blockservice & exchange & bitswap: add non variadic NotifyNewBlock

Variadicts in go are just syntactic sugar around passing a slice, that
means all go memory reachability rules apply, this force the compiler to
heap allocate the variadic slice for virtual call, because the
implementation is allowed to leak the slice (and go's interprocedural
optimisations do not cover virtuals).

Passing a block without variadic will pass the itab either on the stack
or decomposed through registers. Skipping having to allocate a slice.

bitswap/bitswap.go

@@ -96,6 +96,13 @@ func New(ctx context.Context, net network.BitSwapNetwork, bstore blockstore.Bloc
 	return bs
 }
 
+func (bs *Bitswap) NotifyNewBlock(ctx context.Context, blk blocks.Block) error {
+	return multierr.Combine(
+		bs.Client.NotifyNewBlock(ctx, blk),
+		bs.Server.NotifyNewBlock(ctx, blk),
+	)
+}
+
 func (bs *Bitswap) NotifyNewBlocks(ctx context.Context, blks ...blocks.Block) error {
 	return multierr.Combine(
 		bs.Client.NotifyNewBlocks(ctx, blks...),

bitswap/client/client.go

@@ -259,6 +259,16 @@ func (bs *Client) GetBlocks(ctx context.Context, keys []cid.Cid) (<-chan blocks.
 	return session.GetBlocks(ctx, keys)
 }
 
+// NotifyNewBlock announces the existence of blocks to this bitswap service.
+// Bitswap itself doesn't store new blocks. It's the caller responsibility to ensure
+// that those blocks are available in the blockstore before calling this function.
+func (bs *Client) NotifyNewBlock(ctx context.Context, blk blocks.Block) error {
+	// Call to the variadic to avoid code duplication.
+	// This is actually fine to do because no calls is virtual the compiler is able
+	// to see that the slice does not leak and the slice is stack allocated.
+	return bs.NotifyNewBlocks(ctx, blk)
+}
+
 // NotifyNewBlocks announces the existence of blocks to this bitswap service.
 // Bitswap itself doesn't store new blocks. It's the caller responsibility to ensure
 // that those blocks are available in the blockstore before calling this function.

bitswap/server/server.go

@@ -404,6 +404,17 @@ func (bs *Server) Stat() (Stat, error) {
 	return s, nil
 }
 
+// NotifyNewBlock announces the existence of block to this bitswap service. The
+// service will potentially notify its peers.
+// Bitswap itself doesn't store new blocks. It's the caller responsibility to ensure
+// that those blocks are available in the blockstore before calling this function.
+func (bs *Server) NotifyNewBlock(ctx context.Context, blk blocks.Block) error {
+	// Call to the variadic to avoid code duplication.
+	// This is actually fine to do because no calls is virtual the compiler is able
+	// to see that the slice does not leak and the slice is stack allocated.
+	return bs.NotifyNewBlocks(ctx, blk)
+}
+
 // NotifyNewBlocks announces the existence of blocks to this bitswap service. The
 // service will potentially notify its peers.
 // Bitswap itself doesn't store new blocks. It's the caller responsibility to ensure

blockservice/blockservice.go

@@ -157,8 +157,8 @@ func (s *blockService) AddBlock(ctx context.Context, o blocks.Block) error {
 	logger.Debugf("BlockService.BlockAdded %s", c)
 
 	if s.exchange != nil {
-		if err := s.exchange.NotifyNewBlocks(ctx, o); err != nil {
-			logger.Errorf("NotifyNewBlocks: %s", err.Error())
+		if err := s.exchange.NotifyNewBlock(ctx, o); err != nil {
+			logger.Errorf("NotifyNewBlock: %s", err.Error())
 		}
 	}
 
@@ -254,7 +254,7 @@ func getBlock(ctx context.Context, c cid.Cid, bs blockstore.Blockstore, fget fun
 		if err != nil {
 			return nil, err
 		}
-		err = f.NotifyNewBlocks(ctx, blk)
+		err = f.NotifyNewBlock(ctx, blk)
 		if err != nil {
 			return nil, err
 		}
@@ -334,7 +334,6 @@ func getBlocks(ctx context.Context, ks []cid.Cid, bs blockstore.Blockstore, fget
 			return
 		}
 
-		var cache [1]blocks.Block // preallocate once for all iterations
 		for {
 			var b blocks.Block
 			select {
@@ -355,13 +354,11 @@ func getBlocks(ctx context.Context, ks []cid.Cid, bs blockstore.Blockstore, fget
 			}
 
 			// inform the exchange that the blocks are available
-			cache[0] = b
-			err = f.NotifyNewBlocks(ctx, cache[:]...)
+			err = f.NotifyNewBlock(ctx, b)
 			if err != nil {
 				logger.Errorf("could not tell the exchange about new blocks: %s", err)
 				return
 			}
-			cache[0] = nil // early gc
 
 			select {
 			case out <- b:
@@ -391,6 +388,7 @@ func (s *blockService) Close() error {
 }
 
 type notifier interface {
+	NotifyNewBlock(context.Context, blocks.Block) error
 	NotifyNewBlocks(context.Context, ...blocks.Block) error
 }
 

blockservice/blockservice_test.go

@@ -195,6 +195,11 @@ type notifyCountingExchange struct {
 	notifyCount int
 }
 
+func (n *notifyCountingExchange) NotifyNewBlock(ctx context.Context, blocks blocks.Block) error {
+	n.notifyCount++
+	return n.Interface.NotifyNewBlock(ctx, blocks)
+}
+
 func (n *notifyCountingExchange) NotifyNewBlocks(ctx context.Context, blocks ...blocks.Block) error {
 	n.notifyCount += len(blocks)
 	return n.Interface.NotifyNewBlocks(ctx, blocks...)

exchange/interface.go

@@ -13,6 +13,8 @@ import (
 type Interface interface { // type Exchanger interface
 	Fetcher
 
+	// NotifyNewBlock tells the exchange that a new block is available and can be served.
+	NotifyNewBlock(ctx context.Context, blocks blocks.Block) error
 	// NotifyNewBlocks tells the exchange that new blocks are available and can be served.
 	NotifyNewBlocks(ctx context.Context, blocks ...blocks.Block) error
 

exchange/offline/offline.go

@@ -34,6 +34,12 @@ func (e *offlineExchange) GetBlock(ctx context.Context, k cid.Cid) (blocks.Block
 	return blk, err
 }
 
+// NotifyNewBlock tells the exchange that a new block is available and can be served.
+func (e *offlineExchange) NotifyNewBlock(ctx context.Context, block blocks.Block) error {
+	// as an offline exchange we have nothing to do
+	return nil
+}
+
 // NotifyNewBlocks tells the exchange that new blocks are available and can be served.
 func (e *offlineExchange) NotifyNewBlocks(ctx context.Context, blocks ...blocks.Block) error {
 	// as an offline exchange we have nothing to do