diff --git a/src/inc/taoserror.h b/src/inc/taoserror.h
index c913b2cf2a6fb1506d5c6d9b1d483ec063bede01..7c7e7ec31ab88a1f048767b9cc4aa486bfa788cd 100644
--- a/src/inc/taoserror.h
+++ b/src/inc/taoserror.h
@@ -267,6 +267,12 @@ TAOS_DEFINE_ERROR(TSDB_CODE_SYN_NOT_ENABLED,              0, 0x0901, "Sync modul
 TAOS_DEFINE_ERROR(TSDB_CODE_SYN_INVALID_VERSION,          0, 0x0902, "Invalid Sync version")
 TAOS_DEFINE_ERROR(TSDB_CODE_SYN_CONFIRM_EXPIRED,          0, 0x0903, "Sync confirm expired")
 TAOS_DEFINE_ERROR(TSDB_CODE_SYN_TOO_MANY_FWDINFO,         0, 0x0904, "Too many sync fwd infos")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_MISMATCHED_PROTOCOL,      0, 0x0905, "Mismatched protocol")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_MISMATCHED_CLUSTERID,     0, 0x0906, "Mismatched clusterId")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_MISMATCHED_SIGNATURE,     0, 0x0907, "Mismatched signature")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_INVALID_CHECKSUM,         0, 0x0908, "Invalid msg checksum")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_INVALID_MSGLEN,           0, 0x0909, "Invalid msg length")
+TAOS_DEFINE_ERROR(TSDB_CODE_SYN_INVALID_MSGTYPE,          0, 0x090A, "Invalid msg type")
 
 // wal
 TAOS_DEFINE_ERROR(TSDB_CODE_WAL_APP_ERROR,                0, 0x1000, "Unexpected generic error in wal")
diff --git a/src/inc/tsync.h b/src/inc/tsync.h
index 0ce2a1a495b7826635d07ac9139cb77b306c9330..4dae86bbed538a0801251f62723a471215655e24 100644
--- a/src/inc/tsync.h
+++ b/src/inc/tsync.h
@@ -119,10 +119,6 @@ int32_t syncGetNodesRole(int64_t rid, SNodesRole *);
 extern char *syncRole[];
 
 //global configurable parameters
-extern int32_t  tsMaxSyncNum;
-extern int32_t  tsSyncTcpThreads;
-extern int32_t  tsSyncTimer;
-extern int32_t  tsMaxFwdInfo;
 extern int32_t  sDebugFlag;
 extern char     tsArbitrator[];
 extern uint16_t tsSyncPort;
diff --git a/src/inc/vnode.h b/src/inc/vnode.h
index 95f1d27b591c2503461826e175c3e768c0db77cc..cbe64484b11462fcf3f107625cb0e00b0ac682f4 100644
--- a/src/inc/vnode.h
+++ b/src/inc/vnode.h
@@ -48,7 +48,7 @@ typedef struct {
   void *   pVnode;
   SRpcMsg  rpcMsg;
   SRspRet  rspRet;
-  char     reserveForSync[16];
+  char     reserveForSync[24];
   SWalHead pHead[];
 } SVWriteMsg;
 
diff --git a/src/mnode/inc/mnodeSdb.h b/src/mnode/inc/mnodeSdb.h
index 31ea2da640ef3b20b84ca769a22637332d6ffe34..e4df562d81c7ef91fe1ff62eba6611d76e0a3ff1 100644
--- a/src/mnode/inc/mnodeSdb.h
+++ b/src/mnode/inc/mnodeSdb.h
@@ -59,7 +59,7 @@ typedef struct SSdbRow {
   SMnodeMsg *pMsg;
   int32_t  (*fpReq)(SMnodeMsg *pMsg);
   int32_t  (*fpRsp)(SMnodeMsg *pMsg, int32_t code);
-  char       reserveForSync[16];
+  char       reserveForSync[24];
   SWalHead   pHead[];
 } SSdbRow;
 
diff --git a/src/sync/CMakeLists.txt b/src/sync/CMakeLists.txt
index 60271c771ca0a01bd449cb878fe2269759250fd3..aa38a56f38146bafda8a10ca786bf085bb4ea339 100644
--- a/src/sync/CMakeLists.txt
+++ b/src/sync/CMakeLists.txt
@@ -5,12 +5,12 @@ INCLUDE_DIRECTORIES(inc)
 AUX_SOURCE_DIRECTORY(src SRC)
   
 IF (TD_LINUX)
-  LIST(REMOVE_ITEM SRC src/tarbitrator.c)
+  LIST(REMOVE_ITEM SRC src/syncArbitrator.c)
   ADD_LIBRARY(sync ${SRC})
   TARGET_LINK_LIBRARIES(sync tutil pthread common)
 
-  LIST(APPEND BIN_SRC src/tarbitrator.c)
-  LIST(APPEND BIN_SRC src/taosTcpPool.c)
+  LIST(APPEND BIN_SRC src/syncArbitrator.c)
+  LIST(APPEND BIN_SRC src/syncTcp.c)
   ADD_EXECUTABLE(tarbitrator ${BIN_SRC})
   TARGET_LINK_LIBRARIES(tarbitrator sync common osdetail tutil)
 
diff --git a/src/sync/inc/syncInt.h b/src/sync/inc/syncInt.h
index 2be25447c4a6b45863718ef2b6c402961fecb93f..d855c651f93a58d46e064e67d287f135684f4954 100644
--- a/src/sync/inc/syncInt.h
+++ b/src/sync/inc/syncInt.h
@@ -13,12 +13,14 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef TDENGINE_SYNCINT_H
-#define TDENGINE_SYNCINT_H
+#ifndef TDENGINE_SYNC_INT_H
+#define TDENGINE_SYNC_INT_H
 
 #ifdef __cplusplus
 extern "C" {
 #endif
+#include "syncMsg.h"
+#include "twal.h"
 
 #define sFatal(...) { if (sDebugFlag & DEBUG_FATAL) { taosPrintLog("SYN FATAL ", sDebugFlag, __VA_ARGS__); }}
 #define sError(...) { if (sDebugFlag & DEBUG_ERROR) { taosPrintLog("SYN ERROR ", sDebugFlag, __VA_ARGS__); }}
@@ -27,86 +29,22 @@ extern "C" {
 #define sDebug(...) { if (sDebugFlag & DEBUG_DEBUG) { taosPrintLog("SYN ", sDebugFlag, __VA_ARGS__); }}
 #define sTrace(...) { if (sDebugFlag & DEBUG_TRACE) { taosPrintLog("SYN ", sDebugFlag, __VA_ARGS__); }}
 
-typedef enum {
-  TAOS_SMSG_SYNC_DATA     = 1,
-  TAOS_SMSG_FORWARD       = 2,
-  TAOS_SMSG_FORWARD_RSP   = 3,
-  TAOS_SMSG_SYNC_REQ      = 4,
-  TAOS_SMSG_SYNC_RSP      = 5,
-  TAOS_SMSG_SYNC_MUST     = 6,
-  TAOS_SMSG_STATUS        = 7,
-  TAOS_SMSG_SYNC_DATA_RSP = 8,
-} ESyncMsgType;
+#define SYNC_TCP_THREADS 2
+#define SYNC_MAX_NUM 2
 
 #define SYNC_MAX_SIZE (TSDB_MAX_WAL_SIZE + sizeof(SWalHead) + sizeof(SSyncHead) + 16)
 #define SYNC_RECV_BUFFER_SIZE (5*1024*1024)
-#define SYNC_FWD_TIMER  300
-#define SYNC_ROLE_TIMER 10000
-#define SYNC_WAIT_AFTER_CHOOSE_MASTER 3
+
+#define SYNC_MAX_FWDS 512
+#define SYNC_FWD_TIMER 300
+#define SYNC_ROLE_TIMER 15000             // ms
+#define SYNC_CHECK_INTERVAL 1             // ms
+#define SYNC_WAIT_AFTER_CHOOSE_MASTER 10  // ms
 
 #define nodeRole    pNode->peerInfo[pNode->selfIndex]->role
 #define nodeVersion pNode->peerInfo[pNode->selfIndex]->version
 #define nodeSStatus pNode->peerInfo[pNode->selfIndex]->sstatus
 
-#pragma pack(push, 1)
-
-typedef struct {
-  char     type;        // msg type
-  char     pversion;    // protocol version
-  char     reserved[6]; // not used
-  int32_t  vgId;        // vg ID
-  int32_t  len;         // content length, does not include head
-  // char     cont[];      // message content starts from here
-} SSyncHead;
-
-typedef struct {
-  SSyncHead syncHead;
-  uint16_t  port;
-  uint16_t  tranId;
-  char      fqdn[TSDB_FQDN_LEN];
-  int32_t   sourceId;  // only for arbitrator
-} SFirstPkt;
-
-typedef struct {
-  int8_t   sync;
-  int8_t   reserved;
-  uint16_t tranId;
-} SFirstPktRsp;
-
-typedef struct {
-  int8_t    role;
-  uint64_t  version;
-} SPeerStatus;
-
-typedef struct {
-  int8_t      role;
-  int8_t      ack;
-  int8_t      type;
-  int8_t      reserved[3];
-  uint16_t    tranId;
-  uint64_t    version;
-  SPeerStatus peersStatus[];
-} SPeersStatus;
-
-typedef struct {
-  char      name[TSDB_FILENAME_LEN];
-  uint32_t  magic;
-  uint32_t  index;
-  uint64_t  fversion;
-  int64_t   size;
-} SFileInfo;
-
-typedef struct {
-  int8_t    sync;
-} SFileAck;
-
-typedef struct {
-  uint64_t  version;
-  int32_t   code;
-} SFwdRsp;
-  
-#pragma pack(pop)
-
 typedef struct {
   char *  buffer;
   int32_t bufferSize;
@@ -190,7 +128,6 @@ void    syncRestartConnection(SSyncPeer *pPeer);
 void    syncBroadcastStatus(SSyncNode *pNode);
 void    syncAddPeerRef(SSyncPeer *pPeer);
 int32_t syncDecPeerRef(SSyncPeer *pPeer);
-uint16_t syncGenTranId();
 
 #ifdef __cplusplus
 }
diff --git a/src/sync/inc/syncMsg.h b/src/sync/inc/syncMsg.h
new file mode 100644
index 0000000000000000000000000000000000000000..73f4223c882ff9ce544984b37843070cf579c44a
--- /dev/null
+++ b/src/sync/inc/syncMsg.h
@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TDENGINE_SYNC_MSG_H
+#define TDENGINE_SYNC_MSG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+#include "tsync.h"
+
+typedef enum {
+  TAOS_SMSG_START         = 0,
+  TAOS_SMSG_SYNC_DATA     = 1,
+  TAOS_SMSG_SYNC_DATA_RSP = 2,
+  TAOS_SMSG_SYNC_FWD      = 3,
+  TAOS_SMSG_SYNC_FWD_RSP  = 4,
+  TAOS_SMSG_SYNC_REQ      = 5,
+  TAOS_SMSG_SYNC_REQ_RSP  = 6,
+  TAOS_SMSG_SYNC_MUST     = 7,
+  TAOS_SMSG_SYNC_MUST_RSP = 8,
+  TAOS_SMSG_STATUS        = 9,
+  TAOS_SMSG_STATUS_RSP    = 10,
+  TAOS_SMSG_SETUP         = 11,
+  TAOS_SMSG_SETUP_RSP     = 12,
+  TAOS_SMSG_SYNC_FILE     = 13,
+  TAOS_SMSG_SYNC_FILE_RSP = 14,
+  TAOS_SMSG_END           = 15,
+} ESyncMsgType;
+
+typedef enum {
+  SYNC_STATUS_BROADCAST,
+  SYNC_STATUS_BROADCAST_RSP,
+  SYNC_STATUS_SETUP_CONN,
+  SYNC_STATUS_SETUP_CONN_RSP,
+  SYNC_STATUS_EXCHANGE_DATA,
+  SYNC_STATUS_EXCHANGE_DATA_RSP,
+  SYNC_STATUS_CHECK_ROLE,
+  SYNC_STATUS_CHECK_ROLE_RSP
+} ESyncStatusType;
+
+#pragma pack(push, 1)
+
+typedef struct {
+  int8_t   type;       // msg type
+  int8_t   protocol;   // protocol version
+  uint16_t signature;  // fixed value
+  int32_t  code;       //
+  int32_t  cId;        // cluster Id
+  int32_t  vgId;       // vg ID
+  int32_t  len;        // content length, does not include head
+  uint32_t cksum;
+} SSyncHead;
+
+typedef struct {
+  SSyncHead head;
+  uint16_t  port;
+  uint16_t  tranId;
+  int32_t   sourceId;  // only for arbitrator
+  char      fqdn[TSDB_FQDN_LEN];
+} SSyncMsg;
+
+typedef struct {
+  SSyncHead head;
+  int8_t    sync;
+  int8_t    reserved;
+  uint16_t  tranId;
+  int8_t    reserverd[4];
+} SSyncRsp;
+
+typedef struct {
+  int8_t    role;
+  uint64_t  version;
+} SPeerStatus;
+
+typedef struct {
+  SSyncHead   head;
+  int8_t      role;
+  int8_t      ack;
+  int8_t      type;
+  int8_t      reserved[3];
+  uint16_t    tranId;
+  uint64_t    version;
+  SPeerStatus peersStatus[TAOS_SYNC_MAX_REPLICA];
+} SPeersStatus;
+
+typedef struct {
+  SSyncHead head;
+  char      name[TSDB_FILENAME_LEN];
+  uint32_t  magic;
+  uint32_t  index;
+  uint64_t  fversion;
+  int64_t   size;
+} SFileInfo;
+
+typedef struct {
+  SSyncHead head;
+  int8_t    sync;
+} SFileAck;
+
+typedef struct {
+  SSyncHead head;
+  uint64_t  version;
+  int32_t   code;
+} SFwdRsp;
+
+#pragma pack(pop)
+
+#define SYNC_PROTOCOL_VERSION 1
+#define SYNC_SIGNATURE ((uint16_t)(0xCDEF))
+
+extern char *statusType[];
+
+uint16_t syncGenTranId();
+int32_t  syncCheckHead(SSyncHead *pHead);
+
+void syncBuildSyncFwdMsg(SSyncHead *pHead, int32_t vgId, int32_t len);
+void syncBuildSyncFwdRsp(SFwdRsp *pMsg, int32_t vgId, uint64_t version, int32_t code);
+void syncBuildSyncReqMsg(SSyncMsg *pMsg, int32_t vgId);
+void syncBuildSyncDataMsg(SSyncMsg *pMsg, int32_t vgId);
+void syncBuildSyncSetupMsg(SSyncMsg *pMsg, int32_t vgId);
+void syncBuildPeersStatus(SPeersStatus *pMsg, int32_t vgId);
+
+void syncBuildFileAck(SFileAck *pMsg, int32_t vgId);
+void syncBuildFileInfo(SFileInfo *pMsg, int32_t vgId);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // TDENGINE_VNODEPEER_H
diff --git a/src/sync/inc/taosTcpPool.h b/src/sync/inc/syncTcp.h
similarity index 77%
rename from src/sync/inc/taosTcpPool.h
rename to src/sync/inc/syncTcp.h
index 41043b0cd4c886616d5cecd2739eae684052c395..7db51f2a7115ccf23ee42d17cbe62f0798adf260 100644
--- a/src/sync/inc/taosTcpPool.h
+++ b/src/sync/inc/syncTcp.h
@@ -13,16 +13,13 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef TDENGINE_TCP_POOL_H
-#define TDENGINE_TCP_POOL_H
+#ifndef TDENGINE_SYNC_TCP_POOL_H
+#define TDENGINE_SYNC_TCP_POOL_H
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-typedef void *ttpool_h;
-typedef void *tthread_h;
-
 typedef struct {
   int32_t   numOfThreads;
   uint32_t  serverIp;
@@ -33,10 +30,10 @@ typedef struct {
   void    (*processIncomingConn)(int32_t fd, uint32_t ip);
 } SPoolInfo;
 
-ttpool_h taosOpenTcpThreadPool(SPoolInfo *pInfo);
-void     taosCloseTcpThreadPool(ttpool_h);
-void *   taosAllocateTcpConn(void *, void *ahandle, int32_t connFd);
-void     taosFreeTcpConn(void *);
+void *syncOpenTcpThreadPool(SPoolInfo *pInfo);
+void  syncCloseTcpThreadPool(void *);
+void *syncAllocateTcpConn(void *, void *ahandle, int32_t connFd);
+void  syncFreeTcpConn(void *);
 
 #ifdef __cplusplus
 }
diff --git a/src/sync/src/tarbitrator.c b/src/sync/src/syncArbitrator.c
similarity index 82%
rename from src/sync/src/tarbitrator.c
rename to src/sync/src/syncArbitrator.c
index 4016042de2135f732dfeb2bbc3b0fdc65b1b63f6..1cb2b8f30269c572bc76ddf9c04491d9b77bb3bc 100644
--- a/src/sync/src/tarbitrator.c
+++ b/src/sync/src/syncArbitrator.c
@@ -22,17 +22,17 @@
 #include "tsocket.h"
 #include "tglobal.h"
 #include "taoserror.h"
-#include "taosTcpPool.h"
 #include "twal.h"
 #include "tsync.h"
 #include "syncInt.h"
+#include "syncTcp.h"
 
-static void     arbSignalHandler(int32_t signum, siginfo_t *sigInfo, void *context);
-static void     arbProcessIncommingConnection(int32_t connFd, uint32_t sourceIp);
-static void     arbProcessBrokenLink(void *param);
-static int32_t  arbProcessPeerMsg(void *param, void *buffer);
-static tsem_t   tsArbSem;
-static ttpool_h tsArbTcpPool;
+static void    arbSignalHandler(int32_t signum, siginfo_t *sigInfo, void *context);
+static void    arbProcessIncommingConnection(int32_t connFd, uint32_t sourceIp);
+static void    arbProcessBrokenLink(void *param);
+static int32_t arbProcessPeerMsg(void *param, void *buffer);
+static tsem_t  tsArbSem;
+static void *  tsArbTcpPool;
 
 typedef struct {
   char    id[TSDB_EP_LEN + 24];
@@ -90,7 +90,7 @@ int32_t main(int32_t argc, char *argv[]) {
   info.processBrokenLink = arbProcessBrokenLink;
   info.processIncomingMsg = arbProcessPeerMsg;
   info.processIncomingConn = arbProcessIncommingConnection;
-  tsArbTcpPool = taosOpenTcpThreadPool(&info);
+  tsArbTcpPool = syncOpenTcpThreadPool(&info);
 
   if (tsArbTcpPool == NULL) {
     sDebug("failed to open TCP thread pool, exit...");
@@ -101,8 +101,8 @@ int32_t main(int32_t argc, char *argv[]) {
 
   tsem_wait(&tsArbSem);
 
-  taosCloseTcpThreadPool(tsArbTcpPool);
-  sInfo("TAOS arbitrator is shut down\n");
+  syncCloseTcpThreadPool(tsArbTcpPool);
+  sInfo("TAOS arbitrator is shut down");
   closelog();
 
   return 0;
@@ -113,9 +113,9 @@ static void arbProcessIncommingConnection(int32_t connFd, uint32_t sourceIp) {
   tinet_ntoa(ipstr, sourceIp);
   sDebug("peer TCP connection from ip:%s", ipstr);
 
-  SFirstPkt firstPkt;
-  if (taosReadMsg(connFd, &firstPkt, sizeof(firstPkt)) != sizeof(firstPkt)) {
-    sError("failed to read peer first pkt from ip:%s since %s", ipstr, strerror(errno));
+  SSyncMsg msg;
+  if (taosReadMsg(connFd, &msg, sizeof(SSyncMsg)) != sizeof(SSyncMsg)) {
+    sError("failed to read peer sync msg from ip:%s since %s", ipstr, strerror(errno));
     taosCloseSocket(connFd);
     return;
   }
@@ -127,9 +127,9 @@ static void arbProcessIncommingConnection(int32_t connFd, uint32_t sourceIp) {
     return;
   }
 
-  firstPkt.fqdn[sizeof(firstPkt.fqdn) - 1] = 0;
-  snprintf(pNode->id, sizeof(pNode->id), "vgId:%d, peer:%s:%d", firstPkt.sourceId, firstPkt.fqdn, firstPkt.port);
-  if (firstPkt.syncHead.vgId) {
+  msg.fqdn[TSDB_FQDN_LEN - 1] = 0;
+  snprintf(pNode->id, sizeof(pNode->id), "vgId:%d, peer:%s:%d", msg.sourceId, msg.fqdn, msg.port);
+  if (msg.head.vgId) {
     sDebug("%s, vgId in head is not zero, close the connection", pNode->id);
     tfree(pNode);
     taosCloseSocket(connFd);
@@ -138,7 +138,7 @@ static void arbProcessIncommingConnection(int32_t connFd, uint32_t sourceIp) {
 
   sDebug("%s, arbitrator request is accepted", pNode->id);
   pNode->nodeFd = connFd;
-  pNode->pConn = taosAllocateTcpConn(tsArbTcpPool, pNode, connFd);
+  pNode->pConn = syncAllocateTcpConn(tsArbTcpPool, pNode, connFd);
 
   return;
 }
@@ -156,8 +156,8 @@ static int32_t arbProcessPeerMsg(void *param, void *buffer) {
   int32_t    bytes = 0;
   char *     cont = (char *)buffer;
 
-  int32_t hlen = taosReadMsg(pNode->nodeFd, &head, sizeof(head));
-  if (hlen != sizeof(head)) {
+  int32_t hlen = taosReadMsg(pNode->nodeFd, &head, sizeof(SSyncHead));
+  if (hlen != sizeof(SSyncHead)) {
     sDebug("%s, failed to read msg, hlen:%d", pNode->id, hlen);
     return -1;
   }
diff --git a/src/sync/src/syncMain.c b/src/sync/src/syncMain.c
index aae5dab3cdd5d394307dbbc8c5c4b0040a05d4a7..ac79b486061c191506e527e031e93069759abbb0 100644
--- a/src/sync/src/syncMain.c
+++ b/src/sync/src/syncMain.c
@@ -23,26 +23,19 @@
 #include "tsocket.h"
 #include "tglobal.h"
 #include "taoserror.h"
-#include "taosTcpPool.h"
 #include "tqueue.h"
 #include "twal.h"
 #include "tsync.h"
+#include "syncTcp.h"
 #include "syncInt.h"
 
-// global configurable
-int32_t tsMaxSyncNum = 2;
-int32_t tsSyncTcpThreads = 2;
-int32_t tsMaxFwdInfo = 512;
-int32_t tsSyncTimer = 1;
+int32_t tsSyncNum = 0;  // number of sync in process in whole system
+char    tsNodeFqdn[TSDB_FQDN_LEN] = {0};
 
-// module global, not configurable
-int32_t tsSyncNum;  // number of sync in process in whole system
-char    tsNodeFqdn[TSDB_FQDN_LEN];
-
-static ttpool_h tsTcpPool;
-static void *   tsSyncTmrCtrl = NULL;
-static void *   tsVgIdHash;
-static int32_t  tsSyncRefId = -1;
+static void *  tsTcpPool = NULL;
+static void *  tsSyncTmrCtrl = NULL;
+static void *  tsVgIdHash = NULL;
+static int32_t tsSyncRefId = -1;
 
 // local functions
 static void    syncProcessSyncRequest(char *pMsg, SSyncPeer *pPeer);
@@ -80,36 +73,10 @@ char *syncStatus[] = {
   "invalid"
 };
 
-typedef enum {
-  SYNC_STATUS_BROADCAST,
-  SYNC_STATUS_BROADCAST_RSP,
-  SYNC_STATUS_SETUP_CONN,
-  SYNC_STATUS_SETUP_CONN_RSP,
-  SYNC_STATUS_EXCHANGE_DATA,
-  SYNC_STATUS_EXCHANGE_DATA_RSP,
-  SYNC_STATUS_CHECK_ROLE,
-  SYNC_STATUS_CHECK_ROLE_RSP
-} ESyncStatusType;
-
-char *statusType[] = {
-  "broadcast",
-  "broadcast-rsp",
-  "setup-conn",
-  "setup-conn-rsp",
-  "exchange-data",
-  "exchange-data-rsp",
-  "check-role",
-  "check-role-rsp"
-};
-
-uint16_t syncGenTranId() {
-  return taosRand() & 0XFFFF;
-}
-
 int32_t syncInit() {
   SPoolInfo info = {0};
 
-  info.numOfThreads = tsSyncTcpThreads;
+  info.numOfThreads = SYNC_TCP_THREADS;
   info.serverIp = 0;
   info.port = tsSyncPort;
   info.bufferSize = SYNC_MAX_SIZE;
@@ -117,7 +84,7 @@ int32_t syncInit() {
   info.processIncomingMsg = syncProcessPeerMsg;
   info.processIncomingConn = syncProcessIncommingConnection;
 
-  tsTcpPool = taosOpenTcpThreadPool(&info);
+  tsTcpPool = syncOpenTcpThreadPool(&info);
   if (tsTcpPool == NULL) {
     sError("failed to init tcpPool");
     return -1;
@@ -126,16 +93,16 @@ int32_t syncInit() {
   tsSyncTmrCtrl = taosTmrInit(1000, 50, 10000, "SYNC");
   if (tsSyncTmrCtrl == NULL) {
     sError("failed to init tmrCtrl");
-    taosCloseTcpThreadPool(tsTcpPool);
+    syncCloseTcpThreadPool(tsTcpPool);
     tsTcpPool = NULL;
     return -1;
   }
 
   tsVgIdHash = taosHashInit(TSDB_MIN_VNODES, taosGetDefaultHashFunction(TSDB_DATA_TYPE_INT), true, HASH_ENTRY_LOCK);
   if (tsVgIdHash == NULL) {
-    sError("failed to init tsVgIdHash");
+    sError("failed to init vgIdHash");
     taosTmrCleanUp(tsSyncTmrCtrl);
-    taosCloseTcpThreadPool(tsTcpPool);
+    syncCloseTcpThreadPool(tsTcpPool);
     tsTcpPool = NULL;
     tsSyncTmrCtrl = NULL;
     return -1;
@@ -155,7 +122,7 @@ int32_t syncInit() {
 
 void syncCleanUp() {
   if (tsTcpPool) {
-    taosCloseTcpThreadPool(tsTcpPool);
+    syncCloseTcpThreadPool(tsTcpPool);
     tsTcpPool = NULL;
   }
 
@@ -236,7 +203,7 @@ int64_t syncStart(const SSyncInfo *pInfo) {
   sInfo("vgId:%d, %d replicas are configured, quorum:%d role:%s", pNode->vgId, pNode->replica, pNode->quorum,
         syncRole[nodeRole]);
 
-  pNode->pSyncFwds = calloc(sizeof(SSyncFwds) + tsMaxFwdInfo * sizeof(SFwdInfo), 1);
+  pNode->pSyncFwds = calloc(sizeof(SSyncFwds) + SYNC_MAX_FWDS * sizeof(SFwdInfo), 1);
   if (pNode->pSyncFwds == NULL) {
     sError("vgId:%d, no memory to allocate syncFwds", pNode->vgId);
     terrno = TAOS_SYSTEM_ERROR(errno);
@@ -336,6 +303,11 @@ int32_t syncReconfig(int64_t rid, const SSyncCfg *pNewCfg) {
       newPeers[i] = pNode->peerInfo[j];
     }
 
+    if (newPeers[i] == NULL) {
+      sError("vgId:%d, failed to reconfig", pNode->vgId);
+      return TSDB_CODE_SYN_INVALID_CONFIG;
+    }
+
     if ((strcmp(pNewNode->nodeFqdn, tsNodeFqdn) == 0) && (pNewNode->nodePort == tsSyncPort)) {
       pNode->selfIndex = i;
     }
@@ -384,21 +356,13 @@ void syncConfirmForward(int64_t rid, uint64_t version, int32_t code) {
 
   SSyncPeer *pPeer = pNode->pMaster;
   if (pPeer && pNode->quorum > 1) {
-    char msg[sizeof(SSyncHead) + sizeof(SFwdRsp)] = {0};
-
-    SSyncHead *pHead = (SSyncHead *)msg;
-    pHead->type = TAOS_SMSG_FORWARD_RSP;
-    pHead->len = sizeof(SFwdRsp);
-
-    SFwdRsp *pFwdRsp = (SFwdRsp *)(msg + sizeof(SSyncHead));
-    pFwdRsp->version = version;
-    pFwdRsp->code = code;
+    SFwdRsp rsp;
+    syncBuildSyncFwdRsp(&rsp, pNode->vgId, version, code);
 
-    int32_t msgLen = sizeof(SSyncHead) + sizeof(SFwdRsp);
-    if (taosWriteMsg(pPeer->peerFd, msg, msgLen) == msgLen) {
-      sTrace("%s, forward-rsp is sent, code:%x hver:%" PRIu64, pPeer->id, code, version);
+    if (taosWriteMsg(pPeer->peerFd, &rsp, sizeof(SFwdRsp)) == sizeof(SFwdRsp)) {
+      sTrace("%s, forward-rsp is sent, code:0x%x hver:%" PRIu64, pPeer->id, code, version);
     } else {
-      sDebug("%s, failed to send forward ack, restart", pPeer->id);
+      sDebug("%s, failed to send forward-rsp, restart", pPeer->id);
       syncRestartConnection(pPeer);
     }
   }
@@ -509,7 +473,7 @@ static void syncClosePeerConn(SSyncPeer *pPeer) {
   taosClose(pPeer->syncFd);
   if (pPeer->peerFd >= 0) {
     pPeer->peerFd = -1;
-    taosFreeTcpConn(pPeer->pConn);
+    syncFreeTcpConn(pPeer->pConn);
   }
 }
 
@@ -779,7 +743,7 @@ static void syncRestartPeer(SSyncPeer *pPeer) {
   int32_t ret = strcmp(pPeer->fqdn, tsNodeFqdn);
   if (ret > 0 || (ret == 0 && pPeer->port > tsSyncPort)) {
     sDebug("%s, check peer connection in 1000 ms", pPeer->id);
-    taosTmrReset(syncCheckPeerConnection, tsSyncTimer * 1000, pPeer, tsSyncTmrCtrl, &pPeer->timer);
+    taosTmrReset(syncCheckPeerConnection, SYNC_CHECK_INTERVAL, pPeer, tsSyncTmrCtrl, &pPeer->timer);
   }
 }
 
@@ -857,7 +821,7 @@ static void syncRecoverFromMaster(SSyncPeer *pPeer) {
   taosTmrStopA(&pPeer->timer);
 
   // Ensure the sync of mnode not interrupted
-  if (pNode->vgId != 1 && tsSyncNum >= tsMaxSyncNum) {
+  if (pNode->vgId != 1 && tsSyncNum >= SYNC_MAX_NUM) {
     sInfo("%s, %d syncs are in process, try later", pPeer->id, tsSyncNum);
     taosTmrReset(syncTryRecoverFromMaster, 500 + (pNode->vgId * 10) % 200, pPeer, tsSyncTmrCtrl, &pPeer->timer);
     return;
@@ -865,56 +829,42 @@ static void syncRecoverFromMaster(SSyncPeer *pPeer) {
 
   sDebug("%s, try to sync", pPeer->id);
 
-  SFirstPkt firstPkt;
-  memset(&firstPkt, 0, sizeof(firstPkt));
-  firstPkt.syncHead.type = TAOS_SMSG_SYNC_REQ;
-  firstPkt.syncHead.vgId = pNode->vgId;
-  firstPkt.syncHead.len = sizeof(firstPkt) - sizeof(SSyncHead);
-  firstPkt.tranId = syncGenTranId();
-  tstrncpy(firstPkt.fqdn, tsNodeFqdn, sizeof(firstPkt.fqdn));
-  firstPkt.port = tsSyncPort;
-  taosTmrReset(syncNotStarted, tsSyncTimer * 1000, pPeer, tsSyncTmrCtrl, &pPeer->timer);
-
-  if (taosWriteMsg(pPeer->peerFd, &firstPkt, sizeof(firstPkt)) != sizeof(firstPkt)) {
+  SSyncMsg msg;
+  syncBuildSyncReqMsg(&msg, pNode->vgId);
+
+  taosTmrReset(syncNotStarted, SYNC_CHECK_INTERVAL, pPeer, tsSyncTmrCtrl, &pPeer->timer);
+
+  if (taosWriteMsg(pPeer->peerFd, &msg, sizeof(SSyncMsg)) != sizeof(SSyncMsg)) {
     sError("%s, failed to send sync-req to peer", pPeer->id);
   } else {
-    sInfo("%s, sync-req is sent to peer, tranId:%u, sstatus:%s", pPeer->id, firstPkt.tranId, syncStatus[nodeSStatus]);
+    sInfo("%s, sync-req is sent to peer, tranId:%u, sstatus:%s", pPeer->id, msg.tranId, syncStatus[nodeSStatus]);
   }
 }
 
-static void syncProcessFwdResponse(char *cont, SSyncPeer *pPeer) {
+static void syncProcessFwdResponse(SFwdRsp *pFwdRsp, SSyncPeer *pPeer) {
   SSyncNode *pNode = pPeer->pSyncNode;
-  SFwdRsp *  pFwdRsp = (SFwdRsp *)cont;
   SSyncFwds *pSyncFwds = pNode->pSyncFwds;
   SFwdInfo * pFwdInfo;
 
   sTrace("%s, forward-rsp is received, code:%x hver:%" PRIu64, pPeer->id, pFwdRsp->code, pFwdRsp->version);
   SFwdInfo *pFirst = pSyncFwds->fwdInfo + pSyncFwds->first;
 
-  bool found = false;
   if (pFirst->version <= pFwdRsp->version && pSyncFwds->fwds > 0) {
     // find the forwardInfo from first
     for (int32_t i = 0; i < pSyncFwds->fwds; ++i) {
-      pFwdInfo = pSyncFwds->fwdInfo + (i + pSyncFwds->first) % tsMaxFwdInfo;
+      pFwdInfo = pSyncFwds->fwdInfo + (i + pSyncFwds->first) % SYNC_MAX_FWDS;
       if (pFwdRsp->version == pFwdInfo->version) {
-        found = true;
         syncProcessFwdAck(pNode, pFwdInfo, pFwdRsp->code);
         syncRemoveConfirmedFwdInfo(pNode);
-        break;
+        return;
       }
     }
   }
-
-  if (!found) {
-    sTrace("%s, forward-rsp not found first:%d fwds:%d, code:%x hver:%" PRIu64, pPeer->id, pSyncFwds->first,
-           pSyncFwds->fwds, pFwdRsp->code, pFwdRsp->version);
-    syncProcessFwdAck(pNode, pFwdInfo, pFwdRsp->code);
-  }
 }
 
 static void syncProcessForwardFromPeer(char *cont, SSyncPeer *pPeer) {
   SSyncNode *pNode = pPeer->pSyncNode;
-  SWalHead * pHead = (SWalHead *)cont;
+  SWalHead * pHead = (SWalHead *)(cont + sizeof(SSyncHead));
 
   sTrace("%s, forward is received, hver:%" PRIu64 ", len:%d", pPeer->id, pHead->version, pHead->len);
 
@@ -931,9 +881,8 @@ static void syncProcessForwardFromPeer(char *cont, SSyncPeer *pPeer) {
   }
 }
 
-static void syncProcessPeersStatusMsg(char *cont, SSyncPeer *pPeer) {
-  SSyncNode *   pNode = pPeer->pSyncNode;
-  SPeersStatus *pPeersStatus = (SPeersStatus *)cont;
+static void syncProcessPeersStatusMsg(SPeersStatus *pPeersStatus, SSyncPeer *pPeer) {
+  SSyncNode *pNode = pPeer->pSyncNode;
 
   sDebug("%s, status is received, self:%s:%s:%" PRIu64 ", peer:%s:%" PRIu64 ", ack:%d tranId:%u type:%s pfd:%d",
          pPeer->id, syncRole[nodeRole], syncStatus[nodeSStatus], nodeVersion, syncRole[pPeersStatus->role],
@@ -947,23 +896,22 @@ static void syncProcessPeersStatusMsg(char *cont, SSyncPeer *pPeer) {
   }
 }
 
-static int32_t syncReadPeerMsg(SSyncPeer *pPeer, SSyncHead *pHead, char *cont) {
+static int32_t syncReadPeerMsg(SSyncPeer *pPeer, SSyncHead *pHead) {
   if (pPeer->peerFd < 0) return -1;
 
   int32_t hlen = taosReadMsg(pPeer->peerFd, pHead, sizeof(SSyncHead));
   if (hlen != sizeof(SSyncHead)) {
-    sDebug("%s, failed to read msg, hlen:%d", pPeer->id, hlen);
+    sDebug("%s, failed to read msg since %s, hlen:%d", pPeer->id, tstrerror(errno), hlen);
     return -1;
   }
 
-  // head.len = htonl(head.len);
-  if (pHead->len < 0) {
-    sError("%s, invalid pkt length, hlen:%d", pPeer->id, pHead->len);
+  int32_t code = syncCheckHead(pHead);
+  if (code != 0) {
+    sError("%s, failed to check msg head since %s, type:%d", pPeer->id, tstrerror(code), pHead->type);
     return -1;
   }
 
-  assert(pHead->len <= TSDB_MAX_WAL_SIZE);
-  int32_t bytes = taosReadMsg(pPeer->peerFd, cont, pHead->len);
+  int32_t bytes = taosReadMsg(pPeer->peerFd, (char *)pHead + sizeof(SSyncHead), pHead->len);
   if (bytes != pHead->len) {
     sError("%s, failed to read, bytes:%d len:%d", pPeer->id, bytes, pHead->len);
     return -1;
@@ -974,23 +922,22 @@ static int32_t syncReadPeerMsg(SSyncPeer *pPeer, SSyncHead *pHead, char *cont) {
 
 static int32_t syncProcessPeerMsg(void *param, void *buffer) {
   SSyncPeer *pPeer = param;
-  SSyncHead  head;
-  char *     cont = buffer;
-
+  SSyncHead *pHead = buffer;
   SSyncNode *pNode = pPeer->pSyncNode;
+  
   pthread_mutex_lock(&pNode->mutex);
 
-  int32_t code = syncReadPeerMsg(pPeer, &head, cont);
+  int32_t code = syncReadPeerMsg(pPeer, pHead);
 
   if (code == 0) {
-    if (head.type == TAOS_SMSG_FORWARD) {
-      syncProcessForwardFromPeer(cont, pPeer);
-    } else if (head.type == TAOS_SMSG_FORWARD_RSP) {
-      syncProcessFwdResponse(cont, pPeer);
-    } else if (head.type == TAOS_SMSG_SYNC_REQ) {
-      syncProcessSyncRequest(cont, pPeer);
-    } else if (head.type == TAOS_SMSG_STATUS) {
-      syncProcessPeersStatusMsg(cont, pPeer);
+    if (pHead->type == TAOS_SMSG_SYNC_FWD) {
+      syncProcessForwardFromPeer(buffer, pPeer);
+    } else if (pHead->type == TAOS_SMSG_SYNC_FWD_RSP) {
+      syncProcessFwdResponse(buffer, pPeer);
+    } else if (pHead->type == TAOS_SMSG_SYNC_REQ) {
+      syncProcessSyncRequest(buffer, pPeer);
+    } else if (pHead->type == TAOS_SMSG_STATUS) {
+      syncProcessPeersStatusMsg(buffer, pPeer);
     }
   }
 
@@ -999,36 +946,30 @@ static int32_t syncProcessPeerMsg(void *param, void *buffer) {
   return code;
 }
 
-#define statusMsgLen sizeof(SSyncHead) + sizeof(SPeersStatus) + sizeof(SPeerStatus) * TAOS_SYNC_MAX_REPLICA
-
 static void syncSendPeersStatusMsgToPeer(SSyncPeer *pPeer, char ack, int8_t type, uint16_t tranId) {
-  SSyncNode *pNode = pPeer->pSyncNode;
-  char       msg[statusMsgLen] = {0};
-
   if (pPeer->peerFd < 0 || pPeer->ip == 0) return;
 
-  SSyncHead *   pHead = (SSyncHead *)msg;
-  SPeersStatus *pPeersStatus = (SPeersStatus *)(msg + sizeof(SSyncHead));
+  SSyncNode *  pNode = pPeer->pSyncNode;
+  SPeersStatus msg;
 
-  pHead->type = TAOS_SMSG_STATUS;
-  pHead->len = statusMsgLen - sizeof(SSyncHead);
+  memset(&msg, 0, sizeof(SPeersStatus));
+  syncBuildPeersStatus(&msg, pNode->vgId);
 
-  pPeersStatus->version = nodeVersion;
-  pPeersStatus->role = nodeRole;
-  pPeersStatus->ack = ack;
-  pPeersStatus->type = type;
-  pPeersStatus->tranId = tranId;
+  msg.role = nodeRole;
+  msg.ack = ack;
+  msg.type = type;
+  msg.tranId = tranId;
+  msg.version = nodeVersion;
 
   for (int32_t i = 0; i < pNode->replica; ++i) {
-    pPeersStatus->peersStatus[i].role = pNode->peerInfo[i]->role;
-    pPeersStatus->peersStatus[i].version = pNode->peerInfo[i]->version;
+    msg.peersStatus[i].role = pNode->peerInfo[i]->role;
+    msg.peersStatus[i].version = pNode->peerInfo[i]->version;
   }
 
-  if (taosWriteMsg(pPeer->peerFd, msg, statusMsgLen) == statusMsgLen) {
+  if (taosWriteMsg(pPeer->peerFd, &msg, sizeof(SPeersStatus)) == sizeof(SPeersStatus)) {
     sDebug("%s, status is sent, self:%s:%s:%" PRIu64 ", peer:%s:%s:%" PRIu64 ", ack:%d tranId:%u type:%s pfd:%d",
            pPeer->id, syncRole[nodeRole], syncStatus[nodeSStatus], nodeVersion, syncRole[pPeer->role],
-           syncStatus[pPeer->sstatus], pPeer->version, pPeersStatus->ack, pPeersStatus->tranId,
-           statusType[pPeersStatus->type], pPeer->peerFd);
+           syncStatus[pPeer->sstatus], pPeer->version, ack, tranId, statusType[type], pPeer->peerFd);
   } else {
     sDebug("%s, failed to send status msg, restart", pPeer->id);
     syncRestartConnection(pPeer);
@@ -1048,29 +989,23 @@ static void syncSetupPeerConnection(SSyncPeer *pPeer) {
   int32_t connFd = taosOpenTcpClientSocket(pPeer->ip, pPeer->port, 0);
   if (connFd < 0) {
     sDebug("%s, failed to open tcp socket since %s", pPeer->id, strerror(errno));
-    taosTmrReset(syncCheckPeerConnection, tsSyncTimer * 1000, pPeer, tsSyncTmrCtrl, &pPeer->timer);
+    taosTmrReset(syncCheckPeerConnection, SYNC_CHECK_INTERVAL, pPeer, tsSyncTmrCtrl, &pPeer->timer);
     return;
   }
 
-  SFirstPkt firstPkt;
-  memset(&firstPkt, 0, sizeof(firstPkt));
-  firstPkt.syncHead.vgId = pPeer->nodeId ? pNode->vgId : 0;
-  firstPkt.syncHead.type = TAOS_SMSG_STATUS;
-  tstrncpy(firstPkt.fqdn, tsNodeFqdn, sizeof(firstPkt.fqdn));
-  firstPkt.port = tsSyncPort;
-  firstPkt.tranId = syncGenTranId();
-  firstPkt.sourceId = pNode->vgId;  // tell arbitrator its vgId
+  SSyncMsg msg;
+  syncBuildSyncSetupMsg(&msg, pPeer->nodeId ? pNode->vgId : 0);
 
-  if (taosWriteMsg(connFd, &firstPkt, sizeof(firstPkt)) == sizeof(firstPkt)) {
-    sDebug("%s, connection to peer server is setup, pfd:%d sfd:%d tranId:%u", pPeer->id, connFd, pPeer->syncFd, firstPkt.tranId);
+  if (taosWriteMsg(connFd, &msg, sizeof(SSyncMsg)) == sizeof(SSyncMsg)) {
+    sDebug("%s, connection to peer server is setup, pfd:%d sfd:%d tranId:%u", pPeer->id, connFd, pPeer->syncFd, msg.tranId);
     pPeer->peerFd = connFd;
     pPeer->role = TAOS_SYNC_ROLE_UNSYNCED;
-    pPeer->pConn = taosAllocateTcpConn(tsTcpPool, pPeer, connFd);
+    pPeer->pConn = syncAllocateTcpConn(tsTcpPool, pPeer, connFd);
     syncAddPeerRef(pPeer);
   } else {
     sDebug("%s, failed to setup peer connection to server since %s, try later", pPeer->id, strerror(errno));
     taosClose(connFd);
-    taosTmrReset(syncCheckPeerConnection, tsSyncTimer * 1000, pPeer, tsSyncTmrCtrl, &pPeer->timer);
+    taosTmrReset(syncCheckPeerConnection, SYNC_CHECK_INTERVAL, pPeer, tsSyncTmrCtrl, &pPeer->timer);
   }
 }
 
@@ -1116,14 +1051,21 @@ static void syncProcessIncommingConnection(int32_t connFd, uint32_t sourceIp) {
   tinet_ntoa(ipstr, sourceIp);
   sDebug("peer TCP connection from ip:%s", ipstr);
 
-  SFirstPkt firstPkt;
-  if (taosReadMsg(connFd, &firstPkt, sizeof(firstPkt)) != sizeof(firstPkt)) {
-    sError("failed to read peer first pkt from ip:%s since %s", ipstr, strerror(errno));
+  SSyncMsg msg;
+  if (taosReadMsg(connFd, &msg, sizeof(SSyncMsg)) != sizeof(SSyncMsg)) {
+    sError("failed to read peer sync msg from ip:%s since %s", ipstr, strerror(errno));
+    taosCloseSocket(connFd);
+    return;
+  }
+
+  int32_t code = syncCheckHead((SSyncHead *)(&msg));
+  if (code != 0) {
+    sError("failed to check peer sync msg from ip:%s since %s", ipstr, strerror(code));
     taosCloseSocket(connFd);
     return;
   }
 
-  int32_t     vgId = firstPkt.syncHead.vgId;
+  int32_t     vgId = msg.head.vgId;
   SSyncNode **ppNode = taosHashGet(tsVgIdHash, &vgId, sizeof(int32_t));
   if (ppNode == NULL || *ppNode == NULL) {
     sError("vgId:%d, vgId could not be found", vgId);
@@ -1131,7 +1073,7 @@ static void syncProcessIncommingConnection(int32_t connFd, uint32_t sourceIp) {
     return;
   }
 
-  sDebug("vgId:%d, firstPkt is received, tranId:%u", vgId, firstPkt.tranId);
+  sDebug("vgId:%d, sync msg is received, tranId:%u", vgId, msg.tranId);
 
   SSyncNode *pNode = *ppNode;
   pthread_mutex_lock(&pNode->mutex);
@@ -1139,27 +1081,27 @@ static void syncProcessIncommingConnection(int32_t connFd, uint32_t sourceIp) {
   SSyncPeer *pPeer;
   for (i = 0; i < pNode->replica; ++i) {
     pPeer = pNode->peerInfo[i];
-    if (pPeer && (strcmp(pPeer->fqdn, firstPkt.fqdn) == 0) && (pPeer->port == firstPkt.port)) break;
+    if (pPeer && (strcmp(pPeer->fqdn, msg.fqdn) == 0) && (pPeer->port == msg.port)) break;
   }
 
   pPeer = (i < pNode->replica) ? pNode->peerInfo[i] : NULL;
   if (pPeer == NULL) {
-    sError("vgId:%d, peer:%s:%u not configured", pNode->vgId, firstPkt.fqdn, firstPkt.port);
+    sError("vgId:%d, peer:%s:%u not configured", pNode->vgId, msg.fqdn, msg.port);
     taosCloseSocket(connFd);
     // syncSendVpeerCfgMsg(sync);
   } else {
     // first packet tells what kind of link
-    if (firstPkt.syncHead.type == TAOS_SMSG_SYNC_DATA) {
+    if (msg.head.type == TAOS_SMSG_SYNC_DATA) {
       pPeer->syncFd = connFd;
       nodeSStatus = TAOS_SYNC_STATUS_START;
-      sInfo("%s, sync-data pkt from master is received, tranId:%u, set sstatus:%s", pPeer->id, firstPkt.tranId,
+      sInfo("%s, sync-data msg from master is received, tranId:%u, set sstatus:%s", pPeer->id, msg.tranId,
             syncStatus[nodeSStatus]);
       syncCreateRestoreDataThread(pPeer);
     } else {
       sDebug("%s, TCP connection is up, pfd:%d sfd:%d, old pfd:%d", pPeer->id, connFd, pPeer->syncFd, pPeer->peerFd);
       syncClosePeerConn(pPeer);
       pPeer->peerFd = connFd;
-      pPeer->pConn = taosAllocateTcpConn(tsTcpPool, pPeer, connFd);
+      pPeer->pConn = syncAllocateTcpConn(tsTcpPool, pPeer, connFd);
       syncAddPeerRef(pPeer);
       sDebug("%s, ready to exchange data", pPeer->id);
       syncSendPeersStatusMsgToPeer(pPeer, 1, SYNC_STATUS_EXCHANGE_DATA, syncGenTranId());
@@ -1192,15 +1134,15 @@ static int32_t syncSaveFwdInfo(SSyncNode *pNode, uint64_t version, void *mhandle
   SSyncFwds *pSyncFwds = pNode->pSyncFwds;
   int64_t    time = taosGetTimestampMs();
 
-  if (pSyncFwds->fwds >= tsMaxFwdInfo) {
-    // pSyncFwds->first = (pSyncFwds->first + 1) % tsMaxFwdInfo;
+  if (pSyncFwds->fwds >= SYNC_MAX_FWDS) {
+    // pSyncFwds->first = (pSyncFwds->first + 1) % SYNC_MAX_FWDS;
     // pSyncFwds->fwds--;
     sError("vgId:%d, failed to save fwd info, hver:%" PRIu64 " fwds:%d", pNode->vgId, version, pSyncFwds->fwds);
     return TSDB_CODE_SYN_TOO_MANY_FWDINFO;
   }
 
   if (pSyncFwds->fwds > 0) {
-    pSyncFwds->last = (pSyncFwds->last + 1) % tsMaxFwdInfo;
+    pSyncFwds->last = (pSyncFwds->last + 1) % SYNC_MAX_FWDS;
   }
 
   SFwdInfo *pFwdInfo = pSyncFwds->fwdInfo + pSyncFwds->last;
@@ -1223,7 +1165,7 @@ static void syncRemoveConfirmedFwdInfo(SSyncNode *pNode) {
     SFwdInfo *pFwdInfo = pSyncFwds->fwdInfo + pSyncFwds->first;
     if (pFwdInfo->confirmed == 0) break;
 
-    pSyncFwds->first = (pSyncFwds->first + 1) % tsMaxFwdInfo;
+    pSyncFwds->first = (pSyncFwds->first + 1) % SYNC_MAX_FWDS;
     pSyncFwds->fwds--;
     if (pSyncFwds->fwds == 0) pSyncFwds->first = pSyncFwds->last;
     sTrace("vgId:%d, fwd info is removed, hver:%" PRIu64 " fwds:%d", pNode->vgId, pFwdInfo->version, pSyncFwds->fwds);
@@ -1248,7 +1190,7 @@ static void syncProcessFwdAck(SSyncNode *pNode, SFwdInfo *pFwdInfo, int32_t code
   }
 
   if (confirm && pFwdInfo->confirmed == 0) {
-    sTrace("vgId:%d, forward is confirmed, hver:%" PRIu64 " code:%x", pNode->vgId, pFwdInfo->version, pFwdInfo->code);
+    sTrace("vgId:%d, forward is confirmed, hver:%" PRIu64 " code:0x%x", pNode->vgId, pFwdInfo->version, pFwdInfo->code);
     (*pNode->confirmForward)(pNode->vgId, pFwdInfo->mhandle, pFwdInfo->code);
     pFwdInfo->confirmed = 1;
   }
@@ -1289,7 +1231,7 @@ static void syncMonitorFwdInfos(void *param, void *tmrId) {
     if (pSyncFwds->fwds > 0) {
       pthread_mutex_lock(&pNode->mutex);
       for (int32_t i = 0; i < pSyncFwds->fwds; ++i) {
-        SFwdInfo *pFwdInfo = pSyncFwds->fwdInfo + (pSyncFwds->first + i) % tsMaxFwdInfo;
+        SFwdInfo *pFwdInfo = pSyncFwds->fwdInfo + (pSyncFwds->first + i) % SYNC_MAX_FWDS;
         if (ABS(time - pFwdInfo->time) < 2000) break;
 
         sDebug("vgId:%d, forward info expired, hver:%" PRIu64 " curtime:%" PRIu64 " savetime:%" PRIu64, pNode->vgId,
@@ -1334,14 +1276,12 @@ static int32_t syncForwardToPeerImpl(SSyncNode *pNode, void *data, void *mhandle
 
   if (pNode->replica == 1 || nodeRole != TAOS_SYNC_ROLE_MASTER) return 0;
 
-  // only pkt from RPC or CQ can be forwarded
+  // only msg from RPC or CQ can be forwarded
   if (qtype != TAOS_QTYPE_RPC && qtype != TAOS_QTYPE_CQ) return 0;
 
     // a hacker way to improve the performance
   pSyncHead = (SSyncHead *)(((char *)pWalHead) - sizeof(SSyncHead));
-  pSyncHead->type = TAOS_SMSG_FORWARD;
-  pSyncHead->pversion = 0;
-  pSyncHead->len = sizeof(SWalHead) + pWalHead->len;
+  syncBuildSyncFwdMsg(pSyncHead, pNode->vgId, sizeof(SWalHead) + pWalHead->len);
   fwdLen = pSyncHead->len + sizeof(SSyncHead);  // include the WAL and SYNC head
 
   pthread_mutex_lock(&pNode->mutex);
@@ -1371,4 +1311,3 @@ static int32_t syncForwardToPeerImpl(SSyncNode *pNode, void *data, void *mhandle
 
   return code;
 }
-
diff --git a/src/sync/src/syncMsg.c b/src/sync/src/syncMsg.c
new file mode 100644
index 0000000000000000000000000000000000000000..034f9a98a70c7373b74a84d24d478b52d7bf4df9
--- /dev/null
+++ b/src/sync/src/syncMsg.c
@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define _DEFAULT_SOURCE
+#include "os.h"
+#include "taoserror.h"
+#include "tglobal.h"
+#include "tchecksum.h"
+#include "syncInt.h"
+
+char *statusType[] = {
+  "broadcast",
+  "broadcast-rsp",
+  "setup-conn",
+  "setup-conn-rsp",
+  "exchange-data",
+  "exchange-data-rsp",
+  "check-role",
+  "check-role-rsp"
+};
+
+uint16_t syncGenTranId() {
+  return taosRand() & 0XFFFF;
+}
+
+static void syncBuildHead(SSyncHead *pHead) {
+  pHead->protocol = SYNC_PROTOCOL_VERSION;
+  pHead->signature = SYNC_SIGNATURE;
+  pHead->code = 0;
+  pHead->cId = 0;
+  taosCalcChecksumAppend(0, (uint8_t *)pHead, sizeof(SSyncHead));
+}
+
+int32_t syncCheckHead(SSyncHead *pHead) {
+  if (pHead->protocol != SYNC_PROTOCOL_VERSION) return TSDB_CODE_SYN_MISMATCHED_PROTOCOL;
+  if (pHead->signature != SYNC_SIGNATURE) return TSDB_CODE_SYN_MISMATCHED_SIGNATURE;
+  if (pHead->cId != 0) return TSDB_CODE_SYN_MISMATCHED_CLUSTERID;
+  if (pHead->len <= 0 || pHead->len > TSDB_MAX_WAL_SIZE) return TSDB_CODE_SYN_INVALID_MSGLEN;
+  if (pHead->type <= TAOS_SMSG_START || pHead->type >= TAOS_SMSG_END) return TSDB_CODE_SYN_INVALID_MSGTYPE;
+  if (!taosCheckChecksumWhole((uint8_t *)pHead, sizeof(SSyncHead))) return TSDB_CODE_SYN_INVALID_CHECKSUM;
+
+  return TSDB_CODE_SUCCESS;
+}
+
+void syncBuildSyncFwdMsg(SSyncHead *pHead, int32_t vgId, int32_t len) {
+  pHead->type = TAOS_SMSG_SYNC_FWD;
+  pHead->vgId = vgId;
+  pHead->len = len;
+  syncBuildHead(pHead);
+}
+
+void syncBuildSyncFwdRsp(SFwdRsp *pMsg, int32_t vgId, uint64_t version, int32_t code) {
+  pMsg->head.type = TAOS_SMSG_SYNC_FWD_RSP;
+  pMsg->head.vgId = vgId;
+  pMsg->head.len = sizeof(SFwdRsp) - sizeof(SSyncHead);
+  syncBuildHead(&pMsg->head);
+
+  pMsg->version = version;
+  pMsg->code = code;
+}
+
+static void syncBuildMsg(SSyncMsg *pMsg, int32_t vgId, ESyncMsgType type) {
+  pMsg->head.type = type;
+  pMsg->head.vgId = vgId;
+  pMsg->head.len = sizeof(SSyncMsg) - sizeof(SSyncHead);
+  syncBuildHead(&pMsg->head);
+
+  pMsg->port = tsSyncPort;
+  pMsg->tranId = syncGenTranId();
+  pMsg->sourceId = vgId;
+  tstrncpy(pMsg->fqdn, tsNodeFqdn, TSDB_FQDN_LEN);
+}
+
+void syncBuildSyncReqMsg(SSyncMsg *pMsg, int32_t vgId) { syncBuildMsg(pMsg, vgId, TAOS_SMSG_SYNC_REQ); }
+void syncBuildSyncDataMsg(SSyncMsg *pMsg, int32_t vgId) { syncBuildMsg(pMsg, vgId, TAOS_SMSG_SYNC_DATA); }
+void syncBuildSyncSetupMsg(SSyncMsg *pMsg, int32_t vgId) { syncBuildMsg(pMsg, vgId, TAOS_SMSG_SETUP); }
+
+void syncBuildPeersStatus(SPeersStatus *pMsg, int32_t vgId) {
+  pMsg->head.type = TAOS_SMSG_STATUS;
+  pMsg->head.vgId = vgId;
+  pMsg->head.len = sizeof(SPeersStatus) - sizeof(SSyncHead);
+  syncBuildHead(&pMsg->head);
+}
+
+void syncBuildFileAck(SFileAck *pMsg, int32_t vgId) {
+  pMsg->head.type = TAOS_SMSG_SYNC_FILE_RSP;
+  pMsg->head.vgId = vgId;
+  pMsg->head.len = sizeof(SFileAck) - sizeof(SSyncHead);
+  syncBuildHead(&pMsg->head);
+}
+
+void syncBuildFileInfo(SFileInfo *pMsg, int32_t vgId) {
+  pMsg->head.type = TAOS_SMSG_SYNC_FILE;
+  pMsg->head.vgId = vgId;
+  pMsg->head.len = sizeof(SFileInfo) - sizeof(SSyncHead);
+  syncBuildHead(&pMsg->head);
+}
\ No newline at end of file
diff --git a/src/sync/src/syncRestore.c b/src/sync/src/syncRestore.c
index 4247468bcae77dab49f61dd684a80ada9701418c..8651879eb6cb06ff629c694f128b6107bf8f19a2 100644
--- a/src/sync/src/syncRestore.c
+++ b/src/sync/src/syncRestore.c
@@ -56,7 +56,7 @@ static int32_t syncRestoreFile(SSyncPeer *pPeer, uint64_t *fversion) {
   SSyncNode *pNode = pPeer->pSyncNode;
   SFileInfo  minfo; memset(&minfo, 0, sizeof(SFileInfo)); /* = {0}; */
   SFileInfo  sinfo; memset(&sinfo, 0, sizeof(SFileInfo)); /* = {0}; */
-  SFileAck   fileAck = {0};
+  SFileAck   fileAck; memset(&fileAck, 0, sizeof(SFileAck));
   int32_t    code = -1;
   char       name[TSDB_FILENAME_LEN * 2] = {0};
   uint32_t   pindex = 0;  // index in last restore
@@ -69,7 +69,14 @@ static int32_t syncRestoreFile(SSyncPeer *pPeer, uint64_t *fversion) {
     minfo.index = -1;
     int32_t ret = taosReadMsg(pPeer->syncFd, &minfo, sizeof(SFileInfo));
     if (ret != sizeof(SFileInfo) || minfo.index == -1) {
-      sError("%s, failed to read file info while restore file since %s", pPeer->id, strerror(errno));
+      sError("%s, failed to read fileinfo while restore file since %s", pPeer->id, strerror(errno));
+      break;
+    }
+
+    assert(ret == sizeof(SFileInfo));
+    ret = syncCheckHead((SSyncHead *)(&minfo));
+    if (ret != 0) {
+      sError("%s, failed to check fileinfo while restore file since %s", pPeer->id, strerror(ret));
       break;
     }
 
@@ -94,12 +101,13 @@ static int32_t syncRestoreFile(SSyncPeer *pPeer, uint64_t *fversion) {
                                         &sinfo.fversion);
 
     // if file not there or magic is not the same, file shall be synced
-    memset(&fileAck, 0, sizeof(fileAck));
+    memset(&fileAck, 0, sizeof(SFileAck));
+    syncBuildFileAck(&fileAck, pNode->vgId);
     fileAck.sync = (sinfo.magic != minfo.magic || sinfo.name[0] == 0) ? 1 : 0;
 
     // send file ack
-    ret = taosWriteMsg(pPeer->syncFd, &fileAck, sizeof(fileAck));
-    if (ret != sizeof(fileAck)) {
+    ret = taosWriteMsg(pPeer->syncFd, &fileAck, sizeof(SFileAck));
+    if (ret != sizeof(SFileAck)) {
       sError("%s, failed to write file:%s ack while restore file since %s", pPeer->id, minfo.name, strerror(errno));
       break;
     }
@@ -289,12 +297,12 @@ static int32_t syncRestoreDataStepByStep(SSyncPeer *pPeer) {
   uint64_t fversion = 0;
 
   sInfo("%s, start to restore, sstatus:%s", pPeer->id, syncStatus[pPeer->sstatus]);
-  SFirstPktRsp firstPktRsp = {.sync = 1, .tranId = syncGenTranId()};
-  if (taosWriteMsg(pPeer->syncFd, &firstPktRsp, sizeof(SFirstPktRsp)) != sizeof(SFirstPktRsp)) {
-    sError("%s, failed to send sync firstPkt rsp since %s", pPeer->id, strerror(errno));
+  SSyncRsp rsp = {.sync = 1, .tranId = syncGenTranId()};
+  if (taosWriteMsg(pPeer->syncFd, &rsp, sizeof(SSyncRsp)) != sizeof(SSyncRsp)) {
+    sError("%s, failed to send sync rsp since %s", pPeer->id, strerror(errno));
     return -1;
   }
-  sDebug("%s, send firstPktRsp to peer, tranId:%u", pPeer->id, firstPktRsp.tranId);
+  sDebug("%s, send sync rsp to peer, tranId:%u", pPeer->id, rsp.tranId);
 
   sInfo("%s, start to restore file, set sstatus:%s", pPeer->id, syncStatus[nodeSStatus]);
   int32_t code = syncRestoreFile(pPeer, &fversion);
diff --git a/src/sync/src/syncRetrieve.c b/src/sync/src/syncRetrieve.c
index 82e3700c7a4c9df3f89eecb65d1a75fe9f7a012c..02d990313e8c95518e22939c8ab0d41ad05604c2 100644
--- a/src/sync/src/syncRetrieve.c
+++ b/src/sync/src/syncRetrieve.c
@@ -88,7 +88,7 @@ static bool syncAreFilesModified(SSyncNode *pNode, SSyncPeer *pPeer) {
 static int32_t syncRetrieveFile(SSyncPeer *pPeer) {
   SSyncNode *pNode = pPeer->pSyncNode;
   SFileInfo  fileInfo; memset(&fileInfo, 0, sizeof(SFileInfo));
-  SFileAck   fileAck = {0};
+  SFileAck   fileAck; memset(&fileAck, 0, sizeof(SFileAck));
   int32_t    code = -1;
   char       name[TSDB_FILENAME_LEN * 2] = {0};
 
@@ -103,11 +103,12 @@ static int32_t syncRetrieveFile(SSyncPeer *pPeer) {
     fileInfo.size = 0;
     fileInfo.magic = (*pNode->getFileInfo)(pNode->vgId, fileInfo.name, &fileInfo.index, TAOS_SYNC_MAX_INDEX,
                                            &fileInfo.size, &fileInfo.fversion);
+    syncBuildFileInfo(&fileInfo, pNode->vgId);
     sDebug("%s, file:%s info is sent, size:%" PRId64, pPeer->id, fileInfo.name, fileInfo.size);
 
     // send the file info
-    int32_t ret = taosWriteMsg(pPeer->syncFd, &(fileInfo), sizeof(fileInfo));
-    if (ret != sizeof(fileInfo)) {
+    int32_t ret = taosWriteMsg(pPeer->syncFd, &(fileInfo), sizeof(SFileInfo));
+    if (ret != sizeof(SFileInfo)) {
       code = -1;
       sError("%s, failed to write file:%s info while retrieve file since %s", pPeer->id, fileInfo.name, strerror(errno));
       break;
@@ -128,6 +129,13 @@ static int32_t syncRetrieveFile(SSyncPeer *pPeer) {
       break;
     }
 
+    ret = syncCheckHead((SSyncHead*)(&fileAck));
+    if (ret != 0) {
+      code = -1;
+      sError("%s, failed to check file:%s ack while retrieve file since %s", pPeer->id, fileInfo.name, strerror(ret));
+      break;
+    }
+
     // set the peer sync version
     pPeer->sversion = fileInfo.fversion;
 
@@ -405,27 +413,22 @@ static int32_t syncRetrieveWal(SSyncPeer *pPeer) {
 static int32_t syncRetrieveFirstPkt(SSyncPeer *pPeer) {
   SSyncNode *pNode = pPeer->pSyncNode;
 
-  SFirstPkt firstPkt;
-  memset(&firstPkt, 0, sizeof(firstPkt));
-  firstPkt.syncHead.type = TAOS_SMSG_SYNC_DATA;
-  firstPkt.syncHead.vgId = pNode->vgId;
-  firstPkt.tranId = syncGenTranId();
-  tstrncpy(firstPkt.fqdn, tsNodeFqdn, sizeof(firstPkt.fqdn));
-  firstPkt.port = tsSyncPort;
+  SSyncMsg msg;
+  syncBuildSyncDataMsg(&msg, pNode->vgId);
 
-  if (taosWriteMsg(pPeer->syncFd, &firstPkt, sizeof(firstPkt)) != sizeof(firstPkt)) {
-    sError("%s, failed to send sync firstPkt since %s, tranId:%u", pPeer->id, strerror(errno), firstPkt.tranId);
+  if (taosWriteMsg(pPeer->syncFd, &msg, sizeof(SSyncMsg)) != sizeof(SSyncMsg)) {
+    sError("%s, failed to send sync-data msg since %s, tranId:%u", pPeer->id, strerror(errno), msg.tranId);
     return -1;
   }
-  sDebug("%s, send sync-data pkt to peer, tranId:%u", pPeer->id, firstPkt.tranId);
+  sDebug("%s, send sync-data msg to peer, tranId:%u", pPeer->id, msg.tranId);
 
-  SFirstPktRsp firstPktRsp;
-  if (taosReadMsg(pPeer->syncFd, &firstPktRsp, sizeof(SFirstPktRsp)) != sizeof(SFirstPktRsp)) {
-    sError("%s, failed to read sync firstPkt rsp since %s, tranId:%u", pPeer->id, strerror(errno), firstPkt.tranId);
+  SSyncRsp rsp;
+  if (taosReadMsg(pPeer->syncFd, &rsp, sizeof(SSyncRsp)) != sizeof(SSyncRsp)) {
+    sError("%s, failed to read sync-data rsp since %s, tranId:%u", pPeer->id, strerror(errno), msg.tranId);
     return -1;
   }
 
-  sDebug("%s, recv firstPktRsp from peer, tranId:%u", pPeer->id, firstPkt.tranId);
+  sDebug("%s, recv sync-data rsp from peer, tranId:%u rsp-tranId:%u", pPeer->id, msg.tranId, rsp.tranId);
   return 0;
 }
 
diff --git a/src/sync/src/taosTcpPool.c b/src/sync/src/syncTcp.c
similarity index 89%
rename from src/sync/src/taosTcpPool.c
rename to src/sync/src/syncTcp.c
index eb05cf7c6f8d8d9a068b60c54f0ae1426e62c429..7bfdc4e440ee886065a4cd1b8f59d09e09556a47 100644
--- a/src/sync/src/taosTcpPool.c
+++ b/src/sync/src/syncTcp.c
@@ -19,10 +19,10 @@
 #include "tutil.h"
 #include "tsocket.h"
 #include "taoserror.h"
-#include "taosTcpPool.h"
 #include "twal.h"
 #include "tsync.h"
 #include "syncInt.h"
+#include "syncTcp.h"
 
 typedef struct SThreadObj {
   pthread_t thread;
@@ -47,12 +47,12 @@ typedef struct {
   int32_t     closedByApp;
 } SConnObj;
 
-static void *taosAcceptPeerTcpConnection(void *argv);
-static void *taosProcessTcpData(void *param);
-static void  taosStopPoolThread(SThreadObj *pThread);
-static SThreadObj *taosGetTcpThread(SPoolObj *pPool);
+static void *syncAcceptPeerTcpConnection(void *argv);
+static void *syncProcessTcpData(void *param);
+static void  syncStopPoolThread(SThreadObj *pThread);
+static SThreadObj *syncGetTcpThread(SPoolObj *pPool);
 
-void *taosOpenTcpThreadPool(SPoolInfo *pInfo) {
+void *syncOpenTcpThreadPool(SPoolInfo *pInfo) {
   pthread_attr_t thattr;
 
   SPoolObj *pPool = calloc(sizeof(SPoolObj), 1);
@@ -80,7 +80,7 @@ void *taosOpenTcpThreadPool(SPoolInfo *pInfo) {
 
   pthread_attr_init(&thattr);
   pthread_attr_setdetachstate(&thattr, PTHREAD_CREATE_JOINABLE);
-  if (pthread_create(&(pPool->thread), &thattr, (void *)taosAcceptPeerTcpConnection, pPool) != 0) {
+  if (pthread_create(&(pPool->thread), &thattr, (void *)syncAcceptPeerTcpConnection, pPool) != 0) {
     sError("failed to create accept thread for TCP server since %s", strerror(errno));
     close(pPool->acceptFd);
     tfree(pPool->pThread);
@@ -94,7 +94,7 @@ void *taosOpenTcpThreadPool(SPoolInfo *pInfo) {
   return pPool;
 }
 
-void taosCloseTcpThreadPool(void *param) {
+void syncCloseTcpThreadPool(void *param) {
   SPoolObj *  pPool = param;
   SThreadObj *pThread;
 
@@ -103,7 +103,7 @@ void taosCloseTcpThreadPool(void *param) {
 
   for (int32_t i = 0; i < pPool->info.numOfThreads; ++i) {
     pThread = pPool->pThread[i];
-    if (pThread) taosStopPoolThread(pThread);
+    if (pThread) syncStopPoolThread(pThread);
   }
 
   sDebug("%p TCP pool is closed", pPool);
@@ -112,7 +112,7 @@ void taosCloseTcpThreadPool(void *param) {
   tfree(pPool);
 }
 
-void *taosAllocateTcpConn(void *param, void *pPeer, int32_t connFd) {
+void *syncAllocateTcpConn(void *param, void *pPeer, int32_t connFd) {
   struct epoll_event event;
   SPoolObj *pPool = param;
 
@@ -122,7 +122,7 @@ void *taosAllocateTcpConn(void *param, void *pPeer, int32_t connFd) {
     return NULL;
   }
 
-  SThreadObj *pThread = taosGetTcpThread(pPool);
+  SThreadObj *pThread = syncGetTcpThread(pPool);
   if (pThread == NULL) {
     tfree(pConn);
     return NULL;
@@ -149,7 +149,7 @@ void *taosAllocateTcpConn(void *param, void *pPeer, int32_t connFd) {
   return pConn;
 }
 
-void taosFreeTcpConn(void *param) {
+void syncFreeTcpConn(void *param) {
   SConnObj *  pConn = param;
   SThreadObj *pThread = pConn->pThread;
 
@@ -175,7 +175,7 @@ static void taosProcessBrokenLink(SConnObj *pConn) {
 
 #define maxEvents 10
 
-static void *taosProcessTcpData(void *param) {
+static void *syncProcessTcpData(void *param) {
   SThreadObj *pThread = (SThreadObj *)param;
   SPoolObj *  pPool = pThread->pPool;
   SPoolInfo * pInfo = &pPool->info;
@@ -222,7 +222,7 @@ static void *taosProcessTcpData(void *param) {
 
       if (pConn->closedByApp == 0) {
         if ((*pInfo->processIncomingMsg)(pConn->ahandle, buffer) < 0) {
-          taosFreeTcpConn(pConn);
+          syncFreeTcpConn(pConn);
           continue;
         }
       }
@@ -239,7 +239,7 @@ static void *taosProcessTcpData(void *param) {
   return NULL;
 }
 
-static void *taosAcceptPeerTcpConnection(void *argv) {
+static void *syncAcceptPeerTcpConnection(void *argv) {
   SPoolObj * pPool = (SPoolObj *)argv;
   SPoolInfo *pInfo = &pPool->info;
 
@@ -268,7 +268,7 @@ static void *taosAcceptPeerTcpConnection(void *argv) {
   return NULL;
 }
 
-static SThreadObj *taosGetTcpThread(SPoolObj *pPool) {
+static SThreadObj *syncGetTcpThread(SPoolObj *pPool) {
   SThreadObj *pThread = pPool->pThread[pPool->nextId];
 
   if (pThread) return pThread;
@@ -286,7 +286,7 @@ static SThreadObj *taosGetTcpThread(SPoolObj *pPool) {
   pthread_attr_t thattr;
   pthread_attr_init(&thattr);
   pthread_attr_setdetachstate(&thattr, PTHREAD_CREATE_JOINABLE);
-  int32_t ret = pthread_create(&(pThread->thread), &thattr, (void *)taosProcessTcpData, pThread);
+  int32_t ret = pthread_create(&(pThread->thread), &thattr, (void *)syncProcessTcpData, pThread);
   pthread_attr_destroy(&thattr);
 
   if (ret != 0) {
@@ -303,7 +303,7 @@ static SThreadObj *taosGetTcpThread(SPoolObj *pPool) {
   return pThread;
 }
 
-static void taosStopPoolThread(SThreadObj *pThread) {
+static void syncStopPoolThread(SThreadObj *pThread) {
   pthread_t thread = pThread->thread;
   if (!taosCheckPthreadValid(thread)) {
     return;
diff --git a/src/sync/test/syncServer.c b/src/sync/test/syncServer.c
index 5a64a0a36a9c5e0557e78216ba41a48a23cc874b..161105d86c9a45fb1b8827f01701a43a3e08000c 100644
--- a/src/sync/test/syncServer.c
+++ b/src/sync/test/syncServer.c
@@ -100,7 +100,7 @@ int processRpcMsg(void *item) {
     pHead->msgType = pMsg->msgType;
     pHead->len = pMsg->contLen;
 
-    uDebug("ver:%" PRIu64 ", pkt from client processed", pHead->version);
+    uDebug("ver:%" PRIu64 ", rsp from client processed", pHead->version);
     writeIntoWal(pHead);
     syncForwardToPeer(syncHandle, pHead, item, TAOS_QTYPE_RPC);
 
@@ -275,7 +275,7 @@ int getWalInfo(int32_t vgId, char *name, int64_t *index) {
 int writeToCache(int32_t vgId, void *data, int type) {
   SWalHead *pHead = data;
 
-  uDebug("pkt from peer is received, ver:%" PRIu64 " len:%d type:%d", pHead->version, pHead->len, type);
+  uDebug("rsp from peer is received, ver:%" PRIu64 " len:%d type:%d", pHead->version, pHead->len, type);
 
   int   msgSize = pHead->len + sizeof(SWalHead);
   void *pMsg = taosAllocateQitem(msgSize);
diff --git a/tests/script/unique/db/replica_add13.sim b/tests/script/unique/db/replica_add13.sim
index 1df49ba6582b3e1502e9b19ac3b11626175a295e..defe306f2fd413f57f2e3ed471cad8601476a8d4 100644
--- a/tests/script/unique/db/replica_add13.sim
+++ b/tests/script/unique/db/replica_add13.sim
@@ -110,6 +110,7 @@ sql insert into d1.t1 values(1589529000012, 2)
 sql insert into d2.t2 values(1589529000022, 2)
 sql insert into d3.t3 values(1589529000032, 2)
 sql insert into d4.t4 values(1589529000042, 2)
+sleep 1000
 
 sql select * from d1.t1
 if $rows != 2 then
@@ -141,6 +142,7 @@ sql insert into d1.t1 values(1589529000013, 3)
 sql insert into d2.t2 values(1589529000023, 3)
 sql insert into d3.t3 values(1589529000033, 3)
 sql insert into d4.t4 values(1589529000043, 3)
+sleep 1000
 
 sql select * from d1.t1
 if $rows != 3 then
@@ -172,6 +174,7 @@ sql insert into d1.t1 values(1589529000014, 4)
 sql insert into d2.t2 values(1589529000024, 4)
 sql insert into d3.t3 values(1589529000034, 4)
 sql insert into d4.t4 values(1589529000044, 4)
+sleep 1000
 
 sql select * from d1.t1
 print select * from d1.t1 $rows
@@ -207,6 +210,7 @@ sql insert into d1.t1 values(1589529000015, 5)
 sql insert into d2.t2 values(1589529000025, 5)
 sql insert into d3.t3 values(1589529000035, 5)
 sql insert into d4.t4 values(1589529000045, 5)
+sleep 1000
 
 sql select * from d1.t1
 if $rows != 5 then
@@ -238,6 +242,7 @@ sql insert into d1.t1 values(1589529000016, 6)
 sql insert into d2.t2 values(1589529000026, 6)
 sql insert into d3.t3 values(1589529000036, 6)
 sql insert into d4.t4 values(1589529000046, 6)
+sleep 1000
 
 sql select * from d1.t1
 if $rows != 6 then
diff --git a/tests/script/unique/db/replica_add23.sim b/tests/script/unique/db/replica_add23.sim
index 5da73cd117ef218d1421d4f7f6ee7026c9e6bef3..d93894deb89beaadfc0b779acf93caaf42463009 100644
--- a/tests/script/unique/db/replica_add23.sim
+++ b/tests/script/unique/db/replica_add23.sim
@@ -110,6 +110,7 @@ sql insert into d1.t1 values(1588262400002, 2)
 sql insert into d2.t2 values(1588262400002, 2)
 sql insert into d3.t3 values(1588262400002, 2)
 sql insert into d4.t4 values(1588262400002, 2)
+sleep 1000
 
 sql select * from d1.t1
 if $rows != 2 then
@@ -142,6 +143,7 @@ sql insert into d1.t1 values(1588262400003, 3)
 sql insert into d2.t2 values(1588262400003, 3)
 sql insert into d3.t3 values(1588262400003, 3)
 sql insert into d4.t4 values(1588262400003, 3)
+sleep 1000
 
 sql select * from d1.t1
 if $rows != 3 then
@@ -173,6 +175,7 @@ sql insert into d1.t1 values(1588262400004, 4)
 sql insert into d2.t2 values(1588262400004, 4)
 sql insert into d3.t3 values(1588262400004, 4)
 sql insert into d4.t4 values(1588262400004, 4)
+sleep 1000
 
 sql select * from d1.t1
 if $rows != 4 then
@@ -204,6 +207,7 @@ sql insert into d1.t1 values(1588262400005, 5)
 sql insert into d2.t2 values(1588262400005, 5)
 sql insert into d3.t3 values(1588262400005, 5)
 sql insert into d4.t4 values(1588262400005, 5)
+sleep 1000
 
 sql select * from d1.t1
 if $rows != 5 then
@@ -235,6 +239,7 @@ sql insert into d1.t1 values(1588262400006, 6)
 sql insert into d2.t2 values(1588262400006, 6)
 sql insert into d3.t3 values(1588262400006, 6)
 sql insert into d4.t4 values(1588262400006, 6)
+sleep 1000
 
 sql select * from d1.t1
 if $rows != 6 then