Add poller to cache.

pkg/client/cache/store.go

@@ -18,32 +18,47 @@ package cache
 
 import (
 	"sync"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
 )
 
+// Store is a generic object storage interface. Reflector knows how to watch a server
+// and update a store. A generic store is provided, which allows Reflector to be used
+// as a local caching system, and an LRU store, which allows Reflector to work like a
+// queue of items yet to be processed.
+type Store interface {
+	Add(id string, obj interface{})
+	Update(id string, obj interface{})
+	Delete(id string)
+	List() []interface{}
+	Contains() util.StringSet
+	Get(id string) (item interface{}, exists bool)
+}
+
 type cache struct {
 	lock  sync.RWMutex
 	items map[string]interface{}
 }
 
 // Add inserts an item into the cache.
-func (c *cache) Add(ID string, obj interface{}) {
+func (c *cache) Add(id string, obj interface{}) {
 	c.lock.Lock()
 	defer c.lock.Unlock()
-	c.items[ID] = obj
+	c.items[id] = obj
 }
 
 // Update sets an item in the cache to its updated state.
-func (c *cache) Update(ID string, obj interface{}) {
+func (c *cache) Update(id string, obj interface{}) {
 	c.lock.Lock()
 	defer c.lock.Unlock()
-	c.items[ID] = obj
+	c.items[id] = obj
 }
 
 // Delete removes an item from the cache.
-func (c *cache) Delete(ID string, obj interface{}) {
+func (c *cache) Delete(id string) {
 	c.lock.Lock()
 	defer c.lock.Unlock()
-	delete(c.items, ID)
+	delete(c.items, id)
 }
 
 // List returns a list of all the items.
@@ -58,12 +73,25 @@ func (c *cache) List() []interface{} {
 	return list
 }
 
-// Get returns the requested item, or sets exists=false.
-// Get is completely threadsafe as long as you treat all items as immutable.
-func (c *cache) Get(ID string) (item interface{}, exists bool) {
+// Contains returns a util.StringSet containing all IDs of stored the items.
+// This is a snapshot of a moment in time, and one should keep in mind that
+// other go routines can add or remove items after you call this.
+func (c *cache) Contains() util.StringSet {
 	c.lock.RLock()
 	defer c.lock.RUnlock()
-	item, exists = c.items[ID]
+	set := util.StringSet{}
+	for id := range c.items {
+		set.Insert(id)
+	}
+	return set
+}
+
+// Get returns the requested item, or sets exists=false.
+// Get is completely threadsafe as long as you treat all items as immutable.
+func (c *cache) Get(id string) (item interface{}, exists bool) {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	item, exists = c.items[id]
 	return item, exists
 }