diff --git a/src/balance/inc/bnMain.h b/src/balance/inc/bnMain.h
new file mode 100644
index 0000000000..101f5d5fd1
--- /dev/null
+++ b/src/balance/inc/bnMain.h
@@ -0,0 +1,56 @@
+/*
+ * 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_BALANCE_MAIN_H
+#define TDENGINE_BALANCE_MAIN_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+#include "mnodeInt.h"
+#include "mnodeDnode.h"
+
+typedef struct {
+  int32_t     size;
+  int32_t     maxSize;
+  SDnodeObj **list;
+} SBnDnodes;
+
+typedef struct {
+  void *          timer;
+  bool            stop;
+  pthread_mutex_t mutex;
+  pthread_cond_t  cond;
+  pthread_t       thread;
+} SBnThread;
+
+typedef struct {
+  pthread_mutex_t mutex;
+} SBnMgmt;
+
+int32_t bnInit();
+void    bnCleanUp();
+bool    bnStart();
+void    bnCheckStatus();
+void    bnCheckModules();
+
+extern SBnDnodes tsBnDnodes;
+extern void *tsMnodeTmr;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/src/balance/inc/bnScore.h b/src/balance/inc/bnScore.h
new file mode 100644
index 0000000000..48e423b562
--- /dev/null
+++ b/src/balance/inc/bnScore.h
@@ -0,0 +1,34 @@
+/*
+ * 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_BALANCE_SCORE_H
+#define TDENGINE_BALANCE_SCORE_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+#include "bnMain.h"
+
+void  bnInitDnodes();
+void  bnCleanupDnodes();
+void  bnAccquireDnodes();
+void  bnReleaseDnodes();
+float bnTryCalcDnodeScore(SDnodeObj *pDnode, int32_t extraVnode);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/src/balance/inc/bnThread.h b/src/balance/inc/bnThread.h
index d337e963f1..df9b06cf87 100644
--- a/src/balance/inc/bnThread.h
+++ b/src/balance/inc/bnThread.h
@@ -13,17 +13,18 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef TDENGINE_BALANCE_H
-#define TDENGINE_BALANCE_H
+#ifndef TDENGINE_BALANCE_THREAD_H
+#define TDENGINE_BALANCE_THREAD_H
 
 #ifdef __cplusplus
 extern "C" {
 #endif
+#include "bnMain.h"
 
-int32_t bnThreadInit();
-void    bnThreadCleanup();
-void    bnThreadSyncNotify();
-void    bnThreadAsyncNotify();
+int32_t bnInitThread();
+void    bnCleanupThread();
+void    bnNotify();
+void    bnStartTimer(int64_t mseconds);
 
 #ifdef __cplusplus
 }
diff --git a/src/balance/src/balanceMain.c b/src/balance/src/balanceMain.c
index b172867929..9f9d5103be 100644
--- a/src/balance/src/balanceMain.c
+++ b/src/balance/src/balanceMain.c
@@ -33,36 +33,23 @@
 #include "mnodeUser.h"
 #include "mnodeVgroup.h"
 
-/*
- * once sdb work as mater, then tsAccessSquence reset to zero
- * increase tsAccessSquence every balance interval
- */
-extern void *       tsMnodeTmr;
-static void *       tsBalanceTimer = NULL;
-static int32_t      tsBalanceDnodeListSize = 0;
-static SDnodeObj ** tsBalanceDnodeList = NULL;
-static int32_t      tsBalanceDnodeListMallocSize = 16;
-static pthread_mutex_t tsBalanceMutex;
+#include "bnMain.h"
+#include "bnScore.h"
+#include "bnThread.h"
 
-static void  balanceStartTimer(int64_t mseconds);
-static void  balanceInitDnodeList();
-static void  balanceCleanupDnodeList();
-static void  balanceAccquireDnodeList();
-static void  balanceReleaseDnodeList();
-static void  balanceMonitorDnodeModule();
-static float balanceTryCalcDnodeScore(SDnodeObj *pDnode, int32_t extraVnode);
-static int32_t balanceGetScoresMeta(STableMetaMsg *pMeta, SShowObj *pShow, void *pConn);
-static int32_t balanceRetrieveScores(SShowObj *pShow, char *data, int32_t rows, void *pConn);
+static SBnMgmt tsBnMgmt;;
 
-static void balanceLock() {
-  pthread_mutex_lock(&tsBalanceMutex);
+static void  bnMonitorDnodeModule();
+
+static void bnLock() {
+  pthread_mutex_lock(&tsBnMgmt.mutex);
 }
 
-static void balanceUnLock() {
-  pthread_mutex_unlock(&tsBalanceMutex);
+static void bnUnLock() {
+  pthread_mutex_unlock(&tsBnMgmt.mutex);
 }
 
-static bool balanceCheckFree(SDnodeObj *pDnode) {
+static bool bnCheckFree(SDnodeObj *pDnode) {
   if (pDnode->status == TAOS_DN_STATUS_DROPPING || pDnode->status == TAOS_DN_STATUS_OFFLINE) {
     mError("dnode:%d, status:%s not available", pDnode->dnodeId, mnodeGetDnodeStatusStr(pDnode->status));
     return false;
@@ -86,7 +73,7 @@ static bool balanceCheckFree(SDnodeObj *pDnode) {
   return true;
 }
 
-static void balanceDiscardVnode(SVgObj *pVgroup, SVnodeGid *pVnodeGid) {
+static void bnDiscardVnode(SVgObj *pVgroup, SVnodeGid *pVnodeGid) {
   mDebug("vgId:%d, dnode:%d is dropping", pVgroup->vgId, pVnodeGid->dnodeId);
 
   SDnodeObj *pDnode = mnodeGetDnode(pVnodeGid->dnodeId);
@@ -111,27 +98,26 @@ static void balanceDiscardVnode(SVgObj *pVgroup, SVnodeGid *pVnodeGid) {
   mnodeUpdateVgroup(pVgroup);
 }
 
-static void balanceSwapVnodeGid(SVnodeGid *pVnodeGid1, SVnodeGid *pVnodeGid2) {
+static void bnSwapVnodeGid(SVnodeGid *pVnodeGid1, SVnodeGid *pVnodeGid2) {
   // SVnodeGid tmp = *pVnodeGid1;
   // *pVnodeGid1 = *pVnodeGid2;
   // *pVnodeGid2 = tmp;
 }
 
-int32_t balanceAllocVnodes(SVgObj *pVgroup) {
+int32_t bnAllocVnodes(SVgObj *pVgroup) {
   static int32_t randIndex = 0;
   int32_t dnode = 0;
   int32_t vnodes = 0;
 
-  balanceLock();
-
-  balanceAccquireDnodeList();
+  bnLock();
+  bnAccquireDnodes();
 
   mDebug("db:%s, try alloc %d vnodes to vgroup, dnodes total:%d, avail:%d", pVgroup->dbName, pVgroup->numOfVnodes,
-         mnodeGetDnodesNum(), tsBalanceDnodeListSize);
+         mnodeGetDnodesNum(), tsBnDnodes.size);
   for (int32_t i = 0; i < pVgroup->numOfVnodes; ++i) {
-    for (; dnode < tsBalanceDnodeListSize; ++dnode) {
-      SDnodeObj *pDnode = tsBalanceDnodeList[dnode];
-      if (balanceCheckFree(pDnode)) {
+    for (; dnode < tsBnDnodes.size; ++dnode) {
+      SDnodeObj *pDnode = tsBnDnodes.list[dnode];
+      if (bnCheckFree(pDnode)) {
         SVnodeGid *pVnodeGid = pVgroup->vnodeGid + i;
         pVnodeGid->dnodeId = pDnode->dnodeId;
         pVnodeGid->pDnode = pDnode;
@@ -148,8 +134,8 @@ int32_t balanceAllocVnodes(SVgObj *pVgroup) {
   }
 
   if (vnodes != pVgroup->numOfVnodes) {
-    balanceReleaseDnodeList();
-    balanceUnLock();
+    bnReleaseDnodes();
+    bnUnLock();
 
     mDebug("db:%s, need vnodes:%d, but alloc:%d", pVgroup->dbName, pVgroup->numOfVnodes, vnodes);
 
@@ -179,33 +165,33 @@ int32_t balanceAllocVnodes(SVgObj *pVgroup) {
   if (pVgroup->numOfVnodes == 1) {
   } else if (pVgroup->numOfVnodes == 2) {
     if (randIndex++ % 2 == 0) {
-      balanceSwapVnodeGid(pVgroup->vnodeGid, pVgroup->vnodeGid + 1);
+      bnSwapVnodeGid(pVgroup->vnodeGid, pVgroup->vnodeGid + 1);
     }
   } else {
     int32_t randVal = randIndex++ % 6;
     if (randVal == 1) {  // 1, 0, 2
-      balanceSwapVnodeGid(pVgroup->vnodeGid + 0, pVgroup->vnodeGid + 1);
+      bnSwapVnodeGid(pVgroup->vnodeGid + 0, pVgroup->vnodeGid + 1);
     } else if (randVal == 2) {  // 1, 2, 0
-      balanceSwapVnodeGid(pVgroup->vnodeGid + 0, pVgroup->vnodeGid + 1);
-      balanceSwapVnodeGid(pVgroup->vnodeGid + 1, pVgroup->vnodeGid + 2);
+      bnSwapVnodeGid(pVgroup->vnodeGid + 0, pVgroup->vnodeGid + 1);
+      bnSwapVnodeGid(pVgroup->vnodeGid + 1, pVgroup->vnodeGid + 2);
     } else if (randVal == 3) {  // 2, 1, 0
-      balanceSwapVnodeGid(pVgroup->vnodeGid + 0, pVgroup->vnodeGid + 2);
+      bnSwapVnodeGid(pVgroup->vnodeGid + 0, pVgroup->vnodeGid + 2);
     } else if (randVal == 4) {  // 2, 0, 1
-      balanceSwapVnodeGid(pVgroup->vnodeGid + 0, pVgroup->vnodeGid + 2);
-      balanceSwapVnodeGid(pVgroup->vnodeGid + 1, pVgroup->vnodeGid + 2);
+      bnSwapVnodeGid(pVgroup->vnodeGid + 0, pVgroup->vnodeGid + 2);
+      bnSwapVnodeGid(pVgroup->vnodeGid + 1, pVgroup->vnodeGid + 2);
     }
     if (randVal == 5) {  // 0, 2, 1
-      balanceSwapVnodeGid(pVgroup->vnodeGid + 1, pVgroup->vnodeGid + 2);
+      bnSwapVnodeGid(pVgroup->vnodeGid + 1, pVgroup->vnodeGid + 2);
     } else {
     }  // 0, 1, 2
   }
 
-  balanceReleaseDnodeList();
-  balanceUnLock();
+  bnReleaseDnodes();
+  bnUnLock();
   return TSDB_CODE_SUCCESS;
 }
 
-static bool balanceCheckVgroupReady(SVgObj *pVgroup, SVnodeGid *pRmVnode) {
+static bool bnCheckVgroupReady(SVgObj *pVgroup, SVnodeGid *pRmVnode) {
   if (pVgroup->lbTime + 5 * tsStatusInterval > tsAccessSquence) {
     return false;
   }
@@ -232,7 +218,7 @@ static bool balanceCheckVgroupReady(SVgObj *pVgroup, SVnodeGid *pRmVnode) {
  * desc: remove one vnode from vgroup
  * all vnodes in vgroup should in ready state, except the balancing one
  **/
-static int32_t balanceRemoveVnode(SVgObj *pVgroup) {
+static int32_t bnRemoveVnode(SVgObj *pVgroup) {
   if (pVgroup->numOfVnodes <= 1) return -1;
 
   SVnodeGid *pRmVnode = NULL;
@@ -274,17 +260,17 @@ static int32_t balanceRemoveVnode(SVgObj *pVgroup) {
     pSelVnode = pRmVnode;
   }
 
-  if (!balanceCheckVgroupReady(pVgroup, pSelVnode)) {
+  if (!bnCheckVgroupReady(pVgroup, pSelVnode)) {
     mDebug("vgId:%d, is not ready", pVgroup->vgId);
     return -1;
   } else {
     mDebug("vgId:%d, is ready, discard dnode:%d", pVgroup->vgId, pSelVnode->dnodeId);
-    balanceDiscardVnode(pVgroup, pSelVnode);
+    bnDiscardVnode(pVgroup, pSelVnode);
     return TSDB_CODE_SUCCESS;
   }
 }
 
-static bool balanceCheckDnodeInVgroup(SDnodeObj *pDnode, SVgObj *pVgroup) {
+static bool bnCheckDnodeInVgroup(SDnodeObj *pDnode, SVgObj *pVgroup) {
  for (int32_t i = 0; i < pVgroup->numOfVnodes; ++i) {
     SVnodeGid *pGid = &pVgroup->vnodeGid[i];
     if (pGid->dnodeId == 0) break;
@@ -299,13 +285,13 @@ static bool balanceCheckDnodeInVgroup(SDnodeObj *pDnode, SVgObj *pVgroup) {
 /**
  * desc: add vnode to vgroup, find a new one if dest dnode is null
  **/
-static int32_t balanceAddVnode(SVgObj *pVgroup, SDnodeObj *pSrcDnode, SDnodeObj *pDestDnode) {
+static int32_t bnAddVnode(SVgObj *pVgroup, SDnodeObj *pSrcDnode, SDnodeObj *pDestDnode) {
   if (pDestDnode == NULL) {
-    for (int32_t i = 0; i < tsBalanceDnodeListSize; ++i) {
-      SDnodeObj *pDnode = tsBalanceDnodeList[i];
+    for (int32_t i = 0; i < tsBnDnodes.size; ++i) {
+      SDnodeObj *pDnode = tsBnDnodes.list[i];
       if (pDnode == pSrcDnode) continue;
-      if (balanceCheckDnodeInVgroup(pDnode, pVgroup)) continue;
-      if (!balanceCheckFree(pDnode)) continue;
+      if (bnCheckDnodeInVgroup(pDnode, pVgroup)) continue;
+      if (!bnCheckFree(pDnode)) continue;
       
       pDestDnode = pDnode;
       mDebug("vgId:%d, add vnode to dnode:%d", pVgroup->vgId, pDnode->dnodeId);
@@ -333,25 +319,25 @@ static int32_t balanceAddVnode(SVgObj *pVgroup, SDnodeObj *pSrcDnode, SDnodeObj
   return TSDB_CODE_SUCCESS;
 }
 
-static bool balanceMonitorBalance() {
-  if (tsBalanceDnodeListSize < 2) return false;
+static bool bnMonitorBalance() {
+  if (tsBnDnodes.size < 2) return false;
 
-  for (int32_t src = tsBalanceDnodeListSize - 1; src >= 0; --src) {
-    SDnodeObj *pDnode = tsBalanceDnodeList[src];
-    mDebug("%d-dnode:%d, state:%s, score:%.1f, numOfCores:%d, openVnodes:%d", tsBalanceDnodeListSize - src - 1,
+  for (int32_t src = tsBnDnodes.size - 1; src >= 0; --src) {
+    SDnodeObj *pDnode = tsBnDnodes.list[src];
+    mDebug("%d-dnode:%d, state:%s, score:%.1f, numOfCores:%d, openVnodes:%d", tsBnDnodes.size - src - 1,
            pDnode->dnodeId, mnodeGetDnodeStatusStr(pDnode->status), pDnode->score, pDnode->numOfCores,
            pDnode->openVnodes);
   }
 
-  float scoresDiff = tsBalanceDnodeList[tsBalanceDnodeListSize - 1]->score - tsBalanceDnodeList[0]->score;
+  float scoresDiff = tsBnDnodes.list[tsBnDnodes.size - 1]->score - tsBnDnodes.list[0]->score;
   if (scoresDiff < 0.01) {
-    mDebug("all dnodes:%d is already balanced, scoresDiff:%f", tsBalanceDnodeListSize, scoresDiff);
+    mDebug("all dnodes:%d is already balanced, scoresDiff:%f", tsBnDnodes.size, scoresDiff);
     return false;
   }
 
-  for (int32_t src = tsBalanceDnodeListSize - 1; src > 0; --src) {
-    SDnodeObj *pSrcDnode = tsBalanceDnodeList[src];
-    float srcScore = balanceTryCalcDnodeScore(pSrcDnode, -1);
+  for (int32_t src = tsBnDnodes.size - 1; src > 0; --src) {
+    SDnodeObj *pSrcDnode = tsBnDnodes.list[src];
+    float srcScore = bnTryCalcDnodeScore(pSrcDnode, -1);
     if (tsEnableBalance == 0 && pSrcDnode->status != TAOS_DN_STATUS_DROPPING) {
       continue;
     }
@@ -362,19 +348,19 @@ static bool balanceMonitorBalance() {
       pIter = mnodeGetNextVgroup(pIter, &pVgroup);
       if (pVgroup == NULL) break;
 
-      if (balanceCheckDnodeInVgroup(pSrcDnode, pVgroup)) {
+      if (bnCheckDnodeInVgroup(pSrcDnode, pVgroup)) {
         for (int32_t dest = 0; dest < src; dest++) {
-          SDnodeObj *pDestDnode = tsBalanceDnodeList[dest];
-          if (balanceCheckDnodeInVgroup(pDestDnode, pVgroup)) continue;
+          SDnodeObj *pDestDnode = tsBnDnodes.list[dest];
+          if (bnCheckDnodeInVgroup(pDestDnode, pVgroup)) continue;
 
-          float destScore = balanceTryCalcDnodeScore(pDestDnode, 1);
+          float destScore = bnTryCalcDnodeScore(pDestDnode, 1);
           if (srcScore + 0.0001 < destScore) continue;
-          if (!balanceCheckFree(pDestDnode)) continue;
+          if (!bnCheckFree(pDestDnode)) continue;
           
           mDebug("vgId:%d, balance from dnode:%d to dnode:%d, srcScore:%.1f:%.1f, destScore:%.1f:%.1f",
                  pVgroup->vgId, pSrcDnode->dnodeId, pDestDnode->dnodeId, pSrcDnode->score,
                  srcScore, pDestDnode->score, destScore);
-          balanceAddVnode(pVgroup, pSrcDnode, pDestDnode);
+          bnAddVnode(pVgroup, pSrcDnode, pDestDnode);
           mnodeDecVgroupRef(pVgroup);
           mnodeCancelGetNextVgroup(pIter);
           return true;
@@ -392,7 +378,7 @@ static bool balanceMonitorBalance() {
 // 1. reset balanceAccessSquence to zero
 // 2. reset state of dnodes to offline
 // 3. reset lastAccess of dnodes to zero
-void balanceReset() {
+void bnReset() {
   void *     pIter = NULL;
   SDnodeObj *pDnode = NULL;
   while (1) {
@@ -413,7 +399,7 @@ void balanceReset() {
   tsAccessSquence = 0;
 }
 
-static int32_t balanceMonitorVgroups() {
+static int32_t bnMonitorVgroups() {
   void *  pIter = NULL;
   SVgObj *pVgroup = NULL;
   bool    hasUpdatingVgroup = false;
@@ -429,11 +415,11 @@ static int32_t balanceMonitorVgroups() {
     if (vgReplica > dbReplica) {
       mInfo("vgId:%d, replica:%d numOfVnodes:%d, try remove one vnode", pVgroup->vgId, dbReplica, vgReplica);
       hasUpdatingVgroup = true;
-      code = balanceRemoveVnode(pVgroup);
+      code = bnRemoveVnode(pVgroup);
     } else if (vgReplica < dbReplica) {
       mInfo("vgId:%d, replica:%d numOfVnodes:%d, try add one vnode", pVgroup->vgId, dbReplica, vgReplica);
       hasUpdatingVgroup = true;
-      code = balanceAddVnode(pVgroup, NULL, NULL);
+      code = bnAddVnode(pVgroup, NULL, NULL);
     }
 
     mnodeDecVgroupRef(pVgroup);
@@ -446,7 +432,7 @@ static int32_t balanceMonitorVgroups() {
   return hasUpdatingVgroup;
 }
 
-static bool balanceMonitorDnodeDropping(SDnodeObj *pDnode) {
+static bool bnMonitorDnodeDropping(SDnodeObj *pDnode) {
   mDebug("dnode:%d, in dropping state", pDnode->dnodeId);
 
   void *  pIter = NULL;
@@ -456,7 +442,7 @@ static bool balanceMonitorDnodeDropping(SDnodeObj *pDnode) {
     pIter = mnodeGetNextVgroup(pIter, &pVgroup);
     if (pVgroup == NULL) break;
 
-    hasThisDnode = balanceCheckDnodeInVgroup(pDnode, pVgroup);
+    hasThisDnode = bnCheckDnodeInVgroup(pDnode, pVgroup);
     mnodeDecVgroupRef(pVgroup);
 
     if (hasThisDnode) {
@@ -474,7 +460,7 @@ static bool balanceMonitorDnodeDropping(SDnodeObj *pDnode) {
   return false;
 }
 
-static bool balanceMontiorDropping() {
+static bool bnMontiorDropping() {
   void *pIter = NULL;
   SDnodeObj *pDnode = NULL;
 
@@ -499,7 +485,7 @@ static bool balanceMontiorDropping() {
     }
 
     if (pDnode->status == TAOS_DN_STATUS_DROPPING) {
-      bool ret = balanceMonitorDnodeDropping(pDnode);
+      bool ret = bnMonitorDnodeDropping(pDnode);
       mnodeDecDnodeRef(pDnode);
       mnodeCancelGetNextDnode(pIter);
       return ret;
@@ -509,33 +495,32 @@ static bool balanceMontiorDropping() {
   return false;
 }
 
-static bool balanceStart() {
+bool bnStart() {
   if (!sdbIsMaster()) return false;
 
-  balanceLock();
+  bnLock();
+  bnAccquireDnodes();
 
-  balanceAccquireDnodeList();
+  bnMonitorDnodeModule();
 
-  balanceMonitorDnodeModule();
-
-  bool updateSoon = balanceMontiorDropping();
+  bool updateSoon = bnMontiorDropping();
 
   if (!updateSoon) {
-    updateSoon = balanceMonitorVgroups();
+    updateSoon = bnMonitorVgroups();
   }
 
   if (!updateSoon) {
-    updateSoon = balanceMonitorBalance();
+    updateSoon = bnMonitorBalance();
   }
  
-  balanceReleaseDnodeList();
+  bnReleaseDnodes();
 
-  balanceUnLock();
+  bnUnLock();
 
   return updateSoon;
 }
 
-static void balanceSetVgroupOffline(SDnodeObj* pDnode) {
+static void bnSetVgroupOffline(SDnodeObj* pDnode) {
   void *pIter = NULL;
   while (1) {
     SVgObj *pVgroup;
@@ -551,7 +536,7 @@ static void balanceSetVgroupOffline(SDnodeObj* pDnode) {
   }
 }
 
-static void balanceCheckDnodeAccess() {
+void bnCheckStatus() {
   void *     pIter = NULL;
   SDnodeObj *pDnode = NULL;
 
@@ -564,84 +549,39 @@ static void balanceCheckDnodeAccess() {
         pDnode->offlineReason = TAOS_DN_OFF_STATUS_MSG_TIMEOUT;
         mInfo("dnode:%d, set to offline state, access seq:%d last seq:%d laststat:%d", pDnode->dnodeId, tsAccessSquence,
               pDnode->lastAccess, pDnode->status);
-        balanceSetVgroupOffline(pDnode);
+        bnSetVgroupOffline(pDnode);
       }
     }
     mnodeDecDnodeRef(pDnode);
   }
 }
 
-static void balanceProcessBalanceTimer(void *handle, void *tmrId) {
-  if (!sdbIsMaster()) return;
-
-  tsBalanceTimer = NULL;
-  tsAccessSquence ++;
-
-  balanceCheckDnodeAccess();  
-  bool updateSoon = false;
-
-  if (handle == NULL) {
-    if (tsAccessSquence % tsBalanceInterval == 0) {
-      mDebug("balance function is scheduled by timer");
-      updateSoon = balanceStart();
-    }
-  } else {
-    int64_t mseconds = (int64_t)handle;
-    mDebug("balance function is scheduled by event for %" PRId64 " mseconds arrived", mseconds);
-    updateSoon = balanceStart();
-  }
-
-  if (updateSoon) {
-    balanceStartTimer(1000);
-  } else {
-    taosTmrReset(balanceProcessBalanceTimer, tsStatusInterval * 1000, NULL, tsMnodeTmr, &tsBalanceTimer);
-  }
-}
-
-static void balanceStartTimer(int64_t mseconds) {
-  taosTmrReset(balanceProcessBalanceTimer, mseconds, (void *)mseconds, tsMnodeTmr, &tsBalanceTimer);
-}
-
-void balanceSyncNotify() {
+void bnCheckModules() {
   if (sdbIsMaster()) {
-    balanceLock();
-    balanceAccquireDnodeList();
-    balanceMonitorDnodeModule();
-    balanceReleaseDnodeList();
-    balanceUnLock();
+    bnLock();
+    bnAccquireDnodes();
+    bnMonitorDnodeModule();
+    bnReleaseDnodes();
+    bnUnLock();
   }
 }
 
-void balanceAsyncNotify() {
-  balanceStartTimer(500); 
-}
-
-int32_t balanceInit() {
-  mnodeAddShowMetaHandle(TSDB_MGMT_TABLE_SCORES, balanceGetScoresMeta);
-  mnodeAddShowRetrieveHandle(TSDB_MGMT_TABLE_SCORES, balanceRetrieveScores);
-  mnodeAddShowFreeIterHandle(TSDB_MGMT_TABLE_SCORES, mnodeCancelGetNextDnode);
-  
-  pthread_mutex_init(&tsBalanceMutex, NULL);
-  balanceInitDnodeList();
-  balanceStartTimer(2000);
-  mDebug("balance start fp:%p initialized", balanceProcessBalanceTimer);
-
-  balanceReset();
+int32_t bnInit() {
+  pthread_mutex_init(&tsBnMgmt.mutex, NULL);
+  bnInitDnodes();
+  bnInitThread();
+  bnReset();
   
   return 0;
 }
 
-void balanceCleanUp() {
-  if (tsBalanceTimer != NULL) {
-    taosTmrStopA(&tsBalanceTimer);
-    pthread_mutex_destroy(&tsBalanceMutex);
-    tsBalanceTimer = NULL;
-    mDebug("stop balance timer");
-  }
-  balanceCleanupDnodeList();
+void bnCleanUp() {
+  bnCleanupThread();
+  pthread_mutex_destroy(&tsBnMgmt.mutex);
+  bnCleanupDnodes();
 }
 
-int32_t balanceDropDnode(SDnodeObj *pDnode) {
+int32_t bnDropDnode(SDnodeObj *pDnode) {
   int32_t    totalFreeVnodes = 0;
   void *     pIter = NULL;
   SDnodeObj *pTempDnode = NULL;
@@ -650,7 +590,7 @@ int32_t balanceDropDnode(SDnodeObj *pDnode) {
     pIter = mnodeGetNextDnode(pIter, &pTempDnode);
     if (pTempDnode == NULL) break;
 
-    if (pTempDnode != pDnode && balanceCheckFree(pTempDnode)) {
+    if (pTempDnode != pDnode && bnCheckFree(pTempDnode)) {
       totalFreeVnodes += (TSDB_MAX_VNODES - pTempDnode->openVnodes);
     }
 
@@ -665,298 +605,19 @@ int32_t balanceDropDnode(SDnodeObj *pDnode) {
   pDnode->status = TAOS_DN_STATUS_DROPPING;
   mnodeUpdateDnode(pDnode);
   
-  balanceStartTimer(1100);
+  bnStartTimer(1100);
 
   return TSDB_CODE_SUCCESS;
 }
 
-static int32_t balanceCalcCpuScore(SDnodeObj *pDnode) {
-  if (pDnode->cpuAvgUsage < 80)
-    return 0;
-  else if (pDnode->cpuAvgUsage < 90)
-    return 10;
-  else
-    return 50;
-}
 
-static int32_t balanceCalcMemoryScore(SDnodeObj *pDnode) {
-  if (pDnode->memoryAvgUsage < 80)
-    return 0;
-  else if (pDnode->memoryAvgUsage < 90)
-    return 10;
-  else
-    return 50;
-}
 
-static int32_t balanceCalcDiskScore(SDnodeObj *pDnode) {
-  if (pDnode->diskAvgUsage < 80)
-    return 0;
-  else if (pDnode->diskAvgUsage < 90)
-    return 10;
-  else
-    return 50;
-}
-
-static int32_t balanceCalcBandwidthScore(SDnodeObj *pDnode) {
-  if (pDnode->bandwidthUsage < 30)
-    return 0;
-  else if (pDnode->bandwidthUsage < 80)
-    return 10;
-  else
-    return 50;
-}
-
-static float balanceCalcModuleScore(SDnodeObj *pDnode) {
-  if (pDnode->numOfCores <= 0) return 0;
-  if (pDnode->isMgmt) {
-     return (float)tsMnodeEqualVnodeNum / pDnode->numOfCores;
-  }
-  return 0;
-}
-
-static float balanceCalcVnodeScore(SDnodeObj *pDnode, int32_t extra) {
-  if (pDnode->status == TAOS_DN_STATUS_DROPPING || pDnode->status == TAOS_DN_STATUS_OFFLINE) return 100000000;
-  if (pDnode->numOfCores <= 0) return 0;
-  return (float)(pDnode->openVnodes + extra) / pDnode->numOfCores;
-}
-
-/**
- * calc singe score, such as cpu/memory/disk/bandwitdh/vnode
- * 1. get the score config
- * 2. if the value is out of range, use border data
- * 3. otherwise use interpolation method
- **/
-void balanceCalcDnodeScore(SDnodeObj *pDnode) {
-  pDnode->score = balanceCalcCpuScore(pDnode) + balanceCalcMemoryScore(pDnode) + balanceCalcDiskScore(pDnode) +
-                  balanceCalcBandwidthScore(pDnode) + balanceCalcModuleScore(pDnode) +
-                  balanceCalcVnodeScore(pDnode, 0) + pDnode->customScore;
-}
-
-float balanceTryCalcDnodeScore(SDnodeObj *pDnode, int32_t extra) {
-  int32_t systemScore = balanceCalcCpuScore(pDnode) + balanceCalcMemoryScore(pDnode) + balanceCalcDiskScore(pDnode) +
-                        balanceCalcBandwidthScore(pDnode);
-  float moduleScore = balanceCalcModuleScore(pDnode);
-  float vnodeScore = balanceCalcVnodeScore(pDnode, extra);
-
-  float score = systemScore + moduleScore + vnodeScore +  pDnode->customScore;
-  return score;
-}
-
-static void balanceInitDnodeList() {
-  tsBalanceDnodeList = calloc(tsBalanceDnodeListMallocSize, sizeof(SDnodeObj *));
-}
-
-static void balanceCleanupDnodeList() {
-  if (tsBalanceDnodeList != NULL) {
-    free(tsBalanceDnodeList);
-    tsBalanceDnodeList = NULL;
-  }
-}
-
-static void balanceCheckDnodeListSize(int32_t dnodesNum) {
-  if (tsBalanceDnodeListMallocSize <= dnodesNum) {
-    tsBalanceDnodeListMallocSize = dnodesNum * 2;
-    tsBalanceDnodeList = realloc(tsBalanceDnodeList, tsBalanceDnodeListMallocSize * sizeof(SDnodeObj *));
-  }
-}
-
-void balanceAccquireDnodeList() {
-  int32_t dnodesNum = mnodeGetDnodesNum();
-  balanceCheckDnodeListSize(dnodesNum);
-
-  void *     pIter = NULL;
-  SDnodeObj *pDnode = NULL;
-  int32_t    dnodeIndex = 0;
-
-  while (1) {
-    if (dnodeIndex >= dnodesNum) {
-      mnodeCancelGetNextDnode(pIter);
-      break;
-    }
-
-    pIter = mnodeGetNextDnode(pIter, &pDnode);
-    if (pDnode == NULL) break;
-    if (pDnode->status == TAOS_DN_STATUS_OFFLINE) {
-      mnodeDecDnodeRef(pDnode);
-      continue;
-    }
-
-    balanceCalcDnodeScore(pDnode);
-    
-    int32_t orderIndex = dnodeIndex;
-    for (; orderIndex > 0; --orderIndex) {
-      if (pDnode->score > tsBalanceDnodeList[orderIndex - 1]->score) {
-        break;
-      }
-      tsBalanceDnodeList[orderIndex] = tsBalanceDnodeList[orderIndex - 1];
-    }
-    tsBalanceDnodeList[orderIndex] = pDnode;
-    dnodeIndex++;
-  }
-
-  tsBalanceDnodeListSize = dnodeIndex;
-}
-
-void balanceReleaseDnodeList() {
-  for (int32_t i = 0; i < tsBalanceDnodeListSize; ++i) {
-    SDnodeObj *pDnode = tsBalanceDnodeList[i];
-    if (pDnode != NULL) {
-      mnodeDecDnodeRef(pDnode);
-    }
-  }
-}
-
-static int32_t balanceGetScoresMeta(STableMetaMsg *pMeta, SShowObj *pShow, void *pConn) {
-  SUserObj *pUser = mnodeGetUserFromConn(pConn);
-  if (pUser == NULL) return 0;
-
-  if (strcmp(pUser->pAcct->user, "root") != 0)  {
-    mnodeDecUserRef(pUser);
-    return TSDB_CODE_MND_NO_RIGHTS;
-  }
-
-  int32_t cols = 0;
-  SSchema *pSchema = pMeta->schema;
-
-  pShow->bytes[cols] = 2;
-  pSchema[cols].type = TSDB_DATA_TYPE_SMALLINT;
-  strcpy(pSchema[cols].name, "id");
-  pSchema[cols].bytes = htons(pShow->bytes[cols]);
-  cols++;
-
-  pShow->bytes[cols] = 4;
-  pSchema[cols].type = TSDB_DATA_TYPE_FLOAT;
-  strcpy(pSchema[cols].name, "system scores");
-  pSchema[cols].bytes = htons(pShow->bytes[cols]);
-  cols++;
-
-  pShow->bytes[cols] = 4;
-  pSchema[cols].type = TSDB_DATA_TYPE_FLOAT;
-  strcpy(pSchema[cols].name, "custom scores");
-  pSchema[cols].bytes = htons(pShow->bytes[cols]);
-  cols++;
-
-  pShow->bytes[cols] = 4;
-  pSchema[cols].type = TSDB_DATA_TYPE_FLOAT;
-  strcpy(pSchema[cols].name, "module scores");
-  pSchema[cols].bytes = htons(pShow->bytes[cols]);
-  cols++;
-
-  pShow->bytes[cols] = 4;
-  pSchema[cols].type = TSDB_DATA_TYPE_FLOAT;
-  strcpy(pSchema[cols].name, "vnode scores");
-  pSchema[cols].bytes = htons(pShow->bytes[cols]);
-  cols++;
-
-  pShow->bytes[cols] = 4;
-  pSchema[cols].type = TSDB_DATA_TYPE_FLOAT;
-  strcpy(pSchema[cols].name, "total scores");
-  pSchema[cols].bytes = htons(pShow->bytes[cols]);
-  cols++;
-
-  pShow->bytes[cols] = 4;
-  pSchema[cols].type = TSDB_DATA_TYPE_INT;
-  strcpy(pSchema[cols].name, "open vnodes");
-  pSchema[cols].bytes = htons(pShow->bytes[cols]);
-  cols++;
-
-  pShow->bytes[cols] = 4;
-  pSchema[cols].type = TSDB_DATA_TYPE_INT;
-  strcpy(pSchema[cols].name, "cpu cores");
-  pSchema[cols].bytes = htons(pShow->bytes[cols]);
-  cols++;
-
-  pShow->bytes[cols] = 18 + VARSTR_HEADER_SIZE;
-  pSchema[cols].type = TSDB_DATA_TYPE_BINARY;
-  strcpy(pSchema[cols].name, "balance state");
-  pSchema[cols].bytes = htons(pShow->bytes[cols]);
-  cols++;
-
-  pMeta->numOfColumns = htons(cols);
-  pShow->numOfColumns = cols;
-
-  pShow->offset[0] = 0;
-  for (int32_t i = 1; i < cols; ++i) {
-    pShow->offset[i] = pShow->offset[i - 1] + pShow->bytes[i - 1];
-  }
-
-  pShow->numOfRows = mnodeGetDnodesNum();
-  pShow->rowSize = pShow->offset[cols - 1] + pShow->bytes[cols - 1];
-  pShow->pIter = NULL;
-
-  mnodeDecUserRef(pUser);
-
-  return 0;
-}
-
-static int32_t balanceRetrieveScores(SShowObj *pShow, char *data, int32_t rows, void *pConn) {
-  int32_t    numOfRows = 0;
-  SDnodeObj *pDnode = NULL;
-  char *     pWrite;
-  int32_t    cols = 0;
-  
-  while (numOfRows < rows) {
-    pShow->pIter = mnodeGetNextDnode(pShow->pIter, &pDnode);
-    if (pDnode == NULL) break;
-
-    int32_t systemScore = balanceCalcCpuScore(pDnode) + balanceCalcMemoryScore(pDnode) + balanceCalcDiskScore(pDnode) +
-                      balanceCalcBandwidthScore(pDnode);
-    float moduleScore = balanceCalcModuleScore(pDnode);
-    float vnodeScore = balanceCalcVnodeScore(pDnode, 0);
-
-    cols = 0;
-
-    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
-    *(int16_t *)pWrite = pDnode->dnodeId;
-    cols++;
-
-    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
-    *(float *)pWrite = systemScore;
-    cols++;
-
-    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
-    *(float *)pWrite = pDnode->customScore;
-    cols++;
-
-    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
-    *(float *)pWrite = (int32_t)moduleScore;
-    cols++;
-
-    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
-    *(float *)pWrite = (int32_t)vnodeScore;
-    cols++;
-
-    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
-    *(float *)pWrite = (int32_t)(vnodeScore + moduleScore + pDnode->customScore + systemScore);
-    cols++;
-
-    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
-    *(int32_t *)pWrite = pDnode->openVnodes;
-    cols++;
-
-    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
-    *(int32_t *)pWrite = pDnode->numOfCores;
-    cols++;
-
-    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
-    STR_TO_VARSTR(pWrite, mnodeGetDnodeStatusStr(pDnode->status));
-    cols++;
-
-    numOfRows++;
-    mnodeDecDnodeRef(pDnode);
-  }
-
-  mnodeVacuumResult(data, pShow->numOfColumns, numOfRows, rows, pShow);
-  pShow->numOfReads += numOfRows;
-  return numOfRows;
-}
-
-static void balanceMonitorDnodeModule() {
+static void bnMonitorDnodeModule() {
   int32_t numOfMnodes = mnodeGetMnodesNum();
   if (numOfMnodes >= tsNumOfMnodes) return;
 
-  for (int32_t i = 0; i < tsBalanceDnodeListSize; ++i) {
-    SDnodeObj *pDnode = tsBalanceDnodeList[i];
+  for (int32_t i = 0; i < tsBnDnodes.size; ++i) {
+    SDnodeObj *pDnode = tsBnDnodes.list[i];
     if (pDnode == NULL) break;
 
     if (pDnode->isMgmt || pDnode->status == TAOS_DN_STATUS_DROPPING || pDnode->status == TAOS_DN_STATUS_OFFLINE) {
@@ -980,7 +641,7 @@ static void balanceMonitorDnodeModule() {
   }
 }
 
-int32_t balanceAlterDnode(struct SDnodeObj *pSrcDnode, int32_t vnodeId, int32_t dnodeId) {
+int32_t bnAlterDnode(struct SDnodeObj *pSrcDnode, int32_t vnodeId, int32_t dnodeId) {
   if (!sdbIsMaster()) {
     mError("dnode:%d, failed to alter vgId:%d to dnode:%d, for self not master", pSrcDnode->dnodeId, vnodeId, dnodeId);
     return TSDB_CODE_MND_DNODE_NOT_EXIST;
@@ -1004,29 +665,29 @@ int32_t balanceAlterDnode(struct SDnodeObj *pSrcDnode, int32_t vnodeId, int32_t
     return TSDB_CODE_MND_DNODE_NOT_EXIST;
   }
 
-  balanceLock();
-  balanceAccquireDnodeList();
+  bnLock();
+  bnAccquireDnodes();
 
   int32_t code = TSDB_CODE_SUCCESS;
-  if (!balanceCheckDnodeInVgroup(pSrcDnode, pVgroup)) {
+  if (!bnCheckDnodeInVgroup(pSrcDnode, pVgroup)) {
     mError("dnode:%d, failed to alter vgId:%d to dnode:%d, vgroup not in dnode:%d", pSrcDnode->dnodeId, vnodeId,
            dnodeId, pSrcDnode->dnodeId);
     code = TSDB_CODE_MND_VGROUP_NOT_IN_DNODE;
-  } else if (balanceCheckDnodeInVgroup(pDestDnode, pVgroup)) {
+  } else if (bnCheckDnodeInVgroup(pDestDnode, pVgroup)) {
     mError("dnode:%d, failed to alter vgId:%d to dnode:%d, vgroup already in dnode:%d", pSrcDnode->dnodeId, vnodeId,
            dnodeId, dnodeId);
     code = TSDB_CODE_MND_VGROUP_ALREADY_IN_DNODE;
-  } else if (!balanceCheckFree(pDestDnode)) {
+  } else if (!bnCheckFree(pDestDnode)) {
     mError("dnode:%d, failed to alter vgId:%d to dnode:%d, for dnode:%d not free", pSrcDnode->dnodeId, vnodeId, dnodeId,
            dnodeId);
     code = TSDB_CODE_MND_DNODE_NOT_FREE;
   } else {
-    code = balanceAddVnode(pVgroup, pSrcDnode, pDestDnode);
+    code = bnAddVnode(pVgroup, pSrcDnode, pDestDnode);
     mInfo("dnode:%d, alter vgId:%d to dnode:%d, result:%s", pSrcDnode->dnodeId, vnodeId, dnodeId, tstrerror(code));
   }
 
-  balanceReleaseDnodeList();
-  balanceUnLock();
+  bnReleaseDnodes();
+  bnUnLock();
 
   mnodeDecVgroupRef(pVgroup);
   mnodeDecDnodeRef(pDestDnode);
diff --git a/src/balance/src/bnScore.c b/src/balance/src/bnScore.c
new file mode 100644
index 0000000000..db5d515fbf
--- /dev/null
+++ b/src/balance/src/bnScore.c
@@ -0,0 +1,328 @@
+/*
+ * 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 "tutil.h"
+#include "tbalance.h"
+#include "tsync.h"
+#include "tsync.h"
+#include "ttimer.h"
+#include "tglobal.h"
+#include "tdataformat.h"
+#include "dnode.h"
+#include "mnode.h"
+#include "mnodeDef.h"
+#include "mnodeInt.h"
+#include "mnodeDnode.h"
+#include "mnodeDb.h"
+#include "mnodeMnode.h"
+#include "mnodeSdb.h"
+#include "mnodeShow.h"
+#include "mnodeUser.h"
+#include "mnodeVgroup.h"
+
+#include "bnScore.h"
+
+SBnDnodes tsBnDnodes;
+
+static int32_t bnGetScoresMeta(STableMetaMsg *pMeta, SShowObj *pShow, void *pConn);
+static int32_t bnRetrieveScores(SShowObj *pShow, char *data, int32_t rows, void *pConn);
+
+static int32_t bnCalcCpuScore(SDnodeObj *pDnode) {
+  if (pDnode->cpuAvgUsage < 80)
+    return 0;
+  else if (pDnode->cpuAvgUsage < 90)
+    return 10;
+  else
+    return 50;
+}
+
+static int32_t bnCalcMemoryScore(SDnodeObj *pDnode) {
+  if (pDnode->memoryAvgUsage < 80)
+    return 0;
+  else if (pDnode->memoryAvgUsage < 90)
+    return 10;
+  else
+    return 50;
+}
+
+static int32_t bnCalcDiskScore(SDnodeObj *pDnode) {
+  if (pDnode->diskAvgUsage < 80)
+    return 0;
+  else if (pDnode->diskAvgUsage < 90)
+    return 10;
+  else
+    return 50;
+}
+
+static int32_t bnCalcBandScore(SDnodeObj *pDnode) {
+  if (pDnode->bandwidthUsage < 30)
+    return 0;
+  else if (pDnode->bandwidthUsage < 80)
+    return 10;
+  else
+    return 50;
+}
+
+static float bnCalcModuleScore(SDnodeObj *pDnode) {
+  if (pDnode->numOfCores <= 0) return 0;
+  if (pDnode->isMgmt) {
+    return (float)tsMnodeEqualVnodeNum / pDnode->numOfCores;
+  }
+  return 0;
+}
+
+static float bnCalcVnodeScore(SDnodeObj *pDnode, int32_t extra) {
+  if (pDnode->status == TAOS_DN_STATUS_DROPPING || pDnode->status == TAOS_DN_STATUS_OFFLINE) return 100000000;
+  if (pDnode->numOfCores <= 0) return 0;
+  return (float)(pDnode->openVnodes + extra) / pDnode->numOfCores;
+}
+
+/**
+ * calc singe score, such as cpu/memory/disk/bandwitdh/vnode
+ * 1. get the score config
+ * 2. if the value is out of range, use border data
+ * 3. otherwise use interpolation method
+ **/
+static void bnCalcDnodeScore(SDnodeObj *pDnode) {
+  pDnode->score = bnCalcCpuScore(pDnode) + bnCalcMemoryScore(pDnode) + bnCalcDiskScore(pDnode) +
+                  bnCalcBandScore(pDnode) + bnCalcModuleScore(pDnode) + bnCalcVnodeScore(pDnode, 0) +
+                  pDnode->customScore;
+}
+
+float bnTryCalcDnodeScore(SDnodeObj *pDnode, int32_t extra) {
+  int32_t systemScore = bnCalcCpuScore(pDnode) + bnCalcMemoryScore(pDnode) + bnCalcDiskScore(pDnode) +
+                        bnCalcBandScore(pDnode);
+  float moduleScore = bnCalcModuleScore(pDnode);
+  float vnodeScore = bnCalcVnodeScore(pDnode, extra);
+
+  float score = systemScore + moduleScore + vnodeScore +  pDnode->customScore;
+  return score;
+}
+
+void bnInitDnodes() {
+  mnodeAddShowMetaHandle(TSDB_MGMT_TABLE_SCORES, bnGetScoresMeta);
+  mnodeAddShowRetrieveHandle(TSDB_MGMT_TABLE_SCORES, bnRetrieveScores);
+  mnodeAddShowFreeIterHandle(TSDB_MGMT_TABLE_SCORES, mnodeCancelGetNextDnode);
+
+  memset(&tsBnDnodes, 0, sizeof(SBnDnodes));
+  tsBnDnodes.maxSize = 16;
+  tsBnDnodes.list = calloc(tsBnDnodes.maxSize, sizeof(SDnodeObj *));
+}
+
+void bnCleanupDnodes() {
+  if (tsBnDnodes.list != NULL) {
+    free(tsBnDnodes.list);
+    tsBnDnodes.list = NULL;
+  }
+}
+
+static void bnCheckDnodesSize(int32_t dnodesNum) {
+  if (tsBnDnodes.maxSize <= dnodesNum) {
+    tsBnDnodes.maxSize = dnodesNum * 2;
+    tsBnDnodes.list = realloc(tsBnDnodes.list, tsBnDnodes.maxSize * sizeof(SDnodeObj *));
+  }
+}
+
+void bnAccquireDnodes() {
+  int32_t dnodesNum = mnodeGetDnodesNum();
+  bnCheckDnodesSize(dnodesNum);
+
+  void *     pIter = NULL;
+  SDnodeObj *pDnode = NULL;
+  int32_t    dnodeIndex = 0;
+
+  while (1) {
+    if (dnodeIndex >= dnodesNum) {
+      mnodeCancelGetNextDnode(pIter);
+      break;
+    }
+
+    pIter = mnodeGetNextDnode(pIter, &pDnode);
+    if (pDnode == NULL) break;
+    if (pDnode->status == TAOS_DN_STATUS_OFFLINE) {
+      mnodeDecDnodeRef(pDnode);
+      continue;
+    }
+
+    bnCalcDnodeScore(pDnode);
+    
+    int32_t orderIndex = dnodeIndex;
+    for (; orderIndex > 0; --orderIndex) {
+      if (pDnode->score > tsBnDnodes.list[orderIndex - 1]->score) {
+        break;
+      }
+      tsBnDnodes.list[orderIndex] = tsBnDnodes.list[orderIndex - 1];
+    }
+    tsBnDnodes.list[orderIndex] = pDnode;
+    dnodeIndex++;
+  }
+
+  tsBnDnodes.size = dnodeIndex;
+}
+
+void bnReleaseDnodes() {
+  for (int32_t i = 0; i < tsBnDnodes.size; ++i) {
+    SDnodeObj *pDnode = tsBnDnodes.list[i];
+    if (pDnode != NULL) {
+      mnodeDecDnodeRef(pDnode);
+    }
+  }
+}
+
+static int32_t bnGetScoresMeta(STableMetaMsg *pMeta, SShowObj *pShow, void *pConn) {
+  SUserObj *pUser = mnodeGetUserFromConn(pConn);
+  if (pUser == NULL) return 0;
+
+  if (strcmp(pUser->pAcct->user, "root") != 0) {
+    mnodeDecUserRef(pUser);
+    return TSDB_CODE_MND_NO_RIGHTS;
+  }
+
+  int32_t  cols = 0;
+  SSchema *pSchema = pMeta->schema;
+
+  pShow->bytes[cols] = 2;
+  pSchema[cols].type = TSDB_DATA_TYPE_SMALLINT;
+  strcpy(pSchema[cols].name, "id");
+  pSchema[cols].bytes = htons(pShow->bytes[cols]);
+  cols++;
+
+  pShow->bytes[cols] = 4;
+  pSchema[cols].type = TSDB_DATA_TYPE_FLOAT;
+  strcpy(pSchema[cols].name, "system scores");
+  pSchema[cols].bytes = htons(pShow->bytes[cols]);
+  cols++;
+
+  pShow->bytes[cols] = 4;
+  pSchema[cols].type = TSDB_DATA_TYPE_FLOAT;
+  strcpy(pSchema[cols].name, "custom scores");
+  pSchema[cols].bytes = htons(pShow->bytes[cols]);
+  cols++;
+
+  pShow->bytes[cols] = 4;
+  pSchema[cols].type = TSDB_DATA_TYPE_FLOAT;
+  strcpy(pSchema[cols].name, "module scores");
+  pSchema[cols].bytes = htons(pShow->bytes[cols]);
+  cols++;
+
+  pShow->bytes[cols] = 4;
+  pSchema[cols].type = TSDB_DATA_TYPE_FLOAT;
+  strcpy(pSchema[cols].name, "vnode scores");
+  pSchema[cols].bytes = htons(pShow->bytes[cols]);
+  cols++;
+
+  pShow->bytes[cols] = 4;
+  pSchema[cols].type = TSDB_DATA_TYPE_FLOAT;
+  strcpy(pSchema[cols].name, "total scores");
+  pSchema[cols].bytes = htons(pShow->bytes[cols]);
+  cols++;
+
+  pShow->bytes[cols] = 4;
+  pSchema[cols].type = TSDB_DATA_TYPE_INT;
+  strcpy(pSchema[cols].name, "open vnodes");
+  pSchema[cols].bytes = htons(pShow->bytes[cols]);
+  cols++;
+
+  pShow->bytes[cols] = 4;
+  pSchema[cols].type = TSDB_DATA_TYPE_INT;
+  strcpy(pSchema[cols].name, "cpu cores");
+  pSchema[cols].bytes = htons(pShow->bytes[cols]);
+  cols++;
+
+  pShow->bytes[cols] = 18 + VARSTR_HEADER_SIZE;
+  pSchema[cols].type = TSDB_DATA_TYPE_BINARY;
+  strcpy(pSchema[cols].name, "balance state");
+  pSchema[cols].bytes = htons(pShow->bytes[cols]);
+  cols++;
+
+  pMeta->numOfColumns = htons(cols);
+  pShow->numOfColumns = cols;
+
+  pShow->offset[0] = 0;
+  for (int32_t i = 1; i < cols; ++i) {
+    pShow->offset[i] = pShow->offset[i - 1] + pShow->bytes[i - 1];
+  }
+
+  pShow->numOfRows = mnodeGetDnodesNum();
+  pShow->rowSize = pShow->offset[cols - 1] + pShow->bytes[cols - 1];
+  pShow->pIter = NULL;
+
+  mnodeDecUserRef(pUser);
+
+  return 0;
+}
+
+static int32_t bnRetrieveScores(SShowObj *pShow, char *data, int32_t rows, void *pConn) {
+  int32_t    numOfRows = 0;
+  SDnodeObj *pDnode = NULL;
+  char *     pWrite;
+  int32_t    cols = 0;
+
+  while (numOfRows < rows) {
+    pShow->pIter = mnodeGetNextDnode(pShow->pIter, &pDnode);
+    if (pDnode == NULL) break;
+
+    int32_t systemScore = bnCalcCpuScore(pDnode) + bnCalcMemoryScore(pDnode) + bnCalcDiskScore(pDnode) + bnCalcBandScore(pDnode);
+    float moduleScore = bnCalcModuleScore(pDnode);
+    float vnodeScore = bnCalcVnodeScore(pDnode, 0);
+
+    cols = 0;
+
+    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
+    *(int16_t *)pWrite = pDnode->dnodeId;
+    cols++;
+
+    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
+    *(float *)pWrite = systemScore;
+    cols++;
+
+    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
+    *(float *)pWrite = pDnode->customScore;
+    cols++;
+
+    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
+    *(float *)pWrite = (int32_t)moduleScore;
+    cols++;
+
+    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
+    *(float *)pWrite = (int32_t)vnodeScore;
+    cols++;
+
+    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
+    *(float *)pWrite = (int32_t)(vnodeScore + moduleScore + pDnode->customScore + systemScore);
+    cols++;
+
+    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
+    *(int32_t *)pWrite = pDnode->openVnodes;
+    cols++;
+
+    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
+    *(int32_t *)pWrite = pDnode->numOfCores;
+    cols++;
+
+    pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
+    STR_TO_VARSTR(pWrite, mnodeGetDnodeStatusStr(pDnode->status));
+    cols++;
+
+    numOfRows++;
+    mnodeDecDnodeRef(pDnode);
+  }
+
+  mnodeVacuumResult(data, pShow->numOfColumns, numOfRows, rows, pShow);
+  pShow->numOfReads += numOfRows;
+  return numOfRows;
+}
diff --git a/src/balance/src/bnThread.c b/src/balance/src/bnThread.c
index 12cb2cf992..39eb6d0e31 100644
--- a/src/balance/src/bnThread.c
+++ b/src/balance/src/bnThread.c
@@ -34,14 +34,10 @@
 #include "mnodeUser.h"
 #include "mnodeVgroup.h"
 
-typedef struct {
-  bool            stop;
-  pthread_mutex_t mutex;
-  pthread_cond_t  cond;
-  pthread_t       thread;
-} SBalanceThread;
 
-static SBalanceThread tsBnThread;
+#include "bnThread.h"
+
+static SBnThread tsBnThread;
 
 static void *bnThreadFunc(void *arg) {
   while (1) {
@@ -52,14 +48,16 @@ static void *bnThreadFunc(void *arg) {
     }
 
     pthread_cond_wait(&tsBnThread.cond, &tsBnThread.mutex);
-
+    bool updateSoon = bnStart();
+    bnStartTimer(updateSoon ? 1000 : -1);
     pthread_mutex_unlock(&(tsBnThread.mutex));
   }
 
   return NULL;
 }
 
-int32_t bnThreadInit() {
+int32_t bnInitThread() {
+  memset(&tsBnThread, 0, sizeof(SBnThread));
   tsBnThread.stop = false;
   pthread_mutex_init(&tsBnThread.mutex, NULL);
   pthread_cond_init(&tsBnThread.cond, NULL);
@@ -75,13 +73,20 @@ int32_t bnThreadInit() {
     return -1;
   }
 
+  bnStartTimer(2000);
   mDebug("balance thread is created");
   return 0;
 }
 
-void bnThreadCleanup() {
+void bnCleanupThread() {
   mDebug("balance thread will be cleanup");
 
+  if (tsBnThread.timer != NULL) {
+    taosTmrStopA(&tsBnThread.timer);
+    tsBnThread.timer = NULL;
+    mDebug("stop balance timer");
+  }
+
   pthread_mutex_lock(&tsBnThread.mutex);
   tsBnThread.stop = true;
   pthread_cond_signal(&tsBnThread.cond);
@@ -92,16 +97,47 @@ void bnThreadCleanup() {
   pthread_mutex_destroy(&tsBnThread.mutex);
 }
 
-void bnThreadSyncNotify() {
-  mDebug("balance thread sync notify");
-  pthread_mutex_lock(&tsBnThread.mutex);
-  pthread_cond_signal(&tsBnThread.cond);
-  pthread_mutex_unlock(&(tsBnThread.mutex));
-}
-
-void bnThreadAsyncNotify() {
+static void bnPostSignal() {
   mDebug("balance thread async notify");
   pthread_mutex_lock(&tsBnThread.mutex);
   pthread_cond_signal(&tsBnThread.cond);
   pthread_mutex_unlock(&(tsBnThread.mutex));
 }
+
+/*
+ * once sdb work as mater, then tsAccessSquence reset to zero
+ * increase tsAccessSquence every balance interval
+ */
+
+static void bnProcessTimer(void *handle, void *tmrId) {
+  if (!sdbIsMaster()) return;
+
+  tsBnThread.timer = NULL;
+  tsAccessSquence++;
+
+  bnCheckStatus();
+
+  if (handle == NULL) {
+    if (tsAccessSquence % tsBalanceInterval == 0) {
+      mDebug("balance function is scheduled by timer");
+      bnPostSignal();
+    }
+  } else {
+    int64_t mseconds = (int64_t)handle;
+    mDebug("balance function is scheduled by event for %" PRId64 " mseconds arrived", mseconds);
+    bnPostSignal();
+  }
+}
+
+void bnStartTimer(int64_t mseconds) {
+  bool updateSoon = (mseconds != -1);
+  if (updateSoon) {
+    taosTmrReset(bnProcessTimer, mseconds, (void *)mseconds, tsMnodeTmr, &tsBnThread.timer);
+  } else {
+    taosTmrReset(bnProcessTimer, tsStatusInterval * 1000, NULL, tsMnodeTmr, &tsBnThread.timer);
+  }
+}
+
+void bnNotify() {
+  bnStartTimer(500); 
+}
diff --git a/src/inc/tbalance.h b/src/inc/tbalance.h
index f0da4a3747..b9f4e3c608 100644
--- a/src/inc/tbalance.h
+++ b/src/inc/tbalance.h
@@ -23,14 +23,14 @@ extern "C" {
 struct SVgObj;
 struct SDnodeObj;
 
-int32_t balanceInit();
-void    balanceCleanUp();
-void    balanceAsyncNotify();
-void    balanceSyncNotify();
-void    balanceReset();
-int32_t balanceAllocVnodes(struct SVgObj *pVgroup);
-int32_t balanceAlterDnode(struct SDnodeObj *pDnode, int32_t vnodeId, int32_t dnodeId);
-int32_t balanceDropDnode(struct SDnodeObj *pDnode);
+int32_t bnInit();
+void    bnCleanUp();
+void    bnNotify();
+void    bnCheckModules();
+void    bnReset();
+int32_t bnAllocVnodes(struct SVgObj *pVgroup);
+int32_t bnAlterDnode(struct SDnodeObj *pDnode, int32_t vnodeId, int32_t dnodeId);
+int32_t bnDropDnode(struct SDnodeObj *pDnode);
 
 #ifdef __cplusplus
 }
diff --git a/src/mnode/src/mnodeDb.c b/src/mnode/src/mnodeDb.c
index 69e8f076e9..63bd066c36 100644
--- a/src/mnode/src/mnodeDb.c
+++ b/src/mnode/src/mnodeDb.c
@@ -1004,7 +1004,7 @@ static int32_t mnodeAlterDbCb(SMnodeMsg *pMsg, int32_t code) {
   mDebug("db:%s, all vgroups is altered", pDb->name);
   mLInfo("db:%s, is alterd by %s", pDb->name, mnodeGetUserFromMsg(pMsg));
 
-  balanceAsyncNotify();
+  bnNotify();
 
   return TSDB_CODE_SUCCESS;
 }
diff --git a/src/mnode/src/mnodeDnode.c b/src/mnode/src/mnodeDnode.c
index 65f4060392..0d429f5797 100644
--- a/src/mnode/src/mnodeDnode.c
+++ b/src/mnode/src/mnodeDnode.c
@@ -115,7 +115,7 @@ static int32_t mnodeDnodeActionDelete(SSdbRow *pRow) {
   mnodeDropAllDnodeVgroups(pDnode);
 #endif  
   mnodeDropMnodeLocal(pDnode->dnodeId);
-  balanceAsyncNotify();
+  bnNotify();
   mnodeUpdateDnodeEps();
 
   mDebug("dnode:%d, all vgroups is dropped from sdb", pDnode->dnodeId);
@@ -347,7 +347,7 @@ static int32_t mnodeProcessCfgDnodeMsg(SMnodeMsg *pMsg) {
       return TSDB_CODE_MND_INVALID_DNODE_CFG_OPTION;
     }
 
-    int32_t code = balanceAlterDnode(pDnode, vnodeId, dnodeId);
+    int32_t code = bnAlterDnode(pDnode, vnodeId, dnodeId);
     mnodeDecDnodeRef(pDnode);
     return code;
   } else {
@@ -591,8 +591,8 @@ static int32_t mnodeProcessDnodeStatusMsg(SMnodeMsg *pMsg) {
     mInfo("dnode:%d, from offline to online", pDnode->dnodeId);
     pDnode->status = TAOS_DN_STATUS_READY;
     pDnode->offlineReason = TAOS_DN_OFF_ONLINE;
-    balanceSyncNotify();
-    balanceAsyncNotify();
+    bnCheckModules();
+    bnNotify();
   }
 
   if (openVnodes != pDnode->openVnodes) {
@@ -708,7 +708,7 @@ static int32_t mnodeDropDnodeByEp(char *ep, SMnodeMsg *pMsg) {
 #ifndef _SYNC
   int32_t code = mnodeDropDnode(pDnode, pMsg);
 #else
-  int32_t code = balanceDropDnode(pDnode);
+  int32_t code = bnDropDnode(pDnode);
 #endif  
   mnodeDecDnodeRef(pDnode);
   return code;
@@ -1182,12 +1182,12 @@ static char* mnodeGetDnodeAlternativeRoleStr(int32_t alternativeRole) {
 
 #ifndef _SYNC
 
-int32_t balanceInit() { return TSDB_CODE_SUCCESS; }
-void    balanceCleanUp() {}
-void    balanceAsyncNotify() {}
-void    balanceSyncNotify() {}
-void    balanceReset() {}
-int32_t balanceAlterDnode(struct SDnodeObj *pDnode, int32_t vnodeId, int32_t dnodeId) { return TSDB_CODE_SYN_NOT_ENABLED; }
+int32_t bnInit() { return TSDB_CODE_SUCCESS; }
+void    bnCleanUp() {}
+void    bnNotify() {}
+void    bnCheckModules() {}
+void    bnReset() {}
+int32_t bnAlterDnode(struct SDnodeObj *pDnode, int32_t vnodeId, int32_t dnodeId) { return TSDB_CODE_SYN_NOT_ENABLED; }
 
 char* syncRole[] = {
   "offline",
@@ -1197,7 +1197,7 @@ char* syncRole[] = {
   "master"
 };
 
-int32_t balanceAllocVnodes(SVgObj *pVgroup) {
+int32_t bnAllocVnodes(SVgObj *pVgroup) {
   void *     pIter = NULL;
   SDnodeObj *pDnode = NULL;
   SDnodeObj *pSelDnode = NULL;
diff --git a/src/mnode/src/mnodeMain.c b/src/mnode/src/mnodeMain.c
index d15b32da54..9c8bc6c35b 100644
--- a/src/mnode/src/mnodeMain.c
+++ b/src/mnode/src/mnodeMain.c
@@ -58,7 +58,7 @@ static const SMnodeComponent tsMnodeComponents[] = {
   {"tables",  mnodeInitTables,  mnodeCleanupTables},  
   {"mnodes",  mnodeInitMnodes,  mnodeCleanupMnodes},
   {"sdb",     sdbInit,          sdbCleanUp},
-  {"balance", balanceInit,      balanceCleanUp},
+  {"balance", bnInit,           bnCleanUp},
   {"grant",   grantInit,        grantCleanUp},
   {"show",    mnodeInitShow,    mnodeCleanUpShow}
 };
diff --git a/src/mnode/src/mnodeSdb.c b/src/mnode/src/mnodeSdb.c
index 40e2e1cfcc..07b3ef09ec 100644
--- a/src/mnode/src/mnodeSdb.c
+++ b/src/mnode/src/mnodeSdb.c
@@ -244,7 +244,7 @@ static void sdbNotifyRole(int32_t vgId, int8_t role) {
   sdbInfo("vgId:1, mnode role changed from %s to %s", syncRole[tsSdbMgmt.role], syncRole[role]);
 
   if (role == TAOS_SYNC_ROLE_MASTER && tsSdbMgmt.role != TAOS_SYNC_ROLE_MASTER) {
-    balanceReset();
+    bnReset();
   }
   tsSdbMgmt.role = role;
 
diff --git a/src/mnode/src/mnodeVgroup.c b/src/mnode/src/mnodeVgroup.c
index 3e974f417f..7cf9e35bd2 100644
--- a/src/mnode/src/mnodeVgroup.c
+++ b/src/mnode/src/mnodeVgroup.c
@@ -563,7 +563,7 @@ int32_t mnodeCreateVgroup(SMnodeMsg *pMsg) {
   pVgroup->numOfVnodes = pDb->cfg.replications;
   pVgroup->createdTime = taosGetTimestampMs();
   pVgroup->accessState = TSDB_VN_ALL_ACCCESS;
-  int32_t code = balanceAllocVnodes(pVgroup);
+  int32_t code = bnAllocVnodes(pVgroup);
   if (code != TSDB_CODE_SUCCESS) {
     mError("db:%s, no enough dnode to alloc %d vnodes to vgroup, reason:%s", pDb->name, pVgroup->numOfVnodes,
            tstrerror(code));