remove buffer timing in bitswap in favor of manual batching

bitswap.go

@@ -43,7 +43,7 @@ func New(ctx context.Context, p peer.Peer,
 		routing:       routing,
 		sender:        network,
 		wantlist:      u.NewKeySet(),
-		blockRequests: make(chan u.Key, 32),
+		batchRequests: make(chan []u.Key, 32),
 	}
 	network.SetDelegate(bs)
 	go bs.run(ctx)
@@ -66,7 +66,10 @@ type bitswap struct {
 
 	notifications notifications.PubSub
 
-	blockRequests chan u.Key
+	// Requests for a set of related blocks
+	// the assumption is made that the same peer is likely to
+	// have more than a single block in the set
+	batchRequests chan []u.Key
 
 	// strategy listens to network traffic and makes decisions about how to
 	// interact with partners.
@@ -97,7 +100,7 @@ func (bs *bitswap) GetBlock(parent context.Context, k u.Key) (*blocks.Block, err
 	promise := bs.notifications.Subscribe(ctx, k)
 
 	select {
-	case bs.blockRequests <- k:
+	case bs.batchRequests <- []u.Key{k}:
 	case <-parent.Done():
 		return nil, parent.Err()
 	}
@@ -159,51 +162,32 @@ func (bs *bitswap) run(ctx context.Context) {
 	// Every so often, we should resend out our current want list
 	rebroadcastTime := time.Second * 5
 
-	var providers <-chan peer.Peer // NB: must be initialized to zero value
-	broadcastSignal := time.After(bs.strategy.GetRebroadcastDelay())
+	broadcastSignal := time.NewTicker(bs.strategy.GetRebroadcastDelay())
 
-	// Number of unsent keys for the current batch
-	unsentKeys := 0
 	for {
 		select {
-		case <-broadcastSignal:
-			unsentKeys = 0
+		case <-broadcastSignal.C:
 			wantlist := bs.wantlist.Keys()
 			if len(wantlist) == 0 {
 				continue
 			}
-			if providers == nil {
-				// rely on semi randomness of maps
-				firstKey := wantlist[0]
-				providers = bs.routing.FindProvidersAsync(ctx, firstKey, maxProvidersPerRequest)
-			}
+			providers := bs.routing.FindProvidersAsync(ctx, wantlist[0], maxProvidersPerRequest)
+
 			err := bs.sendWantListTo(ctx, providers)
 			if err != nil {
 				log.Errorf("error sending wantlist: %s", err)
 			}
-			providers = nil
-			broadcastSignal = time.After(bs.strategy.GetRebroadcastDelay())
-
-		case k := <-bs.blockRequests:
-			if unsentKeys == 0 {
-				providers = bs.routing.FindProvidersAsync(ctx, k, maxProvidersPerRequest)
+		case ks := <-bs.batchRequests:
+			if len(ks) == 0 {
+				log.Warning("Received batch request for zero blocks")
+				continue
 			}
-			unsentKeys++
+			providers := bs.routing.FindProvidersAsync(ctx, ks[0], maxProvidersPerRequest)
 
-			if unsentKeys >= bs.strategy.GetBatchSize() {
-				// send wantlist to providers
 			err := bs.sendWantListTo(ctx, providers)
 			if err != nil {
 				log.Errorf("error sending wantlist: %s", err)
 			}
-				unsentKeys = 0
-				broadcastSignal = time.After(bs.strategy.GetRebroadcastDelay())
-				providers = nil
-			} else {
-				// set a timeout to wait for more blocks or send current wantlist
-
-				broadcastSignal = time.After(bs.strategy.GetBatchDelay())
-			}
 		case <-ctx.Done():
 			return
 		}

bitswap_test.go

@@ -345,7 +345,7 @@ func session(net tn.Network, rs mock.RoutingServer, id peer.ID) instance {
 		routing:       htc,
 		sender:        adapter,
 		wantlist:      util.NewKeySet(),
-		blockRequests: make(chan util.Key, 32),
+		batchRequests: make(chan []util.Key, 32),
 	}
 	adapter.SetDelegate(bs)
 	go bs.run(context.TODO())