diff --git a/core/service/servicegroup.go b/core/service/servicegroup.go
index 0968a627..98d6ff2d 100644
--- a/core/service/servicegroup.go
+++ b/core/service/servicegroup.go
@@ -25,29 +25,29 @@ type (
 		Stopper
 	}
 
-	// A Group is a group of services.
-	Group struct {
+	// A ServiceGroup is a group of services.
+	ServiceGroup struct {
 		services []Service
 		stopOnce func()
 	}
 )
 
-// NewGroup returns a Group.
-func NewGroup() *Group {
-	sg := new(Group)
+// NewServiceGroup returns a ServiceGroup.
+func NewServiceGroup() *ServiceGroup {
+	sg := new(ServiceGroup)
 	sg.stopOnce = syncx.Once(sg.doStop)
 	return sg
 }
 
 // Add adds service into sg.
-func (sg *Group) Add(service Service) {
+func (sg *ServiceGroup) Add(service Service) {
 	sg.services = append(sg.services, service)
 }
 
-// Start starts the Group.
+// Start starts the ServiceGroup.
 // There should not be any logic code after calling this method, because this method is a blocking one.
 // Also, quitting this method will close the logx output.
-func (sg *Group) Start() {
+func (sg *ServiceGroup) Start() {
 	proc.AddShutdownListener(func() {
 		log.Println("Shutting down...")
 		sg.stopOnce()
@@ -56,12 +56,12 @@ func (sg *Group) Start() {
 	sg.doStart()
 }
 
-// Stop stops the Group.
-func (sg *Group) Stop() {
+// Stop stops the ServiceGroup.
+func (sg *ServiceGroup) Stop() {
 	sg.stopOnce()
 }
 
-func (sg *Group) doStart() {
+func (sg *ServiceGroup) doStart() {
 	routineGroup := threading.NewRoutineGroup()
 
 	for i := range sg.services {
@@ -74,7 +74,7 @@ func (sg *Group) doStart() {
 	routineGroup.Wait()
 }
 
-func (sg *Group) doStop() {
+func (sg *ServiceGroup) doStop() {
 	for _, service := range sg.services {
 		service.Stop()
 	}
diff --git a/core/service/servicegroup_test.go b/core/service/servicegroup_test.go
index e431cad5..7f2165dd 100644
--- a/core/service/servicegroup_test.go
+++ b/core/service/servicegroup_test.go
@@ -41,7 +41,7 @@ func TestServiceGroup(t *testing.T) {
 	multipliers := []int{2, 3, 5, 7}
 	want := 1
 
-	group := NewGroup()
+	group := NewServiceGroup()
 	for _, multiplier := range multipliers {
 		want *= multiplier
 		service := newMockedService(multiplier)
@@ -68,7 +68,7 @@ func TestServiceGroup_WithStart(t *testing.T) {
 	var wait sync.WaitGroup
 	var lock sync.Mutex
 	wait.Add(len(multipliers))
-	group := NewGroup()
+	group := NewServiceGroup()
 	for _, multiplier := range multipliers {
 		var mul = multiplier
 		group.Add(WithStart(func() {
@@ -95,7 +95,7 @@ func TestServiceGroup_WithStarter(t *testing.T) {
 	var wait sync.WaitGroup
 	var lock sync.Mutex
 	wait.Add(len(multipliers))
-	group := NewGroup()
+	group := NewServiceGroup()
 	for _, multiplier := range multipliers {
 		var mul = multiplier
 		group.Add(WithStarter(mockedStarter{
diff --git a/core/stat/alert.go b/core/stat/alert.go
index 61993954..afa43d42 100644
--- a/core/stat/alert.go
+++ b/core/stat/alert.go
@@ -37,6 +37,7 @@ func init() {
 	}
 }
 
+// Report reports given message.
 func Report(msg string) {
 	lock.RLock()
 	fn := reporter
@@ -63,6 +64,7 @@ func Report(msg string) {
 	}
 }
 
+// SetReporter sets the given reporter.
 func SetReporter(fn func(string)) {
 	lock.Lock()
 	defer lock.Unlock()
diff --git a/core/stat/alert_polyfill.go b/core/stat/alert_polyfill.go
index cef947bc..d76e6c53 100644
--- a/core/stat/alert_polyfill.go
+++ b/core/stat/alert_polyfill.go
@@ -2,8 +2,10 @@
 
 package stat
 
+// Report reports given message.
 func Report(string) {
 }
 
+// SetReporter sets the given reporter.
 func SetReporter(func(string)) {
 }
diff --git a/core/stat/metrics.go b/core/stat/metrics.go
index d8981e39..f3c8b430 100644
--- a/core/stat/metrics.go
+++ b/core/stat/metrics.go
@@ -7,20 +7,23 @@ import (
 
 	"github.com/tal-tech/go-zero/core/executors"
 	"github.com/tal-tech/go-zero/core/logx"
+	"github.com/tal-tech/go-zero/core/syncx"
 )
 
 var (
-	LogInterval = time.Minute
-
+	logInterval  = time.Minute
 	writerLock   sync.Mutex
 	reportWriter Writer = nil
+	logEnabled          = syncx.ForAtomicBool(true)
 )
 
 type (
+	// Writer interface wraps the Write method.
 	Writer interface {
 		Write(report *StatReport) error
 	}
 
+	// A StatReport is a stat report entry.
 	StatReport struct {
 		Name          string  `json:"name"`
 		Timestamp     int64   `json:"tm"`
@@ -34,18 +37,26 @@ type (
 		Top99p9th     float32 `json:"t99p9"`
 	}
 
+	// A Metrics is used to log and report stat reports.
 	Metrics struct {
 		executor  *executors.PeriodicalExecutor
 		container *metricsContainer
 	}
 )
 
+// DisableLog disables logs of stats.
+func DisableLog() {
+	logEnabled.Set(false)
+}
+
+// SetReportWriter sets the report writer.
 func SetReportWriter(writer Writer) {
 	writerLock.Lock()
 	reportWriter = writer
 	writerLock.Unlock()
 }
 
+// NewMetrics returns a Metrics.
 func NewMetrics(name string) *Metrics {
 	container := &metricsContainer{
 		name: name,
@@ -53,21 +64,24 @@ func NewMetrics(name string) *Metrics {
 	}
 
 	return &Metrics{
-		executor:  executors.NewPeriodicalExecutor(LogInterval, container),
+		executor:  executors.NewPeriodicalExecutor(logInterval, container),
 		container: container,
 	}
 }
 
+// Add adds task to m.
 func (m *Metrics) Add(task Task) {
 	m.executor.Add(task)
 }
 
+// AddDrop adds a drop to m.
 func (m *Metrics) AddDrop() {
 	m.executor.Add(Task{
 		Drop: true,
 	})
 }
 
+// SetName sets the name of m.
 func (m *Metrics) SetName(name string) {
 	m.executor.Sync(func() {
 		m.container.name = name
@@ -113,7 +127,7 @@ func (c *metricsContainer) Execute(v interface{}) {
 		Name:          c.name,
 		Timestamp:     time.Now().Unix(),
 		Pid:           c.pid,
-		ReqsPerSecond: float32(size) / float32(LogInterval/time.Second),
+		ReqsPerSecond: float32(size) / float32(logInterval/time.Second),
 		Drops:         drops,
 	}
 
@@ -192,10 +206,12 @@ func getTopDuration(tasks []Task) float32 {
 
 func log(report *StatReport) {
 	writeReport(report)
-	logx.Statf("(%s) - qps: %.1f/s, drops: %d, avg time: %.1fms, med: %.1fms, "+
-		"90th: %.1fms, 99th: %.1fms, 99.9th: %.1fms",
-		report.Name, report.ReqsPerSecond, report.Drops, report.Average, report.Median,
-		report.Top90th, report.Top99th, report.Top99p9th)
+	if logEnabled.True() {
+		logx.Statf("(%s) - qps: %.1f/s, drops: %d, avg time: %.1fms, med: %.1fms, "+
+			"90th: %.1fms, 99th: %.1fms, 99.9th: %.1fms",
+			report.Name, report.ReqsPerSecond, report.Drops, report.Average, report.Median,
+			report.Top90th, report.Top99th, report.Top99p9th)
+	}
 }
 
 func writeReport(report *StatReport) {
diff --git a/core/stat/metrics_test.go b/core/stat/metrics_test.go
index a8dd93f4..4da547ed 100644
--- a/core/stat/metrics_test.go
+++ b/core/stat/metrics_test.go
@@ -6,9 +6,14 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/tal-tech/go-zero/core/logx"
 )
 
 func TestMetrics(t *testing.T) {
+	logx.Disable()
+	DisableLog()
+	defer logEnabled.Set(true)
+
 	counts := []int{1, 5, 10, 100, 1000, 1000}
 	for _, count := range counts {
 		m := NewMetrics("foo")
diff --git a/core/stat/remotewriter.go b/core/stat/remotewriter.go
index 66091a05..a4c5ba71 100644
--- a/core/stat/remotewriter.go
+++ b/core/stat/remotewriter.go
@@ -12,12 +12,15 @@ import (
 
 const httpTimeout = time.Second * 5
 
+// ErrWriteFailed is an error that indicates failed to submit a StatReport.
 var ErrWriteFailed = errors.New("submit failed")
 
+// A RemoteWriter is a writer to write StatReport.
 type RemoteWriter struct {
 	endpoint string
 }
 
+// NewRemoteWriter returns a RemoteWriter.
 func NewRemoteWriter(endpoint string) Writer {
 	return &RemoteWriter{
 		endpoint: endpoint,
diff --git a/core/stat/task.go b/core/stat/task.go
index 41c1ee22..637e0b76 100644
--- a/core/stat/task.go
+++ b/core/stat/task.go
@@ -2,6 +2,7 @@ package stat
 
 import "time"
 
+// A Task is a task that is reported to Metrics.
 type Task struct {
 	Drop        bool
 	Duration    time.Duration
diff --git a/core/stat/usage.go b/core/stat/usage.go
index 7d50fbc8..b6a5e3df 100644
--- a/core/stat/usage.go
+++ b/core/stat/usage.go
@@ -44,6 +44,7 @@ func init() {
 	}()
 }
 
+// CpuUsage returns current cpu usage.
 func CpuUsage() int64 {
 	return atomic.LoadInt64(&cpuUsage)
 }