Merge pull request #4658 from ipfs/fix/session-cleanup

shutdown notifications engine when closing a bitswap session

exchange/bitswap/message/message.go

@@ -50,7 +50,7 @@ type Exportable interface {
 
 type impl struct {
 	full     bool
-	wantlist map[string]Entry
+	wantlist map[string]*Entry
 	blocks   map[string]blocks.Block
 }
 
@@ -61,7 +61,7 @@ func New(full bool) BitSwapMessage {
 func newMsg(full bool) *impl {
 	return &impl{
 		blocks:   make(map[string]blocks.Block),
-		wantlist: make(map[string]Entry),
+		wantlist: make(map[string]*Entry),
 		full:     full,
 	}
 }
@@ -122,7 +122,7 @@ func (m *impl) Empty() bool {
 func (m *impl) Wantlist() []Entry {
 	out := make([]Entry, 0, len(m.wantlist))
 	for _, e := range m.wantlist {
-		out = append(out, e)
+		out = append(out, *e)
 	}
 	return out
 }
@@ -151,7 +151,7 @@ func (m *impl) addEntry(c *cid.Cid, priority int, cancel bool) {
 		e.Priority = priority
 		e.Cancel = cancel
 	} else {
-		m.wantlist[k] = Entry{
+		m.wantlist[k] = &Entry{
 			Entry: &wantlist.Entry{
 				Cid:      c,
 				Priority: priority,

exchange/bitswap/notifications/notifications.go

@@ -2,6 +2,7 @@ package notifications
 
 import (
 	"context"
+	"sync"
 
 	blocks "gx/ipfs/Qmej7nf81hi2x2tvjRBF3mcp74sQyuDH4VMYDGd1YtXjb2/go-block-format"
 
@@ -18,18 +19,43 @@ type PubSub interface {
 }
 
 func New() PubSub {
-	return &impl{*pubsub.New(bufferSize)}
+	return &impl{
+		wrapped: *pubsub.New(bufferSize),
+		cancel:  make(chan struct{}),
+	}
 }
 
 type impl struct {
 	wrapped pubsub.PubSub
+
+	// These two fields make up a shutdown "lock".
+	// We need them as calling, e.g., `Unsubscribe` after calling `Shutdown`
+	// blocks forever and fixing this in pubsub would be rather invasive.
+	cancel chan struct{}
+	wg     sync.WaitGroup
 }
 
 func (ps *impl) Publish(block blocks.Block) {
+	ps.wg.Add(1)
+	defer ps.wg.Done()
+
+	select {
+	case <-ps.cancel:
+		// Already shutdown, bail.
+		return
+	default:
+	}
+
 	ps.wrapped.Pub(block, block.Cid().KeyString())
 }
 
+// Not safe to call more than once.
 func (ps *impl) Shutdown() {
+	// Interrupt in-progress subscriptions.
+	close(ps.cancel)
+	// Wait for them to finish.
+	ps.wg.Wait()
+	// shutdown the pubsub.
 	ps.wrapped.Shutdown()
 }
 
@@ -44,12 +70,34 @@ func (ps *impl) Subscribe(ctx context.Context, keys ...*cid.Cid) <-chan blocks.B
 		close(blocksCh)
 		return blocksCh
 	}
+
+	// prevent shutdown
+	ps.wg.Add(1)
+
+	// check if shutdown *after* preventing shutdowns.
+	select {
+	case <-ps.cancel:
+		// abort, allow shutdown to continue.
+		ps.wg.Done()
+		close(blocksCh)
+		return blocksCh
+	default:
+	}
+
 	ps.wrapped.AddSubOnceEach(valuesCh, toStrings(keys)...)
 	go func() {
-		defer close(blocksCh)
+		defer func() {
-		defer ps.wrapped.Unsub(valuesCh) // with a len(keys) buffer, this is an optimization
+			ps.wrapped.Unsub(valuesCh)
+			close(blocksCh)
+
+			// Unblock shutdown.
+			ps.wg.Done()
+		}()
+
 		for {
 			select {
+			case <-ps.cancel:
+				return
 			case <-ctx.Done():
 				return
 			case val, ok := <-valuesCh:
@@ -61,6 +109,8 @@ func (ps *impl) Subscribe(ctx context.Context, keys ...*cid.Cid) <-chan blocks.B
 					return
 				}
 				select {
+				case <-ps.cancel:
+					return
 				case <-ctx.Done():
 					return
 				case blocksCh <- block: // continue

exchange/bitswap/notifications/notifications_test.go

@@ -100,6 +100,25 @@ func TestDuplicateSubscribe(t *testing.T) {
 	assertBlocksEqual(t, e1, r2)
 }
 
+func TestShutdownBeforeUnsubscribe(t *testing.T) {
+	e1 := blocks.NewBlock([]byte("1"))
+
+	n := New()
+	ctx, cancel := context.WithCancel(context.Background())
+	ch := n.Subscribe(ctx, e1.Cid()) // no keys provided
+	n.Shutdown()
+	cancel()
+
+	select {
+	case _, ok := <-ch:
+		if ok {
+			t.Fatal("channel should have been closed")
+		}
+	default:
+		t.Fatal("channel should have been closed")
+	}
+}
+
 func TestSubscribeIsANoopWhenCalledWithNoKeys(t *testing.T) {
 	n := New()
 	defer n.Shutdown()

exchange/bitswap/session.go

@@ -83,6 +83,15 @@ func (bs *Bitswap) NewSession(ctx context.Context) *Session {
 }
 
 func (bs *Bitswap) removeSession(s *Session) {
+	s.notif.Shutdown()
+
+	live := make([]*cid.Cid, 0, len(s.liveWants))
+	for c := range s.liveWants {
+		cs, _ := cid.Cast([]byte(c))
+		live = append(live, cs)
+	}
+	bs.CancelWants(live, s.id)
+
 	bs.sessLk.Lock()
 	defer bs.sessLk.Unlock()
 	for i := 0; i < len(bs.sessions); i++ {
@@ -270,8 +279,9 @@ func (s *Session) receiveBlock(ctx context.Context, blk blocks.Block) {
 }
 
 func (s *Session) wantBlocks(ctx context.Context, ks []*cid.Cid) {
+	now := time.Now()
 	for _, c := range ks {
-		s.liveWants[c.KeyString()] = time.Now()
+		s.liveWants[c.KeyString()] = now
 	}
 	s.bs.wm.WantBlocks(ctx, ks, s.activePeersArr, s.id)
 }

exchange/bitswap/session_test.go

@@ -285,3 +285,36 @@ func TestMultipleSessions(t *testing.T) {
 	}
 	_ = blkch
 }
+
+func TestWantlistClearsOnCancel(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	vnet := getVirtualNetwork()
+	sesgen := NewTestSessionGenerator(vnet)
+	defer sesgen.Close()
+	bgen := blocksutil.NewBlockGenerator()
+
+	blks := bgen.Blocks(10)
+	var cids []*cid.Cid
+	for _, blk := range blks {
+		cids = append(cids, blk.Cid())
+	}
+
+	inst := sesgen.Instances(1)
+
+	a := inst[0]
+
+	ctx1, cancel1 := context.WithCancel(ctx)
+	ses := a.Exchange.NewSession(ctx1)
+
+	_, err := ses.GetBlocks(ctx, cids)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cancel1()
+
+	if len(a.Exchange.GetWantlist()) > 0 {
+		t.Fatal("expected empty wantlist")
+	}
+}

exchange/bitswap/testnet/virtual.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"sync"
+	"time"
 
 	bsmsg "github.com/ipfs/go-ipfs/exchange/bitswap/message"
 	bsnet "github.com/ipfs/go-ipfs/exchange/bitswap/network"
@@ -22,7 +23,7 @@ var log = logging.Logger("bstestnet")
 
 func VirtualNetwork(rs mockrouting.Server, d delay.D) Network {
 	return &network{
-		clients:       make(map[peer.ID]bsnet.Receiver),
+		clients:       make(map[peer.ID]*receiverQueue),
 		delay:         d,
 		routingserver: rs,
 		conns:         make(map[string]struct{}),
@@ -31,12 +32,28 @@ func VirtualNetwork(rs mockrouting.Server, d delay.D) Network {
 
 type network struct {
 	mu            sync.Mutex
-	clients       map[peer.ID]bsnet.Receiver
+	clients       map[peer.ID]*receiverQueue
 	routingserver mockrouting.Server
 	delay         delay.D
 	conns         map[string]struct{}
 }
 
+type message struct {
+	from       peer.ID
+	msg        bsmsg.BitSwapMessage
+	shouldSend time.Time
+}
+
+// receiverQueue queues up a set of messages to be sent, and sends them *in
+// order* with their delays respected as much as sending them in order allows
+// for
+type receiverQueue struct {
+	receiver bsnet.Receiver
+	queue    []*message
+	active   bool
+	lk       sync.Mutex
+}
+
 func (n *network) Adapter(p testutil.Identity) bsnet.BitSwapNetwork {
 	n.mu.Lock()
 	defer n.mu.Unlock()
@@ -46,7 +63,7 @@ func (n *network) Adapter(p testutil.Identity) bsnet.BitSwapNetwork {
 		network: n,
 		routing: n.routingserver.Client(p),
 	}
-	n.clients[p.ID()] = client
+	n.clients[p.ID()] = &receiverQueue{receiver: client}
 	return client
 }
 
@@ -64,7 +81,7 @@ func (n *network) SendMessage(
 	ctx context.Context,
 	from peer.ID,
 	to peer.ID,
-	message bsmsg.BitSwapMessage) error {
+	mes bsmsg.BitSwapMessage) error {
 
 	n.mu.Lock()
 	defer n.mu.Unlock()
@@ -77,7 +94,12 @@ func (n *network) SendMessage(
 	// nb: terminate the context since the context wouldn't actually be passed
 	// over the network in a real scenario
 
-	go n.deliver(receiver, from, message)
+	msg := &message{
+		from:       from,
+		msg:        mes,
+		shouldSend: time.Now().Add(n.delay.Get()),
+	}
+	receiver.enqueue(msg)
 
 	return nil
 }
@@ -191,11 +213,38 @@ func (nc *networkClient) ConnectTo(_ context.Context, p peer.ID) error {
 
 	// TODO: add handling for disconnects
 
-	otherClient.PeerConnected(nc.local)
+	otherClient.receiver.PeerConnected(nc.local)
 	nc.Receiver.PeerConnected(p)
 	return nil
 }
 
+func (rq *receiverQueue) enqueue(m *message) {
+	rq.lk.Lock()
+	defer rq.lk.Unlock()
+	rq.queue = append(rq.queue, m)
+	if !rq.active {
+		rq.active = true
+		go rq.process()
+	}
+}
+
+func (rq *receiverQueue) process() {
+	for {
+		rq.lk.Lock()
+		if len(rq.queue) == 0 {
+			rq.active = false
+			rq.lk.Unlock()
+			return
+		}
+		m := rq.queue[0]
+		rq.queue = rq.queue[1:]
+		rq.lk.Unlock()
+
+		time.Sleep(time.Until(m.shouldSend))
+		rq.receiver.ReceiveMessage(context.TODO(), m.from, m.msg)
+	}
+}
+
 func tagForPeers(a, b peer.ID) string {
 	if a < b {
 		return string(a + b)