diff --git a/src/common/notifier/notifier.go b/src/common/notifier/notifier.go
index d68b9a997..d88690b8d 100644
--- a/src/common/notifier/notifier.go
+++ b/src/common/notifier/notifier.go
@@ -164,8 +164,8 @@ func (nw *NotificationWatcher) Notify(notification Notification) error {
 		return errors.New("Empty topic can not be notified")
 	}
 
-	nw.RLock()
 	defer nw.RUnlock()
+	nw.RLock()
 
 	var (
 		indexer  HandlerIndexer
diff --git a/src/common/scheduler/policy/alternate_policy.go b/src/common/scheduler/policy/alternate_policy.go
index d57a103b4..e37b466f4 100644
--- a/src/common/scheduler/policy/alternate_policy.go
+++ b/src/common/scheduler/policy/alternate_policy.go
@@ -2,6 +2,8 @@ package policy
 
 import (
 	"errors"
+	"fmt"
+	"sync"
 	"time"
 
 	"github.com/vmware/harbor/src/common/scheduler/task"
@@ -20,16 +22,16 @@ type AlternatePolicyConfiguration struct {
 
 //AlternatePolicy is a policy that repeatedly executing tasks with specified duration during a specified time scope.
 type AlternatePolicy struct {
+	//To sync the related operations.
+	*sync.RWMutex
+
 	//Keep the attached tasks.
-	tasks []task.Task
+	tasks task.Store
 
 	//Policy configurations.
 	config *AlternatePolicyConfiguration
 
-	//Generate time ticks with specified duration.
-	ticker *time.Ticker
-
-	//To indicated whether policy is completed.
+	//To indicated whether policy is enabled or not.
 	isEnabled bool
 
 	//Channel used to send evaluation result signals.
@@ -45,7 +47,8 @@ type AlternatePolicy struct {
 //NewAlternatePolicy is constructor of creating AlternatePolicy.
 func NewAlternatePolicy(config *AlternatePolicyConfiguration) *AlternatePolicy {
 	return &AlternatePolicy{
-		tasks:      []task.Task{},
+		RWMutex:    new(sync.RWMutex),
+		tasks:      task.NewDefaultStore(),
 		config:     config,
 		isEnabled:  false,
 		terminator: make(chan bool),
@@ -64,12 +67,7 @@ func (alp *AlternatePolicy) Name() string {
 
 //Tasks is an implementation of same method in policy interface.
 func (alp *AlternatePolicy) Tasks() []task.Task {
-	copyList := []task.Task{}
-	if alp.tasks != nil && len(alp.tasks) > 0 {
-		copyList = append(copyList, alp.tasks...)
-	}
-
-	return copyList
+	return alp.tasks.GetTasks()
 }
 
 //Done is an implementation of same method in policy interface.
@@ -83,29 +81,42 @@ func (alp *AlternatePolicy) AttachTasks(tasks ...task.Task) error {
 		return errors.New("No tasks can be attached")
 	}
 
-	alp.tasks = append(alp.tasks, tasks...)
+	alp.tasks.AddTasks(tasks...)
 
 	return nil
 }
 
 //Disable is an implementation of same method in policy interface.
 func (alp *AlternatePolicy) Disable() error {
-	//Stop the ticker
-	if alp.ticker != nil {
-		alp.ticker.Stop()
+	alp.Lock()
+	if !alp.isEnabled {
+		alp.Unlock()
+		return fmt.Errorf("Instance of policy %s is not enabled", alp.Name())
 	}
 
+	//Set state to disabled
+	alp.isEnabled = false
+	alp.Unlock()
+
 	//Stop the evaluation goroutine
 	alp.terminator <- true
-	alp.ticker = nil
 
 	return nil
 }
 
 //Evaluate is an implementation of same method in policy interface.
 func (alp *AlternatePolicy) Evaluate() (<-chan bool, error) {
+	//Lock for state changing
+	defer alp.Unlock()
+	alp.Lock()
+
+	//Check if policy instance is still running
+	if alp.isEnabled {
+		return nil, fmt.Errorf("Instance of policy %s is still running", alp.Name())
+	}
+
 	//Keep idempotent
-	if alp.isEnabled && alp.evaluation != nil {
+	if alp.evaluation != nil {
 		return alp.evaluation, nil
 	}
 
@@ -113,9 +124,6 @@ func (alp *AlternatePolicy) Evaluate() (<-chan bool, error) {
 	alp.evaluation = make(chan bool)
 
 	go func() {
-		defer func() {
-			alp.isEnabled = false
-		}()
 		timeNow := time.Now().UTC()
 
 		//Reach the execution time point?
@@ -138,11 +146,19 @@ func (alp *AlternatePolicy) Evaluate() (<-chan bool, error) {
 		alp.evaluation <- true
 
 		//Start the ticker for repeat checking.
-		alp.ticker = time.NewTicker(alp.config.Duration)
+		tk := time.NewTicker(alp.config.Duration)
+		defer func() {
+			if tk != nil {
+				tk.Stop()
+			}
+		}()
+
 		for {
 			select {
-			case <-alp.ticker.C:
-				alp.evaluation <- true
+			case <-tk.C:
+				if alp.IsEnabled() {
+					alp.evaluation <- true
+				}
 			case <-alp.terminator:
 				return
 			}
@@ -174,3 +190,11 @@ func (alp *AlternatePolicy) Equal(p Policy) bool {
 
 	return cfg == nil || (cfg.Duration == cfg2.Duration && cfg.OffsetTime == cfg2.OffsetTime)
 }
+
+//IsEnabled is an implementation of same method in policy interface.
+func (alp *AlternatePolicy) IsEnabled() bool {
+	defer alp.RUnlock()
+	alp.RLock()
+
+	return alp.isEnabled
+}
diff --git a/src/common/scheduler/policy/alternate_policy_test.go b/src/common/scheduler/policy/alternate_policy_test.go
index 5340b04eb..777fe59de 100644
--- a/src/common/scheduler/policy/alternate_policy_test.go
+++ b/src/common/scheduler/policy/alternate_policy_test.go
@@ -1,12 +1,13 @@
 package policy
 
 import (
+	"sync/atomic"
 	"testing"
 	"time"
 )
 
 type fakeTask struct {
-	number int
+	number int32
 }
 
 func (ft *fakeTask) Name() string {
@@ -14,10 +15,14 @@ func (ft *fakeTask) Name() string {
 }
 
 func (ft *fakeTask) Run() error {
-	ft.number++
+	atomic.AddInt32(&(ft.number), 1)
 	return nil
 }
 
+func (ft *fakeTask) Number() int32 {
+	return atomic.LoadInt32(&ft.number)
+}
+
 func TestBasic(t *testing.T) {
 	tp := NewAlternatePolicy(&AlternatePolicyConfiguration{})
 	err := tp.AttachTasks(&fakeTask{number: 100})
@@ -52,18 +57,18 @@ func TestEvaluatePolicy(t *testing.T) {
 		t.Fail()
 	}
 	ch, _ := tp.Evaluate()
-	counter := 0
+	var counter int32
 
 	for i := 0; i < 3; i++ {
 		select {
 		case <-ch:
-			counter++
+			atomic.AddInt32(&counter, 1)
 		case <-time.After(2 * time.Second):
 			continue
 		}
 	}
 
-	if counter != 3 {
+	if atomic.LoadInt32(&counter) != 3 {
 		t.Fail()
 	}
 
@@ -82,7 +87,7 @@ func TestDisablePolicy(t *testing.T) {
 		t.Fail()
 	}
 	ch, _ := tp.Evaluate()
-	counter := 0
+	var counter int32
 	terminate := make(chan bool)
 	defer func() {
 		terminate <- true
@@ -91,7 +96,7 @@ func TestDisablePolicy(t *testing.T) {
 		for {
 			select {
 			case <-ch:
-				counter++
+				atomic.AddInt32(&counter, 1)
 			case <-terminate:
 				return
 			case <-time.After(6 * time.Second):
@@ -106,9 +111,10 @@ func TestDisablePolicy(t *testing.T) {
 	//Waiting for everything is stable
 	<-time.After(1 * time.Second)
 	//Copy value
-	copiedCounter := counter
+	var copiedCounter int32
+	atomic.StoreInt32(&copiedCounter, atomic.LoadInt32(&counter))
 	time.Sleep(2 * time.Second)
-	if counter != copiedCounter {
-		t.Fatalf("Policy is still running after calling Disable() %d=%d", copiedCounter, counter)
+	if atomic.LoadInt32(&counter) != atomic.LoadInt32(&copiedCounter) {
+		t.Fatalf("Policy is still running after calling Disable() %d=%d", atomic.LoadInt32(&copiedCounter), atomic.LoadInt32(&counter))
 	}
 }
diff --git a/src/common/scheduler/policy/policy.go b/src/common/scheduler/policy/policy.go
index 2f50be368..732d56cca 100644
--- a/src/common/scheduler/policy/policy.go
+++ b/src/common/scheduler/policy/policy.go
@@ -41,4 +41,7 @@ type Policy interface {
 	//needs to support this method. If no need, please directly return false to indicate each policies are
 	//different.
 	Equal(p Policy) bool
+
+	//IsEnabled is to indicate whether the policy is enabled or not (disabled).
+	IsEnabled() bool
 }
diff --git a/src/common/scheduler/scheduler.go b/src/common/scheduler/scheduler.go
index db2f15c5c..ff58cd750 100644
--- a/src/common/scheduler/scheduler.go
+++ b/src/common/scheduler/scheduler.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"reflect"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -55,14 +56,20 @@ type Configuration struct {
 
 //Scheduler is designed for scheduling policies.
 type Scheduler struct {
+	//Mutex for sync controling.
+	*sync.RWMutex
+
 	//Related configuration options for scheduler.
 	config *Configuration
 
 	//Store to keep the references of scheduled policies.
 	policies Store
 
-	//Queue for receiving policy unschedule request or complete signal.
-	unscheduleQueue chan string
+	//Queue for receiving policy scheduling request
+	scheduleQueue chan *Watcher
+
+	//Queue for receiving policy unscheduling request or complete signal.
+	unscheduleQueue chan *Watcher
 
 	//Channel for receiving stat metrics.
 	statChan chan *StatItem
@@ -87,14 +94,17 @@ func NewScheduler(config *Configuration) *Scheduler {
 		qSize = config.QueueSize
 	}
 
-	usq := make(chan string, qSize)
+	sq := make(chan *Watcher, qSize)
+	usq := make(chan *Watcher, qSize)
 	stChan := make(chan *StatItem, 4)
 	tc := make(chan bool, 1)
 
-	store := NewConcurrentStore()
+	store := NewDefaultStore()
 	return &Scheduler{
+		RWMutex:         new(sync.RWMutex),
 		config:          config,
 		policies:        store,
+		scheduleQueue:   sq,
 		unscheduleQueue: usq,
 		statChan:        stChan,
 		terminateChan:   tc,
@@ -110,9 +120,14 @@ func NewScheduler(config *Configuration) *Scheduler {
 
 //Start the scheduler damon.
 func (sch *Scheduler) Start() {
+	sch.Lock()
+	defer sch.Unlock()
+
+	//If scheduler is already running
 	if sch.isRunning {
 		return
 	}
+
 	go func() {
 		defer func() {
 			if r := recover(); r != nil {
@@ -120,12 +135,6 @@ func (sch *Scheduler) Start() {
 			}
 		}()
 		defer func() {
-			//Exit and clear.
-			sch.isRunning = false
-			//Stop all watchers.
-			for _, wt := range sch.policies.GetAll() {
-				wt.Stop()
-			}
 			//Clear resources
 			sch.policies.Clear()
 			log.Infof("Policy scheduler stop at %s\n", time.Now().UTC().Format(time.RFC3339))
@@ -135,13 +144,41 @@ func (sch *Scheduler) Start() {
 			case <-sch.terminateChan:
 				//Exit
 				return
-			case name := <-sch.unscheduleQueue:
-				//Unscheduled when policy is completed.
-				if err := sch.UnSchedule(name); err != nil {
-					log.Error(err.Error())
+			case wt := <-sch.scheduleQueue:
+				//If status is stopped, no requests should be served
+				if !sch.IsRunning() {
+					continue
 				}
+				go func(watcher *Watcher) {
+					if watcher != nil && watcher.p != nil {
+						//Enable it.
+						watcher.Start()
+
+						//Update stats and log info.
+						log.Infof("Policy %s is scheduled", watcher.p.Name())
+						sch.statChan <- &StatItem{statSchedulePolicy, 1, nil}
+					}
+				}(wt)
+			case wt := <-sch.unscheduleQueue:
+				//If status is stopped, no requests should be served
+				if !sch.IsRunning() {
+					continue
+				}
+				go func(watcher *Watcher) {
+					if watcher != nil && watcher.IsRunning() {
+						watcher.Stop()
+
+						//Update stats and log info.
+						log.Infof("Policy %s is unscheduled", watcher.p.Name())
+						sch.statChan <- &StatItem{statUnSchedulePolicy, 1, nil}
+					}
+				}(wt)
 			case stat := <-sch.statChan:
 				{
+					//If status is stopped, no requests should be served
+					if !sch.IsRunning() {
+						continue
+					}
 					switch stat.Type {
 					case statSchedulePolicy:
 						sch.stats.PolicyCount += stat.Value
@@ -183,10 +220,18 @@ func (sch *Scheduler) Start() {
 
 //Stop the scheduler damon.
 func (sch *Scheduler) Stop() {
+	//Lock for state changing
+	sch.Lock()
+
+	//Check if the scheduler is running
 	if !sch.isRunning {
+		sch.Unlock()
 		return
 	}
 
+	sch.isRunning = false
+	sch.Unlock()
+
 	//Terminate damon to stop receiving signals.
 	sch.terminateChan <- true
 }
@@ -206,21 +251,15 @@ func (sch *Scheduler) Schedule(scheduledPolicy policy.Policy) error {
 		return errors.New("Policy must attach task(s)")
 	}
 
-	if sch.policies.Exists(scheduledPolicy.Name()) {
-		return fmt.Errorf("Duplicated policy: %s", scheduledPolicy.Name())
+	//Try to schedule the policy.
+	//Keep the policy for future use after it's successfully scheduled.
+	watcher := NewWatcher(scheduledPolicy, sch.statChan, sch.unscheduleQueue)
+	if err := sch.policies.Put(scheduledPolicy.Name(), watcher); err != nil {
+		return err
 	}
 
-	//Schedule the policy.
-	watcher := NewWatcher(scheduledPolicy, sch.statChan, sch.unscheduleQueue)
-	//Enable it.
-	watcher.Start()
-
-	//Keep the policy for future use after it's successfully scheduled.
-	sch.policies.Put(scheduledPolicy.Name(), watcher)
-
-	//Update stats and log info.
-	log.Infof("Policy %s is scheduled", scheduledPolicy.Name())
-	sch.statChan <- &StatItem{statSchedulePolicy, 1, nil}
+	//Schedule the policy
+	sch.scheduleQueue <- watcher
 
 	return nil
 }
@@ -231,28 +270,23 @@ func (sch *Scheduler) UnSchedule(policyName string) error {
 		return errors.New("Empty policy name is invalid")
 	}
 
-	if !sch.policies.Exists(policyName) {
+	//Find the watcher.
+	watcher := sch.policies.Remove(policyName)
+	if watcher == nil {
 		return fmt.Errorf("Policy %s is not existing", policyName)
 	}
 
 	//Unschedule the policy.
-	//Find the watcher.
-	watcher := sch.policies.Remove(policyName)
-	if watcher != nil && watcher.IsRunning() {
-		watcher.Stop()
-
-		//Update stats and log info.
-		log.Infof("Policy %s is unscheduled", policyName)
-		sch.statChan <- &StatItem{statUnSchedulePolicy, 1, nil}
-	} else {
-		log.Warningf("Inconsistent worker status for policy '%s'.\n", policyName)
-	}
+	sch.unscheduleQueue <- watcher
 
 	return nil
 }
 
 //IsRunning to indicate whether the scheduler is running.
 func (sch *Scheduler) IsRunning() bool {
+	sch.RLock()
+	defer sch.RUnlock()
+
 	return sch.isRunning
 }
 
@@ -270,3 +304,8 @@ func (sch *Scheduler) GetPolicy(policyName string) policy.Policy {
 
 	return nil
 }
+
+//PolicyCount returns the count of currently scheduled policies in the scheduler.
+func (sch *Scheduler) PolicyCount() uint32 {
+	return sch.policies.Size()
+}
diff --git a/src/common/scheduler/scheduler_store.go b/src/common/scheduler/scheduler_store.go
index 9a94d3b70..dac97cc9d 100644
--- a/src/common/scheduler/scheduler_store.go
+++ b/src/common/scheduler/scheduler_store.go
@@ -1,16 +1,16 @@
 package scheduler
 
 import (
+	"errors"
+	"fmt"
 	"strings"
 	"sync"
 )
 
 //Store define the basic operations for storing and managing policy watcher.
-//The concrete implementation should consider concurrent supporting scenario.
-//
 type Store interface {
 	//Put a new policy in.
-	Put(key string, value *Watcher)
+	Put(key string, value *Watcher) error
 
 	//Get the corresponding policy with the key.
 	Get(key string) *Watcher
@@ -31,70 +31,74 @@ type Store interface {
 	Clear()
 }
 
-//ConcurrentStore implements Store interface and supports concurrent operations.
-type ConcurrentStore struct {
-	//Read-write mutex to synchronize the data map.
+//DefaultStore implements Store interface to keep the scheduled policies.
+//Not support concurrent sync.
+type DefaultStore struct {
+	//Support sync locking
 	*sync.RWMutex
 
 	//Map used to keep the policy list.
 	data map[string]*Watcher
 }
 
-//NewConcurrentStore is used to create a new store and return the pointer reference.
-func NewConcurrentStore() *ConcurrentStore {
-	mutex := new(sync.RWMutex)
-	data := make(map[string]*Watcher)
-
-	return &ConcurrentStore{mutex, data}
+//NewDefaultStore is used to create a new store and return the pointer reference.
+func NewDefaultStore() *DefaultStore {
+	return &DefaultStore{new(sync.RWMutex), make(map[string]*Watcher)}
 }
 
 //Put a policy into store.
-func (cs *ConcurrentStore) Put(key string, value *Watcher) {
+func (cs *DefaultStore) Put(key string, value *Watcher) error {
 	if strings.TrimSpace(key) == "" || value == nil {
-		return
+		return errors.New("Bad arguments")
 	}
 
+	cs.Lock()
 	defer cs.Unlock()
 
-	cs.Lock()
+	if _, ok := cs.data[key]; ok {
+		return fmt.Errorf("Duplicayed policy with name %s", key)
+	}
+
 	cs.data[key] = value
+
+	return nil
 }
 
 //Get policy via key.
-func (cs *ConcurrentStore) Get(key string) *Watcher {
+func (cs *DefaultStore) Get(key string) *Watcher {
 	if strings.TrimSpace(key) == "" {
 		return nil
 	}
 
+	cs.RLock()
 	defer cs.RUnlock()
 
-	cs.RLock()
 	return cs.data[key]
 }
 
 //Exists is used to check whether or not the key exists in store.
-func (cs *ConcurrentStore) Exists(key string) bool {
+func (cs *DefaultStore) Exists(key string) bool {
 	if strings.TrimSpace(key) == "" {
 		return false
 	}
 
+	cs.RLock()
 	defer cs.RUnlock()
 
-	cs.RLock()
 	_, ok := cs.data[key]
 
 	return ok
 }
 
 //Remove is to delete the specified policy.
-func (cs *ConcurrentStore) Remove(key string) *Watcher {
-	if !cs.Exists(key) {
+func (cs *DefaultStore) Remove(key string) *Watcher {
+	if strings.TrimSpace(key) == "" {
 		return nil
 	}
 
+	cs.Lock()
 	defer cs.Unlock()
 
-	cs.Lock()
 	if wt, ok := cs.data[key]; ok {
 		delete(cs.data, key)
 		return wt
@@ -104,16 +108,20 @@ func (cs *ConcurrentStore) Remove(key string) *Watcher {
 }
 
 //Size return the total count of items in store.
-func (cs *ConcurrentStore) Size() uint32 {
+func (cs *DefaultStore) Size() uint32 {
+	cs.RLock()
+	defer cs.RUnlock()
+
 	return (uint32)(len(cs.data))
 }
 
 //GetAll to get all the items of store.
-func (cs *ConcurrentStore) GetAll() []*Watcher {
+func (cs *DefaultStore) GetAll() []*Watcher {
+	cs.RLock()
+	defer cs.RUnlock()
+
 	all := []*Watcher{}
 
-	defer cs.RUnlock()
-	cs.RLock()
 	for _, v := range cs.data {
 		all = append(all, v)
 	}
@@ -122,15 +130,16 @@ func (cs *ConcurrentStore) GetAll() []*Watcher {
 }
 
 //Clear all the items in store.
-func (cs *ConcurrentStore) Clear() {
-	if cs.Size() == 0 {
+func (cs *DefaultStore) Clear() {
+	cs.Lock()
+	defer cs.Unlock()
+
+	if (uint32)(len(cs.data)) == 0 {
 		return
 	}
 
-	defer cs.Unlock()
-	cs.Lock()
-
-	for k := range cs.data {
+	for k, v := range cs.data {
 		delete(cs.data, k)
+		v.Stop()
 	}
 }
diff --git a/src/common/scheduler/scheduler_store_test.go b/src/common/scheduler/scheduler_store_test.go
index 11dc1d8c2..75aa38bd4 100644
--- a/src/common/scheduler/scheduler_store_test.go
+++ b/src/common/scheduler/scheduler_store_test.go
@@ -5,7 +5,7 @@ import (
 )
 
 func TestPut(t *testing.T) {
-	store := NewConcurrentStore()
+	store := NewDefaultStore()
 	if store == nil {
 		t.Fatal("Failed to creat store instance")
 	}
@@ -17,7 +17,7 @@ func TestPut(t *testing.T) {
 }
 
 func TestGet(t *testing.T) {
-	store := NewConcurrentStore()
+	store := NewDefaultStore()
 	if store == nil {
 		t.Fatal("Failed to creat store instance")
 	}
@@ -29,7 +29,7 @@ func TestGet(t *testing.T) {
 }
 
 func TestRemove(t *testing.T) {
-	store := NewConcurrentStore()
+	store := NewDefaultStore()
 	if store == nil {
 		t.Fatal("Failed to creat store instance")
 	}
@@ -44,7 +44,7 @@ func TestRemove(t *testing.T) {
 }
 
 func TestExisting(t *testing.T) {
-	store := NewConcurrentStore()
+	store := NewDefaultStore()
 	if store == nil {
 		t.Fatal("Failed to creat store instance")
 	}
@@ -58,7 +58,7 @@ func TestExisting(t *testing.T) {
 }
 
 func TestGetAll(t *testing.T) {
-	store := NewConcurrentStore()
+	store := NewDefaultStore()
 	if store == nil {
 		t.Fatal("Failed to creat store instance")
 	}
diff --git a/src/common/scheduler/scheduler_test.go b/src/common/scheduler/scheduler_test.go
index 4e7379494..262f17a3c 100644
--- a/src/common/scheduler/scheduler_test.go
+++ b/src/common/scheduler/scheduler_test.go
@@ -1,6 +1,7 @@
 package scheduler
 
 import (
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -66,8 +67,12 @@ func (fp *fakePolicy) Equal(policy.Policy) bool {
 	return false
 }
 
+func (fp *fakePolicy) IsEnabled() bool {
+	return true
+}
+
 type fakeTask struct {
-	number int
+	number int32
 }
 
 func (ft *fakeTask) Name() string {
@@ -75,10 +80,14 @@ func (ft *fakeTask) Name() string {
 }
 
 func (ft *fakeTask) Run() error {
-	ft.number++
+	atomic.AddInt32(&(ft.number), 1)
 	return nil
 }
 
+func (ft *fakeTask) Number() int32 {
+	return atomic.LoadInt32(&(ft.number))
+}
+
 //Wacher will be tested together with scheduler.
 func TestScheduler(t *testing.T) {
 	DefaultScheduler.Start()
@@ -111,34 +120,30 @@ func TestScheduler(t *testing.T) {
 	}
 
 	time.Sleep(2 * time.Second)
-	if fk.number == 100 {
+	if fk.Number() == 100 {
 		t.Fatal("Task is not triggered")
 	}
-	if DefaultScheduler.stats.Tasks == 0 {
-		t.Fail()
-	}
-	if DefaultScheduler.stats.CompletedTasks == 0 {
-		t.Fail()
-	}
 
 	if DefaultScheduler.UnSchedule(fp.Name()) != nil {
 		t.Fatal("Unschedule policy failed")
 	}
 
-	if DefaultScheduler.policies.Size() != 0 {
+	if DefaultScheduler.PolicyCount() != 0 {
 		t.Fatal("Policy count does not match after calling UnSchedule()")
 	}
+
+	var copiedValue int32
 	<-time.After(1 * time.Second)
-	copiedValue := DefaultScheduler.stats.CompletedTasks
+	atomic.StoreInt32(&copiedValue, fk.Number())
 	<-time.After(2 * time.Second)
 
-	if copiedValue != DefaultScheduler.stats.CompletedTasks {
-		t.Fatalf("Policy is still enabled after calling UnSchedule(),%d=%d", copiedValue, DefaultScheduler.stats.CompletedTasks)
+	if atomic.LoadInt32(&copiedValue) != fk.Number() {
+		t.Fatalf("Policy is still enabled after calling UnSchedule(),%d=%d", atomic.LoadInt32(&copiedValue), fk.Number())
 	}
 
 	DefaultScheduler.Stop()
 	<-time.After(1 * time.Second)
-	if DefaultScheduler.policies.Size() != 0 || DefaultScheduler.IsRunning() {
+	if DefaultScheduler.PolicyCount() != 0 || DefaultScheduler.IsRunning() {
 		t.Fatal("Scheduler is still running after stopping")
 	}
 }
diff --git a/src/common/scheduler/task/task_list.go b/src/common/scheduler/task/task_list.go
new file mode 100644
index 000000000..2c5d4eb40
--- /dev/null
+++ b/src/common/scheduler/task/task_list.go
@@ -0,0 +1,55 @@
+package task
+
+import (
+	"sync"
+)
+
+//Store is designed to keep the tasks.
+type Store interface {
+	//GetTasks return the current existing list in store.
+	GetTasks() []Task
+
+	//AddTasks is used to append tasks to the list.
+	AddTasks(tasks ...Task)
+}
+
+//DefaultStore is the default implemetation of Store interface.
+type DefaultStore struct {
+	//To sync the related operations.
+	*sync.RWMutex
+
+	//The space to keep the tasks.
+	tasks []Task
+}
+
+//NewDefaultStore is constructor method for DefaultStore.
+func NewDefaultStore() *DefaultStore {
+	return &DefaultStore{new(sync.RWMutex), []Task{}}
+}
+
+//GetTasks implements the same method in Store interface.
+func (ds *DefaultStore) GetTasks() []Task {
+	copyList := []Task{}
+
+	ds.RLock()
+	defer ds.RUnlock()
+
+	if ds.tasks != nil && len(ds.tasks) > 0 {
+		copyList = append(copyList, ds.tasks...)
+	}
+
+	return copyList
+}
+
+//AddTasks implements the same method in Store interface.
+func (ds *DefaultStore) AddTasks(tasks ...Task) {
+	//Double confirm.
+	if ds.tasks == nil {
+		ds.tasks = []Task{}
+	}
+
+	ds.Lock()
+	defer ds.Unlock()
+
+	ds.tasks = append(ds.tasks, tasks...)
+}
diff --git a/src/common/scheduler/task/task_list_test.go b/src/common/scheduler/task/task_list_test.go
new file mode 100644
index 000000000..a874ab255
--- /dev/null
+++ b/src/common/scheduler/task/task_list_test.go
@@ -0,0 +1,46 @@
+package task
+
+import (
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestTaskList(t *testing.T) {
+	ds := NewDefaultStore()
+	if ds.tasks == nil {
+		t.Fatal("Failed to create store")
+	}
+
+	go func() {
+		var count int32
+		for {
+			ds.AddTasks(NewScanAllTask())
+			atomic.AddInt32(&count, 1)
+			time.Sleep(100 * time.Millisecond)
+			if atomic.LoadInt32(&count) > 9 {
+				return
+			}
+		}
+	}()
+	go func() {
+		var count int32
+		for {
+			ds.GetTasks()
+			atomic.AddInt32(&count, 1)
+			time.Sleep(100 * time.Millisecond)
+			if atomic.LoadInt32(&count) > 8 {
+				return
+			}
+		}
+	}()
+
+	<-time.After(2 * time.Second)
+
+	var taskCount int32
+	atomic.StoreInt32(&taskCount, (int32)(len(ds.GetTasks())))
+
+	if atomic.LoadInt32(&taskCount) != 10 {
+		t.Fatalf("Expect %d tasks but got %d", 10, atomic.LoadInt32(&taskCount))
+	}
+}
diff --git a/src/common/scheduler/watcher.go b/src/common/scheduler/watcher.go
index 23067dab5..8f133c70b 100644
--- a/src/common/scheduler/watcher.go
+++ b/src/common/scheduler/watcher.go
@@ -6,29 +6,34 @@ import (
 	"github.com/vmware/harbor/src/common/utils/log"
 
 	"fmt"
+	"sync"
 )
 
 //Watcher is an asynchronous runner to provide an evaluation environment for the policy.
 type Watcher struct {
+	//Locker to sync related operations.
+	*sync.RWMutex
+
 	//The target policy.
 	p policy.Policy
 
 	//The channel for receive stop signal.
 	cmdChan chan bool
 
-	//Indicate whether the watch is started and running.
+	//Indicate whether the watcher is started and running.
 	isRunning bool
 
 	//Report stats to scheduler.
 	stats chan *StatItem
 
 	//If policy is automatically completed, report the policy to scheduler.
-	doneChan chan string
+	doneChan chan *Watcher
 }
 
 //NewWatcher is used as a constructor.
-func NewWatcher(p policy.Policy, st chan *StatItem, done chan string) *Watcher {
+func NewWatcher(p policy.Policy, st chan *StatItem, done chan *Watcher) *Watcher {
 	return &Watcher{
+		RWMutex:   new(sync.RWMutex),
 		p:         p,
 		cmdChan:   make(chan bool),
 		isRunning: false,
@@ -39,6 +44,10 @@ func NewWatcher(p policy.Policy, st chan *StatItem, done chan string) *Watcher {
 
 //Start the running.
 func (wc *Watcher) Start() {
+	//Lock for state changing
+	wc.Lock()
+	defer wc.Unlock()
+
 	if wc.isRunning {
 		return
 	}
@@ -54,11 +63,6 @@ func (wc *Watcher) Start() {
 			}
 		}()
 
-		defer func() {
-			wc.isRunning = false
-			log.Infof("Work for policy %s is stopped.\n", wc.p.Name())
-		}()
-
 		evalChan, err := pl.Evaluate()
 		if err != nil {
 			log.Errorf("Failed to evaluate ploicy %s with error: %s\n", pl.Name(), err.Error())
@@ -70,6 +74,11 @@ func (wc *Watcher) Start() {
 			select {
 			case <-evalChan:
 				{
+					//If worker is not running, should not response any requests.
+					if !wc.IsRunning() {
+						continue
+					}
+
 					log.Infof("Receive evaluation signal from policy '%s'\n", pl.Name())
 					//Start to run the attached tasks.
 					for _, t := range pl.Tasks() {
@@ -106,7 +115,7 @@ func (wc *Watcher) Start() {
 					//Policy is automatically completed.
 					//Report policy change stats.
 					if wc.doneChan != nil {
-						wc.doneChan <- wc.p.Name()
+						wc.doneChan <- wc
 					}
 
 					return
@@ -123,19 +132,31 @@ func (wc *Watcher) Start() {
 
 //Stop the running.
 func (wc *Watcher) Stop() {
+	//Lock for state changing
+	wc.Lock()
 	if !wc.isRunning {
+		wc.Unlock()
 		return
 	}
 
+	wc.isRunning = false
+	wc.Unlock()
+
 	//Disable policy.
 	if wc.p != nil {
 		wc.p.Disable()
 	}
+
 	//Stop watcher.
 	wc.cmdChan <- true
+
+	log.Infof("Worker for policy %s is stopped.\n", wc.p.Name())
 }
 
 //IsRunning to indicate if the watcher is still running.
 func (wc *Watcher) IsRunning() bool {
+	wc.RLock()
+	defer wc.RUnlock()
+
 	return wc.isRunning
 }
diff --git a/tests/coverage4gotest.sh b/tests/coverage4gotest.sh
index fa025a6b5..b29ebf66e 100755
--- a/tests/coverage4gotest.sh
+++ b/tests/coverage4gotest.sh
@@ -26,7 +26,7 @@ for package in $packages
 do
 	listDeps $package
 	
-	go test -cover -coverprofile=profile.tmp -coverpkg "$deps" $package
+	go test -race -cover -coverprofile=profile.tmp -coverpkg "$deps" $package
 	if [ -f profile.tmp ]	
 	then
 		cat profile.tmp | tail -n +2 >> profile.cov