diff --git a/src/inc/tsync.h b/src/inc/tsync.h
new file mode 100644
index 0000000000..39c116c9cb
--- /dev/null
+++ b/src/inc/tsync.h
@@ -0,0 +1,110 @@
+/*
+ * 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_H
+#define TDENGINE_SYNC_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define TAOS_SYNC_MAX_REPLICA 5
+
+typedef enum _TAOS_SYNC_ROLE {
+  TAOS_SYNC_ROLE_OFFLINE,
+  TAOS_SYNC_ROLE_UNSYNCED,
+  TAOS_SYNC_ROLE_SLAVE,
+  TAOS_SYNC_ROLE_MASTER,
+} ESyncRole;
+
+typedef enum _TAOS_SYNC_STATUS {
+  TAOS_SYNC_STATUS_INIT,
+  TAOS_SYNC_STATUS_START,
+  TAOS_SYNC_STATUS_FILE,
+  TAOS_SYNC_STATUS_CACHE,
+} ESyncStatus;
+
+typedef struct {
+  uint32_t  nodeId;    // node ID assigned by TDengine
+  uint32_t  nodeIp;    // node IP address
+  char      name[TSDB_FILENAME_LEN]; // external node name 
+} SNodeInfo;
+
+typedef struct {
+  uint32_t   arbitratorIp;  // arbitrator IP address
+  int8_t     quorum;    // number of confirms required, >=1 
+  int8_t     replica;   // number of replications, >=1
+  SNodeInfo  nodeInfo[TAOS_SYNC_MAX_REPLICA];
+} SSyncCfg;
+
+typedef struct {
+  int       selfIndex;
+  uint32_t  nodeId[TAOS_SYNC_MAX_REPLICA];
+  int       role[TAOS_SYNC_MAX_REPLICA];  
+} SNodesRole;
+ 
+typedef struct {
+  char       label[20]; // for debug purpose 
+  char       path[128]; // path to the file
+  int8_t     replica;   // number of replications, >=1
+  int8_t     quorum;    // number of confirms required, >=1 
+  int32_t    vgId;      // vgroup ID
+  void      *ahandle;   // handle provided by APP 
+  uint64_t   version;   // initial version
+  uint32_t   arbitratorIp; 
+  SNodeInfo  nodeInfo[TAOS_SYNC_MAX_REPLICA];
+ 
+  // if name is null, get the file from index or after, used by master
+  // if name is provided, get the named file at the specified index, used by unsynced node
+  // it returns the file magic number and size, if file not there, magic shall be 0.
+  uint32_t   (*getFileInfo)(char *name, int *index, int *size); 
+
+  // get the wal file from index or after
+  // return value, -1: error, 1:more wal files, 0:last WAL. if name[0]==0, no WAL file
+  int        (*getWalInfo)(char *name, int *index); 
+ 
+  // when a forward pkt is received, call this to handle data 
+  int        (*writeToCache)(void *ahandle, SWalHead *, int type);
+
+  // when forward is confirmed by peer, master call this API to notify app
+  void       (*confirmForward)(void *ahandle, void *mhandle, int32_t code);
+
+  // when role is changed, call this to notify app
+  void       (*notifyRole)(void *ahandle, int8_t role);
+} SSyncInfo;
+
+typedef void* tsync_h;
+
+tsync_h syncStart(SSyncInfo *);
+void    syncStop(tsync_h shandle);
+int     syncReconfig(tsync_h shandle, SSyncInfo *);
+int     syncForwardToPeer(tsync_h shandle, SWalHead *pHead, void *mhandle);
+void    syncConfirmForward(tsync_h shandle, uint64_t version, int32_t code);
+void    syncRecover(tsync_h shandle);      // recover from other nodes:
+int     syncGetNodesRole(tsync_h shandle, SNodesRole *);
+
+extern  char *syncRole[];
+
+extern  int   tsMaxSyncNum;
+extern  int   tsSyncTcpThreads;
+extern  int   tsMaxWatchFiles;
+extern  short tsSyncPort;
+extern  int   tsMaxFwdInfo; 
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // TDENGINE_SYNC_H
diff --git a/src/inc/twal.h b/src/inc/twal.h
index bac5f87215..3648f5ae29 100644
--- a/src/inc/twal.h
+++ b/src/inc/twal.h
@@ -33,6 +33,11 @@ typedef struct {
   char      cont[];
 } SWalHead;
 
+typedef struct {
+  int8_t    commitLog; // commitLog
+  int8_t    wals;      // number of WAL files;
+} SWalCfg;
+
 typedef void* twal_h;  // WAL HANDLE
 
 twal_h  walOpen(char *path, int max, int level);