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| // GetPods returns the cached pods if they are not outdated; otherwise, it |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