.Minion, error) {
if r.expired() {
if err := r.refresh(ctx, false); err != nil {
return nil, err
}
}
r.lock.RLock()
defer r.lock.RUnlock()
for _, node := range r.nodes.Items {
if node.ID == nodeID {
return &node, nil
}
}
return nil, ErrDoesNotExist
}
func (r *CachingRegistry) DeleteMinion(ctx api.Context, nodeID string) error {
if err := r.delegate.DeleteMinion(ctx, nodeID); err != nil {
return err
}
return r.refresh(ctx, true)
}
func (r *CachingRegistry) CreateMinion(ctx api.Context, minion *api.Minion) error {
if err := r.delegate.CreateMinion(ctx, minion); err != nil {
return err
}
return r.refresh(ctx, true)
}
func (r *CachingRegistry) ListMinions(ctx api.Context) (*api.MinionList, error) {
if r.expired() {
if err := r.refresh(ctx, false); err != nil {
return r.nodes, err
}
}
return r.nodes, nil
}
func (r *CachingRegistry) expired() bool {
var unix int64
atomic.SwapInt64(&unix, r.lastUpdate)
return r.clock.Now().Sub(time.Unix(r.lastUpdate, 0)) > r.ttl
}
// refresh updates the current store. It double checks expired under lock with the assumption
// of optimistic concurrency with the other functions.
func (r *CachingRegistry) refresh(ctx api.Context, force bool) error {
r.lock.Lock()
defer r.lock.Unlock()
if force || r.expired() {
var err error
r.nodes, err = r.delegate.ListMinions(ctx)
time := r.clock.Now()
atomic.SwapInt64(&r.lastUpdate, time.Unix())
return err
}
return nil
}