server: change monitor API design

https://github.com/osrg/gobgp/issues/1763#issuecomment-437594975

Follow Chris's proposal; consistent with the rest of the APIs.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

3 files changed, 43 insertions, 91 deletions

diff --git a/docs/sources/lib.md b/docs/sources/lib.md
index c76133f9..ba481797 100644
--- a/docs/sources/lib.md
+++ b/docs/sources/lib.md
@@ -39,15 +39,8 @@ func main() {
 	}
 
 	// monitor the change of the peer state
-	if pm, err := s.NewPeerMonitor(&api.MonitorPeerRequest{}); err != nil {
+	if err := s.MonitorPeer(context.Background(), &api.MonitorPeerRequest{}, func(p *api.Peer){log.Info(p)}); err != nil {
 		log.Fatal(err)
-	} else {
-		defer pm.Close()
-		go func() {
-		      for v := range pm.Inbox {
-				  log.Info(v)
-		      }
-		}()
 	}
 
 	// neighbor configuration
diff --git a/pkg/server/grpc_server.go b/pkg/server/grpc_server.go
index 86c756a9..0aac4cf0 100644
--- a/pkg/server/grpc_server.go
+++ b/pkg/server/grpc_server.go
@@ -166,41 +166,34 @@ func (s *server) ListPath(r *api.ListPathRequest, stream api.GobgpApi_ListPathSe
 }
 
 func (s *server) MonitorTable(arg *api.MonitorTableRequest, stream api.GobgpApi_MonitorTableServer) error {
-	tm, err := s.bgpServer.NewTableMonitor(arg)
-	if err != nil {
-		return err
-	}
-	return func() error {
-		defer tm.Close()
-
-		for v := range tm.Inbox {
-			if err := stream.Send(&api.MonitorTableResponse{
-				Path: v,
-			}); err != nil {
-				return err
-			}
+	ctx, cancel := context.WithCancel(context.Background())
+	var err error
+	s.bgpServer.MonitorTable(ctx, arg, func(p *api.Path) {
+		if err = stream.Send(&api.MonitorTableResponse{
+			Path: p,
+		}); err != nil {
+			cancel()
+			return
 		}
-		return nil
-	}()
+	})
+	<-ctx.Done()
+	return err
 }
 
 func (s *server) MonitorPeer(arg *api.MonitorPeerRequest, stream api.GobgpApi_MonitorPeerServer) error {
-	pm, err := s.bgpServer.NewPeerMonitor(arg)
-	if err != nil {
-		return err
-	}
-	return func() error {
-		defer pm.Close()
-
-		for v := range pm.Inbox {
-			if err := stream.Send(&api.MonitorPeerResponse{
-				Peer: v,
-			}); err != nil {
-				return err
-			}
+	ctx, cancel := context.WithCancel(context.Background())
+	var err error
+	err = s.bgpServer.MonitorPeer(ctx, arg, func(p *api.Peer) {
+		if err = stream.Send(&api.MonitorPeerResponse{
+			Peer: p,
+		}); err != nil {
+			fmt.Println("try to cancel")
+			cancel()
+			return
 		}
-		return nil
-	}()
+	})
+	<-ctx.Done()
+	return err
 }
 
 func (s *server) ResetPeer(ctx context.Context, r *api.ResetPeerRequest) (*empty.Empty, error) {
diff --git a/pkg/server/server.go b/pkg/server/server.go
index 749750f9..4fd4aa25 100644
--- a/pkg/server/server.go
+++ b/pkg/server/server.go
@@ -3379,19 +3379,9 @@ func (s *BgpServer) ResetRpki(ctx context.Context, r *api.ResetRpkiRequest) erro
 	}, false)
 }
 
-type TableMonitor struct {
-	Inbox chan *api.Path
-	done  chan interface{}
-	w     *watcher
-}
-
-func (tm *TableMonitor) Close() {
-	close(tm.done)
-}
-
-func (s *BgpServer) NewTableMonitor(r *api.MonitorTableRequest) (*TableMonitor, error) {
+func (s *BgpServer) MonitorTable(ctx context.Context, r *api.MonitorTableRequest, fn func(*api.Path)) error {
 	if r == nil {
-		return nil, fmt.Errorf("nil request")
+		return fmt.Errorf("nil request")
 	}
 	w, err := func() (*watcher, error) {
 		switch r.Type {
@@ -3407,18 +3397,12 @@ func (s *BgpServer) NewTableMonitor(r *api.MonitorTableRequest) (*TableMonitor,
 		}
 	}()
 	if err != nil {
-		return nil, err
+		return err
 	}
 
-	tm := &TableMonitor{
-		Inbox: make(chan *api.Path),
-		done:  make(chan interface{}),
-		w:     w,
-	}
 	go func() {
 		defer func() {
-			close(tm.Inbox)
-			tm.w.Stop()
+			w.Stop()
 		}()
 		family := bgp.RouteFamily(0)
 		if r.Family != nil {
@@ -3427,7 +3411,7 @@ func (s *BgpServer) NewTableMonitor(r *api.MonitorTableRequest) (*TableMonitor,
 
 		for {
 			select {
-			case ev := <-tm.w.Event():
+			case ev := <-w.Event():
 				var pl []*table.Path
 				switch msg := ev.(type) {
 				case *watchEventBestPath:
@@ -3448,47 +3432,33 @@ func (s *BgpServer) NewTableMonitor(r *api.MonitorTableRequest) (*TableMonitor,
 						continue
 					}
 					select {
-					case tm.Inbox <- toPathApi(path, nil):
-					case <-tm.done:
+					case <-ctx.Done():
 						return
+					default:
+						fn(toPathApi(path, nil))
 					}
 				}
-			case <-tm.done:
+			case <-ctx.Done():
 				return
 			}
 		}
 	}()
-
-	return tm, nil
-}
-
-type PeerMonitor struct {
-	Inbox chan *api.Peer
-	done  chan interface{}
-	w     *watcher
-}
-
-func (pm *PeerMonitor) Close() {
-	close(pm.done)
+	return nil
 }
 
-func (s *BgpServer) NewPeerMonitor(r *api.MonitorPeerRequest) (*PeerMonitor, error) {
+func (s *BgpServer) MonitorPeer(ctx context.Context, r *api.MonitorPeerRequest, fn func(*api.Peer)) error {
 	if r == nil {
-		return nil, fmt.Errorf("nil request")
-	}
-	pm := &PeerMonitor{
-		Inbox: make(chan *api.Peer),
-		done:  make(chan interface{}),
-		w:     s.watch(watchPeerState(r.Current)),
+		return fmt.Errorf("nil request")
 	}
+
 	go func() {
+		w := s.watch(watchPeerState(r.Current))
 		defer func() {
-			close(pm.Inbox)
-			pm.w.Stop()
+			w.Stop()
 		}()
 		for {
 			select {
-			case m := <-pm.w.Event():
+			case m := <-w.Event():
 				msg := m.(*watchEventPeerState)
 				if len(r.Address) > 0 && r.Address != msg.PeerAddress.String() && r.Address != msg.PeerInterface {
 					break
@@ -3514,17 +3484,13 @@ func (s *BgpServer) NewPeerMonitor(r *api.MonitorPeerRequest) (*PeerMonitor, err
 						RemotePort:   uint32(msg.PeerPort),
 					},
 				}
-				select {
-				case pm.Inbox <- p:
-				case <-pm.done:
-					return
-				}
-			case <-pm.done:
+				fn(p)
+			case <-ctx.Done():
 				return
 			}
 		}
 	}()
-	return pm, nil
+	return nil
 }
 
 type watchEventType string