diff --git a/internal/indexnode/task_scheduler.go b/internal/indexnode/task_scheduler.go
index 90d1356a776a5cf43a440f7315aa94b54f7101d6..fb693340459ff054ec2fcac5eb539b17e2f0acd4 100644
--- a/internal/indexnode/task_scheduler.go
+++ b/internal/indexnode/task_scheduler.go
@@ -26,6 +26,7 @@ import (
 	oplog "github.com/opentracing/opentracing-go/log"
 )
 
+// TaskQueue is a queue used to store tasks.
 type TaskQueue interface {
 	utChan() <-chan int
 	utEmpty() bool
@@ -39,6 +40,7 @@ type TaskQueue interface {
 	//tryToRemoveUselessIndexBuildTask(indexID UniqueID) []UniqueID
 }
 
+// BaseTaskQueue is a basic instance of TaskQueue.
 type BaseTaskQueue struct {
 	unissuedTasks *list.List
 	activeTasks   map[UniqueID]task
@@ -89,6 +91,7 @@ func (queue *BaseTaskQueue) addUnissuedTask(t task) error {
 //	return queue.unissuedTasks.Front().Value.(task)
 //}
 
+// PopUnissuedTask pops a task from tasks queue.
 func (queue *BaseTaskQueue) PopUnissuedTask() task {
 	queue.utLock.Lock()
 	defer queue.utLock.Unlock()
@@ -103,6 +106,7 @@ func (queue *BaseTaskQueue) PopUnissuedTask() task {
 	return ft.Value.(task)
 }
 
+// AddActiveTask adds a task to activeTasks.
 func (queue *BaseTaskQueue) AddActiveTask(t task) {
 	queue.atLock.Lock()
 	defer queue.atLock.Unlock()
@@ -116,6 +120,7 @@ func (queue *BaseTaskQueue) AddActiveTask(t task) {
 	queue.activeTasks[tID] = t
 }
 
+// PopActiveTask tasks out a task from activateTask and the task will be executed.
 func (queue *BaseTaskQueue) PopActiveTask(tID UniqueID) task {
 	queue.atLock.Lock()
 	defer queue.atLock.Unlock()
@@ -150,6 +155,7 @@ func (queue *BaseTaskQueue) PopActiveTask(tID UniqueID) task {
 //	return indexBuildIDs
 //}
 
+// Enqueue adds a task to TaskQueue.
 func (queue *BaseTaskQueue) Enqueue(t task) error {
 	err := t.OnEnqueue()
 	if err != nil {
@@ -158,10 +164,12 @@ func (queue *BaseTaskQueue) Enqueue(t task) error {
 	return queue.addUnissuedTask(t)
 }
 
+// IndexBuildTaskQueue is a task queue used to store building index tasks.
 type IndexBuildTaskQueue struct {
 	BaseTaskQueue
 }
 
+// NewIndexBuildTaskQueue creates a new IndexBuildTaskQueue.
 func NewIndexBuildTaskQueue(sched *TaskScheduler) *IndexBuildTaskQueue {
 	return &IndexBuildTaskQueue{
 		BaseTaskQueue: BaseTaskQueue{
@@ -174,6 +182,7 @@ func NewIndexBuildTaskQueue(sched *TaskScheduler) *IndexBuildTaskQueue {
 	}
 }
 
+// TaskScheduler is a scheduler of indexing tasks.
 type TaskScheduler struct {
 	IndexBuildQueue TaskQueue
 
@@ -184,6 +193,7 @@ type TaskScheduler struct {
 	cancel        context.CancelFunc
 }
 
+// NewTaskScheduler creates a new task scheduler of indexing tasks.
 func NewTaskScheduler(ctx context.Context,
 	kv kv.BaseKV) (*TaskScheduler, error) {
 	ctx1, cancel := context.WithCancel(ctx)
@@ -280,6 +290,7 @@ func (sched *TaskScheduler) indexBuildLoop() {
 	}
 }
 
+// Start stats the task scheduler of indexing tasks.
 func (sched *TaskScheduler) Start() error {
 
 	sched.wg.Add(1)
@@ -287,6 +298,7 @@ func (sched *TaskScheduler) Start() error {
 	return nil
 }
 
+// Close closes the task scheduler of indexing tasks.
 func (sched *TaskScheduler) Close() {
 	sched.cancel()
 	sched.wg.Wait()