fix: Choose wrong shard leader during balance channel(#29525) (#29532)

issue: #29523
pr: #29525

readable shard leader should still be the old one during channel
balance, if the new shard leader is not ready.
This PR fixed that query coord choose wrong shard leader during balance
channel

Signed-off-by: Wei Liu <[email protected]>

internal/querycoordv2/services.go

@@ -881,9 +881,8 @@ func (s *Server) GetShardLeaders(ctx context.Context, req *querypb.GetShardLeade
 		log := log.With(zap.String("channel", channel.GetChannelName()))
 
 		leaders := s.dist.LeaderViewManager.GetLeadersByShard(channel.GetChannelName())
-		leaders = filterDupLeaders(s.meta.ReplicaManager, leaders)
-		ids := make([]int64, 0, len(leaders))
-		addrs := make([]string, 0, len(leaders))
+
+		readableLeaders := make(map[int64]*meta.LeaderView)
 
 		var channelErr error
 		if len(leaders) == 0 {
@@ -944,11 +943,10 @@ func (s *Server) GetShardLeaders(ctx context.Context, req *querypb.GetShardLeade
 				continue
 			}
 
-			ids = append(ids, info.ID())
-			addrs = append(addrs, info.Addr())
+			readableLeaders[leader.ID] = leader
 		}
 
-		if len(ids) == 0 {
+		if len(readableLeaders) == 0 {
 			msg := fmt.Sprintf("channel %s is not available in any replica", channel.GetChannelName())
 			log.Warn(msg, zap.Error(channelErr))
 			resp.Status = merr.Status(
@@ -957,6 +955,15 @@ func (s *Server) GetShardLeaders(ctx context.Context, req *querypb.GetShardLeade
 			return resp, nil
 		}
 
+		readableLeaders = filterDupLeaders(s.meta.ReplicaManager, readableLeaders)
+		ids := make([]int64, 0, len(leaders))
+		addrs := make([]string, 0, len(leaders))
+		for _, leader := range readableLeaders {
+			info := s.nodeMgr.Get(leader.ID)
+			ids = append(ids, info.ID())
+			addrs = append(addrs, info.Addr())
+		}
+
 		resp.Shards = append(resp.Shards, &querypb.ShardLeadersList{
 			ChannelName: channel.GetChannelName(),
 			NodeIds:     ids,