diff --git a/tools/functional-tester/tester/checks.go b/tools/functional-tester/tester/checks.go
index 8817bcca4..f18e391ad 100644
--- a/tools/functional-tester/tester/checks.go
+++ b/tools/functional-tester/tester/checks.go
@@ -39,14 +39,14 @@ type hashAndRevGetter interface {
 }
 
 type hashChecker struct {
-	logger *zap.Logger
-	hrg    hashAndRevGetter
+	lg  *zap.Logger
+	hrg hashAndRevGetter
 }
 
-func newHashChecker(logger *zap.Logger, hrg hashAndRevGetter) Checker {
+func newHashChecker(lg *zap.Logger, hrg hashAndRevGetter) Checker {
 	return &hashChecker{
-		logger: logger,
-		hrg:    hrg,
+		lg:  lg,
+		hrg: hrg,
 	}
 }
 
@@ -62,7 +62,7 @@ func (hc *hashChecker) checkRevAndHashes() (err error) {
 	for i := 0; i < retries; i++ {
 		revs, hashes, err = hc.hrg.getRevisionHash()
 		if err != nil {
-			hc.logger.Warn(
+			hc.lg.Warn(
 				"failed to get revision and hash",
 				zap.Int("retries", i),
 				zap.Error(err),
@@ -73,7 +73,7 @@ func (hc *hashChecker) checkRevAndHashes() (err error) {
 			if sameRev && sameHashes {
 				return nil
 			}
-			hc.logger.Warn(
+			hc.lg.Warn(
 				"retrying; etcd cluster is not stable",
 				zap.Int("retries", i),
 				zap.Bool("same-revisions", sameRev),
@@ -97,7 +97,7 @@ func (hc *hashChecker) Check() error {
 }
 
 type leaseChecker struct {
-	logger *zap.Logger
+	lg *zap.Logger
 
 	endpoint string // TODO: use Member
 
@@ -157,7 +157,7 @@ func (lc *leaseChecker) checkShortLivedLease(ctx context.Context, leaseID int64)
 			return nil
 		}
 		if err != nil {
-			lc.logger.Debug(
+			lc.lg.Debug(
 				"retrying; Lease TimeToLive failed",
 				zap.Int("retries", i),
 				zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -167,7 +167,7 @@ func (lc *leaseChecker) checkShortLivedLease(ctx context.Context, leaseID int64)
 		}
 		if resp.TTL > 0 {
 			dur := time.Duration(resp.TTL) * time.Second
-			lc.logger.Debug(
+			lc.lg.Debug(
 				"lease has not been expired, wait until expire",
 				zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
 				zap.Int64("ttl", resp.TTL),
@@ -175,7 +175,7 @@ func (lc *leaseChecker) checkShortLivedLease(ctx context.Context, leaseID int64)
 			)
 			time.Sleep(dur)
 		} else {
-			lc.logger.Debug(
+			lc.lg.Debug(
 				"lease expired but not yet revoked",
 				zap.Int("retries", i),
 				zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -195,7 +195,7 @@ func (lc *leaseChecker) checkShortLivedLease(ctx context.Context, leaseID int64)
 func (lc *leaseChecker) checkLease(ctx context.Context, expired bool, leaseID int64) error {
 	keysExpired, err := lc.hasKeysAttachedToLeaseExpired(ctx, leaseID)
 	if err != nil {
-		lc.logger.Warn(
+		lc.lg.Warn(
 			"hasKeysAttachedToLeaseExpired failed",
 			zap.String("endpoint", lc.endpoint),
 			zap.Error(err),
@@ -204,7 +204,7 @@ func (lc *leaseChecker) checkLease(ctx context.Context, expired bool, leaseID in
 	}
 	leaseExpired, err := lc.hasLeaseExpired(ctx, leaseID)
 	if err != nil {
-		lc.logger.Warn(
+		lc.lg.Warn(
 			"hasLeaseExpired failed",
 			zap.String("endpoint", lc.endpoint),
 			zap.Error(err),
@@ -248,7 +248,7 @@ func (lc *leaseChecker) hasLeaseExpired(ctx context.Context, leaseID int64) (boo
 		} else {
 			return resp.TTL == -1, nil
 		}
-		lc.logger.Warn(
+		lc.lg.Warn(
 			"hasLeaseExpired getLeaseByID failed",
 			zap.String("endpoint", lc.endpoint),
 			zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -267,7 +267,7 @@ func (lc *leaseChecker) hasKeysAttachedToLeaseExpired(ctx context.Context, lease
 		RangeEnd: []byte(clientv3.GetPrefixRangeEnd(fmt.Sprintf("%d", leaseID))),
 	}, grpc.FailFast(false))
 	if err != nil {
-		lc.logger.Warn(
+		lc.lg.Warn(
 			"hasKeysAttachedToLeaseExpired failed",
 			zap.String("endpoint", lc.endpoint),
 			zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
diff --git a/tools/functional-tester/tester/cluster.go b/tools/functional-tester/tester/cluster.go
index f94287515..60b14097b 100644
--- a/tools/functional-tester/tester/cluster.go
+++ b/tools/functional-tester/tester/cluster.go
@@ -38,7 +38,7 @@ import (
 
 // Cluster defines tester cluster.
 type Cluster struct {
-	logger *zap.Logger
+	lg *zap.Logger
 
 	agentConns    []*grpc.ClientConn
 	agentClients  []rpcpb.TransportClient
@@ -61,15 +61,15 @@ type Cluster struct {
 	cs              int
 }
 
-func newCluster(logger *zap.Logger, fpath string) (*Cluster, error) {
-	logger.Info("reading configuration file", zap.String("path", fpath))
+func newCluster(lg *zap.Logger, fpath string) (*Cluster, error) {
+	lg.Info("reading configuration file", zap.String("path", fpath))
 	bts, err := ioutil.ReadFile(fpath)
 	if err != nil {
 		return nil, err
 	}
-	logger.Info("opened configuration file", zap.String("path", fpath))
+	lg.Info("opened configuration file", zap.String("path", fpath))
 
-	clus := &Cluster{logger: logger}
+	clus := &Cluster{lg: lg}
 	if err = yaml.Unmarshal(bts, clus); err != nil {
 		return nil, err
 	}
@@ -192,8 +192,8 @@ var dialOpts = []grpc.DialOption{
 }
 
 // NewCluster creates a client from a tester configuration.
-func NewCluster(logger *zap.Logger, fpath string) (*Cluster, error) {
-	clus, err := newCluster(logger, fpath)
+func NewCluster(lg *zap.Logger, fpath string) (*Cluster, error) {
+	clus, err := newCluster(lg, fpath)
 	if err != nil {
 		return nil, err
 	}
@@ -205,21 +205,21 @@ func NewCluster(logger *zap.Logger, fpath string) (*Cluster, error) {
 	clus.failures = make([]Failure, 0)
 
 	for i, ap := range clus.Members {
-		logger.Info("connecting", zap.String("agent-address", ap.AgentAddr))
+		clus.lg.Info("connecting", zap.String("agent-address", ap.AgentAddr))
 		var err error
 		clus.agentConns[i], err = grpc.Dial(ap.AgentAddr, dialOpts...)
 		if err != nil {
 			return nil, err
 		}
 		clus.agentClients[i] = rpcpb.NewTransportClient(clus.agentConns[i])
-		logger.Info("connected", zap.String("agent-address", ap.AgentAddr))
+		clus.lg.Info("connected", zap.String("agent-address", ap.AgentAddr))
 
-		logger.Info("creating stream", zap.String("agent-address", ap.AgentAddr))
+		clus.lg.Info("creating stream", zap.String("agent-address", ap.AgentAddr))
 		clus.agentStreams[i], err = clus.agentClients[i].Transport(context.Background())
 		if err != nil {
 			return nil, err
 		}
-		logger.Info("created stream", zap.String("agent-address", ap.AgentAddr))
+		clus.lg.Info("created stream", zap.String("agent-address", ap.AgentAddr))
 	}
 
 	mux := http.NewServeMux()
@@ -246,18 +246,18 @@ func NewCluster(logger *zap.Logger, fpath string) (*Cluster, error) {
 }
 
 func (clus *Cluster) serveTesterServer() {
-	clus.logger.Info(
+	clus.lg.Info(
 		"started tester HTTP server",
 		zap.String("tester-address", clus.Tester.TesterAddr),
 	)
 	err := clus.testerHTTPServer.ListenAndServe()
-	clus.logger.Info(
+	clus.lg.Info(
 		"tester HTTP server returned",
 		zap.String("tester-address", clus.Tester.TesterAddr),
 		zap.Error(err),
 	)
 	if err != nil && err != http.ErrServerClosed {
-		clus.logger.Fatal("tester HTTP errored", zap.Error(err))
+		clus.lg.Fatal("tester HTTP errored", zap.Error(err))
 	}
 }
 
@@ -291,7 +291,7 @@ func (clus *Cluster) updateFailures() {
 		case "FAILPOINTS":
 			fpFailures, fperr := failpointFailures(clus)
 			if len(fpFailures) == 0 {
-				clus.logger.Info("no failpoints found!", zap.Error(fperr))
+				clus.lg.Info("no failpoints found!", zap.Error(fperr))
 			}
 			clus.failures = append(clus.failures, fpFailures...)
 		case "NO_FAIL":
@@ -316,13 +316,13 @@ func (clus *Cluster) shuffleFailures() {
 	n := len(clus.failures)
 	cp := coprime(n)
 
-	clus.logger.Info("shuffling test failure cases", zap.Int("total", n))
+	clus.lg.Info("shuffling test failure cases", zap.Int("total", n))
 	fs := make([]Failure, n)
 	for i := 0; i < n; i++ {
 		fs[i] = clus.failures[(cp*i+offset)%n]
 	}
 	clus.failures = fs
-	clus.logger.Info("shuffled test failure cases", zap.Int("total", n))
+	clus.lg.Info("shuffled test failure cases", zap.Int("total", n))
 }
 
 /*
@@ -354,7 +354,7 @@ func gcd(x, y int) int {
 }
 
 func (clus *Cluster) updateStresserChecker() {
-	clus.logger.Info(
+	clus.lg.Info(
 		"updating stressers",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
@@ -367,7 +367,7 @@ func (clus *Cluster) updateStresserChecker() {
 	clus.stresser = cs
 
 	if clus.Tester.ConsistencyCheck {
-		clus.checker = newHashChecker(clus.logger, hashAndRevGetter(clus))
+		clus.checker = newHashChecker(clus.lg, hashAndRevGetter(clus))
 		if schk := cs.Checker(); schk != nil {
 			clus.checker = newCompositeChecker([]Checker{clus.checker, schk})
 		}
@@ -375,7 +375,7 @@ func (clus *Cluster) updateStresserChecker() {
 		clus.checker = newNoChecker()
 	}
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"updated stressers",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
@@ -383,13 +383,13 @@ func (clus *Cluster) updateStresserChecker() {
 }
 
 func (clus *Cluster) startStresser() (err error) {
-	clus.logger.Info(
+	clus.lg.Info(
 		"starting stressers",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
 	)
 	err = clus.stresser.Stress()
-	clus.logger.Info(
+	clus.lg.Info(
 		"started stressers",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
@@ -398,13 +398,13 @@ func (clus *Cluster) startStresser() (err error) {
 }
 
 func (clus *Cluster) closeStresser() {
-	clus.logger.Info(
+	clus.lg.Info(
 		"closing stressers",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
 	)
 	clus.stresser.Close()
-	clus.logger.Info(
+	clus.lg.Info(
 		"closed stressers",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
@@ -412,13 +412,13 @@ func (clus *Cluster) closeStresser() {
 }
 
 func (clus *Cluster) pauseStresser() {
-	clus.logger.Info(
+	clus.lg.Info(
 		"pausing stressers",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
 	)
 	clus.stresser.Pause()
-	clus.logger.Info(
+	clus.lg.Info(
 		"paused stressers",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
@@ -431,7 +431,7 @@ func (clus *Cluster) checkConsistency() (err error) {
 			return
 		}
 		if err = clus.updateRevision(); err != nil {
-			clus.logger.Warn(
+			clus.lg.Warn(
 				"updateRevision failed",
 				zap.Error(err),
 			)
@@ -440,20 +440,20 @@ func (clus *Cluster) checkConsistency() (err error) {
 		err = clus.startStresser()
 	}()
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"checking consistency and invariant of cluster",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
 		zap.String("desc", clus.failures[clus.cs].Desc()),
 	)
 	if err = clus.checker.Check(); err != nil {
-		clus.logger.Warn(
+		clus.lg.Warn(
 			"checker.Check failed",
 			zap.Error(err),
 		)
 		return err
 	}
-	clus.logger.Info(
+	clus.lg.Info(
 		"checked consistency and invariant of cluster",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
@@ -488,7 +488,7 @@ func (clus *Cluster) broadcastOperation(op rpcpb.Operation) error {
 				strings.Contains(err.Error(), "rpc error: code = Unavailable desc = transport is closing") {
 				// agent server has already closed;
 				// so this error is expected
-				clus.logger.Info(
+				clus.lg.Info(
 					"successfully destroyed",
 					zap.String("member", clus.Members[i].EtcdClientEndpoint),
 				)
@@ -511,13 +511,13 @@ func (clus *Cluster) sendOperation(idx int, op rpcpb.Operation) error {
 		clus.agentRequests[idx].Operation = op
 	}
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"sending request",
 		zap.String("operation", op.String()),
 		zap.String("to", clus.Members[idx].EtcdClientEndpoint),
 	)
 	err := clus.agentStreams[idx].Send(clus.agentRequests[idx])
-	clus.logger.Info(
+	clus.lg.Info(
 		"sent request",
 		zap.String("operation", op.String()),
 		zap.String("to", clus.Members[idx].EtcdClientEndpoint),
@@ -527,14 +527,14 @@ func (clus *Cluster) sendOperation(idx int, op rpcpb.Operation) error {
 		return err
 	}
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"receiving response",
 		zap.String("operation", op.String()),
 		zap.String("from", clus.Members[idx].EtcdClientEndpoint),
 	)
 	resp, err := clus.agentStreams[idx].Recv()
 	if resp != nil {
-		clus.logger.Info(
+		clus.lg.Info(
 			"received response",
 			zap.String("operation", op.String()),
 			zap.String("from", clus.Members[idx].EtcdClientEndpoint),
@@ -543,7 +543,7 @@ func (clus *Cluster) sendOperation(idx int, op rpcpb.Operation) error {
 			zap.Error(err),
 		)
 	} else {
-		clus.logger.Info(
+		clus.lg.Info(
 			"received empty response",
 			zap.String("operation", op.String()),
 			zap.String("from", clus.Members[idx].EtcdClientEndpoint),
@@ -562,26 +562,26 @@ func (clus *Cluster) sendOperation(idx int, op rpcpb.Operation) error {
 
 // DestroyEtcdAgents terminates all tester connections to agents and etcd servers.
 func (clus *Cluster) DestroyEtcdAgents() {
-	clus.logger.Info("destroying etcd servers and agents")
+	clus.lg.Info("destroying etcd servers and agents")
 	err := clus.broadcastOperation(rpcpb.Operation_DestroyEtcdAgent)
 	if err != nil {
-		clus.logger.Warn("failed to destroy etcd servers and agents", zap.Error(err))
+		clus.lg.Warn("failed to destroy etcd servers and agents", zap.Error(err))
 	} else {
-		clus.logger.Info("destroyed etcd servers and agents")
+		clus.lg.Info("destroyed etcd servers and agents")
 	}
 
 	for i, conn := range clus.agentConns {
-		clus.logger.Info("closing connection to agent", zap.String("agent-address", clus.Members[i].AgentAddr))
+		clus.lg.Info("closing connection to agent", zap.String("agent-address", clus.Members[i].AgentAddr))
 		err := conn.Close()
-		clus.logger.Info("closed connection to agent", zap.String("agent-address", clus.Members[i].AgentAddr), zap.Error(err))
+		clus.lg.Info("closed connection to agent", zap.String("agent-address", clus.Members[i].AgentAddr), zap.Error(err))
 	}
 
 	if clus.testerHTTPServer != nil {
-		clus.logger.Info("closing tester HTTP server", zap.String("tester-address", clus.Tester.TesterAddr))
+		clus.lg.Info("closing tester HTTP server", zap.String("tester-address", clus.Tester.TesterAddr))
 		ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
 		err := clus.testerHTTPServer.Shutdown(ctx)
 		cancel()
-		clus.logger.Info("closed tester HTTP server", zap.String("tester-address", clus.Tester.TesterAddr), zap.Error(err))
+		clus.lg.Info("closed tester HTTP server", zap.String("tester-address", clus.Tester.TesterAddr), zap.Error(err))
 	}
 }
 
@@ -595,13 +595,13 @@ func (clus *Cluster) WaitHealth() error {
 	// reasonable workload (https://github.com/coreos/etcd/issues/2698)
 	for i := 0; i < 60; i++ {
 		for _, m := range clus.Members {
-			clus.logger.Info(
+			clus.lg.Info(
 				"writing health key",
 				zap.Int("retries", i),
 				zap.String("endpoint", m.EtcdClientEndpoint),
 			)
 			if err = m.WriteHealthKey(); err != nil {
-				clus.logger.Warn(
+				clus.lg.Warn(
 					"writing health key failed",
 					zap.Int("retries", i),
 					zap.String("endpoint", m.EtcdClientEndpoint),
@@ -609,14 +609,14 @@ func (clus *Cluster) WaitHealth() error {
 				)
 				break
 			}
-			clus.logger.Info(
+			clus.lg.Info(
 				"wrote health key",
 				zap.Int("retries", i),
 				zap.String("endpoint", m.EtcdClientEndpoint),
 			)
 		}
 		if err == nil {
-			clus.logger.Info(
+			clus.lg.Info(
 				"writing health key success on all members",
 				zap.Int("retries", i),
 			)
@@ -683,7 +683,7 @@ func (clus *Cluster) compactKV(rev int64, timeout time.Duration) (err error) {
 	for i, m := range clus.Members {
 		conn, derr := m.DialEtcdGRPCServer()
 		if derr != nil {
-			clus.logger.Warn(
+			clus.lg.Warn(
 				"compactKV dial failed",
 				zap.String("endpoint", m.EtcdClientEndpoint),
 				zap.Error(derr),
@@ -693,7 +693,7 @@ func (clus *Cluster) compactKV(rev int64, timeout time.Duration) (err error) {
 		}
 		kvc := pb.NewKVClient(conn)
 
-		clus.logger.Info(
+		clus.lg.Info(
 			"compacting",
 			zap.String("endpoint", m.EtcdClientEndpoint),
 			zap.Int64("compact-revision", rev),
@@ -709,14 +709,14 @@ func (clus *Cluster) compactKV(rev int64, timeout time.Duration) (err error) {
 		succeed := true
 		if cerr != nil {
 			if strings.Contains(cerr.Error(), "required revision has been compacted") && i > 0 {
-				clus.logger.Info(
+				clus.lg.Info(
 					"compact error is ignored",
 					zap.String("endpoint", m.EtcdClientEndpoint),
 					zap.Int64("compact-revision", rev),
 					zap.Error(cerr),
 				)
 			} else {
-				clus.logger.Warn(
+				clus.lg.Warn(
 					"compact failed",
 					zap.String("endpoint", m.EtcdClientEndpoint),
 					zap.Int64("compact-revision", rev),
@@ -728,7 +728,7 @@ func (clus *Cluster) compactKV(rev int64, timeout time.Duration) (err error) {
 		}
 
 		if succeed {
-			clus.logger.Info(
+			clus.lg.Info(
 				"compacted",
 				zap.String("endpoint", m.EtcdClientEndpoint),
 				zap.Int64("compact-revision", rev),
@@ -753,14 +753,14 @@ func (clus *Cluster) checkCompact(rev int64) error {
 }
 
 func (clus *Cluster) defrag() error {
-	clus.logger.Info(
+	clus.lg.Info(
 		"defragmenting",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
 	)
 	for _, m := range clus.Members {
 		if err := m.Defrag(); err != nil {
-			clus.logger.Warn(
+			clus.lg.Warn(
 				"defrag failed",
 				zap.Int("round", clus.rd),
 				zap.Int("case", clus.cs),
@@ -769,7 +769,7 @@ func (clus *Cluster) defrag() error {
 			return err
 		}
 	}
-	clus.logger.Info(
+	clus.lg.Info(
 		"defragmented",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
diff --git a/tools/functional-tester/tester/cluster_tester.go b/tools/functional-tester/tester/cluster_tester.go
index 8e2b4662c..9d6928ce8 100644
--- a/tools/functional-tester/tester/cluster_tester.go
+++ b/tools/functional-tester/tester/cluster_tester.go
@@ -37,7 +37,7 @@ func (clus *Cluster) StartTester() {
 		clus.rd = round
 
 		if err := clus.doRound(); err != nil {
-			clus.logger.Warn(
+			clus.lg.Warn(
 				"doRound failed; returning",
 				zap.Int("round", clus.rd),
 				zap.Int("case", clus.cs),
@@ -60,21 +60,21 @@ func (clus *Cluster) StartTester() {
 		preModifiedKey = currentModifiedKey
 		timeout := 10 * time.Second
 		timeout += time.Duration(modifiedKey/compactQPS) * time.Second
-		clus.logger.Info(
+		clus.lg.Info(
 			"compacting",
 			zap.Int("round", clus.rd),
 			zap.Int("case", clus.cs),
 			zap.Duration("timeout", timeout),
 		)
 		if err := clus.compact(revToCompact, timeout); err != nil {
-			clus.logger.Warn(
+			clus.lg.Warn(
 				"compact failed",
 				zap.Int("round", clus.rd),
 				zap.Int("case", clus.cs),
 				zap.Error(err),
 			)
 			if err = clus.cleanup(); err != nil {
-				clus.logger.Warn(
+				clus.lg.Warn(
 					"cleanup failed",
 					zap.Int("round", clus.rd),
 					zap.Int("case", clus.cs),
@@ -87,7 +87,7 @@ func (clus *Cluster) StartTester() {
 		}
 		if round > 0 && round%500 == 0 { // every 500 rounds
 			if err := clus.defrag(); err != nil {
-				clus.logger.Warn(
+				clus.lg.Warn(
 					"defrag failed; returning",
 					zap.Int("round", clus.rd),
 					zap.Int("case", clus.cs),
@@ -99,7 +99,7 @@ func (clus *Cluster) StartTester() {
 		}
 	}
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"functional-tester passed",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
@@ -111,7 +111,7 @@ func (clus *Cluster) doRound() error {
 		clus.shuffleFailures()
 	}
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"starting round",
 		zap.Int("round", clus.rd),
 		zap.Strings("failures", clus.failureStrings()),
@@ -121,12 +121,12 @@ func (clus *Cluster) doRound() error {
 
 		caseTotalCounter.WithLabelValues(f.Desc()).Inc()
 
-		clus.logger.Info("wait health before injecting failures")
+		clus.lg.Info("wait health before injecting failures")
 		if err := clus.WaitHealth(); err != nil {
 			return fmt.Errorf("wait full health error: %v", err)
 		}
 
-		clus.logger.Info(
+		clus.lg.Info(
 			"injecting failure",
 			zap.Int("round", clus.rd),
 			zap.Int("case", clus.cs),
@@ -135,7 +135,7 @@ func (clus *Cluster) doRound() error {
 		if err := f.Inject(clus); err != nil {
 			return fmt.Errorf("injection error: %v", err)
 		}
-		clus.logger.Info(
+		clus.lg.Info(
 			"injected failure",
 			zap.Int("round", clus.rd),
 			zap.Int("case", clus.cs),
@@ -145,7 +145,7 @@ func (clus *Cluster) doRound() error {
 		// if run local, recovering server may conflict
 		// with stressing client ports
 		// TODO: use unix for local tests
-		clus.logger.Info(
+		clus.lg.Info(
 			"recovering failure",
 			zap.Int("round", clus.rd),
 			zap.Int("case", clus.cs),
@@ -154,26 +154,26 @@ func (clus *Cluster) doRound() error {
 		if err := f.Recover(clus); err != nil {
 			return fmt.Errorf("recovery error: %v", err)
 		}
-		clus.logger.Info(
+		clus.lg.Info(
 			"recovered failure",
 			zap.Int("round", clus.rd),
 			zap.Int("case", clus.cs),
 			zap.String("desc", f.Desc()),
 		)
 
-		clus.logger.Info("pausing stresser after failure recovery, before wait health")
+		clus.lg.Info("pausing stresser after failure recovery, before wait health")
 		clus.pauseStresser()
 
-		clus.logger.Info("wait health after recovering failures")
+		clus.lg.Info("wait health after recovering failures")
 		if err := clus.WaitHealth(); err != nil {
 			return fmt.Errorf("wait full health error: %v", err)
 		}
-		clus.logger.Info("check consistency after recovering failures")
+		clus.lg.Info("check consistency after recovering failures")
 		if err := clus.checkConsistency(); err != nil {
 			return fmt.Errorf("tt.checkConsistency error (%v)", err)
 		}
 
-		clus.logger.Info(
+		clus.lg.Info(
 			"failure case passed",
 			zap.Int("round", clus.rd),
 			zap.Int("case", clus.cs),
@@ -181,7 +181,7 @@ func (clus *Cluster) doRound() error {
 		)
 	}
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"finished round",
 		zap.Int("round", clus.rd),
 		zap.Strings("failures", clus.failureStrings()),
@@ -196,7 +196,7 @@ func (clus *Cluster) updateRevision() error {
 		break // just need get one of the current revisions
 	}
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"updated current revision",
 		zap.Int64("current-revision", clus.currentRevision),
 	)
@@ -204,7 +204,7 @@ func (clus *Cluster) updateRevision() error {
 }
 
 func (clus *Cluster) compact(rev int64, timeout time.Duration) (err error) {
-	clus.logger.Info("pausing stresser before compact")
+	clus.lg.Info("pausing stresser before compact")
 	clus.pauseStresser()
 	defer func() {
 		if err == nil {
@@ -212,7 +212,7 @@ func (clus *Cluster) compact(rev int64, timeout time.Duration) (err error) {
 		}
 	}()
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"compacting storage",
 		zap.Int64("current-revision", clus.currentRevision),
 		zap.Int64("compact-revision", rev),
@@ -220,19 +220,19 @@ func (clus *Cluster) compact(rev int64, timeout time.Duration) (err error) {
 	if err = clus.compactKV(rev, timeout); err != nil {
 		return err
 	}
-	clus.logger.Info(
+	clus.lg.Info(
 		"compacted storage",
 		zap.Int64("current-revision", clus.currentRevision),
 		zap.Int64("compact-revision", rev),
 	)
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"checking compaction",
 		zap.Int64("current-revision", clus.currentRevision),
 		zap.Int64("compact-revision", rev),
 	)
 	if err = clus.checkCompact(rev); err != nil {
-		clus.logger.Warn(
+		clus.lg.Warn(
 			"checkCompact failed",
 			zap.Int64("current-revision", clus.currentRevision),
 			zap.Int64("compact-revision", rev),
@@ -240,7 +240,7 @@ func (clus *Cluster) compact(rev int64, timeout time.Duration) (err error) {
 		)
 		return err
 	}
-	clus.logger.Info(
+	clus.lg.Info(
 		"confirmed compaction",
 		zap.Int64("current-revision", clus.currentRevision),
 		zap.Int64("compact-revision", rev),
@@ -254,7 +254,7 @@ func (clus *Cluster) failed() {
 		return
 	}
 
-	clus.logger.Info(
+	clus.lg.Info(
 		"exiting on failure",
 		zap.Int("round", clus.rd),
 		zap.Int("case", clus.cs),
@@ -275,7 +275,7 @@ func (clus *Cluster) cleanup() error {
 
 	clus.closeStresser()
 	if err := clus.FailArchive(); err != nil {
-		clus.logger.Warn(
+		clus.lg.Warn(
 			"cleanup failed",
 			zap.Int("round", clus.rd),
 			zap.Int("case", clus.cs),
@@ -284,7 +284,7 @@ func (clus *Cluster) cleanup() error {
 		return err
 	}
 	if err := clus.Restart(); err != nil {
-		clus.logger.Warn(
+		clus.lg.Warn(
 			"restart failed",
 			zap.Int("round", clus.rd),
 			zap.Int("case", clus.cs),
diff --git a/tools/functional-tester/tester/failure_case_delay.go b/tools/functional-tester/tester/failure_case_delay.go
index ba6d5a291..882a61888 100644
--- a/tools/functional-tester/tester/failure_case_delay.go
+++ b/tools/functional-tester/tester/failure_case_delay.go
@@ -30,7 +30,7 @@ func (f *failureDelay) Inject(clus *Cluster) error {
 		return err
 	}
 	if f.delayDuration > 0 {
-		clus.logger.Info(
+		clus.lg.Info(
 			"sleeping in failureDelay",
 			zap.Duration("delay", f.delayDuration),
 			zap.String("case", f.Failure.Desc()),
diff --git a/tools/functional-tester/tester/stress.go b/tools/functional-tester/tester/stress.go
index d23a88e9b..646fed1f8 100644
--- a/tools/functional-tester/tester/stress.go
+++ b/tools/functional-tester/tester/stress.go
@@ -21,6 +21,7 @@ import (
 	"go.uber.org/zap"
 )
 
+// Stresser defines stressing client operations.
 type Stresser interface {
 	// Stress starts to stress the etcd cluster
 	Stress() error
@@ -38,7 +39,7 @@ type Stresser interface {
 func newStresser(clus *Cluster, idx int) Stresser {
 	stressers := make([]Stresser, len(clus.Tester.StressTypes))
 	for i, stype := range clus.Tester.StressTypes {
-		clus.logger.Info("creating stresser", zap.String("type", stype))
+		clus.lg.Info("creating stresser", zap.String("type", stype))
 
 		switch stype {
 		case "NO_STRESS":
@@ -48,7 +49,7 @@ func newStresser(clus *Cluster, idx int) Stresser {
 			// TODO: Too intensive stressing clients can panic etcd member with
 			// 'out of memory' error. Put rate limits in server side.
 			stressers[i] = &keyStresser{
-				logger:            clus.logger,
+				lg:                clus.lg,
 				Endpoint:          clus.Members[idx].EtcdClientEndpoint,
 				keySize:           int(clus.Tester.StressKeySize),
 				keyLargeSize:      int(clus.Tester.StressKeySizeLarge),
@@ -61,7 +62,7 @@ func newStresser(clus *Cluster, idx int) Stresser {
 
 		case "LEASE":
 			stressers[i] = &leaseStresser{
-				logger:       clus.logger,
+				lg:           clus.lg,
 				endpoint:     clus.Members[idx].EtcdClientEndpoint,
 				numLeases:    10, // TODO: configurable
 				keysPerLease: 10, // TODO: configurable
diff --git a/tools/functional-tester/tester/stress_key.go b/tools/functional-tester/tester/stress_key.go
index fc291beec..49fba0b26 100644
--- a/tools/functional-tester/tester/stress_key.go
+++ b/tools/functional-tester/tester/stress_key.go
@@ -33,7 +33,7 @@ import (
 )
 
 type keyStresser struct {
-	logger *zap.Logger
+	lg *zap.Logger
 
 	Endpoint string // TODO: use Member
 
@@ -96,7 +96,7 @@ func (s *keyStresser) Stress() error {
 		go s.run(ctx)
 	}
 
-	s.logger.Info(
+	s.lg.Info(
 		"key stresser started in background",
 		zap.String("endpoint", s.Endpoint),
 	)
@@ -150,7 +150,7 @@ func (s *keyStresser) run(ctx context.Context) {
 			// from stresser.Cancel method:
 			return
 		default:
-			s.logger.Warn(
+			s.lg.Warn(
 				"key stresser exited with error",
 				zap.String("endpoint", s.Endpoint),
 				zap.Error(err),
@@ -169,7 +169,7 @@ func (s *keyStresser) Close() {
 	s.conn.Close()
 	s.wg.Wait()
 
-	s.logger.Info(
+	s.lg.Info(
 		"key stresser is closed",
 		zap.String("endpoint", s.Endpoint),
 	)
diff --git a/tools/functional-tester/tester/stress_lease.go b/tools/functional-tester/tester/stress_lease.go
index bf65d294a..3c5f3c2d9 100644
--- a/tools/functional-tester/tester/stress_lease.go
+++ b/tools/functional-tester/tester/stress_lease.go
@@ -37,7 +37,7 @@ const (
 )
 
 type leaseStresser struct {
-	logger *zap.Logger
+	lg *zap.Logger
 
 	endpoint string
 	cancel   func()
@@ -122,7 +122,7 @@ func (ls *leaseStresser) setupOnce() error {
 }
 
 func (ls *leaseStresser) Stress() error {
-	ls.logger.Info(
+	ls.lg.Info(
 		"lease stresser is started",
 		zap.String("endpoint", ls.endpoint),
 	)
@@ -161,22 +161,22 @@ func (ls *leaseStresser) run() {
 			return
 		}
 
-		ls.logger.Debug(
+		ls.lg.Debug(
 			"lease stresser is creating leases",
 			zap.String("endpoint", ls.endpoint),
 		)
 		ls.createLeases()
-		ls.logger.Debug(
+		ls.lg.Debug(
 			"lease stresser created leases",
 			zap.String("endpoint", ls.endpoint),
 		)
 
-		ls.logger.Debug(
+		ls.lg.Debug(
 			"lease stresser is dropped leases",
 			zap.String("endpoint", ls.endpoint),
 		)
 		ls.randomlyDropLeases()
-		ls.logger.Debug(
+		ls.lg.Debug(
 			"lease stresser dropped leases",
 			zap.String("endpoint", ls.endpoint),
 		)
@@ -206,7 +206,7 @@ func (ls *leaseStresser) createAliveLeases() {
 			defer wg.Done()
 			leaseID, err := ls.createLeaseWithKeys(TTL)
 			if err != nil {
-				ls.logger.Debug(
+				ls.lg.Debug(
 					"createLeaseWithKeys failed",
 					zap.String("endpoint", ls.endpoint),
 					zap.Error(err),
@@ -244,7 +244,7 @@ func (ls *leaseStresser) createShortLivedLeases() {
 func (ls *leaseStresser) createLeaseWithKeys(ttl int64) (int64, error) {
 	leaseID, err := ls.createLease(ttl)
 	if err != nil {
-		ls.logger.Debug(
+		ls.lg.Debug(
 			"createLease failed",
 			zap.String("endpoint", ls.endpoint),
 			zap.Error(err),
@@ -252,7 +252,7 @@ func (ls *leaseStresser) createLeaseWithKeys(ttl int64) (int64, error) {
 		return -1, err
 	}
 
-	ls.logger.Debug(
+	ls.lg.Debug(
 		"createLease created lease",
 		zap.String("endpoint", ls.endpoint),
 		zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -273,7 +273,7 @@ func (ls *leaseStresser) randomlyDropLeases() {
 			// if randomlyDropLease encountered an error such as context is cancelled, remove the lease from aliveLeases
 			// because we can't tell whether the lease is dropped or not.
 			if err != nil {
-				ls.logger.Debug(
+				ls.lg.Debug(
 					"randomlyDropLease failed",
 					zap.String("endpoint", ls.endpoint),
 					zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -285,7 +285,7 @@ func (ls *leaseStresser) randomlyDropLeases() {
 			if !dropped {
 				return
 			}
-			ls.logger.Debug(
+			ls.lg.Debug(
 				"randomlyDropLease dropped a lease",
 				zap.String("endpoint", ls.endpoint),
 				zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -314,7 +314,7 @@ func (ls *leaseStresser) keepLeaseAlive(leaseID int64) {
 		select {
 		case <-time.After(500 * time.Millisecond):
 		case <-ls.ctx.Done():
-			ls.logger.Debug(
+			ls.lg.Debug(
 				"keepLeaseAlive context canceled",
 				zap.String("endpoint", ls.endpoint),
 				zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -328,7 +328,7 @@ func (ls *leaseStresser) keepLeaseAlive(leaseID int64) {
 			renewTime, ok := ls.aliveLeases.read(leaseID)
 			if ok && renewTime.Add(TTL/2*time.Second).Before(time.Now()) {
 				ls.aliveLeases.remove(leaseID)
-				ls.logger.Debug(
+				ls.lg.Debug(
 					"keepLeaseAlive lease has not been renewed, dropped it",
 					zap.String("endpoint", ls.endpoint),
 					zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -338,7 +338,7 @@ func (ls *leaseStresser) keepLeaseAlive(leaseID int64) {
 		}
 
 		if err != nil {
-			ls.logger.Debug(
+			ls.lg.Debug(
 				"keepLeaseAlive lease creates stream error",
 				zap.String("endpoint", ls.endpoint),
 				zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -351,14 +351,14 @@ func (ls *leaseStresser) keepLeaseAlive(leaseID int64) {
 			continue
 		}
 
-		ls.logger.Debug(
+		ls.lg.Debug(
 			"keepLeaseAlive stream sends lease keepalive request",
 			zap.String("endpoint", ls.endpoint),
 			zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
 		)
 		err = stream.Send(&pb.LeaseKeepAliveRequest{ID: leaseID})
 		if err != nil {
-			ls.logger.Debug(
+			ls.lg.Debug(
 				"keepLeaseAlive stream failed to send lease keepalive request",
 				zap.String("endpoint", ls.endpoint),
 				zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -367,14 +367,14 @@ func (ls *leaseStresser) keepLeaseAlive(leaseID int64) {
 			continue
 		}
 		leaseRenewTime := time.Now()
-		ls.logger.Debug(
+		ls.lg.Debug(
 			"keepLeaseAlive stream sent lease keepalive request",
 			zap.String("endpoint", ls.endpoint),
 			zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
 		)
 		respRC, err := stream.Recv()
 		if err != nil {
-			ls.logger.Debug(
+			ls.lg.Debug(
 				"keepLeaseAlive stream failed to receive lease keepalive response",
 				zap.String("endpoint", ls.endpoint),
 				zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -385,7 +385,7 @@ func (ls *leaseStresser) keepLeaseAlive(leaseID int64) {
 		// lease expires after TTL become 0
 		// don't send keepalive if the lease has expired
 		if respRC.TTL <= 0 {
-			ls.logger.Debug(
+			ls.lg.Debug(
 				"keepLeaseAlive stream received lease keepalive response TTL <= 0",
 				zap.String("endpoint", ls.endpoint),
 				zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -395,7 +395,7 @@ func (ls *leaseStresser) keepLeaseAlive(leaseID int64) {
 			return
 		}
 		// renew lease timestamp only if lease is present
-		ls.logger.Debug(
+		ls.lg.Debug(
 			"keepLeaseAlive renewed a lease",
 			zap.String("endpoint", ls.endpoint),
 			zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -444,7 +444,7 @@ func (ls *leaseStresser) randomlyDropLease(leaseID int64) (bool, error) {
 		}
 	}
 
-	ls.logger.Debug(
+	ls.lg.Debug(
 		"randomlyDropLease error",
 		zap.String("endpoint", ls.endpoint),
 		zap.String("lease-id", fmt.Sprintf("%016x", leaseID)),
@@ -458,7 +458,7 @@ func (ls *leaseStresser) Pause() {
 }
 
 func (ls *leaseStresser) Close() {
-	ls.logger.Info(
+	ls.lg.Info(
 		"lease stresser is closing",
 		zap.String("endpoint", ls.endpoint),
 	)
@@ -466,7 +466,7 @@ func (ls *leaseStresser) Close() {
 	ls.runWg.Wait()
 	ls.aliveWg.Wait()
 	ls.conn.Close()
-	ls.logger.Info(
+	ls.lg.Info(
 		"lease stresser is closed",
 		zap.String("endpoint", ls.endpoint),
 	)
@@ -478,7 +478,7 @@ func (ls *leaseStresser) ModifiedKeys() int64 {
 
 func (ls *leaseStresser) Checker() Checker {
 	return &leaseChecker{
-		logger:   ls.logger,
+		lg:       ls.lg,
 		endpoint: ls.endpoint,
 		ls:       ls,
 	}