TD-1238 add error code while unable to resolve fqdn

src/inc/taoserror.h

@@ -66,6 +66,7 @@ TAOS_DEFINE_ERROR(TSDB_CODE_RPC_INVALID_MSG_TYPE,         0, 0x0011, "Invalid me
 TAOS_DEFINE_ERROR(TSDB_CODE_RPC_INVALID_RESPONSE_TYPE,    0, 0x0012, "Invalid response type")
 TAOS_DEFINE_ERROR(TSDB_CODE_RPC_INVALID_TIME_STAMP,       0, 0x0013, "Invalid timestamp")
 TAOS_DEFINE_ERROR(TSDB_CODE_APP_NOT_READY,                0, 0x0014, "Database not ready")
+TAOS_DEFINE_ERROR(TSDB_CODE_RPC_FQDN_ERROR,               0, 0x000C, "Unable to resolve FQDN")
 
 //common & util
 TAOS_DEFINE_ERROR(TSDB_CODE_COM_OPS_NOT_SUPPORT,          0, 0x0100, "Operation not supported")

src/rpc/src/rpcMain.c

@@ -563,7 +563,7 @@ static SRpcConn *rpcOpenConn(SRpcInfo *pRpc, char *peerFqdn, uint16_t peerPort,
   uint32_t peerIp = taosGetIpFromFqdn(peerFqdn);
   if (peerIp == 0xFFFFFFFF) {
     tError("%s, failed to resolve FQDN:%s", pRpc->label, peerFqdn); 
-    terrno = TSDB_CODE_RPC_APP_ERROR; 
+    terrno = TSDB_CODE_RPC_FQDN_ERROR; 
     return NULL;
   }