diff --git a/.golangci.yml b/.golangci.yml
index e09011c45be..e5b5fe1ab56 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -226,5 +226,4 @@ issues:
       linters:
         - errcheck
   include:
-    # remove the comment after the path is ready
-    # - EXC0012
+    - EXC0012
diff --git a/tools/pd-api-bench/cases/cases.go b/tools/pd-api-bench/cases/cases.go
index d81e7e0fa9d..f863d3248c6 100644
--- a/tools/pd-api-bench/cases/cases.go
+++ b/tools/pd-api-bench/cases/cases.go
@@ -80,12 +80,12 @@ func (c *Config) Clone() *Config {
 
 // Case is the interface for all cases.
 type Case interface {
-	Name() string
-	SetQPS(int64)
-	GetQPS() int64
-	SetBurst(int64)
-	GetBurst() int64
-	GetConfig() *Config
+	getName() string
+	setQPS(int64)
+	getQPS() int64
+	setBurst(int64)
+	getBurst() int64
+	getConfig() *Config
 }
 
 type baseCase struct {
@@ -93,35 +93,35 @@ type baseCase struct {
 	cfg  *Config
 }
 
-func (c *baseCase) Name() string {
+func (c *baseCase) getName() string {
 	return c.name
 }
 
-func (c *baseCase) SetQPS(qps int64) {
+func (c *baseCase) setQPS(qps int64) {
 	c.cfg.QPS = qps
 }
 
-func (c *baseCase) GetQPS() int64 {
+func (c *baseCase) getQPS() int64 {
 	return c.cfg.QPS
 }
 
-func (c *baseCase) SetBurst(burst int64) {
+func (c *baseCase) setBurst(burst int64) {
 	c.cfg.Burst = burst
 }
 
-func (c *baseCase) GetBurst() int64 {
+func (c *baseCase) getBurst() int64 {
 	return c.cfg.Burst
 }
 
-func (c *baseCase) GetConfig() *Config {
+func (c *baseCase) getConfig() *Config {
 	return c.cfg.Clone()
 }
 
 // EtcdCase is the interface for all etcd api cases.
 type EtcdCase interface {
 	Case
-	Init(context.Context, *clientv3.Client) error
-	Unary(context.Context, *clientv3.Client) error
+	init(context.Context, *clientv3.Client) error
+	unary(context.Context, *clientv3.Client) error
 }
 
 // EtcdCreateFn is function type to create EtcdCase.
@@ -138,7 +138,7 @@ var EtcdCaseFnMap = map[string]EtcdCreateFn{
 // GRPCCase is the interface for all gRPC cases.
 type GRPCCase interface {
 	Case
-	Unary(context.Context, pd.Client) error
+	unary(context.Context, pd.Client) error
 }
 
 // GRPCCreateFn is function type to create GRPCCase.
@@ -159,7 +159,7 @@ var GRPCCaseFnMap = map[string]GRPCCreateFn{
 // HTTPCase is the interface for all HTTP cases.
 type HTTPCase interface {
 	Case
-	Do(context.Context, pdHttp.Client) error
+	do(context.Context, pdHttp.Client) error
 }
 
 // HTTPCreateFn is function type to create HTTPCase.
@@ -186,7 +186,7 @@ func newMinResolvedTS() func() HTTPCase {
 	}
 }
 
-func (c *minResolvedTS) Do(ctx context.Context, cli pdHttp.Client) error {
+func (c *minResolvedTS) do(ctx context.Context, cli pdHttp.Client) error {
 	minResolvedTS, storesMinResolvedTS, err := cli.GetMinResolvedTSByStoresIDs(ctx, storesID)
 	if Debug {
 		log.Info("do HTTP case", zap.String("case", c.name), zap.Uint64("min-resolved-ts", minResolvedTS), zap.Any("store-min-resolved-ts", storesMinResolvedTS), zap.Error(err))
@@ -214,7 +214,7 @@ func newRegionStats() func() HTTPCase {
 	}
 }
 
-func (c *regionsStats) Do(ctx context.Context, cli pdHttp.Client) error {
+func (c *regionsStats) do(ctx context.Context, cli pdHttp.Client) error {
 	upperBound := totalRegion / c.regionSample
 	if upperBound < 1 {
 		upperBound = 1
@@ -248,7 +248,7 @@ func newUpdateGCSafePoint() func() GRPCCase {
 	}
 }
 
-func (*updateGCSafePoint) Unary(ctx context.Context, cli pd.Client) error {
+func (*updateGCSafePoint) unary(ctx context.Context, cli pd.Client) error {
 	s := time.Now().Unix()
 	_, err := cli.UpdateGCSafePoint(ctx, uint64(s))
 	if err != nil {
@@ -272,7 +272,7 @@ func newUpdateServiceGCSafePoint() func() GRPCCase {
 	}
 }
 
-func (*updateServiceGCSafePoint) Unary(ctx context.Context, cli pd.Client) error {
+func (*updateServiceGCSafePoint) unary(ctx context.Context, cli pd.Client) error {
 	s := time.Now().Unix()
 	id := rand.Int63n(100) + 1
 	_, err := cli.UpdateServiceGCSafePoint(ctx, strconv.FormatInt(id, 10), id, uint64(s))
@@ -297,7 +297,7 @@ func newGetRegion() func() GRPCCase {
 	}
 }
 
-func (*getRegion) Unary(ctx context.Context, cli pd.Client) error {
+func (*getRegion) unary(ctx context.Context, cli pd.Client) error {
 	id := rand.Intn(totalRegion)*4 + 1
 	_, err := cli.GetRegion(ctx, generateKeyForSimulator(id))
 	if err != nil {
@@ -321,7 +321,7 @@ func newGetRegionEnableFollower() func() GRPCCase {
 	}
 }
 
-func (*getRegionEnableFollower) Unary(ctx context.Context, cli pd.Client) error {
+func (*getRegionEnableFollower) unary(ctx context.Context, cli pd.Client) error {
 	id := rand.Intn(totalRegion)*4 + 1
 	_, err := cli.GetRegion(ctx, generateKeyForSimulator(id), pd.WithAllowFollowerHandle())
 	if err != nil {
@@ -347,7 +347,7 @@ func newScanRegions() func() GRPCCase {
 	}
 }
 
-func (c *scanRegions) Unary(ctx context.Context, cli pd.Client) error {
+func (c *scanRegions) unary(ctx context.Context, cli pd.Client) error {
 	upperBound := totalRegion / c.regionSample
 	random := rand.Intn(upperBound)
 	startID := c.regionSample*random*4 + 1
@@ -375,7 +375,7 @@ func newTso() func() GRPCCase {
 	}
 }
 
-func (*tso) Unary(ctx context.Context, cli pd.Client) error {
+func (*tso) unary(ctx context.Context, cli pd.Client) error {
 	_, _, err := cli.GetTS(ctx)
 	if err != nil {
 		return err
@@ -398,7 +398,7 @@ func newGetStore() func() GRPCCase {
 	}
 }
 
-func (*getStore) Unary(ctx context.Context, cli pd.Client) error {
+func (*getStore) unary(ctx context.Context, cli pd.Client) error {
 	storeIdx := rand.Intn(totalStore)
 	_, err := cli.GetStore(ctx, storesID[storeIdx])
 	if err != nil {
@@ -422,7 +422,7 @@ func newGetStores() func() GRPCCase {
 	}
 }
 
-func (*getStores) Unary(ctx context.Context, cli pd.Client) error {
+func (*getStores) unary(ctx context.Context, cli pd.Client) error {
 	_, err := cli.GetAllStores(ctx)
 	if err != nil {
 		return err
@@ -451,7 +451,7 @@ func newGetKV() func() EtcdCase {
 	}
 }
 
-func (*getKV) Init(ctx context.Context, cli *clientv3.Client) error {
+func (*getKV) init(ctx context.Context, cli *clientv3.Client) error {
 	for i := 0; i < 100; i++ {
 		_, err := cli.Put(ctx, fmt.Sprintf("/test/0001/%4d", i), fmt.Sprintf("%4d", i))
 		if err != nil {
@@ -461,7 +461,7 @@ func (*getKV) Init(ctx context.Context, cli *clientv3.Client) error {
 	return nil
 }
 
-func (*getKV) Unary(ctx context.Context, cli *clientv3.Client) error {
+func (*getKV) unary(ctx context.Context, cli *clientv3.Client) error {
 	_, err := cli.Get(ctx, "/test/0001", clientv3.WithPrefix())
 	return err
 }
@@ -481,9 +481,9 @@ func newPutKV() func() EtcdCase {
 	}
 }
 
-func (*putKV) Init(context.Context, *clientv3.Client) error { return nil }
+func (*putKV) init(context.Context, *clientv3.Client) error { return nil }
 
-func (*putKV) Unary(ctx context.Context, cli *clientv3.Client) error {
+func (*putKV) unary(ctx context.Context, cli *clientv3.Client) error {
 	_, err := cli.Put(ctx, "/test/0001/0000", "test")
 	return err
 }
@@ -503,9 +503,9 @@ func newDeleteKV() func() EtcdCase {
 	}
 }
 
-func (*deleteKV) Init(context.Context, *clientv3.Client) error { return nil }
+func (*deleteKV) init(context.Context, *clientv3.Client) error { return nil }
 
-func (*deleteKV) Unary(ctx context.Context, cli *clientv3.Client) error {
+func (*deleteKV) unary(ctx context.Context, cli *clientv3.Client) error {
 	_, err := cli.Delete(ctx, "/test/0001/0000")
 	return err
 }
@@ -525,9 +525,9 @@ func newTxnKV() func() EtcdCase {
 	}
 }
 
-func (*txnKV) Init(context.Context, *clientv3.Client) error { return nil }
+func (*txnKV) init(context.Context, *clientv3.Client) error { return nil }
 
-func (*txnKV) Unary(ctx context.Context, cli *clientv3.Client) error {
+func (*txnKV) unary(ctx context.Context, cli *clientv3.Client) error {
 	txn := cli.Txn(ctx)
 	txn = txn.If(clientv3.Compare(clientv3.Value("/test/0001/0000"), "=", "test"))
 	txn = txn.Then(clientv3.OpPut("/test/0001/0000", "test2"))
diff --git a/tools/pd-api-bench/cases/controller.go b/tools/pd-api-bench/cases/controller.go
index e19c79c0f3e..a77474db3a7 100644
--- a/tools/pd-api-bench/cases/controller.go
+++ b/tools/pd-api-bench/cases/controller.go
@@ -62,7 +62,7 @@ func (c *Coordinator) GetHTTPCase(name string) (*Config, error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
 	if controller, ok := c.http[name]; ok {
-		return controller.GetConfig(), nil
+		return controller.getConfig(), nil
 	}
 	return nil, errors.Errorf("case %v does not exist", name)
 }
@@ -72,7 +72,7 @@ func (c *Coordinator) GetGRPCCase(name string) (*Config, error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
 	if controller, ok := c.grpc[name]; ok {
-		return controller.GetConfig(), nil
+		return controller.getConfig(), nil
 	}
 	return nil, errors.Errorf("case %v does not exist", name)
 }
@@ -82,7 +82,7 @@ func (c *Coordinator) GetEtcdCase(name string) (*Config, error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
 	if controller, ok := c.etcd[name]; ok {
-		return controller.GetConfig(), nil
+		return controller.getConfig(), nil
 	}
 	return nil, errors.Errorf("case %v does not exist", name)
 }
@@ -93,7 +93,7 @@ func (c *Coordinator) GetAllHTTPCases() map[string]*Config {
 	defer c.mu.RUnlock()
 	ret := make(map[string]*Config)
 	for name, c := range c.http {
-		ret[name] = c.GetConfig()
+		ret[name] = c.getConfig()
 	}
 	return ret
 }
@@ -104,7 +104,7 @@ func (c *Coordinator) GetAllGRPCCases() map[string]*Config {
 	defer c.mu.RUnlock()
 	ret := make(map[string]*Config)
 	for name, c := range c.grpc {
-		ret[name] = c.GetConfig()
+		ret[name] = c.getConfig()
 	}
 	return ret
 }
@@ -115,7 +115,7 @@ func (c *Coordinator) GetAllEtcdCases() map[string]*Config {
 	defer c.mu.RUnlock()
 	ret := make(map[string]*Config)
 	for name, c := range c.etcd {
-		ret[name] = c.GetConfig()
+		ret[name] = c.getConfig()
 	}
 	return ret
 }
@@ -131,9 +131,9 @@ func (c *Coordinator) SetHTTPCase(name string, cfg *Config) error {
 			c.http[name] = controller
 		}
 		controller.stop()
-		controller.SetQPS(cfg.QPS)
+		controller.setQPS(cfg.QPS)
 		if cfg.Burst > 0 {
-			controller.SetBurst(cfg.Burst)
+			controller.setBurst(cfg.Burst)
 		}
 		controller.run()
 	} else {
@@ -153,9 +153,9 @@ func (c *Coordinator) SetGRPCCase(name string, cfg *Config) error {
 			c.grpc[name] = controller
 		}
 		controller.stop()
-		controller.SetQPS(cfg.QPS)
+		controller.setQPS(cfg.QPS)
 		if cfg.Burst > 0 {
-			controller.SetBurst(cfg.Burst)
+			controller.setBurst(cfg.Burst)
 		}
 		controller.run()
 	} else {
@@ -175,9 +175,9 @@ func (c *Coordinator) SetEtcdCase(name string, cfg *Config) error {
 			c.etcd[name] = controller
 		}
 		controller.stop()
-		controller.SetQPS(cfg.QPS)
+		controller.setQPS(cfg.QPS)
 		if cfg.Burst > 0 {
-			controller.SetBurst(cfg.Burst)
+			controller.setBurst(cfg.Burst)
 		}
 		controller.run()
 	} else {
@@ -207,15 +207,15 @@ func newHTTPController(ctx context.Context, clis []pdHttp.Client, fn HTTPCreateF
 
 // run tries to run the HTTP api bench.
 func (c *httpController) run() {
-	if c.GetQPS() <= 0 || c.cancel != nil {
+	if c.getQPS() <= 0 || c.cancel != nil {
 		return
 	}
 	c.ctx, c.cancel = context.WithCancel(c.pctx)
-	qps := c.GetQPS()
-	burst := c.GetBurst()
+	qps := c.getQPS()
+	burst := c.getBurst()
 	cliNum := int64(len(c.clients))
 	tt := time.Duration(base*burst*cliNum/qps) * time.Microsecond
-	log.Info("begin to run http case", zap.String("case", c.Name()), zap.Int64("qps", qps), zap.Int64("burst", burst), zap.Duration("interval", tt))
+	log.Info("begin to run http case", zap.String("case", c.getName()), zap.Int64("qps", qps), zap.Int64("burst", burst), zap.Duration("interval", tt))
 	for _, hCli := range c.clients {
 		c.wg.Add(1)
 		go func(hCli pdHttp.Client) {
@@ -229,9 +229,9 @@ func (c *httpController) run() {
 					for {
 						select {
 						case <-ticker.C:
-							err := c.Do(c.ctx, hCli)
+							err := c.do(c.ctx, hCli)
 							if err != nil {
-								log.Error("meet error when doing HTTP request", zap.String("case", c.Name()), zap.Error(err))
+								log.Error("meet error when doing HTTP request", zap.String("case", c.getName()), zap.Error(err))
 							}
 						case <-c.ctx.Done():
 							log.Info("got signal to exit running HTTP case")
@@ -276,15 +276,15 @@ func newGRPCController(ctx context.Context, clis []pd.Client, fn GRPCCreateFn) *
 
 // run tries to run the gRPC api bench.
 func (c *gRPCController) run() {
-	if c.GetQPS() <= 0 || c.cancel != nil {
+	if c.getQPS() <= 0 || c.cancel != nil {
 		return
 	}
 	c.ctx, c.cancel = context.WithCancel(c.pctx)
-	qps := c.GetQPS()
-	burst := c.GetBurst()
+	qps := c.getQPS()
+	burst := c.getBurst()
 	cliNum := int64(len(c.clients))
 	tt := time.Duration(base*burst*cliNum/qps) * time.Microsecond
-	log.Info("begin to run gRPC case", zap.String("case", c.Name()), zap.Int64("qps", qps), zap.Int64("burst", burst), zap.Duration("interval", tt))
+	log.Info("begin to run gRPC case", zap.String("case", c.getName()), zap.Int64("qps", qps), zap.Int64("burst", burst), zap.Duration("interval", tt))
 	for _, cli := range c.clients {
 		c.wg.Add(1)
 		go func(cli pd.Client) {
@@ -298,9 +298,9 @@ func (c *gRPCController) run() {
 					for {
 						select {
 						case <-ticker.C:
-							err := c.Unary(c.ctx, cli)
+							err := c.unary(c.ctx, cli)
 							if err != nil {
-								log.Error("meet error when doing gRPC request", zap.String("case", c.Name()), zap.Error(err))
+								log.Error("meet error when doing gRPC request", zap.String("case", c.getName()), zap.Error(err))
 							}
 						case <-c.ctx.Done():
 							log.Info("got signal to exit running gRPC case")
@@ -345,18 +345,18 @@ func newEtcdController(ctx context.Context, clis []*clientv3.Client, fn EtcdCrea
 
 // run tries to run the gRPC api bench.
 func (c *etcdController) run() {
-	if c.GetQPS() <= 0 || c.cancel != nil {
+	if c.getQPS() <= 0 || c.cancel != nil {
 		return
 	}
 	c.ctx, c.cancel = context.WithCancel(c.pctx)
-	qps := c.GetQPS()
-	burst := c.GetBurst()
+	qps := c.getQPS()
+	burst := c.getBurst()
 	cliNum := int64(len(c.clients))
 	tt := time.Duration(base*burst*cliNum/qps) * time.Microsecond
-	log.Info("begin to run etcd case", zap.String("case", c.Name()), zap.Int64("qps", qps), zap.Int64("burst", burst), zap.Duration("interval", tt))
-	err := c.Init(c.ctx, c.clients[0])
+	log.Info("begin to run etcd case", zap.String("case", c.getName()), zap.Int64("qps", qps), zap.Int64("burst", burst), zap.Duration("interval", tt))
+	err := c.init(c.ctx, c.clients[0])
 	if err != nil {
-		log.Error("init error", zap.String("case", c.Name()), zap.Error(err))
+		log.Error("init error", zap.String("case", c.getName()), zap.Error(err))
 		return
 	}
 	for _, cli := range c.clients {
@@ -372,9 +372,9 @@ func (c *etcdController) run() {
 					for {
 						select {
 						case <-ticker.C:
-							err := c.Unary(c.ctx, cli)
+							err := c.unary(c.ctx, cli)
 							if err != nil {
-								log.Error("meet error when doing etcd request", zap.String("case", c.Name()), zap.Error(err))
+								log.Error("meet error when doing etcd request", zap.String("case", c.getName()), zap.Error(err))
 							}
 						case <-c.ctx.Done():
 							log.Info("got signal to exit running etcd case")
diff --git a/tools/pd-ctl/pdctl/command/global.go b/tools/pd-ctl/pdctl/command/global.go
index c5c633de217..c7e0cfd691d 100644
--- a/tools/pd-ctl/pdctl/command/global.go
+++ b/tools/pd-ctl/pdctl/command/global.go
@@ -33,6 +33,7 @@ import (
 )
 
 const (
+	// PDControlCallerID is used to set the caller ID for PD client
 	PDControlCallerID = "pd-ctl"
 	clusterPrefix     = "pd/api/v1/cluster"
 )
diff --git a/tools/pd-heartbeat-bench/metrics/util.go b/tools/pd-heartbeat-bench/metrics/util.go
index e409cf10815..f747e5b507f 100644
--- a/tools/pd-heartbeat-bench/metrics/util.go
+++ b/tools/pd-heartbeat-bench/metrics/util.go
@@ -32,12 +32,12 @@ import (
 
 var (
 	prometheusCli        api.Client
-	finalMetrics2Collect []Metric
+	finalMetrics2Collect []metric
 	avgRegionStats       report.Stats
 	avgStoreTime         float64
 	collectRound         = 1.0
 
-	metrics2Collect = []Metric{
+	metrics2Collect = []metric{
 		{promSQL: cpuMetric, name: "max cpu usage(%)", max: true},
 		{promSQL: memoryMetric, name: "max memory usage(G)", max: true},
 		{promSQL: goRoutineMetric, name: "max go routines", max: true},
@@ -69,7 +69,7 @@ var (
 	}
 )
 
-type Metric struct {
+type metric struct {
 	promSQL string
 	name    string
 	value   float64
@@ -77,9 +77,10 @@ type Metric struct {
 	max bool
 }
 
+// InitMetric2Collect initializes the metrics to collect
 func InitMetric2Collect(endpoint string) (withMetric bool) {
 	for _, name := range breakdownNames {
-		metrics2Collect = append(metrics2Collect, Metric{
+		metrics2Collect = append(metrics2Collect, metric{
 			promSQL: hbBreakdownMetricByName(name),
 			name:    name,
 		})
@@ -94,7 +95,7 @@ func InitMetric2Collect(endpoint string) (withMetric bool) {
 		log.Error("parse prometheus url error", zap.Error(err))
 		return false
 	}
-	prometheusCli, err = NewPrometheusClient(*cu)
+	prometheusCli, err = newPrometheusClient(*cu)
 	if err != nil {
 		log.Error("create prometheus client error", zap.Error(err))
 		return false
@@ -108,7 +109,7 @@ func InitMetric2Collect(endpoint string) (withMetric bool) {
 	return true
 }
 
-func NewPrometheusClient(prometheusURL url.URL) (api.Client, error) {
+func newPrometheusClient(prometheusURL url.URL) (api.Client, error) {
 	client, err := api.NewClient(api.Config{
 		Address: prometheusURL.String(),
 	})
@@ -122,6 +123,7 @@ func NewPrometheusClient(prometheusURL url.URL) (api.Client, error) {
 // WarmUpRound wait for the first round to warm up
 const WarmUpRound = 1
 
+// CollectMetrics collects the metrics
 func CollectMetrics(curRound int, wait time.Duration) {
 	if curRound < WarmUpRound {
 		return
@@ -183,7 +185,7 @@ func getMetric(cli api.Client, query string, ts time.Time) ([]float64, error) {
 	return value, nil
 }
 
-func formatMetrics(ms []Metric) string {
+func formatMetrics(ms []metric) string {
 	res := ""
 	for _, m := range ms {
 		res += "[" + m.name + "]" + " " + fmt.Sprintf("%.10f", m.value) + " "
@@ -191,6 +193,7 @@ func formatMetrics(ms []Metric) string {
 	return res
 }
 
+// CollectRegionAndStoreStats collects the region and store stats
 func CollectRegionAndStoreStats(regionStats *report.Stats, storeTime *float64) {
 	if regionStats != nil && storeTime != nil {
 		collect(*regionStats, *storeTime)
@@ -211,6 +214,7 @@ func collect(regionStats report.Stats, storeTime float64) {
 	avgStoreTime = average(avgStoreTime, storeTime)
 }
 
+// OutputConclusion outputs the final conclusion
 func OutputConclusion() {
 	logFields := RegionFields(avgRegionStats,
 		zap.Float64("avg store time", avgStoreTime),
@@ -219,6 +223,7 @@ func OutputConclusion() {
 	log.Info("final metrics collected", logFields...)
 }
 
+// RegionFields returns the fields for region stats
 func RegionFields(stats report.Stats, fields ...zap.Field) []zap.Field {
 	return append([]zap.Field{
 		zap.String("total", fmt.Sprintf("%.4fs", stats.Total.Seconds())),
diff --git a/tools/pd-simulator/simulator/client.go b/tools/pd-simulator/simulator/client.go
index 8acf3ccd9ab..224d54b05d6 100644
--- a/tools/pd-simulator/simulator/client.go
+++ b/tools/pd-simulator/simulator/client.go
@@ -40,13 +40,13 @@ import (
 // Client is a PD (Placement Driver) client.
 // It should not be used after calling Close().
 type Client interface {
-	AllocID(context.Context) (uint64, error)
+	allocID(context.Context) (uint64, error)
 	PutStore(context.Context, *metapb.Store) error
 	StoreHeartbeat(context.Context, *pdpb.StoreStats) error
 	RegionHeartbeat(context.Context, *core.RegionInfo) error
 
-	HeartbeatStreamLoop()
-	ChangeConn(*grpc.ClientConn) error
+	heartbeatStreamLoop()
+	changeConn(*grpc.ClientConn) error
 	Close()
 }
 
@@ -61,15 +61,17 @@ const (
 var (
 	// errFailInitClusterID is returned when failed to load clusterID from all supplied PD addresses.
 	errFailInitClusterID = errors.New("[pd] failed to get cluster id")
-	PDHTTPClient         pdHttp.Client
-	SD                   pd.ServiceDiscovery
-	ClusterID            atomic.Uint64
+	// PDHTTPClient is a client for PD HTTP API.
+	PDHTTPClient pdHttp.Client
+	// SD is a service discovery for PD.
+	SD        pd.ServiceDiscovery
+	clusterID atomic.Uint64
 )
 
 // requestHeader returns a header for fixed ClusterID.
 func requestHeader() *pdpb.RequestHeader {
 	return &pdpb.RequestHeader{
-		ClusterId: ClusterID.Load(),
+		ClusterId: clusterID.Load(),
 	}
 }
 
@@ -110,7 +112,7 @@ func createConn(url string) (*grpc.ClientConn, error) {
 	return cc, nil
 }
 
-func (c *client) ChangeConn(cc *grpc.ClientConn) error {
+func (c *client) changeConn(cc *grpc.ClientConn) error {
 	c.clientConn = cc
 	simutil.Logger.Info("change pd client with endpoints", zap.String("tag", c.tag), zap.String("pd-address", cc.Target()))
 	return nil
@@ -143,7 +145,7 @@ func (c *client) createHeartbeatStream() (pdpb.PD_RegionHeartbeatClient, context
 	return stream, ctx, cancel
 }
 
-func (c *client) HeartbeatStreamLoop() {
+func (c *client) heartbeatStreamLoop() {
 	c.wg.Add(1)
 	defer c.wg.Done()
 	for {
@@ -173,10 +175,10 @@ func (c *client) HeartbeatStreamLoop() {
 			if client := SD.GetServiceClient(); client != nil {
 				_, conn, err := getLeaderURL(ctx, client.GetClientConn())
 				if err != nil {
-					simutil.Logger.Error("[HeartbeatStreamLoop] failed to get leader URL", zap.Error(err))
+					simutil.Logger.Error("[heartbeatStreamLoop] failed to get leader URL", zap.Error(err))
 					continue
 				}
-				if err = c.ChangeConn(conn); err == nil {
+				if err = c.changeConn(conn); err == nil {
 					break
 				}
 			}
@@ -234,6 +236,7 @@ func (c *client) reportRegionHeartbeat(ctx context.Context, stream pdpb.PD_Regio
 	}
 }
 
+// Close closes the client.
 func (c *client) Close() {
 	if c.cancel == nil {
 		simutil.Logger.Info("pd client has been closed", zap.String("tag", c.tag))
@@ -248,7 +251,7 @@ func (c *client) Close() {
 	}
 }
 
-func (c *client) AllocID(ctx context.Context) (uint64, error) {
+func (c *client) allocID(ctx context.Context) (uint64, error) {
 	ctx, cancel := context.WithTimeout(ctx, pdTimeout)
 	resp, err := c.pdClient().AllocID(ctx, &pdpb.AllocIDRequest{
 		Header: requestHeader(),
@@ -263,6 +266,7 @@ func (c *client) AllocID(ctx context.Context) (uint64, error) {
 	return resp.GetId(), nil
 }
 
+// PutStore sends PutStore to PD.
 func (c *client) PutStore(ctx context.Context, store *metapb.Store) error {
 	ctx, cancel := context.WithTimeout(ctx, pdTimeout)
 	newStore := typeutil.DeepClone(store, core.StoreFactory)
@@ -281,6 +285,7 @@ func (c *client) PutStore(ctx context.Context, store *metapb.Store) error {
 	return nil
 }
 
+// StoreHeartbeat sends a StoreHeartbeat to PD.
 func (c *client) StoreHeartbeat(ctx context.Context, newStats *pdpb.StoreStats) error {
 	ctx, cancel := context.WithTimeout(ctx, pdTimeout)
 	resp, err := c.pdClient().StoreHeartbeat(ctx, &pdpb.StoreHeartbeatRequest{
@@ -298,17 +303,18 @@ func (c *client) StoreHeartbeat(ctx context.Context, newStats *pdpb.StoreStats)
 	return nil
 }
 
+// RegionHeartbeat sends a RegionHeartbeat to PD.
 func (c *client) RegionHeartbeat(_ context.Context, region *core.RegionInfo) error {
 	c.reportRegionHeartbeatCh <- region
 	return nil
 }
 
-type RetryClient struct {
+type retryClient struct {
 	client     Client
 	retryCount int
 }
 
-func NewRetryClient(node *Node) *RetryClient {
+func newRetryClient(node *Node) *retryClient {
 	// Init PD client and putting it into node.
 	tag := fmt.Sprintf("store %d", node.Store.Id)
 	var (
@@ -331,8 +337,8 @@ func NewRetryClient(node *Node) *RetryClient {
 	}
 	node.client = client
 
-	// Init RetryClient
-	retryClient := &RetryClient{
+	// Init retryClient
+	retryClient := &retryClient{
 		client:     client,
 		retryCount: retryTimes,
 	}
@@ -342,12 +348,12 @@ func NewRetryClient(node *Node) *RetryClient {
 	})
 	// start heartbeat stream
 	node.receiveRegionHeartbeatCh = receiveRegionHeartbeatCh
-	go client.HeartbeatStreamLoop()
+	go client.heartbeatStreamLoop()
 
 	return retryClient
 }
 
-func (rc *RetryClient) requestWithRetry(f func() (any, error)) (any, error) {
+func (rc *retryClient) requestWithRetry(f func() (any, error)) (any, error) {
 	// execute the function directly
 	if res, err := f(); err == nil {
 		return res, nil
@@ -362,7 +368,7 @@ func (rc *RetryClient) requestWithRetry(f func() (any, error)) (any, error) {
 				simutil.Logger.Error("[retry] failed to get leader URL", zap.Error(err))
 				return nil, err
 			}
-			if err = rc.client.ChangeConn(conn); err != nil {
+			if err = rc.client.changeConn(conn); err != nil {
 				simutil.Logger.Error("failed to change connection", zap.Error(err))
 				return nil, err
 			}
@@ -381,8 +387,8 @@ func getLeaderURL(ctx context.Context, conn *grpc.ClientConn) (string, *grpc.Cli
 	if members.GetHeader().GetError() != nil {
 		return "", nil, errors.New(members.GetHeader().GetError().String())
 	}
-	ClusterID.Store(members.GetHeader().GetClusterId())
-	if ClusterID.Load() == 0 {
+	clusterID.Store(members.GetHeader().GetClusterId())
+	if clusterID.Load() == 0 {
 		return "", nil, errors.New("cluster id is 0")
 	}
 	if members.GetLeader() == nil {
@@ -393,9 +399,9 @@ func getLeaderURL(ctx context.Context, conn *grpc.ClientConn) (string, *grpc.Cli
 	return leaderURL, conn, err
 }
 
-func (rc *RetryClient) AllocID(ctx context.Context) (uint64, error) {
+func (rc *retryClient) allocID(ctx context.Context) (uint64, error) {
 	res, err := rc.requestWithRetry(func() (any, error) {
-		id, err := rc.client.AllocID(ctx)
+		id, err := rc.client.allocID(ctx)
 		return id, err
 	})
 	if err != nil {
@@ -404,7 +410,8 @@ func (rc *RetryClient) AllocID(ctx context.Context) (uint64, error) {
 	return res.(uint64), nil
 }
 
-func (rc *RetryClient) PutStore(ctx context.Context, store *metapb.Store) error {
+// PutStore sends PutStore to PD.
+func (rc *retryClient) PutStore(ctx context.Context, store *metapb.Store) error {
 	_, err := rc.requestWithRetry(func() (any, error) {
 		err := rc.client.PutStore(ctx, store)
 		return nil, err
@@ -412,7 +419,8 @@ func (rc *RetryClient) PutStore(ctx context.Context, store *metapb.Store) error
 	return err
 }
 
-func (rc *RetryClient) StoreHeartbeat(ctx context.Context, newStats *pdpb.StoreStats) error {
+// StoreHeartbeat sends a StoreHeartbeat to PD.
+func (rc *retryClient) StoreHeartbeat(ctx context.Context, newStats *pdpb.StoreStats) error {
 	_, err := rc.requestWithRetry(func() (any, error) {
 		err := rc.client.StoreHeartbeat(ctx, newStats)
 		return nil, err
@@ -420,7 +428,8 @@ func (rc *RetryClient) StoreHeartbeat(ctx context.Context, newStats *pdpb.StoreS
 	return err
 }
 
-func (rc *RetryClient) RegionHeartbeat(ctx context.Context, region *core.RegionInfo) error {
+// RegionHeartbeat sends a RegionHeartbeat to PD.
+func (rc *retryClient) RegionHeartbeat(ctx context.Context, region *core.RegionInfo) error {
 	_, err := rc.requestWithRetry(func() (any, error) {
 		err := rc.client.RegionHeartbeat(ctx, region)
 		return nil, err
@@ -428,15 +437,16 @@ func (rc *RetryClient) RegionHeartbeat(ctx context.Context, region *core.RegionI
 	return err
 }
 
-func (*RetryClient) ChangeConn(_ *grpc.ClientConn) error {
+func (*retryClient) changeConn(_ *grpc.ClientConn) error {
 	panic("unImplement")
 }
 
-func (rc *RetryClient) HeartbeatStreamLoop() {
-	rc.client.HeartbeatStreamLoop()
+func (rc *retryClient) heartbeatStreamLoop() {
+	rc.client.heartbeatStreamLoop()
 }
 
-func (rc *RetryClient) Close() {
+// Close closes the client.
+func (rc *retryClient) Close() {
 	rc.client.Close()
 }
 
@@ -465,10 +475,10 @@ retry:
 			break retry
 		}
 	}
-	if ClusterID.Load() == 0 {
+	if clusterID.Load() == 0 {
 		return "", nil, errors.WithStack(errFailInitClusterID)
 	}
-	simutil.Logger.Info("get cluster id successfully", zap.Uint64("cluster-id", ClusterID.Load()))
+	simutil.Logger.Info("get cluster id successfully", zap.Uint64("cluster-id", clusterID.Load()))
 
 	// Check if the cluster is already bootstrapped.
 	ctx, cancel := context.WithTimeout(ctx, pdTimeout)
@@ -513,7 +523,6 @@ retry:
 }
 
 /* PDHTTPClient is a client for PD HTTP API, these are the functions that are used in the simulator */
-
 func PutPDConfig(config *sc.PDConfig) error {
 	if len(config.PlacementRules) > 0 {
 		ruleOps := make([]*pdHttp.RuleOp, 0)
@@ -541,8 +550,9 @@ func PutPDConfig(config *sc.PDConfig) error {
 	return nil
 }
 
+// ChooseToHaltPDSchedule is used to choose whether to halt the PD schedule
 func ChooseToHaltPDSchedule(halt bool) {
-	HaltSchedule.Store(halt)
+	haltSchedule.Store(halt)
 	PDHTTPClient.SetConfig(context.Background(), map[string]any{
 		"schedule.halt-scheduling": strconv.FormatBool(halt),
 	})
diff --git a/tools/pd-simulator/simulator/config/config.go b/tools/pd-simulator/simulator/config/config.go
index 4d182a2a03f..32c483ceba7 100644
--- a/tools/pd-simulator/simulator/config/config.go
+++ b/tools/pd-simulator/simulator/config/config.go
@@ -130,6 +130,8 @@ func (sc *SimConfig) Adjust(meta *toml.MetaData) error {
 
 	return sc.ServerConfig.Adjust(meta, false)
 }
+
+// Speed returns the tick speed of the simulator.
 func (sc *SimConfig) Speed() uint64 {
 	return uint64(time.Second / sc.SimTickInterval.Duration)
 }
diff --git a/tools/pd-simulator/simulator/drive.go b/tools/pd-simulator/simulator/drive.go
index e602ba2df65..947d0664755 100644
--- a/tools/pd-simulator/simulator/drive.go
+++ b/tools/pd-simulator/simulator/drive.go
@@ -135,7 +135,7 @@ func (d *Driver) allocID() error {
 		return err
 	}
 	ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
-	rootPath := path.Join("/pd", strconv.FormatUint(ClusterID.Load(), 10))
+	rootPath := path.Join("/pd", strconv.FormatUint(clusterID.Load(), 10))
 	allocIDPath := path.Join(rootPath, "alloc_id")
 	_, err = etcdClient.Put(ctx, allocIDPath, string(typeutil.Uint64ToBytes(maxID+1000)))
 	if err != nil {
@@ -171,7 +171,7 @@ func (d *Driver) updateNodesClient() error {
 	PDHTTPClient = pdHttp.NewClientWithServiceDiscovery("pd-simulator", SD)
 
 	for _, node := range d.conn.Nodes {
-		node.client = NewRetryClient(node)
+		node.client = newRetryClient(node)
 	}
 	return nil
 }
@@ -191,6 +191,7 @@ func (d *Driver) Tick() {
 	}()
 }
 
+// StepRegions steps regions.
 func (d *Driver) StepRegions(ctx context.Context) {
 	for {
 		select {
@@ -209,6 +210,7 @@ func (d *Driver) StepRegions(ctx context.Context) {
 	}
 }
 
+// StoresHeartbeat sends heartbeat to all stores.
 func (d *Driver) StoresHeartbeat(ctx context.Context) {
 	config := d.raftEngine.storeConfig
 	storeInterval := uint64(config.RaftStore.StoreHeartBeatInterval.Duration / config.SimTickInterval.Duration)
@@ -229,6 +231,7 @@ func (d *Driver) StoresHeartbeat(ctx context.Context) {
 	}
 }
 
+// RegionsHeartbeat sends heartbeat to all regions.
 func (d *Driver) RegionsHeartbeat(ctx context.Context) {
 	// ensure only wait for the first time heartbeat done
 	firstReport := true
@@ -281,9 +284,9 @@ func (d *Driver) RegionsHeartbeat(ctx context.Context) {
 					}
 				}
 
-				// Only set HaltSchedule to false when the leader count is 80% of the total region count.
+				// Only set haltSchedule to false when the leader count is 80% of the total region count.
 				// using firstReport to avoid the haltSchedule set to true manually.
-				if HaltSchedule.Load() && firstReport {
+				if haltSchedule.Load() && firstReport {
 					storeInterval := uint64(config.RaftStore.StoreHeartBeatInterval.Duration / config.SimTickInterval.Duration)
 					ticker := time.NewTicker(time.Duration(storeInterval))
 					for range ticker.C {
@@ -294,7 +297,7 @@ func (d *Driver) RegionsHeartbeat(ctx context.Context) {
 							leaderCount += store.Status.LeaderCount
 						}
 						// Add halt schedule check to avoid the situation that the leader count is always less than 80%.
-						if leaderCount > int64(float64(d.simConfig.TotalRegion)*0.8) || !HaltSchedule.Load() {
+						if leaderCount > int64(float64(d.simConfig.TotalRegion)*0.8) || !haltSchedule.Load() {
 							ChooseToHaltPDSchedule(false)
 							firstReport = false
 							ticker.Stop()
@@ -310,11 +313,11 @@ func (d *Driver) RegionsHeartbeat(ctx context.Context) {
 	}
 }
 
-var HaltSchedule atomic.Bool
+var haltSchedule atomic.Bool
 
 // Check checks if the simulation is completed.
 func (d *Driver) Check() bool {
-	if !HaltSchedule.Load() {
+	if !haltSchedule.Load() {
 		return false
 	}
 	var stats []info.StoreStats
diff --git a/tools/pd-simulator/simulator/event.go b/tools/pd-simulator/simulator/event.go
index 86da86ed20d..d22f35756ef 100644
--- a/tools/pd-simulator/simulator/event.go
+++ b/tools/pd-simulator/simulator/event.go
@@ -177,7 +177,7 @@ type AddNode struct{}
 func (*AddNode) Run(raft *RaftEngine, _ int64) bool {
 	config := raft.storeConfig
 	nodes := raft.conn.getNodes()
-	id, err := nodes[0].client.AllocID(context.TODO())
+	id, err := nodes[0].client.allocID(context.TODO())
 	if err != nil {
 		simutil.Logger.Error("alloc node id failed", zap.Error(err))
 		return false
@@ -196,7 +196,7 @@ func (*AddNode) Run(raft *RaftEngine, _ int64) bool {
 
 	raft.conn.Nodes[s.ID] = n
 	n.raftEngine = raft
-	n.client = NewRetryClient(n)
+	n.client = newRetryClient(n)
 
 	err = n.Start()
 	if err != nil {
diff --git a/tools/pd-simulator/simulator/raft.go b/tools/pd-simulator/simulator/raft.go
index 9a219d32f9f..7f3bf78622f 100644
--- a/tools/pd-simulator/simulator/raft.go
+++ b/tools/pd-simulator/simulator/raft.go
@@ -294,6 +294,6 @@ func (r *RaftEngine) allocID(storeID uint64) (uint64, error) {
 	if !ok {
 		return 0, errors.Errorf("node %d not found", storeID)
 	}
-	id, err := node.client.AllocID(context.Background())
+	id, err := node.client.allocID(context.Background())
 	return id, errors.WithStack(err)
 }
diff --git a/tools/pd-tso-bench/main.go b/tools/pd-tso-bench/main.go
index 1e59dfd2a2a..96ff2a51d0a 100644
--- a/tools/pd-tso-bench/main.go
+++ b/tools/pd-tso-bench/main.go
@@ -176,7 +176,7 @@ func showStats(ctx context.Context, durCh chan time.Duration) {
 		case <-ticker.C:
 			// runtime.GC()
 			if *verbose {
-				fmt.Println(s.Counter())
+				fmt.Println(s.counter())
 			}
 			total.merge(s)
 			s = newStats()
@@ -184,8 +184,8 @@ func showStats(ctx context.Context, durCh chan time.Duration) {
 			s.update(d)
 		case <-statCtx.Done():
 			fmt.Println("\nTotal:")
-			fmt.Println(total.Counter())
-			fmt.Println(total.Percentage())
+			fmt.Println(total.counter())
+			fmt.Println(total.percentage())
 			// Calculate the percentiles by using the tDigest algorithm.
 			fmt.Printf("P0.5: %.4fms, P0.8: %.4fms, P0.9: %.4fms, P0.99: %.4fms\n\n", latencyTDigest.Quantile(0.5), latencyTDigest.Quantile(0.8), latencyTDigest.Quantile(0.9), latencyTDigest.Quantile(0.99))
 			if *verbose {
@@ -329,7 +329,7 @@ func (s *stats) merge(other *stats) {
 	s.oneThousandCnt += other.oneThousandCnt
 }
 
-func (s *stats) Counter() string {
+func (s *stats) counter() string {
 	return fmt.Sprintf(
 		"count: %d, max: %.4fms, min: %.4fms, avg: %.4fms\n<1ms: %d, >1ms: %d, >2ms: %d, >5ms: %d, >10ms: %d, >30ms: %d, >50ms: %d, >100ms: %d, >200ms: %d, >400ms: %d, >800ms: %d, >1s: %d",
 		s.count, float64(s.maxDur.Nanoseconds())/float64(time.Millisecond), float64(s.minDur.Nanoseconds())/float64(time.Millisecond), float64(s.totalDur.Nanoseconds())/float64(s.count)/float64(time.Millisecond),
@@ -337,7 +337,7 @@ func (s *stats) Counter() string {
 		s.eightHundredCnt, s.oneThousandCnt)
 }
 
-func (s *stats) Percentage() string {
+func (s *stats) percentage() string {
 	return fmt.Sprintf(
 		"count: %d, <1ms: %2.2f%%, >1ms: %2.2f%%, >2ms: %2.2f%%, >5ms: %2.2f%%, >10ms: %2.2f%%, >30ms: %2.2f%%, >50ms: %2.2f%%, >100ms: %2.2f%%, >200ms: %2.2f%%, >400ms: %2.2f%%, >800ms: %2.2f%%, >1s: %2.2f%%", s.count,
 		s.calculate(s.submilliCnt), s.calculate(s.milliCnt), s.calculate(s.twoMilliCnt), s.calculate(s.fiveMilliCnt), s.calculate(s.tenMSCnt), s.calculate(s.thirtyCnt), s.calculate(s.fiftyCnt),
diff --git a/tools/pd-ut/alloc/server.go b/tools/pd-ut/alloc/server.go
index a5643001142..ffa3bce0aa5 100644
--- a/tools/pd-ut/alloc/server.go
+++ b/tools/pd-ut/alloc/server.go
@@ -30,6 +30,7 @@ import (
 
 var statusAddress = flag.String("status-addr", "0.0.0.0:0", "status address")
 
+// RunHTTPServer runs a HTTP server to provide alloc address.
 func RunHTTPServer() *http.Server {
 	err := os.Setenv(tempurl.AllocURLFromUT, fmt.Sprintf("http://%s/alloc", *statusAddress))
 	if err != nil {