diff --git a/include/util/taoserror.h b/include/util/taoserror.h
index d009f16f6214fbf6f6a78d3b1d144d98f51ec27c..b1eb17a00ff4adb450215c33e66199a5ef784b89 100644
--- a/include/util/taoserror.h
+++ b/include/util/taoserror.h
@@ -195,6 +195,9 @@ int32_t* taosGetErrno();
 #define TSDB_CODE_MND_SNODE_NOT_EXIST           TAOS_DEF_ERROR_CODE(0, 0x0355)
 #define TSDB_CODE_MND_BNODE_ALREADY_EXIST       TAOS_DEF_ERROR_CODE(0, 0x0356)
 #define TSDB_CODE_MND_BNODE_NOT_EXIST           TAOS_DEF_ERROR_CODE(0, 0x0357)
+#define TSDB_CODE_MND_TOO_FEW_MNODES            TAOS_DEF_ERROR_CODE(0, 0x0358)
+#define TSDB_CODE_MND_MNODE_DEPLOYED            TAOS_DEF_ERROR_CODE(0, 0x0359)
+#define TSDB_CODE_MND_CANT_DROP_MASTER          TAOS_DEF_ERROR_CODE(0, 0x035A)
 
 // mnode-acct
 #define TSDB_CODE_MND_ACCT_ALREADY_EXIST        TAOS_DEF_ERROR_CODE(0, 0x0360)
diff --git a/source/dnode/mgmt/inc/mmInt.h b/source/dnode/mgmt/inc/mmInt.h
index df63e220595010f289e97097d515153cd0c39ee4..74b1cc44bf58767b9c2345c574b3243280aac18e 100644
--- a/source/dnode/mgmt/inc/mmInt.h
+++ b/source/dnode/mgmt/inc/mmInt.h
@@ -62,6 +62,7 @@ int32_t mmProcessSyncMsg(SMgmtWrapper *pWrapper, SNodeMsg *pMsg);
 int32_t mmProcessReadMsg(SMgmtWrapper *pWrapper, SNodeMsg *pMsg);
 int32_t mmProcessQueryMsg(SMgmtWrapper *pWrapper, SNodeMsg *pMsg);
 int32_t mmProcessMonitorMsg(SMgmtWrapper *pWrapper, SNodeMsg *pMsg);
+
 int32_t mmPutMsgToQueryQueue(SMgmtWrapper *pWrapper, SRpcMsg *pRpc);
 int32_t mmPutMsgToReadQueue(SMgmtWrapper *pWrapper, SRpcMsg *pRpc);
 int32_t mmPutMsgToWriteQueue(SMgmtWrapper *pWrapper, SRpcMsg *pRpc);
diff --git a/source/dnode/mgmt/mm/mmInt.c b/source/dnode/mgmt/mm/mmInt.c
index 8d4ac80e7291b75f3830694ed3e396b63caef861..64daf09bf928388cff41881694ecf54dbbbd2e2c 100644
--- a/source/dnode/mgmt/mm/mmInt.c
+++ b/source/dnode/mgmt/mm/mmInt.c
@@ -48,15 +48,13 @@ static void mmInitOption(SMnodeMgmt *pMgmt, SMnodeOpt *pOption) {
 }
 
 static void mmBuildOptionForDeploy(SMnodeMgmt *pMgmt, SMnodeOpt *pOption) {
-  SDnode *pDnode = pMgmt->pDnode;
-
   mmInitOption(pMgmt, pOption);
   pOption->replica = 1;
   pOption->selfIndex = 0;
   SReplica *pReplica = &pOption->replicas[0];
   pReplica->id = 1;
-  pReplica->port = pDnode->serverPort;
-  tstrncpy(pReplica->fqdn, pDnode->localFqdn, TSDB_FQDN_LEN);
+  pReplica->port = pMgmt->pDnode->serverPort;
+  tstrncpy(pReplica->fqdn, pMgmt->pDnode->localFqdn, TSDB_FQDN_LEN);
   pOption->deploy = true;
 
   pMgmt->selfIndex = pOption->selfIndex;
@@ -151,12 +149,9 @@ static void mmCloseImp(SMnodeMgmt *pMgmt) {
 
 int32_t mmAlter(SMnodeMgmt *pMgmt, SDAlterMnodeReq *pReq) {
   SMnodeOpt option = {0};
-  if (pReq != NULL) {
-    if (mmBuildOptionFromReq(pMgmt, &option, pReq) != 0) {
-      return -1;
-    }
+  if (mmBuildOptionFromReq(pMgmt, &option, pReq) != 0) {
+    return -1;
   }
-
   return mndAlter(pMgmt->pMnode, &option);
 }
 
@@ -240,4 +235,3 @@ void mmSetMgmtFp(SMgmtWrapper *pWrapper) {
   pWrapper->name = "mnode";
   pWrapper->fp = mgmtFp;
 }
-
diff --git a/source/dnode/mgmt/mm/mmWorker.c b/source/dnode/mgmt/mm/mmWorker.c
index 44bac6190663db80c280b87bd892a54194cf2cad..c575266b44a5849163fa5c92c421581d1b917ce2 100644
--- a/source/dnode/mgmt/mm/mmWorker.c
+++ b/source/dnode/mgmt/mm/mmWorker.c
@@ -16,6 +16,15 @@
 #define _DEFAULT_SOURCE
 #include "mmInt.h"
 
+static inline void mmSendRsp(SNodeMsg *pMsg, int32_t code) {
+  SRpcMsg rsp = {.handle = pMsg->rpcMsg.handle,
+                 .ahandle = pMsg->rpcMsg.ahandle,
+                 .code = code,
+                 .pCont = pMsg->pRsp,
+                 .contLen = pMsg->rspLen};
+  tmsgSendRsp(&rsp);
+}
+
 static void mmProcessQueue(SQueueInfo *pInfo, SNodeMsg *pMsg) {
   SMnodeMgmt *pMgmt = pInfo->ahandle;
 
@@ -35,8 +44,7 @@ static void mmProcessQueue(SQueueInfo *pInfo, SNodeMsg *pMsg) {
   if (pRpc->msgType & 1U) {
     if (pRpc->handle != NULL && code != TSDB_CODE_MND_ACTION_IN_PROGRESS) {
       if (code != 0 && terrno != 0) code = terrno;
-      SRpcMsg rsp = {.handle = pRpc->handle, .code = code, .contLen = pMsg->rspLen, .pCont = pMsg->pRsp};
-      tmsgSendRsp(&rsp);
+      mmSendRsp(pMsg, code);
     }
   }
 
@@ -48,7 +56,7 @@ static void mmProcessQueue(SQueueInfo *pInfo, SNodeMsg *pMsg) {
 static void mmProcessQueryQueue(SQueueInfo *pInfo, SNodeMsg *pMsg) {
   SMnodeMgmt *pMgmt = pInfo->ahandle;
 
-  dTrace("msg:%p, get from mnode query queue", pMsg);
+  dTrace("msg:%p, get from mnode-query queue", pMsg);
   SRpcMsg *pRpc = &pMsg->rpcMsg;
   int32_t  code = -1;
 
@@ -58,8 +66,7 @@ static void mmProcessQueryQueue(SQueueInfo *pInfo, SNodeMsg *pMsg) {
   if (pRpc->msgType & 1U) {
     if (pRpc->handle != NULL && code != 0) {
       dError("msg:%p, failed to process since %s", pMsg, terrstr());
-      SRpcMsg rsp = {.handle = pRpc->handle, .code = code, .ahandle = pRpc->ahandle};
-      tmsgSendRsp(&rsp);
+      mmSendRsp(pMsg, code);
     }
   }
 
@@ -98,11 +105,8 @@ int32_t mmProcessQueryMsg(SMgmtWrapper *pWrapper, SNodeMsg *pMsg) {
 }
 
 int32_t mmProcessMonitorMsg(SMgmtWrapper *pWrapper, SNodeMsg *pMsg) {
-  SMnodeMgmt    *pMgmt = pWrapper->pMgmt;
-  SSingleWorker *pWorker = &pMgmt->monitorWorker;
-
-  dTrace("msg:%p, put into worker:%s", pMsg, pWorker->name);
-  taosWriteQitem(pWorker->queue, pMsg);
+  SMnodeMgmt *pMgmt = pWrapper->pMgmt;
+  mmPutMsgToWorker(&pMgmt->monitorWorker, pMsg);
   return 0;
 }
 
diff --git a/source/dnode/mnode/impl/inc/mndInt.h b/source/dnode/mnode/impl/inc/mndInt.h
index 1cb0c78aa536a9982940e4d5424a1dc9bc86072b..0197e68531d5ed307f27a4ca5a507d1791f70724 100644
--- a/source/dnode/mnode/impl/inc/mndInt.h
+++ b/source/dnode/mnode/impl/inc/mndInt.h
@@ -100,6 +100,7 @@ typedef struct {
 } SGrantInfo;
 
 typedef struct SMnode {
+  int32_t           selfId;
   int64_t           clusterId;
   int8_t            replica;
   int8_t            selfIndex;
@@ -121,7 +122,7 @@ typedef struct SMnode {
   SHashObj         *infosMeta;
   SGrantInfo        grant;
   MndMsgFp          msgFp[TDMT_MAX];
-  SMsgCb            msgCb;  
+  SMsgCb            msgCb;
 } SMnode;
 
 void    mndSetMsgHandle(SMnode *pMnode, tmsg_t msgType, MndMsgFp fp);
diff --git a/source/dnode/mnode/impl/inc/mndMnode.h b/source/dnode/mnode/impl/inc/mndMnode.h
index 5df13915632469075f995fd33c2b36ee79aa9271..8041cc8fefe44d4c696d4ab33d82de57c0164f0f 100644
--- a/source/dnode/mnode/impl/inc/mndMnode.h
+++ b/source/dnode/mnode/impl/inc/mndMnode.h
@@ -22,12 +22,14 @@
 extern "C" {
 #endif
 
-int32_t mndInitMnode(SMnode *pMnode);
-void    mndCleanupMnode(SMnode *pMnode);
-bool    mndIsMnode(SMnode *pMnode, int32_t dnodeId);
-void    mndGetMnodeEpSet(SMnode *pMnode, SEpSet *pEpSet);
-char   *mndGetRoleStr(int32_t role);
-void    mndUpdateMnodeRole(SMnode *pMnode);
+int32_t     mndInitMnode(SMnode *pMnode);
+void        mndCleanupMnode(SMnode *pMnode);
+SMnodeObj  *mndAcquireMnode(SMnode *pMnode, int32_t mnodeId);
+void        mndReleaseMnode(SMnode *pMnode, SMnodeObj *pObj);
+bool        mndIsMnode(SMnode *pMnode, int32_t dnodeId);
+void        mndGetMnodeEpSet(SMnode *pMnode, SEpSet *pEpSet);
+void        mndUpdateMnodeRole(SMnode *pMnode);
+const char *mndGetRoleStr(int32_t role);
 
 #ifdef __cplusplus
 }
diff --git a/source/dnode/mnode/impl/src/mndBnode.c b/source/dnode/mnode/impl/src/mndBnode.c
index a8b1ec393b67d9fb67c6fc4b6fa91ddf40e07b40..652e5794dfa0142458e8be338b85521efbe3e659 100644
--- a/source/dnode/mnode/impl/src/mndBnode.c
+++ b/source/dnode/mnode/impl/src/mndBnode.c
@@ -396,7 +396,7 @@ static int32_t mndProcessDropBnodeReq(SNodeMsg *pReq) {
   mDebug("bnode:%d, start to drop", dropReq.dnodeId);
 
   if (dropReq.dnodeId <= 0) {
-    terrno = TSDB_CODE_SDB_APP_ERROR;
+    terrno = TSDB_CODE_INVALID_MSG;
     goto _OVER;
   }
 
diff --git a/source/dnode/mnode/impl/src/mndDb.c b/source/dnode/mnode/impl/src/mndDb.c
index 260b1db410fc5bbb3bb177ebf2320146fea70e18..60de1c2723e89cce9f811e6a9dff4e9ce6c5691a 100644
--- a/source/dnode/mnode/impl/src/mndDb.c
+++ b/source/dnode/mnode/impl/src/mndDb.c
@@ -1040,7 +1040,7 @@ static void mndBuildDBVgroupInfo(SDbObj *pDb, SMnode *pMnode, SArray *pVgList) {
   SSdb   *pSdb = pMnode->pSdb;
 
   void *pIter = NULL;
-  while (true) {
+  while (1) {
     SVgObj *pVgroup = NULL;
     pIter = sdbFetch(pSdb, SDB_VGROUP, pIter, (void **)&pVgroup);
     if (pIter == NULL) break;
diff --git a/source/dnode/mnode/impl/src/mndDnode.c b/source/dnode/mnode/impl/src/mndDnode.c
index c38106b9157bb773b322d48b41e67b9555948010..6a16f0920416ac06eeade1e4769ec09d6fd84c43 100644
--- a/source/dnode/mnode/impl/src/mndDnode.c
+++ b/source/dnode/mnode/impl/src/mndDnode.c
@@ -552,6 +552,7 @@ static int32_t mndProcessDropDnodeReq(SNodeMsg *pReq) {
   int32_t        code = -1;
   SUserObj      *pUser = NULL;
   SDnodeObj     *pDnode = NULL;
+  SMnodeObj     *pMObj = NULL;
   SMDropMnodeReq dropReq = {0};
 
   if (tDeserializeSCreateDropMQSBNodeReq(pReq->rpcMsg.pCont, pReq->rpcMsg.contLen, &dropReq) != 0) {
@@ -572,6 +573,12 @@ static int32_t mndProcessDropDnodeReq(SNodeMsg *pReq) {
     goto DROP_DNODE_OVER;
   }
 
+  pMObj = mndAcquireMnode(pMnode, dropReq.dnodeId);
+  if (pMObj != NULL) {
+    terrno = TSDB_CODE_MND_MNODE_DEPLOYED;
+    goto DROP_DNODE_OVER;
+  }
+
   pUser = mndAcquireUser(pMnode, pReq->user);
   if (pUser == NULL) {
     terrno = TSDB_CODE_MND_NO_USER_FROM_CONN;
@@ -592,6 +599,7 @@ DROP_DNODE_OVER:
 
   mndReleaseDnode(pMnode, pDnode);
   mndReleaseUser(pMnode, pUser);
+  mndReleaseMnode(pMnode, pMObj);
 
   return code;
 }
diff --git a/source/dnode/mnode/impl/src/mndMnode.c b/source/dnode/mnode/impl/src/mndMnode.c
index 8543ac7c7df78049ece92fd530ac6b2ac252cf4b..c4f928e8a9f15c687b5291dd5f0ac66cb94317b6 100644
--- a/source/dnode/mnode/impl/src/mndMnode.c
+++ b/source/dnode/mnode/impl/src/mndMnode.c
@@ -21,8 +21,8 @@
 #include "mndTrans.h"
 #include "mndUser.h"
 
-#define TSDB_MNODE_VER_NUMBER   1
-#define TSDB_MNODE_RESERVE_SIZE 64
+#define MNODE_VER_NUMBER   1
+#define MNODE_RESERVE_SIZE 64
 
 static int32_t  mndCreateDefaultMnode(SMnode *pMnode);
 static SSdbRaw *mndMnodeActionEncode(SMnodeObj *pObj);
@@ -64,21 +64,20 @@ int32_t mndInitMnode(SMnode *pMnode) {
 
 void mndCleanupMnode(SMnode *pMnode) {}
 
-static SMnodeObj *mndAcquireMnode(SMnode *pMnode, int32_t mnodeId) {
-  SSdb      *pSdb = pMnode->pSdb;
-  SMnodeObj *pObj = sdbAcquire(pSdb, SDB_MNODE, &mnodeId);
+SMnodeObj *mndAcquireMnode(SMnode *pMnode, int32_t mnodeId) {
+  SMnodeObj *pObj = sdbAcquire(pMnode->pSdb, SDB_MNODE, &mnodeId);
   if (pObj == NULL && terrno == TSDB_CODE_SDB_OBJ_NOT_THERE) {
     terrno = TSDB_CODE_MND_MNODE_NOT_EXIST;
   }
   return pObj;
 }
 
-static void mndReleaseMnode(SMnode *pMnode, SMnodeObj *pObj) {
+void mndReleaseMnode(SMnode *pMnode, SMnodeObj *pObj) {
   SSdb *pSdb = pMnode->pSdb;
-  sdbRelease(pSdb, pObj);
+  sdbRelease(pMnode->pSdb, pObj);
 }
 
-char *mndGetRoleStr(int32_t showType) {
+const char *mndGetRoleStr(int32_t showType) {
   switch (showType) {
     case TAOS_SYNC_STATE_FOLLOWER:
       return "unsynced";
@@ -130,18 +129,18 @@ static int32_t mndCreateDefaultMnode(SMnode *pMnode) {
 static SSdbRaw *mndMnodeActionEncode(SMnodeObj *pObj) {
   terrno = TSDB_CODE_OUT_OF_MEMORY;
 
-  SSdbRaw *pRaw = sdbAllocRaw(SDB_MNODE, TSDB_MNODE_VER_NUMBER, sizeof(SMnodeObj) + TSDB_MNODE_RESERVE_SIZE);
-  if (pRaw == NULL) goto MNODE_ENCODE_OVER;
+  SSdbRaw *pRaw = sdbAllocRaw(SDB_MNODE, MNODE_VER_NUMBER, sizeof(SMnodeObj) + MNODE_RESERVE_SIZE);
+  if (pRaw == NULL) goto _OVER;
 
   int32_t dataPos = 0;
-  SDB_SET_INT32(pRaw, dataPos, pObj->id, MNODE_ENCODE_OVER)
-  SDB_SET_INT64(pRaw, dataPos, pObj->createdTime, MNODE_ENCODE_OVER)
-  SDB_SET_INT64(pRaw, dataPos, pObj->updateTime, MNODE_ENCODE_OVER)
-  SDB_SET_RESERVE(pRaw, dataPos, TSDB_MNODE_RESERVE_SIZE, MNODE_ENCODE_OVER)
+  SDB_SET_INT32(pRaw, dataPos, pObj->id, _OVER)
+  SDB_SET_INT64(pRaw, dataPos, pObj->createdTime, _OVER)
+  SDB_SET_INT64(pRaw, dataPos, pObj->updateTime, _OVER)
+  SDB_SET_RESERVE(pRaw, dataPos, MNODE_RESERVE_SIZE, _OVER)
 
   terrno = 0;
 
-MNODE_ENCODE_OVER:
+_OVER:
   if (terrno != 0) {
     mError("mnode:%d, failed to encode to raw:%p since %s", pObj->id, pRaw, terrstr());
     sdbFreeRaw(pRaw);
@@ -158,26 +157,26 @@ static SSdbRow *mndMnodeActionDecode(SSdbRaw *pRaw) {
   int8_t sver = 0;
   if (sdbGetRawSoftVer(pRaw, &sver) != 0) return NULL;
 
-  if (sver != TSDB_MNODE_VER_NUMBER) {
+  if (sver != MNODE_VER_NUMBER) {
     terrno = TSDB_CODE_SDB_INVALID_DATA_VER;
-    goto MNODE_DECODE_OVER;
+    goto _OVER;
   }
 
   SSdbRow *pRow = sdbAllocRow(sizeof(SMnodeObj));
-  if (pRow == NULL) goto MNODE_DECODE_OVER;
+  if (pRow == NULL) goto _OVER;
 
   SMnodeObj *pObj = sdbGetRowObj(pRow);
-  if (pObj == NULL) goto MNODE_DECODE_OVER;
+  if (pObj == NULL) goto _OVER;
 
   int32_t dataPos = 0;
-  SDB_GET_INT32(pRaw, dataPos, &pObj->id, MNODE_DECODE_OVER)
-  SDB_GET_INT64(pRaw, dataPos, &pObj->createdTime, MNODE_DECODE_OVER)
-  SDB_GET_INT64(pRaw, dataPos, &pObj->updateTime, MNODE_DECODE_OVER)
-  SDB_GET_RESERVE(pRaw, dataPos, TSDB_MNODE_RESERVE_SIZE, MNODE_DECODE_OVER)
+  SDB_GET_INT32(pRaw, dataPos, &pObj->id, _OVER)
+  SDB_GET_INT64(pRaw, dataPos, &pObj->createdTime, _OVER)
+  SDB_GET_INT64(pRaw, dataPos, &pObj->updateTime, _OVER)
+  SDB_GET_RESERVE(pRaw, dataPos, MNODE_RESERVE_SIZE, _OVER)
 
   terrno = 0;
 
-MNODE_DECODE_OVER:
+_OVER:
   if (terrno != 0) {
     mError("mnode:%d, failed to decode from raw:%p since %s", pObj->id, pRaw, terrstr());
     taosMemoryFreeClear(pRow);
@@ -188,8 +187,6 @@ MNODE_DECODE_OVER:
   return pRow;
 }
 
-static void mnodeResetMnode(SMnodeObj *pObj) { pObj->role = TAOS_SYNC_STATE_FOLLOWER; }
-
 static int32_t mndMnodeActionInsert(SSdb *pSdb, SMnodeObj *pObj) {
   mTrace("mnode:%d, perform insert action, row:%p", pObj->id, pObj);
   pObj->pDnode = sdbAcquire(pSdb, SDB_DNODE, &pObj->id);
@@ -199,7 +196,7 @@ static int32_t mndMnodeActionInsert(SSdb *pSdb, SMnodeObj *pObj) {
     return -1;
   }
 
-  mnodeResetMnode(pObj);
+  pObj->role = TAOS_SYNC_STATE_FOLLOWER;
   return 0;
 }
 
@@ -233,7 +230,6 @@ bool mndIsMnode(SMnode *pMnode, int32_t dnodeId) {
 
 void mndGetMnodeEpSet(SMnode *pMnode, SEpSet *pEpSet) {
   SSdb *pSdb = pMnode->pSdb;
-
   pEpSet->numOfEps = 0;
 
   void *pIter = NULL;
@@ -241,14 +237,15 @@ void mndGetMnodeEpSet(SMnode *pMnode, SEpSet *pEpSet) {
     SMnodeObj *pObj = NULL;
     pIter = sdbFetch(pSdb, SDB_MNODE, pIter, (void **)&pObj);
     if (pIter == NULL) break;
-    if (pObj->pDnode == NULL) break;
-
-    if (pObj->role == TAOS_SYNC_STATE_LEADER) {
-      pEpSet->inUse = pEpSet->numOfEps;
+    if (pObj->pDnode == NULL) {
+      mError("mnode:%d, no corresponding dnode exists", pObj->id);
+    } else {
+      if (pObj->role == TAOS_SYNC_STATE_LEADER) {
+        pEpSet->inUse = pEpSet->numOfEps;
+      }
+      addEpIntoEpSet(pEpSet, pObj->pDnode->fqdn, pObj->pDnode->port);
+      sdbRelease(pSdb, pObj);
     }
-
-    addEpIntoEpSet(pEpSet, pObj->pDnode->fqdn, pObj->pDnode->port);
-    sdbRelease(pSdb, pObj);
   }
 }
 
@@ -364,18 +361,18 @@ static int32_t mndCreateMnode(SMnode *pMnode, SNodeMsg *pReq, SDnodeObj *pDnode,
   mnodeObj.updateTime = mnodeObj.createdTime;
 
   STrans *pTrans = mndTransCreate(pMnode, TRN_POLICY_RETRY, TRN_TYPE_CREATE_MNODE, &pReq->rpcMsg);
-  if (pTrans == NULL) goto CREATE_MNODE_OVER;
+  if (pTrans == NULL) goto _OVER;
 
   mDebug("trans:%d, used to create mnode:%d", pTrans->id, pCreate->dnodeId);
-  if (mndSetCreateMnodeRedoLogs(pMnode, pTrans, &mnodeObj) != 0) goto CREATE_MNODE_OVER;
-  if (mndSetCreateMnodeCommitLogs(pMnode, pTrans, &mnodeObj) != 0) goto CREATE_MNODE_OVER;
-  if (mndSetCreateMnodeRedoActions(pMnode, pTrans, pDnode, &mnodeObj) != 0) goto CREATE_MNODE_OVER;
+  if (mndSetCreateMnodeRedoLogs(pMnode, pTrans, &mnodeObj) != 0) goto _OVER;
+  if (mndSetCreateMnodeCommitLogs(pMnode, pTrans, &mnodeObj) != 0) goto _OVER;
+  if (mndSetCreateMnodeRedoActions(pMnode, pTrans, pDnode, &mnodeObj) != 0) goto _OVER;
 
-  if (mndTransPrepare(pMnode, pTrans) != 0) goto CREATE_MNODE_OVER;
+  if (mndTransPrepare(pMnode, pTrans) != 0) goto _OVER;
 
   code = 0;
 
-CREATE_MNODE_OVER:
+_OVER:
   mndTransDrop(pTrans);
   return code;
 }
@@ -390,7 +387,7 @@ static int32_t mndProcessCreateMnodeReq(SNodeMsg *pReq) {
 
   if (tDeserializeSCreateDropMQSBNodeReq(pReq->rpcMsg.pCont, pReq->rpcMsg.contLen, &createReq) != 0) {
     terrno = TSDB_CODE_INVALID_MSG;
-    goto CREATE_MNODE_OVER;
+    goto _OVER;
   }
 
   mDebug("mnode:%d, start to create", createReq.dnodeId);
@@ -398,31 +395,31 @@ static int32_t mndProcessCreateMnodeReq(SNodeMsg *pReq) {
   pObj = mndAcquireMnode(pMnode, createReq.dnodeId);
   if (pObj != NULL) {
     terrno = TSDB_CODE_MND_MNODE_ALREADY_EXIST;
-    goto CREATE_MNODE_OVER;
+    goto _OVER;
   } else if (terrno != TSDB_CODE_MND_MNODE_NOT_EXIST) {
-    goto CREATE_MNODE_OVER;
+    goto _OVER;
   }
 
   pDnode = mndAcquireDnode(pMnode, createReq.dnodeId);
   if (pDnode == NULL) {
     terrno = TSDB_CODE_MND_DNODE_NOT_EXIST;
-    goto CREATE_MNODE_OVER;
+    goto _OVER;
   }
 
   pUser = mndAcquireUser(pMnode, pReq->user);
   if (pUser == NULL) {
     terrno = TSDB_CODE_MND_NO_USER_FROM_CONN;
-    goto CREATE_MNODE_OVER;
+    goto _OVER;
   }
 
   if (mndCheckNodeAuth(pUser)) {
-    goto CREATE_MNODE_OVER;
+    goto _OVER;
   }
 
   code = mndCreateMnode(pMnode, pReq, pDnode, &createReq);
   if (code == 0) code = TSDB_CODE_MND_ACTION_IN_PROGRESS;
 
-CREATE_MNODE_OVER:
+_OVER:
   if (code != 0 && code != TSDB_CODE_MND_ACTION_IN_PROGRESS) {
     mError("mnode:%d, failed to create since %s", createReq.dnodeId, terrstr());
   }
@@ -531,18 +528,18 @@ static int32_t mndDropMnode(SMnode *pMnode, SNodeMsg *pReq, SMnodeObj *pObj) {
   int32_t code = -1;
 
   STrans *pTrans = mndTransCreate(pMnode, TRN_POLICY_RETRY, TRN_TYPE_DROP_MNODE, &pReq->rpcMsg);
-  if (pTrans == NULL) goto DROP_MNODE_OVER;
+  if (pTrans == NULL) goto _OVER;
 
   mDebug("trans:%d, used to drop mnode:%d", pTrans->id, pObj->id);
 
-  if (mndSetDropMnodeRedoLogs(pMnode, pTrans, pObj) != 0) goto DROP_MNODE_OVER;
-  if (mndSetDropMnodeCommitLogs(pMnode, pTrans, pObj) != 0) goto DROP_MNODE_OVER;
-  if (mndSetDropMnodeRedoActions(pMnode, pTrans, pObj->pDnode, pObj) != 0) goto DROP_MNODE_OVER;
-  if (mndTransPrepare(pMnode, pTrans) != 0) goto DROP_MNODE_OVER;
+  if (mndSetDropMnodeRedoLogs(pMnode, pTrans, pObj) != 0) goto _OVER;
+  if (mndSetDropMnodeCommitLogs(pMnode, pTrans, pObj) != 0) goto _OVER;
+  if (mndSetDropMnodeRedoActions(pMnode, pTrans, pObj->pDnode, pObj) != 0) goto _OVER;
+  if (mndTransPrepare(pMnode, pTrans) != 0) goto _OVER;
 
   code = 0;
 
-DROP_MNODE_OVER:
+_OVER:
   mndTransDrop(pTrans);
   return code;
 }
@@ -556,35 +553,45 @@ static int32_t mndProcessDropMnodeReq(SNodeMsg *pReq) {
 
   if (tDeserializeSCreateDropMQSBNodeReq(pReq->rpcMsg.pCont, pReq->rpcMsg.contLen, &dropReq) != 0) {
     terrno = TSDB_CODE_INVALID_MSG;
-    goto DROP_MNODE_OVER;
+    goto _OVER;
   }
 
   mDebug("mnode:%d, start to drop", dropReq.dnodeId);
 
   if (dropReq.dnodeId <= 0) {
-    terrno = TSDB_CODE_SDB_APP_ERROR;
-    goto DROP_MNODE_OVER;
+    terrno = TSDB_CODE_INVALID_MSG;
+    goto _OVER;
   }
 
   pObj = mndAcquireMnode(pMnode, dropReq.dnodeId);
   if (pObj == NULL) {
-    goto DROP_MNODE_OVER;
+    goto _OVER;
+  }
+
+  if (pMnode->selfId == dropReq.dnodeId) {
+    terrno = TSDB_CODE_MND_CANT_DROP_MASTER;
+    goto _OVER;
+  }
+
+  if (sdbGetSize(pMnode->pSdb, SDB_MNODE) <= 1) {
+    terrno = TSDB_CODE_MND_TOO_FEW_MNODES;
+    goto _OVER;
   }
 
   pUser = mndAcquireUser(pMnode, pReq->user);
   if (pUser == NULL) {
     terrno = TSDB_CODE_MND_NO_USER_FROM_CONN;
-    goto DROP_MNODE_OVER;
+    goto _OVER;
   }
 
   if (mndCheckNodeAuth(pUser)) {
-    goto DROP_MNODE_OVER;
+    goto _OVER;
   }
 
   code = mndDropMnode(pMnode, pReq, pObj);
   if (code == 0) code = TSDB_CODE_MND_ACTION_IN_PROGRESS;
 
-DROP_MNODE_OVER:
+_OVER:
   if (code != 0 && code != TSDB_CODE_MND_ACTION_IN_PROGRESS) {
     mError("mnode:%d, failed to drop since %s", dropReq.dnodeId, terrstr());
   }
@@ -687,7 +694,7 @@ static int32_t mndRetrieveMnodes(SNodeMsg *pReq, SShowObj *pShow, char *data, in
     cols++;
 
     pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
-    char *roles = mndGetRoleStr(pObj->role);
+    const char *roles = mndGetRoleStr(pObj->role);
     STR_WITH_MAXSIZE_TO_VARSTR(pWrite, roles, pShow->bytes[cols]);
     cols++;
 
diff --git a/source/dnode/mnode/impl/src/mndQnode.c b/source/dnode/mnode/impl/src/mndQnode.c
index 5204bc95bb3060e02846b7d45ce2fcddfc590269..24bd897b63abf8e9a7ae146fd5e5bc534fc64c7e 100644
--- a/source/dnode/mnode/impl/src/mndQnode.c
+++ b/source/dnode/mnode/impl/src/mndQnode.c
@@ -398,7 +398,7 @@ static int32_t mndProcessDropQnodeReq(SNodeMsg *pReq) {
   mDebug("qnode:%d, start to drop", dropReq.dnodeId);
 
   if (dropReq.dnodeId <= 0) {
-    terrno = TSDB_CODE_SDB_APP_ERROR;
+    terrno = TSDB_CODE_INVALID_MSG;
     goto _OVER;
   }
 
@@ -453,7 +453,7 @@ static int32_t mndProcessQnodeListReq(SNodeMsg *pReq) {
     goto _OVER;
   }
 
-  while (true) {
+  while (1) {
     void *pIter = sdbFetch(pSdb, SDB_QNODE, NULL, (void **)&pObj);
     if (pIter == NULL) break;
 
diff --git a/source/dnode/mnode/impl/src/mndSnode.c b/source/dnode/mnode/impl/src/mndSnode.c
index 87e5962f6bff37eef30b134c9de5b687bd8c4460..731dcd087a705b3a87a9f39e29abf625d14a8ee9 100644
--- a/source/dnode/mnode/impl/src/mndSnode.c
+++ b/source/dnode/mnode/impl/src/mndSnode.c
@@ -406,7 +406,7 @@ static int32_t mndProcessDropSnodeReq(SNodeMsg *pReq) {
   mDebug("snode:%d, start to drop", dropReq.dnodeId);
 
   if (dropReq.dnodeId <= 0) {
-    terrno = TSDB_CODE_SDB_APP_ERROR;
+    terrno = TSDB_CODE_INVALID_MSG;
     goto _OVER;
   }
 
diff --git a/source/dnode/mnode/impl/src/mndSync.c b/source/dnode/mnode/impl/src/mndSync.c
index 8a14d882da7f2aef289fbdca4bd3a5e929d14070..15a70e33115ee648a80d403a0e95ce3ac73de4b2 100644
--- a/source/dnode/mnode/impl/src/mndSync.c
+++ b/source/dnode/mnode/impl/src/mndSync.c
@@ -105,7 +105,6 @@ static int32_t mndRestoreWal(SMnode *pMnode) {
     if (walEndSnapshot(pWal) < 0) {
       goto WAL_RESTORE_OVER;
     }
-
   }
 
   code = 0;
@@ -129,7 +128,9 @@ int32_t mndInitSync(SMnode *pMnode) {
     return -1;
   }
 
-  pMgmt->state = TAOS_SYNC_STATE_LEADER;
+  if (pMnode->selfId == 1) {
+    pMgmt->state = TAOS_SYNC_STATE_LEADER;
+  }
   pMgmt->pSyncNode = NULL;
   return 0;
 }
diff --git a/source/dnode/mnode/impl/src/mnode.c b/source/dnode/mnode/impl/src/mnode.c
index 86bbc0257bd0f805233a9befeac7c8c394f75a5a..5a1780530c257cc7c37ac11cbcd1f40db383481d 100644
--- a/source/dnode/mnode/impl/src/mnode.c
+++ b/source/dnode/mnode/impl/src/mnode.c
@@ -215,7 +215,6 @@ static int32_t mndInitSteps(SMnode *pMnode, bool deploy) {
   } else {
     if (mndAllocStep(pMnode, "mnode-sdb-read", mndReadSdb, NULL) != 0) return -1;
   }
-  // if (mndAllocStep(pMnode, "mnode-timer", mndInitTimer, NULL) != 0) return -1;
   if (mndAllocStep(pMnode, "mnode-profile", mndInitProfile, mndCleanupProfile) != 0) return -1;
   if (mndAllocStep(pMnode, "mnode-show", mndInitShow, mndCleanupShow) != 0) return -1;
   if (mndAllocStep(pMnode, "mnode-query", mndInitQuery, mndCleanupQuery) != 0) return -1;
@@ -272,6 +271,7 @@ static void mndSetOptions(SMnode *pMnode, const SMnodeOpt *pOption) {
   pMnode->selfIndex = pOption->selfIndex;
   memcpy(&pMnode->replicas, pOption->replicas, sizeof(SReplica) * TSDB_MAX_REPLICA);
   pMnode->msgCb = pOption->msgCb;
+  pMnode->selfId = pOption->replicas[pOption->selfIndex].id;
 }
 
 SMnode *mndOpen(const char *path, const SMnodeOpt *pOption) {
diff --git a/source/util/src/terror.c b/source/util/src/terror.c
index e4771c95f8eac1f10365137dc8850c912c93b76f..a14ba94515af340c3d711298030bc2fee8614031 100644
--- a/source/util/src/terror.c
+++ b/source/util/src/terror.c
@@ -201,6 +201,9 @@ TAOS_DEFINE_ERROR(TSDB_CODE_MND_SNODE_ALREADY_EXIST,      "Snode already exists"
 TAOS_DEFINE_ERROR(TSDB_CODE_MND_SNODE_NOT_EXIST,          "Snode not there")
 TAOS_DEFINE_ERROR(TSDB_CODE_MND_BNODE_ALREADY_EXIST,      "Bnode already exists")
 TAOS_DEFINE_ERROR(TSDB_CODE_MND_BNODE_NOT_EXIST,          "Bnode not there")
+TAOS_DEFINE_ERROR(TSDB_CODE_MND_TOO_FEW_MNODES,           "Too few mnodes")
+TAOS_DEFINE_ERROR(TSDB_CODE_MND_MNODE_DEPLOYED,           "Mnode deployed in this dnode")
+TAOS_DEFINE_ERROR(TSDB_CODE_MND_CANT_DROP_MASTER,         "Can't drop mnode which is master")
 
 // mnode-acct
 TAOS_DEFINE_ERROR(TSDB_CODE_MND_ACCT_ALREADY_EXIST,       "Account already exists")