diff --git a/base/task/monitor.go b/base/task/monitor.go
deleted file mode 100644
index 6c70a89e5..000000000
--- a/base/task/monitor.go
+++ /dev/null
@@ -1,256 +0,0 @@
-// Copyright 2021 gorse Project Authors
-//
-// 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 task
-
-import (
-	"sort"
-	"strings"
-	"sync"
-	"time"
-
-	mapset "github.com/deckarep/golang-set/v2"
-)
-
-type Status string
-
-const (
-	StatusPending   Status = "Pending"
-	StatusComplete  Status = "Complete"
-	StatusRunning   Status = "Running"
-	StatusSuspended Status = "Suspended"
-	StatusFailed    Status = "Failed"
-)
-
-// Task progress information.
-type Task struct {
-	Name       string
-	Status     Status
-	Done       int
-	Total      int
-	StartTime  time.Time
-	FinishTime time.Time
-	Error      string
-}
-
-func NewTask(name string, total int) *Task {
-	return &Task{
-		Name:       name,
-		Status:     StatusRunning,
-		Done:       0,
-		Total:      total,
-		StartTime:  time.Now(),
-		FinishTime: time.Time{},
-	}
-}
-
-func (t *Task) Update(done int) {
-	t.Done = done
-	t.Status = StatusRunning
-}
-
-func (t *Task) Add(done int) {
-	if t != nil {
-		t.Status = StatusRunning
-		t.Done += done
-	}
-}
-
-func (t *Task) Finish() {
-	if t != nil {
-		t.Status = StatusComplete
-		t.Done = t.Total
-		t.FinishTime = time.Now()
-	}
-}
-
-func (t *Task) Suspend(flag bool) {
-	if t != nil {
-		if flag {
-			t.Status = StatusSuspended
-		} else {
-			t.Status = StatusRunning
-		}
-	}
-}
-
-func (t *Task) Fail(err string) {
-	if t != nil {
-		t.Error = err
-		t.Status = StatusFailed
-	}
-}
-
-func (t *Task) SubTask(done int) *SubTask {
-	if t == nil {
-		return nil
-	}
-	return &SubTask{
-		Parent: t,
-		Start:  t.Done,
-		End:    t.Done + done,
-	}
-}
-
-type SubTask struct {
-	Start  int
-	End    int
-	Parent *Task
-}
-
-func (t *SubTask) Add(done int) {
-	if t != nil {
-		t.Parent.Add(done)
-	}
-}
-
-func (t *SubTask) Finish() {
-	if t != nil {
-		t.Parent.Update(t.End)
-	}
-}
-
-// Monitor monitors the progress of all tasks.
-type Monitor struct {
-	TaskLock sync.Mutex
-	Tasks    map[string]*Task
-}
-
-// NewTaskMonitor creates a Monitor and add pending tasks.
-func NewTaskMonitor() *Monitor {
-	return &Monitor{
-		Tasks: make(map[string]*Task),
-	}
-}
-
-func (tm *Monitor) GetTask(name string) *Task {
-	tm.TaskLock.Lock()
-	defer tm.TaskLock.Unlock()
-	return tm.Tasks[name]
-}
-
-// Pending a task.
-func (tm *Monitor) Pending(name string) {
-	tm.TaskLock.Lock()
-	defer tm.TaskLock.Unlock()
-	tm.Tasks[name] = &Task{
-		Name:   name,
-		Status: StatusPending,
-	}
-}
-
-// Start a task.
-func (tm *Monitor) Start(name string, total int) *Task {
-	tm.TaskLock.Lock()
-	defer tm.TaskLock.Unlock()
-	t := NewTask(name, total)
-	tm.Tasks[name] = t
-	return t
-}
-
-// Finish a task.
-func (tm *Monitor) Finish(name string) {
-	tm.TaskLock.Lock()
-	defer tm.TaskLock.Unlock()
-	task, exist := tm.Tasks[name]
-	if exist {
-		task.Finish()
-	}
-}
-
-// Update the progress of a task.
-func (tm *Monitor) Update(name string, done int) {
-	tm.TaskLock.Lock()
-	defer tm.TaskLock.Unlock()
-	tm.Tasks[name].Update(done)
-}
-
-// Add the progress of a task.
-func (tm *Monitor) Add(name string, done int) {
-	tm.TaskLock.Lock()
-	defer tm.TaskLock.Unlock()
-	tm.Tasks[name].Add(done)
-}
-
-// Suspend a task.
-func (tm *Monitor) Suspend(name string, flag bool) {
-	tm.TaskLock.Lock()
-	defer tm.TaskLock.Unlock()
-	tm.Tasks[name].Suspend(flag)
-}
-
-func (tm *Monitor) Fail(name, err string) {
-	tm.TaskLock.Lock()
-	defer tm.TaskLock.Unlock()
-	tm.Tasks[name].Fail(err)
-}
-
-// List all tasks and remove tasks from disconnected workers.
-func (tm *Monitor) List(workers ...string) []Task {
-	tm.TaskLock.Lock()
-	defer tm.TaskLock.Unlock()
-	workerSet := mapset.NewSet(workers...)
-	var task []Task
-	for name, t := range tm.Tasks {
-		// remove tasks from disconnected workers
-		if strings.Contains(name, "[") && strings.Contains(name, "]") {
-			begin := strings.Index(name, "[") + 1
-			end := strings.Index(name, "]")
-			if !workerSet.Contains(name[begin:end]) {
-				delete(tm.Tasks, name)
-				continue
-			}
-		}
-		task = append(task, *t)
-	}
-	sort.Sort(Tasks(task))
-	return task
-}
-
-// Get the progress of a task.
-func (tm *Monitor) Get(name string) int {
-	tm.TaskLock.Lock()
-	defer tm.TaskLock.Unlock()
-	task, exist := tm.Tasks[name]
-	if exist {
-		return task.Done
-	}
-	return 0
-}
-
-// Tasks is used to sort []Task.
-type Tasks []Task
-
-// Len is used to sort []Task.
-func (t Tasks) Len() int {
-	return len(t)
-}
-
-// Swap is used to sort []Task.
-func (t Tasks) Swap(i, j int) {
-	t[i], t[j] = t[j], t[i]
-}
-
-// Less is used to sort []Task.
-func (t Tasks) Less(i, j int) bool {
-	if t[i].Status != StatusPending && t[j].Status == StatusPending {
-		return true
-	} else if t[i].Status == StatusPending && t[j].Status != StatusPending {
-		return false
-	} else if t[i].Status == StatusPending && t[j].Status == StatusPending {
-		return t[i].Name < t[j].Name
-	} else {
-		return t[i].StartTime.Before(t[j].StartTime)
-	}
-}
diff --git a/base/task/monitor_test.go b/base/task/monitor_test.go
deleted file mode 100644
index d0f07d8b5..000000000
--- a/base/task/monitor_test.go
+++ /dev/null
@@ -1,87 +0,0 @@
-// Copyright 2021 gorse Project Authors
-//
-// 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 task
-
-import (
-	"github.com/samber/lo"
-	"github.com/stretchr/testify/assert"
-	"testing"
-)
-
-func TestTaskMonitor(t *testing.T) {
-	taskMonitor := NewTaskMonitor()
-	taskMonitor.Start("a", 100)
-	assert.Equal(t, 0, taskMonitor.Get("a"))
-	assert.Equal(t, "a", taskMonitor.Tasks["a"].Name)
-	assert.Equal(t, 100, taskMonitor.Tasks["a"].Total)
-	assert.Equal(t, 0, taskMonitor.Tasks["a"].Done)
-	assert.Equal(t, StatusRunning, taskMonitor.Tasks["a"].Status)
-
-	taskMonitor.Update("a", 50)
-	assert.Equal(t, 50, taskMonitor.Get("a"))
-	assert.Equal(t, "a", taskMonitor.Tasks["a"].Name)
-	assert.Equal(t, 100, taskMonitor.Tasks["a"].Total)
-	assert.Equal(t, 50, taskMonitor.Tasks["a"].Done)
-	assert.Equal(t, StatusRunning, taskMonitor.Tasks["a"].Status)
-	taskMonitor.Suspend("a", true)
-	assert.Equal(t, StatusSuspended, taskMonitor.Tasks["a"].Status)
-	taskMonitor.Suspend("a", false)
-	assert.Equal(t, StatusRunning, taskMonitor.Tasks["a"].Status)
-
-	taskMonitor.Add("a", 30)
-	assert.Equal(t, 80, taskMonitor.Get("a"))
-	assert.Equal(t, "a", taskMonitor.Tasks["a"].Name)
-	assert.Equal(t, 100, taskMonitor.Tasks["a"].Total)
-	assert.Equal(t, 80, taskMonitor.Tasks["a"].Done)
-	assert.Equal(t, StatusRunning, taskMonitor.Tasks["a"].Status)
-
-	taskMonitor.Finish("a")
-	assert.Equal(t, 100, taskMonitor.Get("a"))
-	assert.Equal(t, "a", taskMonitor.Tasks["a"].Name)
-	assert.Equal(t, 100, taskMonitor.Tasks["a"].Total)
-	assert.Equal(t, 100, taskMonitor.Tasks["a"].Done)
-	assert.Equal(t, StatusComplete, taskMonitor.Tasks["a"].Status)
-
-	taskMonitor.Start("b", 100)
-	taskMonitor.Fail("b", "error")
-	assert.Equal(t, "error", taskMonitor.Tasks["b"].Error)
-	assert.Equal(t, StatusFailed, taskMonitor.Tasks["b"].Status)
-
-	taskMonitor.Pending("c")
-	assert.Equal(t, StatusPending, taskMonitor.Tasks["c"].Status)
-
-	taskMonitor.Start("d [a]", 100)
-	taskMonitor.Start("d [b]", 100)
-	tasks := taskMonitor.List("a")
-	assert.ElementsMatch(t, lo.ToSlicePtr(tasks), []*Task{
-		taskMonitor.GetTask("a"),
-		taskMonitor.GetTask("b"),
-		taskMonitor.GetTask("c"),
-		taskMonitor.GetTask("d [a]"),
-	})
-}
-
-func TestSubTask(t *testing.T) {
-	task := NewTask("a", 100)
-	task.Add(10)
-	assert.Equal(t, 10, task.Done)
-	s := task.SubTask(80)
-	assert.Equal(t, 10, s.Start)
-	assert.Equal(t, 90, s.End)
-	s.Add(20)
-	assert.Equal(t, 30, task.Done)
-	s.Finish()
-	assert.Equal(t, 90, task.Done)
-}