rework how refcounted wantlists work

License: MIT
Signed-off-by: Jeromy <[email protected]>

Author: whyrusleeping

core/commands/bitswap.go

@@ -64,7 +64,11 @@ var unwantCmd = &cmds.Command{
 			ks = append(ks, c)
 		}
 
-		bs.CancelWants(ks)
+		// TODO: This should maybe find *all* sessions for this request and cancel them?
+		// (why): in reality, i think this command should be removed. Its
+		// messing with the internal state of bitswap. You should cancel wants
+		// by killing the command that caused the want.
+		bs.CancelWants(ks, 0)
 	},
 }
 

exchange/bitswap/bitswap.go

@@ -169,6 +169,9 @@ type Bitswap struct {
 	// Sessions
 	sessions []*Session
 	sessLk   sync.Mutex
+
+	sessID   uint64
+	sessIDLk sync.Mutex
 }
 
 type blockRequest struct {
@@ -219,7 +222,9 @@ func (bs *Bitswap) GetBlocks(ctx context.Context, keys []*cid.Cid) (<-chan block
 		log.Event(ctx, "Bitswap.GetBlockRequest.Start", k)
 	}
 
-	bs.wm.WantBlocks(ctx, keys, nil)
+	mses := bs.getNextSessionID()
+
+	bs.wm.WantBlocks(ctx, keys, nil, mses)
 
 	// NB: Optimization. Assumes that providers of key[0] are likely to
 	// be able to provide for all keys. This currently holds true in most
@@ -241,7 +246,7 @@ func (bs *Bitswap) GetBlocks(ctx context.Context, keys []*cid.Cid) (<-chan block
 		defer close(out)
 		defer func() {
 			// can't just defer this call on its own, arguments are resolved *when* the defer is created
-			bs.CancelWants(remaining.Keys())
+			bs.CancelWants(remaining.Keys(), mses)
 		}()
 		for {
 			select {
@@ -250,6 +255,7 @@ func (bs *Bitswap) GetBlocks(ctx context.Context, keys []*cid.Cid) (<-chan block
 					return
 				}
 
+				bs.CancelWants([]*cid.Cid{blk.Cid()}, mses)
 				remaining.Remove(blk.Cid())
 				select {
 				case out <- blk:
@@ -270,9 +276,16 @@ func (bs *Bitswap) GetBlocks(ctx context.Context, keys []*cid.Cid) (<-chan block
 	}
 }
 
+func (bs *Bitswap) getNextSessionID() uint64 {
+	bs.sessIDLk.Lock()
+	defer bs.sessIDLk.Unlock()
+	bs.sessID++
+	return bs.sessID
+}
+
 // CancelWant removes a given key from the wantlist
-func (bs *Bitswap) CancelWants(cids []*cid.Cid) {
-	bs.wm.CancelWants(context.Background(), cids, nil)
+func (bs *Bitswap) CancelWants(cids []*cid.Cid, ses uint64) {
+	bs.wm.CancelWants(context.Background(), cids, nil, ses)
 }
 
 // HasBlock announces the existance of a block to this bitswap service. The
@@ -314,7 +327,7 @@ func (bs *Bitswap) SessionsForBlock(c *cid.Cid) []*Session {
 
 	var out []*Session
 	for _, s := range bs.sessions {
-		if s.InterestedIn(c) {
+		if s.interestedIn(c) {
 			out = append(out, s)
 		}
 	}
@@ -346,8 +359,6 @@ func (bs *Bitswap) ReceiveMessage(ctx context.Context, p peer.ID, incoming bsmsg
 		keys = append(keys, block.Cid())
 	}
 
-	bs.wm.CancelWants(context.Background(), keys, nil)
-
 	wg := sync.WaitGroup{}
 	for _, block := range iblocks {
 		wg.Add(1)
@@ -360,7 +371,8 @@ func (bs *Bitswap) ReceiveMessage(ctx context.Context, p peer.ID, incoming bsmsg
 			log.Event(ctx, "Bitswap.GetBlockRequest.End", k)
 
 			for _, ses := range bs.SessionsForBlock(k) {
-				ses.ReceiveBlock(p, b)
+				ses.receiveBlockFrom(p, b)
+				bs.CancelWants([]*cid.Cid{k}, ses.id)
 			}
 			log.Debugf("got block %s from %s", b, p)
 			if err := bs.HasBlock(b); err != nil {

exchange/bitswap/bitswap_test.go

@@ -332,6 +332,11 @@ func TestBasicBitswap(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	time.Sleep(time.Millisecond * 20)
+	if len(instances[1].Exchange.GetWantlist()) != 0 {
+		t.Fatal("shouldnt have anything in wantlist")
+	}
+
 	st0, err := instances[0].Exchange.Stat()
 	if err != nil {
 		t.Fatal(err)

exchange/bitswap/session.go

@@ -16,6 +16,9 @@ import (
 
 const activeWantsLimit = 16
 
+// Session holds state for an individual bitswap transfer operation.
+// This allows bitswap to make smarter decisions about who to send wantlist
+// info to, and who to request blocks from
 type Session struct {
 	ctx            context.Context
 	tofetch        []*cid.Cid
@@ -40,8 +43,12 @@ type Session struct {
 	notif notifications.PubSub
 
 	uuid logging.Loggable
+
+	id uint64
 }
 
+// NewSession creates a new bitswap session whose lifetime is bounded by the
+// given context
 func (bs *Bitswap) NewSession(ctx context.Context) *Session {
 	s := &Session{
 		activePeers:   make(map[peer.ID]struct{}),
@@ -54,6 +61,7 @@ func (bs *Bitswap) NewSession(ctx context.Context) *Session {
 		notif:         notifications.New(),
 		uuid:          loggables.Uuid("GetBlockRequest"),
 		baseTickDelay: time.Millisecond * 500,
+		id:            bs.getNextSessionID(),
 	}
 
 	cache, _ := lru.New(2048)
@@ -73,11 +81,11 @@ type blkRecv struct {
 	blk  blocks.Block
 }
 
-func (s *Session) ReceiveBlock(from peer.ID, blk blocks.Block) {
+func (s *Session) receiveBlockFrom(from peer.ID, blk blocks.Block) {
 	s.incoming <- blkRecv{from: from, blk: blk}
 }
 
-func (s *Session) InterestedIn(c *cid.Cid) bool {
+func (s *Session) interestedIn(c *cid.Cid) bool {
 	return s.interest.Contains(c.KeyString())
 }
 
@@ -134,14 +142,14 @@ func (s *Session) run(ctx context.Context) {
 
 		case <-s.tick.C:
 			var live []*cid.Cid
-			for c, _ := range s.liveWants {
+			for c := range s.liveWants {
 				cs, _ := cid.Cast([]byte(c))
 				live = append(live, cs)
 				s.liveWants[c] = time.Now()
 			}
 
 			// Broadcast these keys to everyone we're connected to
-			s.bs.wm.WantBlocks(ctx, live, nil)
+			s.bs.wm.WantBlocks(ctx, live, nil, s.id)
 
 			if len(live) > 0 {
 				go func() {
@@ -181,7 +189,7 @@ func (s *Session) wantBlocks(ctx context.Context, ks []*cid.Cid) {
 	for _, c := range ks {
 		s.liveWants[c.KeyString()] = time.Now()
 	}
-	s.bs.wm.WantBlocks(ctx, ks, s.activePeersArr)
+	s.bs.wm.WantBlocks(ctx, ks, s.activePeersArr, s.id)
 }
 
 func (s *Session) cancel(keys []*cid.Cid) {
@@ -211,11 +219,15 @@ func (s *Session) fetch(ctx context.Context, keys []*cid.Cid) {
 	}
 }
 
+// GetBlocks fetches a set of blocks within the context of this session and
+// returns a channel that found blocks will be returned on. No order is
+// guaranteed on the returned blocks.
 func (s *Session) GetBlocks(ctx context.Context, keys []*cid.Cid) (<-chan blocks.Block, error) {
 	ctx = logging.ContextWithLoggable(ctx, s.uuid)
 	return getBlocksImpl(ctx, keys, s.notif, s.fetch, s.cancelWants)
 }
 
+// GetBlock fetches a single block
 func (s *Session) GetBlock(parent context.Context, k *cid.Cid) (blocks.Block, error) {
 	return getBlock(parent, k, s.GetBlocks)
 }

exchange/bitswap/wantlist/wantlist.go

@@ -10,8 +10,8 @@ import (
 )
 
 type ThreadSafe struct {
-	lk       sync.RWMutex
-	Wantlist Wantlist
+	lk  sync.RWMutex
+	set map[string]*Entry
 }
 
 // not threadsafe
@@ -23,7 +23,16 @@ type Entry struct {
 	Cid      *cid.Cid
 	Priority int
 
-	RefCnt int
+	SesTrk map[uint64]struct{}
+}
+
+// NewRefEntry creates a new reference tracked wantlist entry
+func NewRefEntry(c *cid.Cid, p int) *Entry {
+	return &Entry{
+		Cid:      c,
+		Priority: p,
+		SesTrk:   make(map[uint64]struct{}),
+	}
 }
 
 type entrySlice []*Entry
@@ -34,7 +43,7 @@ func (es entrySlice) Less(i, j int) bool { return es[i].Priority > es[j].Priorit
 
 func NewThreadSafe() *ThreadSafe {
 	return &ThreadSafe{
-		Wantlist: *New(),
+		set: make(map[string]*Entry),
 	}
 }
 
@@ -44,46 +53,86 @@ func New() *Wantlist {
 	}
 }
 
-func (w *ThreadSafe) Add(k *cid.Cid, priority int) bool {
+func (w *ThreadSafe) Add(c *cid.Cid, priority int, ses uint64) bool {
 	w.lk.Lock()
 	defer w.lk.Unlock()
-	return w.Wantlist.Add(k, priority)
+	k := c.KeyString()
+	if e, ok := w.set[k]; ok {
+		e.SesTrk[ses] = struct{}{}
+		return false
+	}
+
+	w.set[k] = &Entry{
+		Cid:      c,
+		Priority: priority,
+		SesTrk:   map[uint64]struct{}{ses: struct{}{}},
+	}
+
+	return true
 }
 
-func (w *ThreadSafe) AddEntry(e *Entry) bool {
+func (w *ThreadSafe) AddEntry(e *Entry, ses uint64) bool {
 	w.lk.Lock()
 	defer w.lk.Unlock()
-	return w.Wantlist.AddEntry(e)
+	k := e.Cid.KeyString()
+	if ex, ok := w.set[k]; ok {
+		ex.SesTrk[ses] = struct{}{}
+		return false
+	}
+	w.set[k] = e
+	e.SesTrk[ses] = struct{}{}
+	return true
 }
 
-func (w *ThreadSafe) Remove(k *cid.Cid) bool {
+func (w *ThreadSafe) Remove(c *cid.Cid, ses uint64) bool {
 	w.lk.Lock()
 	defer w.lk.Unlock()
-	return w.Wantlist.Remove(k)
+	k := c.KeyString()
+	e, ok := w.set[k]
+	if !ok {
+		return false
+	}
+
+	delete(e.SesTrk, ses)
+	if len(e.SesTrk) == 0 {
+		delete(w.set, k)
+		return true
+	}
+	return false
 }
 
 func (w *ThreadSafe) Contains(k *cid.Cid) (*Entry, bool) {
 	w.lk.RLock()
 	defer w.lk.RUnlock()
-	return w.Wantlist.Contains(k)
+	e, ok := w.set[k.KeyString()]
+	return e, ok
 }
 
 func (w *ThreadSafe) Entries() []*Entry {
 	w.lk.RLock()
 	defer w.lk.RUnlock()
-	return w.Wantlist.Entries()
+	var es entrySlice
+	for _, e := range w.set {
+		es = append(es, e)
+	}
+	return es
 }
 
 func (w *ThreadSafe) SortedEntries() []*Entry {
 	w.lk.RLock()
 	defer w.lk.RUnlock()
-	return w.Wantlist.SortedEntries()
+	var es entrySlice
+	for _, e := range w.set {
+		es = append(es, e)
+	}
+	sort.Sort(es)
+	return es
 }
 
 func (w *ThreadSafe) Len() int {
 	w.lk.RLock()
 	defer w.lk.RUnlock()
-	return w.Wantlist.Len()
+	return len(w.set)
 }
 
 func (w *Wantlist) Len() int {
@@ -92,24 +141,21 @@ func (w *Wantlist) Len() int {
 
 func (w *Wantlist) Add(c *cid.Cid, priority int) bool {
 	k := c.KeyString()
-	if e, ok := w.set[k]; ok {
-		e.RefCnt++
+	if _, ok := w.set[k]; ok {
 		return false
 	}
 
 	w.set[k] = &Entry{
 		Cid:      c,
 		Priority: priority,
-		RefCnt:   1,
 	}
 
 	return true
 }
 
 func (w *Wantlist) AddEntry(e *Entry) bool {
 	k := e.Cid.KeyString()
-	if ex, ok := w.set[k]; ok {
-		ex.RefCnt++
+	if _, ok := w.set[k]; ok {
 		return false
 	}
 	w.set[k] = e
@@ -118,16 +164,12 @@ func (w *Wantlist) AddEntry(e *Entry) bool {
 
 func (w *Wantlist) Remove(c *cid.Cid) bool {
 	k := c.KeyString()
-	e, ok := w.set[k]
+	_, ok := w.set[k]
 	if !ok {
 		return false
 	}
 
-	e.RefCnt--
-	if e.RefCnt <= 0 {
-		delete(w.set, k)
-		return true
-	}
+	delete(w.set, k)
 	return false
 }