TD-2513 let vnode keep work as master if onlineNum=0.5

src/sync/src/syncMain.c

@@ -715,8 +715,12 @@ static SSyncPeer *syncCheckMaster(SSyncNode *pNode) {
 
   if (onlineNum <= replica * 0.5) {
     if (nodeRole != TAOS_SYNC_ROLE_UNSYNCED) {
-      nodeRole = TAOS_SYNC_ROLE_UNSYNCED;
-      sInfo("vgId:%d, self change to unsynced state, online:%d replica:%d", pNode->vgId, onlineNum, replica);
+      if (nodeRole == TAOS_SYNC_ROLE_MASTER && onlineNum == replica * 0.5) {
+        sInfo("vgId:%d, self keep work as master, online:%d replica:%d", pNode->vgId, onlineNum, replica);
+      } else {
+        nodeRole = TAOS_SYNC_ROLE_UNSYNCED;
+        sInfo("vgId:%d, self change to unsynced state, online:%d replica:%d", pNode->vgId, onlineNum, replica);
+      }
       (*pNode->notifyRole)(pNode->vgId, nodeRole);
     }
   } else {

tests/script/unique/dnode/offline3.sim

@@ -84,15 +84,15 @@ step2:
 		return -1
 	endi
 
+sql show vgroups;
+print $data00 $data01 $data02 $data03 $data04 $data05 $data06 $data07 $data08 $data09
+
 sql show dnodes
 print dnode1 $data4_1
 print dnode2 $data4_2
 print dnode3 $data4_3
 print dnode4 $data4_4
 
-sql show vgroups;
-print $data00 $data01 $data02 $data03 $data04 $data05 $data06 $data07 $data08 $data09
-
 if $data4_1 != ready then
   goto step2
 endi