use @maybebtc's ForwardBlocks function

blockservice/blockservice.go

@@ -98,7 +98,7 @@ func (s *BlockService) GetBlock(ctx context.Context, k u.Key) (*blocks.Block, er
 // GetBlocks gets a list of blocks asynchronously and returns through
 // the returned channel.
 // NB: No guarantees are made about order.
-func (s *BlockService) GetBlocks(parent context.Context, ks []u.Key) <-chan *blocks.Block {
+func (s *BlockService) GetBlocks(ctx context.Context, ks []u.Key) <-chan *blocks.Block {
 	out := make(chan *blocks.Block, 32)
 	go func() {
 		var toFetch []u.Key
@@ -112,7 +112,6 @@ func (s *BlockService) GetBlocks(parent context.Context, ks []u.Key) <-chan *blo
 			out <- block
 		}
 
-		ctx, cancel := context.WithCancel(parent)
 		nblocks, err := s.Remote.GetBlocks(ctx, toFetch)
 		if err != nil {
 			log.Errorf("Error with GetBlocks: %s", err)

exchange/bitswap/bitswap.go

@@ -16,6 +16,7 @@ import (
 	strategy "github.com/jbenet/go-ipfs/exchange/bitswap/strategy"
 	peer "github.com/jbenet/go-ipfs/peer"
 	u "github.com/jbenet/go-ipfs/util"
+	async "github.com/jbenet/go-ipfs/util/async"
 	"github.com/jbenet/go-ipfs/util/eventlog"
 )
 
@@ -128,35 +129,12 @@ func (bs *bitswap) GetBlocks(ctx context.Context, keys []u.Key) (<-chan *blocks.
 	promise := bs.notifications.Subscribe(ctx, keys...)
 	select {
 	case bs.batchRequests <- keys:
-		return pipeBlocks(ctx, promise, len(keys)), nil
+		return async.ForwardN(ctx, promise, len(keys)), nil
 	case <-ctx.Done():
 		return nil, ctx.Err()
 	}
 }
 
-func pipeBlocks(ctx context.Context, in <-chan *blocks.Block, count int) <-chan *blocks.Block {
-	out := make(chan *blocks.Block, 1)
-	go func() {
-		defer close(out)
-		for i := 0; i < count; i++ {
-			select {
-			case blk, ok := <-in:
-				if !ok {
-					return
-				}
-				select {
-				case out <- blk:
-				case <-ctx.Done():
-					return
-				}
-			case <-ctx.Done():
-				return
-			}
-		}
-	}()
-	return out
-}
-
 func (bs *bitswap) sendWantListTo(ctx context.Context, peers <-chan peer.Peer) error {
 	if peers == nil {
 		panic("Cant send wantlist to nil peerchan")

util/async/forward.go

@@ -3,8 +3,11 @@ package async
 import (
 	context "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
 	"github.com/jbenet/go-ipfs/blocks"
+	u "github.com/jbenet/go-ipfs/util"
 )
 
+var log = u.Logger("async")
+
 // ForwardN forwards up to |num| blocks to the returned channel.
 func ForwardN(ctx context.Context, in <-chan *blocks.Block, num int) <-chan *blocks.Block {
 	out := make(chan *blocks.Block)
@@ -14,6 +17,7 @@ func ForwardN(ctx context.Context, in <-chan *blocks.Block, num int) <-chan *blo
 			select {
 			case block, ok := <-in:
 				if !ok {
+					log.Error("Forwarder exiting early!")
 					return // otherwise nil value is forwarded to output
 				}
 				select {