add chain group

handler/dns/handler.go

@@ -71,11 +71,7 @@ func (h *dnsHandler) Init(md md.Metadata) (err error) {
 			if addr == "" {
 				continue
 			}
-			h.group.AddNode(&chain.Node{
-				Name:   fmt.Sprintf("target-%d", i),
-				Addr:   addr,
-				Marker: &chain.FailMarker{},
-			})
+			h.group.AddNode(chain.NewNode(fmt.Sprintf("target-%d", i), addr))
 		}
 	}
 	for _, node := range h.group.Nodes() {

handler/forward/local/handler.go

@@ -100,11 +100,15 @@ func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn, opts ...hand
 		log.Error(err)
 		// TODO: the router itself may be failed due to the failed node in the router,
 		// the dead marker may be a wrong operation.
-		target.Marker.Mark()
+		if marker := target.Marker(); marker != nil {
+			marker.Mark()
+		}
 		return err
 	}
 	defer cc.Close()
-	target.Marker.Reset()
+	if marker := target.Marker(); marker != nil {
+		marker.Reset()
+	}
 
 	t := time.Now()
 	log.Debugf("%s <-> %s", conn.RemoteAddr(), target.Addr)

handler/forward/remote/handler.go

@@ -94,11 +94,15 @@ func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn, opts ...hand
 		log.Error(err)
 		// TODO: the router itself may be failed due to the failed node in the router,
 		// the dead marker may be a wrong operation.
-		target.Marker.Mark()
+		if marker := target.Marker(); marker != nil {
+			marker.Mark()
+		}
 		return err
 	}
 	defer cc.Close()
-	target.Marker.Reset()
+	if marker := target.Marker(); marker != nil {
+		marker.Reset()
+	}
 
 	t := time.Now()
 	log.Debugf("%s <-> %s", conn.RemoteAddr(), target.Addr)

handler/relay/forward.go

@@ -37,7 +37,9 @@ func (h *relayHandler) handleForward(ctx context.Context, conn net.Conn, network
 	if err != nil {
 		// TODO: the router itself may be failed due to the failed node in the router,
 		// the dead marker may be a wrong operation.
-		target.Marker.Mark()
+		if marker := target.Marker(); marker != nil {
+			marker.Mark()
+		}
 
 		resp.Status = relay.StatusHostUnreachable
 		resp.WriteTo(conn)
@@ -46,7 +48,9 @@ func (h *relayHandler) handleForward(ctx context.Context, conn net.Conn, network
 		return err
 	}
 	defer cc.Close()
-	target.Marker.Reset()
+	if marker := target.Marker(); marker != nil {
+		marker.Reset()
+	}
 
 	if h.md.noDelay {
 		if _, err := resp.WriteTo(conn); err != nil {