diff --git a/go/pserver/etcd_client.go b/go/pserver/etcd_client.go
index 20041d04d089a08a513b607fa887d45f9f837ebb..1f77787150d16052e3588e9c1795c8d5dafa08e6 100644
--- a/go/pserver/etcd_client.go
+++ b/go/pserver/etcd_client.go
@@ -191,8 +191,8 @@ func (e *EtcdClient) registerPserverEtcd(ctx context.Context) (int, error) {
 
 // PutKey put into etcd with value by key specified
 func (e *EtcdClient) PutKey(key string, value []byte, timeout int) error {
-	ctx, err := context.WithTimeout(context.Background(), time.Second*time.Duration(timeout))
-	_, err = e.Put(ctx, key, value)
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*time.Duration(timeout))
+	_, err := e.etcdClient.Put(ctx, key, string(value))
 	cancel()
 	if err != nil {
 		return err
diff --git a/go/pserver/optimizer_test.go b/go/pserver/optimizer_test.go
index 0b2f4cfa41a630645c128ac13826de9d8b1d521b..d19e9de92e0b33b1d9619adb615a24884097a38f 100644
--- a/go/pserver/optimizer_test.go
+++ b/go/pserver/optimizer_test.go
@@ -19,6 +19,6 @@ func TestOptimizerCreateRelease(t *testing.T) {
 		Param:  p,
 		Config: config,
 	}
-	o := newOptimizer(param)
+	o := newOptimizer(param, nil)
 	o.Cleanup()
 }
diff --git a/go/pserver/service.go b/go/pserver/service.go
index f27feb247d84a0a171bb5115d7f949a6edbb8b41..cb3741af7ab95a1c2084a3fe34a9607309dbd017 100644
--- a/go/pserver/service.go
+++ b/go/pserver/service.go
@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"crypto/md5"
 	"encoding/gob"
+	"encoding/hex"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -67,30 +68,19 @@ type checkpointMeta struct {
 type Checkpoint []parameterCheckPoint
 
 // Gradient is the gradient of the parameter.
+type Gradient Parameter
 
 // Service is the RPC service for pserver.
 type Service struct {
 	initialized        chan struct{}
 	idx                int
-	checkpointInterval int
+	checkpointInterval time.Duration
 	checkpointPath     string
 	client             *EtcdClient
 	mu                 sync.Mutex
 	optMap             map[string]*optimizer
 }
 
-// //serialize ParameterWithConfig to byte stream
-// func GetBytes(content ...interface{}) ([]byte, error) {
-
-// 	var buf bytes.Buffer
-// 	encoder := gob.NewEncoder(&buf)
-// 	err := encoder.Encode(content)
-// 	if err != nil {
-// 		return nil, err
-// 	}
-// 	return buf.Bytes(), nil
-// }
-
 // NewService creates a new service, will bypass etcd registration if no
 // endpoints specified.
 func NewService(idx int, seconds int, path string, client *EtcdClient, cp Checkpoint) (*Service, error) {
@@ -129,7 +119,7 @@ func (s *Service) InitParam(paramWithConfigs ParameterWithConfig, dummy *int) er
 	// TODO(helin): check if paramWithConfigs.Param.Content is
 	// properly memory aligned, if not, make copy to a memory
 	// aligned region.
-	s.optMap[paramWithConfigs.Param.Name] = newOptimizer(paramWithConfigs)
+	s.optMap[paramWithConfigs.Param.Name] = newOptimizer(paramWithConfigs, nil)
 	return nil
 }
 
@@ -218,7 +208,7 @@ func (s *Service) doCheckpoint() error {
 	cpMeta.UUID = s.checkpointPath + strconv.Itoa(s.idx)
 	cpMeta.Timestamp = time.Now().String()
 	h := md5.New()
-	cpMeta.Md5sum = h.Sum(buf.Bytes())
+	cpMeta.Md5sum = hex.EncodeToString(h.Sum(buf.Bytes()))
 
 	cpMetajson, err := json.Marshal(cpMeta)
 	s.client.PutKey(filepath.Join(PsCheckpoint, strconv.Itoa(s.idx)), cpMetajson, 3)
diff --git a/go/pserver/service_test.go b/go/pserver/service_test.go
index 75d4732ea7862a91126bdd45c2c6d96af049ed54..f365a4539a2d0489fb72b3f2ad1a478bb8d1f727 100644
--- a/go/pserver/service_test.go
+++ b/go/pserver/service_test.go
@@ -87,7 +87,8 @@ func TestServiceFull(t *testing.T) {
 }
 
 func TestMultipleInit(t *testing.T) {
-	s, err := pserver.NewService(0)
+	var cp pserver.Checkpoint
+	s, err := pserver.NewService(0, 1, "", nil, cp)
 	if err != nil {
 		t.Error(err)
 	}
@@ -103,7 +104,8 @@ func TestMultipleInit(t *testing.T) {
 }
 
 func TestUninitialized(t *testing.T) {
-	s, err := pserver.NewService(0)
+	var cp pserver.Checkpoint
+	s, err := pserver.NewService(0, 1, "", nil, cp)
 	err = s.SendGrad(pserver.Gradient{}, nil)
 	if err.Error() != pserver.Uninitialized {
 		t.FailNow()
@@ -111,7 +113,8 @@ func TestUninitialized(t *testing.T) {
 }
 
 func TestBlockUntilInitialized(t *testing.T) {
-	s, err := pserver.NewService(0)
+	var cp pserver.Checkpoint
+	s, err := pserver.NewService(0, 1, "", nil, cp)
 	if err != nil {
 		t.Error(err)
 	}
@@ -129,16 +132,6 @@ func TestBlockUntilInitialized(t *testing.T) {
 		ch <- struct{}{}
 	}()
 
-	wg.Add(1)
-	go func() {
-		err := s.Save("", nil)
-		if err != nil {
-			errCh <- err
-		}
-		wg.Done()
-		ch <- struct{}{}
-	}()
-
 	time.Sleep(50 * time.Millisecond)
 
 	select {