Moving client libs to unversioned dir

pkg/client/unversioned/cache/expiration_cache.go

@@ -0,0 +1,191 @@
+/*
+Copyright 2014 The Kubernetes Authors 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 cache
+
+import (
+	"github.com/golang/glog"
+	"k8s.io/kubernetes/pkg/util"
+	"time"
+)
+
+// ExpirationCache implements the store interface
+//	1. All entries are automatically time stamped on insert
+//		a. The key is computed based off the original item/keyFunc
+//		b. The value inserted under that key is the timestamped item
+//	2. Expiration happens lazily on read based on the expiration policy
+//	3. Time-stamps are stripped off unexpired entries before return
+type ExpirationCache struct {
+	cacheStorage     ThreadSafeStore
+	keyFunc          KeyFunc
+	clock            util.Clock
+	expirationPolicy ExpirationPolicy
+}
+
+// ExpirationPolicy dictates when an object expires. Currently only abstracted out
+// so unittests don't rely on the system clock.
+type ExpirationPolicy interface {
+	IsExpired(obj *timestampedEntry) bool
+}
+
+// TTLPolicy implements a ttl based ExpirationPolicy.
+type TTLPolicy struct {
+	//	 >0: Expire entries with an age > ttl
+	//	<=0: Don't expire any entry
+	Ttl time.Duration
+
+	// Clock used to calculate ttl expiration
+	Clock util.Clock
+}
+
+// IsExpired returns true if the given object is older than the ttl, or it can't
+// determine its age.
+func (p *TTLPolicy) IsExpired(obj *timestampedEntry) bool {
+	return p.Ttl > 0 && p.Clock.Since(obj.timestamp) > p.Ttl
+}
+
+// timestampedEntry is the only type allowed in a ExpirationCache.
+type timestampedEntry struct {
+	obj       interface{}
+	timestamp time.Time
+}
+
+// getTimestampedEntry returnes the timestampedEntry stored under the given key.
+func (c *ExpirationCache) getTimestampedEntry(key string) (*timestampedEntry, bool) {
+	item, _ := c.cacheStorage.Get(key)
+	// TODO: Check the cast instead
+	if tsEntry, ok := item.(*timestampedEntry); ok {
+		return tsEntry, true
+	}
+	return nil, false
+}
+
+// getOrExpire retrieves the object from the timestampedEntry iff it hasn't
+// already expired. It kicks-off a go routine to delete expired objects from
+// the store and sets exists=false.
+func (c *ExpirationCache) getOrExpire(key string) (interface{}, bool) {
+	timestampedItem, exists := c.getTimestampedEntry(key)
+	if !exists {
+		return nil, false
+	}
+	if c.expirationPolicy.IsExpired(timestampedItem) {
+		glog.V(4).Infof("Entry %v: %+v has expired", key, timestampedItem.obj)
+		// Since expiration happens lazily on read, don't hold up
+		// the reader trying to acquire a write lock for the delete.
+		// The next reader will retry the delete even if this one
+		// fails; as long as we only return un-expired entries a
+		// reader doesn't need to wait for the result of the delete.
+		go func() {
+			defer util.HandleCrash()
+			c.cacheStorage.Delete(key)
+		}()
+		return nil, false
+	}
+	return timestampedItem.obj, true
+}
+
+// GetByKey returns the item stored under the key, or sets exists=false.
+func (c *ExpirationCache) GetByKey(key string) (interface{}, bool, error) {
+	obj, exists := c.getOrExpire(key)
+	return obj, exists, nil
+}
+
+// Get returns unexpired items. It purges the cache of expired items in the
+// process.
+func (c *ExpirationCache) Get(obj interface{}) (interface{}, bool, error) {
+	key, err := c.keyFunc(obj)
+	if err != nil {
+		return nil, false, KeyError{obj, err}
+	}
+	obj, exists := c.getOrExpire(key)
+	return obj, exists, nil
+}
+
+// List retrieves a list of unexpired items. It purges the cache of expired
+// items in the process.
+func (c *ExpirationCache) List() []interface{} {
+	items := c.cacheStorage.List()
+
+	list := make([]interface{}, 0, len(items))
+	for _, item := range items {
+		obj := item.(*timestampedEntry).obj
+		if key, err := c.keyFunc(obj); err != nil {
+			list = append(list, obj)
+		} else if obj, exists := c.getOrExpire(key); exists {
+			list = append(list, obj)
+		}
+	}
+	return list
+}
+
+// ListKeys returns a list of all keys in the expiration cache.
+func (c *ExpirationCache) ListKeys() []string {
+	return c.cacheStorage.ListKeys()
+}
+
+// Add timestamps an item and inserts it into the cache, overwriting entries
+// that might exist under the same key.
+func (c *ExpirationCache) Add(obj interface{}) error {
+	key, err := c.keyFunc(obj)
+	if err != nil {
+		return KeyError{obj, err}
+	}
+	c.cacheStorage.Add(key, &timestampedEntry{obj, c.clock.Now()})
+	return nil
+}
+
+// Update has not been implemented yet for lack of a use case, so this method
+// simply calls `Add`. This effectively refreshes the timestamp.
+func (c *ExpirationCache) Update(obj interface{}) error {
+	return c.Add(obj)
+}
+
+// Delete removes an item from the cache.
+func (c *ExpirationCache) Delete(obj interface{}) error {
+	key, err := c.keyFunc(obj)
+	if err != nil {
+		return KeyError{obj, err}
+	}
+	c.cacheStorage.Delete(key)
+	return nil
+}
+
+// Replace will convert all items in the given list to TimestampedEntries
+// before attempting the replace operation. The replace operation will
+// delete the contents of the ExpirationCache `c`.
+func (c *ExpirationCache) Replace(list []interface{}) error {
+	items := map[string]interface{}{}
+	ts := c.clock.Now()
+	for _, item := range list {
+		key, err := c.keyFunc(item)
+		if err != nil {
+			return KeyError{item, err}
+		}
+		items[key] = &timestampedEntry{item, ts}
+	}
+	c.cacheStorage.Replace(items)
+	return nil
+}
+
+// NewTTLStore creates and returns a ExpirationCache with a TTLPolicy
+func NewTTLStore(keyFunc KeyFunc, ttl time.Duration) Store {
+	return &ExpirationCache{
+		cacheStorage:     NewThreadSafeStore(Indexers{}, Indices{}),
+		keyFunc:          keyFunc,
+		clock:            util.RealClock{},
+		expirationPolicy: &TTLPolicy{ttl, util.RealClock{}},
+	}
+}