Fix bug and update doc

Signed-off-by: Nzhenshan.cao <zhenshan.cao@zilliz.com>

docs/developer_guides/developer_guides.md

@@ -442,17 +442,17 @@ type TsMsg interface {
   Ts() Timestamp
 }
 
-type TsMsgMarshaler interface {
-  Marshal(input *TsMsg) ([]byte, Status)
-  Unmarshal(input []byte) (*TsMsg, Status)
-}
-
 type MsgPack struct {
   BeginTs Timestamp
   EndTs Timestamp
   Msgs []*TsMsg
 }
 
+type TsMsgMarshaler interface {
+  Marshal(input *TsMsg) ([]byte, Status)
+  Unmarshal(input []byte) (*TsMsg, Status)
+}
+
 type MsgStream interface {
   SetMsgMarshaler(marshal *TsMsgMarshaler, unmarshal *TsMsgMarshaler)
   Produce(*MsgPack) Status
@@ -461,14 +461,17 @@ type MsgStream interface {
 
 type PulsarMsgStream struct {
   client *pulsar.Client
-  produceChannels []string
-  consumeChannels []string
-  
+  msgHashFunc (*MsgPack) map[int32]*MsgPack // return a map from produceChannel idx to *MsgPack
+  producers []*pulsar.Producer
+  consumers []*pulsar.Consumer
   msgMarshaler *TsMsgMarshaler
   msgUnmarshaler *TsMsgMarshaler
 }
 
+func (ms *PulsarMsgStream) SetProducerChannels(channels []string)
+func (ms *PulsarMsgStream) SetConsumerChannels(channels []string)
 func (ms *PulsarMsgStream) SetMsgMarshaler(marshal *TsMsgMarshaler, unmarshal *TsMsgMarshaler)
+func (ms *PulsarMsgStream) SetMsgHashFunc(XXX)
 func (ms *PulsarMsgStream) Produce(*MsgPack) Status
 func (ms *PulsarMsgStream) Consume() *MsgPack //return messages in one time tick