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97 lines
2.6 KiB
Go
97 lines
2.6 KiB
Go
/*
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Copyright 2015 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 container
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import (
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"sync"
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"time"
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)
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var (
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// TODO(yifan): Maybe set the them as parameters for NewCache().
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defaultCachePeriod = time.Second * 2
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)
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type RuntimeCache interface {
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GetPods() ([]*Pod, error)
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ForceUpdateIfOlder(time.Time) error
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}
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type podsGetter interface {
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GetPods(bool) ([]*Pod, error)
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}
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// NewRuntimeCache creates a container runtime cache.
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func NewRuntimeCache(getter podsGetter) (RuntimeCache, error) {
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return &runtimeCache{
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getter: getter,
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}, nil
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}
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// runtimeCache caches a list of pods. It records a timestamp (cacheTime) right
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// before updating the pods, so the timestamp is at most as new as the pods
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// (and can be slightly older). The timestamp always moves forward. Callers are
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// expected not to modify the pods returned from GetPods.
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type runtimeCache struct {
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sync.Mutex
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// The underlying container runtime used to update the cache.
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getter podsGetter
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// Last time when cache was updated.
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cacheTime time.Time
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// The content of the cache.
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pods []*Pod
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}
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// GetPods returns the cached pods if they are not outdated; otherwise, it
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// retrieves the latest pods and return them.
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func (r *runtimeCache) GetPods() ([]*Pod, error) {
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r.Lock()
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defer r.Unlock()
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if time.Since(r.cacheTime) > defaultCachePeriod {
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if err := r.updateCache(); err != nil {
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return nil, err
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}
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}
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return r.pods, nil
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}
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func (r *runtimeCache) ForceUpdateIfOlder(minExpectedCacheTime time.Time) error {
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r.Lock()
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defer r.Unlock()
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if r.cacheTime.Before(minExpectedCacheTime) {
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return r.updateCache()
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}
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return nil
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}
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func (r *runtimeCache) updateCache() error {
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pods, timestamp, err := r.getPodsWithTimestamp()
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if err != nil {
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return err
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}
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r.pods, r.cacheTime = pods, timestamp
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return nil
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}
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// getPodsWithTimestamp records a timestamp and retrieves pods from the getter.
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func (r *runtimeCache) getPodsWithTimestamp() ([]*Pod, time.Time, error) {
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// Always record the timestamp before getting the pods to avoid stale pods.
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timestamp := time.Now()
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pods, err := r.getter.GetPods(false)
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return pods, timestamp, err
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}
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