Merge pull request #5 from xiangli-cmu/master

clean up tree.go and watcher.go

command.go

@@ -33,7 +33,7 @@ func (c *SetCommand) CommandName() string {
 
 // Set the value of key to value
 func (c *SetCommand) Apply(server *raft.Server) (interface{}, error) {
-	return store.Set(c.Key, c.Value, c.ExpireTime, server.CommitIndex())
+	return etcdStore.Set(c.Key, c.Value, c.ExpireTime, server.CommitIndex())
 }
 
 // TestAndSet command
@@ -51,7 +51,7 @@ func (c *TestAndSetCommand) CommandName() string {
 
 // Set the value of key to value
 func (c *TestAndSetCommand) Apply(server *raft.Server) (interface{}, error) {
-	return store.TestAndSet(c.Key, c.PrevValue, c.Value, c.ExpireTime, server.CommitIndex())
+	return etcdStore.TestAndSet(c.Key, c.PrevValue, c.Value, c.ExpireTime, server.CommitIndex())
 }
 
 // Get command
@@ -66,7 +66,7 @@ func (c *GetCommand) CommandName() string {
 
 // Set the value of key to value
 func (c *GetCommand) Apply(server *raft.Server) (interface{}, error) {
-	res := store.Get(c.Key)
+	res := etcdStore.Get(c.Key)
 	return json.Marshal(res)
 }
 
@@ -82,7 +82,7 @@ func (c *ListCommand) CommandName() string {
 
 // Set the value of key to value
 func (c *ListCommand) Apply(server *raft.Server) (interface{}, error) {
-	return store.List(c.Prefix)
+	return etcdStore.List(c.Prefix)
 }
 
 // Delete command
@@ -97,7 +97,7 @@ func (c *DeleteCommand) CommandName() string {
 
 // Delete the key
 func (c *DeleteCommand) Apply(server *raft.Server) (interface{}, error) {
-	return store.Delete(c.Key, server.CommitIndex())
+	return etcdStore.Delete(c.Key, server.CommitIndex())
 }
 
 // Watch command
@@ -112,13 +112,13 @@ func (c *WatchCommand) CommandName() string {
 }
 
 func (c *WatchCommand) Apply(server *raft.Server) (interface{}, error) {
-	ch := make(chan store.Response, 1)
+	watcher := store.CreateWatcher()
 
 	// add to the watchers list
-	store.AddWatcher(c.Key, ch, c.SinceIndex)
+	etcdStore.AddWatcher(c.Key, watcher, c.SinceIndex)
 
 	// wait for the notification for any changing
-	res := <-ch
+	res := <-watcher.C
 
 	return json.Marshal(res)
 }

etcd.go

@@ -113,9 +113,7 @@ type Info struct {
 
 var server *raft.Server
 var serverTransHandler transHandler
-var logger *log.Logger
+var etcdStore *store.Store
-
-var storeMsg chan string
 
 //------------------------------------------------------------------------------
 //
@@ -129,7 +127,6 @@ var storeMsg chan string
 
 func main() {
 	var err error
-	logger = log.New(os.Stdout, "", log.LstdFlags)
 	flag.Parse()
 
 	// Setup commands.
@@ -162,10 +159,10 @@ func main() {
 	serverTransHandler = createTranHandler(st)
 
 	// Setup new raft server.
-	s := store.CreateStore(maxSize)
+	etcdStore = store.CreateStore(maxSize)
 
 	// create raft server
-	server, err = raft.NewServer(name, dirPath, serverTransHandler, s, nil)
+	server, err = raft.NewServer(name, dirPath, serverTransHandler, etcdStore, nil)
 
 	if err != nil {
 		fatal("%v", err)
@@ -226,7 +223,7 @@ func main() {
 
 	if webPort != -1 {
 		// start web
-		s.SetMessager(&storeMsg)
+		etcdStore.SetMessager(&storeMsg)
 		go webHelper()
 		go web.Start(server, webPort)
 	}

handlers.go

@@ -38,6 +38,7 @@ func VoteHttpHandler(w http.ResponseWriter, req *http.Request) {
 func AppendEntriesHttpHandler(w http.ResponseWriter, req *http.Request) {
 	aereq := &raft.AppendEntriesRequest{}
 	err := decodeJsonRequest(req, aereq)
+	
 	if err == nil {
 		debug("[recv] POST http://%s/log/append [%d]", server.Name(), len(aereq.Entries))
 		if resp := server.AppendEntries(aereq); resp != nil {
@@ -121,7 +122,7 @@ func SetHttpHandler(w *http.ResponseWriter, req *http.Request) {
 		duration, err := strconv.Atoi(strDuration)
 
 		if err != nil {
-			warn("raftd: Bad duration: %v", err)
+			warn("Bad duration: %v", err)
 			(*w).WriteHeader(http.StatusInternalServerError)
 			return
 		}
@@ -150,7 +151,7 @@ func TestAndSetHttpHandler(w http.ResponseWriter, req *http.Request) {
 		duration, err := strconv.Atoi(strDuration)
 
 		if err != nil {
-			warn("raftd: Bad duration: %v", err)
+			warn("Bad duration: %v", err)
 			w.WriteHeader(http.StatusInternalServerError)
 			return
 		}
@@ -266,7 +267,7 @@ func ListHttpHandler(w http.ResponseWriter, req *http.Request) {
 	command.Prefix = prefix
 
 	if body, err := command.Apply(server); err != nil {
-		warn("raftd: Unable to write file: %v", err)
+		warn("Unable to write file: %v", err)
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	} else {
@@ -309,7 +310,7 @@ func WatchHttpHandler(w http.ResponseWriter, req *http.Request) {
 	}
 
 	if body, err := command.Apply(server); err != nil {
-		warn("raftd: Unable to write file: %v", err)
+		warn("Unable to write file: %v", err)
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	} else {

store/store.go

@@ -4,87 +4,107 @@ import (
 	"encoding/json"
 	"fmt"
 	"path"
-	"time"
 	"strconv"
+	"time"
 )
 
-// global store
+//------------------------------------------------------------------------------
-var s *Store
+//
-
+// Typedefs
-// CONSTANTS
+//
-const (
+//------------------------------------------------------------------------------
-	ERROR = -1 + iota
-	SET
-	DELETE
-	GET
-)
-
-var PERMANENT = time.Unix(0, 0)
 
+// The main struct of the Key-Value store
 type Store struct {
-	// // use the build-in hash map as the key-value store structure
-	// Nodes map[string]Node `json:"nodes"`
 
-	// use treeMap as the key-value stroe structure
+	// key-value store structure
 	Tree *tree
-	// the string channel to send messages to the outside world
+
-	// now we use it to send changes to the hub of the web service
+	// WatcherHub is where we register all the clients
+	// who issue a watch request
+	watcher *WatcherHub
+
+	// The string channel to send messages to the outside world
+	// Now we use it to send changes to the hub of the web service
 	messager *chan string
 
-	// 
+	// A map to keep the recent response to the clients
 	ResponseMap map[string]Response
 
-	//
+	// The max number of the recent responses we can record
 	ResponseMaxSize int
 
+	// The current number of the recent responses we have recorded
 	ResponseCurrSize uint
 
-	// at some point, we may need to compact the Response
+	// The index of the first recent responses we have
 	ResponseStartIndex uint64
 
-	// current Index
+	// Current index of the raft machine
 	Index uint64
 }
 
+// A Node represents a Value in the Key-Value pair in the store
+// It has its value, expire time and a channel used to update the
+// expire time (since we do countdown in a go routine, we need to
+// communicate with it via channel)
 type Node struct {
+	// The string value of the node
 	Value string `json:"value"`
 
-	// if the node is a permanent one the ExprieTime will be Unix(0,0)
+	// If the node is a permanent one the ExprieTime will be Unix(0,0)
 	// Otherwise after the expireTime, the node will be deleted
 	ExpireTime time.Time `json:"expireTime"`
 
-	// a channel to update the expireTime of the node
+	// A channel to update the expireTime of the node
 	update chan time.Time `json:"-"`
 }
 
+// The response from the store to the user who issue a command
 type Response struct {
-	Action   int    `json:"action"`
+	Action    string `json:"action"`
 	Key       string `json:"key"`
 	PrevValue string `json:"prevValue"`
 	Value     string `json:"value"`
 
-	// if the key existed before the action, this field should be true
+	// If the key existed before the action, this field should be true
-	// if the key did not exist before the action, this field should be false
+	// If the key did not exist before the action, this field should be false
 	Exist bool `json:"exist"`
 
 	Expiration time.Time `json:"expiration"`
 
-	// countdown until expiration in seconds
+	// Time to live in second
 	TTL int64 `json:"ttl"`
 
+	// The command index of the raft machine when the command is executed
 	Index uint64 `json:"index"`
 }
 
+// A listNode represent the simplest Key-Value pair with its type
+// It is only used when do list opeartion
+// We want to have a file system like store, thus we distingush "file"
+// and "directory"
 type ListNode struct {
 	Key   string
 	Value string
 	Type  string
 }
 
-// make a new stroe
+var PERMANENT = time.Unix(0, 0)
+
+//------------------------------------------------------------------------------
+//
+// Methods
+//
+//------------------------------------------------------------------------------
+
+// Create a new stroe
+// Arguement max is the max number of response we want to record
 func CreateStore(max int) *Store {
-	s = new(Store)
+	s := new(Store)
+
 	s.messager = nil
+
 	s.ResponseMap = make(map[string]Response)
 	s.ResponseStartIndex = 0
 	s.ResponseMaxSize = max
@@ -92,9 +112,9 @@ func CreateStore(max int) *Store {
 
 	s.Tree = &tree{
 		&treeNode{
-			Node {
+			Node{
 				"/",
-				time.Unix(0,0),
+				time.Unix(0, 0),
 				nil,
 			},
 			true,
@@ -102,88 +122,87 @@ func CreateStore(max int) *Store {
 		},
 	}
 
+	s.watcher = createWatcherHub()
+
 	return s
 }
 
-// return a pointer to the store
+// Set the messager of the store
-func GetStore() *Store {
-	return s
-}
-
-// set the messager of the store
 func (s *Store) SetMessager(messager *chan string) {
 	s.messager = messager
 }
 
-// set the key to value, return the old value if the key exists
+// Set the key to value with expiration time
-func Set(key string, value string, expireTime time.Time, index uint64) ([]byte, error) {
+func (s *Store) Set(key string, value string, expireTime time.Time, index uint64) ([]byte, error) {
 
-	//update index
+	//Update index
 	s.Index = index
 
-	key = "/" + key
+	key = path.Clean("/" + key)
 
-	key = path.Clean(key)
+	isExpire := !expireTime.Equal(PERMANENT)
 
-	var isExpire bool = false
+	// When the slow follower receive the set command
-
-	isExpire = !expireTime.Equal(PERMANENT)
-
-	// when the slow follower receive the set command
 	// the key may be expired, we should not add the node
 	// also if the node exist, we need to delete the node
 	if isExpire && expireTime.Sub(time.Now()) < 0 {
-		return Delete(key, index)
+		return s.Delete(key, index)
 	}
 
 	var TTL int64
-	// update ttl
+
+	// Update ttl
 	if isExpire {
 		TTL = int64(expireTime.Sub(time.Now()) / time.Second)
 	} else {
+		// For permanent value, we set ttl to -1
 		TTL = -1
 	}
 
-	// get the node
+	// Get the node
 	node, ok := s.Tree.get(key)
 
 	if ok {
-		// if node is not permanent before
+		// Update when node exists
-		// update its expireTime
+
+		// Node is not permanent
 		if !node.ExpireTime.Equal(PERMANENT) {
 
+			// If node is not permanent
+			// Update its expireTime
 			node.update <- expireTime
 
 		} else {
-			// if we want the permanent node to have expire time
+
-			// we need to create a chan and create a go routine
+			// If we want the permanent node to have expire time
+			// We need to create create a go routine with a channel
 			if isExpire {
 				node.update = make(chan time.Time)
-				go expire(key, node.update, expireTime)
+				go s.monitorExpiration(key, node.update, expireTime)
 			}
 
 		}
 
-		// update the information of the node
+		// Update the information of the node
 		s.Tree.set(key, Node{value, expireTime, node.update})
 
-		resp := Response{SET, key, node.Value, value, true, expireTime, TTL, index}
+		resp := Response{"SET", key, node.Value, value, true, expireTime, TTL, index}
+
+		s.watcher.notify(resp)
 
 		msg, err := json.Marshal(resp)
 
-		notify(resp)
+		// Send to the messager
-
-		// send to the messager
 		if s.messager != nil && err == nil {
 
 			*s.messager <- string(msg)
 		}
 
-		updateMap(index, &resp)
+		s.addToResponseMap(index, &resp)
 
 		return msg, err
 
-	// add new node
+		// Add new node
 	} else {
 
 		update := make(chan time.Time)
@@ -191,32 +210,31 @@ func Set(key string, value string, expireTime time.Time, index uint64) ([]byte,
 		s.Tree.set(key, Node{value, expireTime, update})
 
 		if isExpire {
-			go expire(key, update, expireTime)
+			go s.monitorExpiration(key, update, expireTime)
 		}
 
-		resp := Response{SET, key, "", value, false, expireTime, TTL, index}
+		resp := Response{"SET", key, "", value, false, expireTime, TTL, index}
 
 		msg, err := json.Marshal(resp)
 
-		// nofity the watcher
+		// Nofity the watcher
-		notify(resp)
+		s.watcher.notify(resp)
 
-		// notify the web interface
+		// Send to the messager
 		if s.messager != nil && err == nil {
 
 			*s.messager <- string(msg)
 		}
 
-		updateMap(index, &resp)
+		s.addToResponseMap(index, &resp)
 		return msg, err
 	}
 }
 
-// get the value of the key
+// Get the value of the key
-func Get(key string) Response {
+func (s *Store) Get(key string) Response {
-	key = "/" + key
 
-	key = path.Clean(key)
+	key = path.Clean("/" + key)
 
 	node, ok := s.Tree.get(key)
 
@@ -226,22 +244,24 @@ func Get(key string) Response {
 
 		isExpire = !node.ExpireTime.Equal(PERMANENT)
 
-		// update ttl
+		// Update ttl
 		if isExpire {
 			TTL = int64(node.ExpireTime.Sub(time.Now()) / time.Second)
 		} else {
 			TTL = -1
 		}
 
-		return Response{GET, key, node.Value, node.Value, true, node.ExpireTime, TTL, s.Index}
+		return Response{"GET", key, node.Value, node.Value, true, node.ExpireTime, TTL, s.Index}
-	} else {
 
-		return Response{GET, key, "", "", false, time.Unix(0, 0), 0, s.Index}
+	} else {
+		// we do not found the key
+		return Response{"GET", key, "", "", false, time.Unix(0, 0), 0, s.Index}
 	}
 }
 
-// // List all the item in the prefix
+// List all the item in the prefix
-func List(prefix string) ([]byte, error) {
+func (s *Store) List(prefix string) ([]byte, error) {
+
 	nodes, keys, dirs, ok := s.Tree.list(prefix)
 
 	var ln []ListNode
@@ -256,15 +276,14 @@ func List(prefix string) ([]byte, error) {
 	return json.Marshal(ln)
 }
 
-// delete the key
+// Delete the key
-func Delete(key string, index uint64) ([]byte, error) {
+func (s *Store) Delete(key string, index uint64) ([]byte, error) {
-	//update index
-	key = "/" + key
 
+	key = path.Clean("/" + key)
+
+	//Update index
 	s.Index = index
 
-	key = path.Clean(key)
-
 	node, ok := s.Tree.get(key)
 
 	if ok {
@@ -275,17 +294,17 @@ func Delete(key string, index uint64) ([]byte, error) {
 
 		} else {
 
-			// kill the expire go routine
+			// Kill the expire go routine
 			node.update <- PERMANENT
 			s.Tree.delete(key)
 
 		}
 
-		resp := Response{DELETE, key, node.Value, "", true, node.ExpireTime, 0, index}
+		resp := Response{"DELETE", key, node.Value, "", true, node.ExpireTime, 0, index}
 
 		msg, err := json.Marshal(resp)
 
-		notify(resp)
+		s.watcher.notify(resp)
 
 		// notify the messager
 		if s.messager != nil && err == nil {
@@ -293,50 +312,70 @@ func Delete(key string, index uint64) ([]byte, error) {
 			*s.messager <- string(msg)
 		}
 
-		updateMap(index, &resp)
+		s.addToResponseMap(index, &resp)
+
 		return msg, err
 
 	} else {
 
-		resp := Response{DELETE, key, "", "", false, time.Unix(0, 0), 0, index}
+		resp := Response{"DELETE", key, "", "", false, time.Unix(0, 0), 0, index}
 
-		updateMap(index, &resp)
+		s.addToResponseMap(index, &resp)
 
 		return json.Marshal(resp)
 	}
 }
 
-// set the value of the key to the value if the given prevValue is equal to the value of the key
+// Set the value of the key to the value if the given prevValue is equal to the value of the key
-func TestAndSet(key string, prevValue string, value string, expireTime time.Time, index uint64) ([]byte, error) {
+func (s *Store) TestAndSet(key string, prevValue string, value string, expireTime time.Time, index uint64) ([]byte, error) {
-	resp := Get(key)
+	resp := s.Get(key)
 
 	if resp.PrevValue == prevValue {
-		return Set(key, value, expireTime, index)
+
+		// If test success, do set
+		return s.Set(key, value, expireTime, index)
 	} else {
+
+		// If fails, return the result of get which contains the current
+		// status of the key-value pair
 		return json.Marshal(resp)
 	}
+
 }
 
-// should be used as a go routine to delete the key when it expires
+// Add a channel to the watchHub.
-func expire(key string, update chan time.Time, expireTime time.Time) {
+// The watchHub will send response to the channel when any key under the prefix
+// changes [since the sinceIndex if given]
+func (s *Store) AddWatcher(prefix string, watcher *Watcher, sinceIndex uint64) error {
+	return s.watcher.addWatcher(prefix, watcher, sinceIndex, s.ResponseStartIndex, s.Index, &s.ResponseMap)
+}
+
+// This function should be created as a go routine to delete the key-value pair
+// when it reaches expiration time
+
+func (s *Store) monitorExpiration(key string, update chan time.Time, expireTime time.Time) {
+
 	duration := expireTime.Sub(time.Now())
 
 	for {
 		select {
-		// timeout delete the node
+
+		// Timeout delete the node
 		case <-time.After(duration):
 			node, ok := s.Tree.get(key)
+
 			if !ok {
 				return
+
 			} else {
 
 				s.Tree.delete(key)
 
-				resp := Response{DELETE, key, node.Value, "", true, node.ExpireTime, 0, s.Index}
+				resp := Response{"DELETE", key, node.Value, "", true, node.ExpireTime, 0, s.Index}
 
 				msg, err := json.Marshal(resp)
 
-				notify(resp)
+				s.watcher.notify(resp)
 
 				// notify the messager
 				if s.messager != nil && err == nil {
@@ -349,21 +388,25 @@ func expire(key string, update chan time.Time, expireTime time.Time) {
 			}
 
 		case updateTime := <-update:
-			//update duration
+			// Update duration
-			// if the node become a permanent one, the go routine is
+			// If the node become a permanent one, the go routine is
 			// not needed
 			if updateTime.Equal(PERMANENT) {
-				fmt.Println("permanent")
 				return
 			}
-			// update duration
+
+			// Update duration
 			duration = updateTime.Sub(time.Now())
 		}
 	}
 }
 
-func updateMap(index uint64, resp *Response) {
+// When we receive a command that will change the state of the key-value store
+// We will add the result of it to the ResponseMap for the use of watch command
+// Also we may remove the oldest response when we add new one
+func (s *Store) addToResponseMap(index uint64, resp *Response) {
 
+	// zero case
 	if s.ResponseMaxSize == 0 {
 		return
 	}
@@ -372,11 +415,13 @@ func updateMap(index uint64, resp *Response) {
 	s.ResponseMap[strIndex] = *resp
 
 	// unlimited
-	if s.ResponseMaxSize < 0{
+	if s.ResponseMaxSize < 0 {
 		s.ResponseCurrSize++
 		return
 	}
 
+	// if we reach the max point, we need to delete the most latest
+	// response and update the startIndex
 	if s.ResponseCurrSize == uint(s.ResponseMaxSize) {
 		s.ResponseStartIndex++
 		delete(s.ResponseMap, strconv.FormatUint(s.ResponseStartIndex, 10))
@@ -385,8 +430,7 @@ func updateMap(index uint64, resp *Response) {
 	}
 }
 
-
+// Save the current state of the storage system
-// save the current state of the storage system
 func (s *Store) Save() ([]byte, error) {
 	b, err := json.Marshal(s)
 	if err != nil {
@@ -396,31 +440,35 @@ func (s *Store) Save() ([]byte, error) {
 	return b, nil
 }
 
-// recovery the state of the stroage system from a previous state
+// Recovery the state of the stroage system from a previous state
 func (s *Store) Recovery(state []byte) error {
 	err := json.Unmarshal(state, s)
 
-	// clean the expired nodes
+	// The only thing need to change after the recovery is the
-	clean()
+	// node with expiration time, we need to delete all the node
+	// that have been expired and setup go routines to monitor the
+	// other ones
+	s.checkExpiration()
 
 	return err
 }
 
-// clean all expired keys
+// Clean the expired nodes
-func clean() {
+// Set up go routines to mon
-	s.Tree.traverse(cleanNode, false)
+func (s *Store) checkExpiration() {
+	s.Tree.traverse(s.checkNode, false)
 }
 
-
+// Check each node
-func cleanNode(key string, node *Node) {
+func (s *Store) checkNode(key string, node *Node) {
 
 	if node.ExpireTime.Equal(PERMANENT) {
 		return
 	} else {
-
 		if node.ExpireTime.Sub(time.Now()) >= time.Second {
+
 			node.update = make(chan time.Time)
-			go expire(key, node.update, node.ExpireTime)
+			go s.monitorExpiration(key, node.update, node.ExpireTime)
 
 		} else {
 			// we should delete this node

store/watcher.go

@@ -5,43 +5,44 @@ import (
 	"strconv"
 	"strings"
 )
+//------------------------------------------------------------------------------
+//
+// Typedefs
+//
+//------------------------------------------------------------------------------
 
+// WatcherHub is where the client register its watcher
 type WatcherHub struct {
-	watchers map[string][]Watcher
+	watchers map[string][]*Watcher
 }
 
+// Currently watcher only contains a response channel
 type Watcher struct {
-	c     chan Response
+	C     chan Response
 }
 
-// global watcher
+// Create a new watcherHub
-var w *WatcherHub
-
-// init the global watcher
-func init() {
-	w = createWatcherHub()
-}
-
-// create a new watcher
 func createWatcherHub() *WatcherHub {
 	w := new(WatcherHub)
-	w.watchers = make(map[string][]Watcher)
+	w.watchers = make(map[string][]*Watcher)
 	return w
 }
 
-func GetWatcherHub() *WatcherHub {
+// Create a new watcher
-	return w
+func CreateWatcher() *Watcher {
+	return &Watcher{C: make(chan Response, 1)}
 }
 
-// register a function with channel and prefix to the watcher
+// Add a watcher to the watcherHub
-func AddWatcher(prefix string, c chan Response, sinceIndex uint64) error {
+func (w *WatcherHub) addWatcher(prefix string, watcher *Watcher, sinceIndex uint64, 
+	responseStartIndex uint64, currentIndex uint64, resMap *map[string]Response) error {
 
-	prefix = "/" + path.Clean(prefix)
+	prefix = path.Clean("/" + prefix)
 
-	if sinceIndex != 0 && sinceIndex >= s.ResponseStartIndex {
+	if sinceIndex != 0 && sinceIndex >= responseStartIndex {
-		for i := sinceIndex; i <= s.Index; i++ {
+		for i := sinceIndex; i <= currentIndex; i++ {
-			if check(prefix, i) {
+			if checkResponse(prefix, i, resMap) {
-				c <- s.ResponseMap[strconv.FormatUint(i, 10)]
+				watcher.C <- (*resMap)[strconv.FormatUint(i, 10)]
 				return nil
 			}
 		}
@@ -51,25 +52,21 @@ func AddWatcher(prefix string, c chan Response, sinceIndex uint64) error {
 
 	if !ok {
 
-		w.watchers[prefix] = make([]Watcher, 0)
+		w.watchers[prefix] = make([]*Watcher, 0)
-
-		watcher := Watcher{c}
 
 		w.watchers[prefix] = append(w.watchers[prefix], watcher)
 	} else {
 
-		watcher := Watcher{c}
-
 		w.watchers[prefix] = append(w.watchers[prefix], watcher)
 	}
 
 	return nil
 }
 
-// check if the response has what we are watching
+// Check if the response has what we are watching
-func check(prefix string, index uint64) bool {
+func checkResponse(prefix string, index uint64, resMap *map[string]Response) bool {
 
-	resp, ok := s.ResponseMap[strconv.FormatUint(index, 10)]
+	resp, ok := (*resMap)[strconv.FormatUint(index, 10)]
 
 	if !ok {
 		// not storage system command
@@ -89,8 +86,8 @@ func check(prefix string, index uint64) bool {
 }
 
 
-// notify the watcher a action happened
+// Notify the watcher a action happened
-func notify(resp Response) error {
+func (w *WatcherHub) notify(resp Response) error {
 	resp.Key = path.Clean(resp.Key)
 
 	segments := strings.Split(resp.Key, "/")
@@ -104,10 +101,10 @@ func notify(resp Response) error {
 
 		if ok {
 
-			newWatchers := make([]Watcher, 0)
+			newWatchers := make([]*Watcher, 0)
 			// notify all the watchers
 			for _, watcher := range watchers {
-				watcher.c <- resp
+				watcher.C <- resp
 			}
 
 			if len(newWatchers) == 0 {