feat(bitswap:network) propagate errors up the stack

Rather than pushing errors back down to lower layers, propagate the
errors upward.

This commit adds a `ReceiveError` method to BitSwap's network receiver.

Still TODO: rm the error return value from:

    net.service.handler.HandleMessage

This is inspired by delegation patterns in found in the wild.

bitswap.go

 package bitswap
 
 import (
-	"errors"
-
 	context "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/datastore.go"
 
@@ -120,14 +118,16 @@ func (bs *bitswap) HasBlock(ctx context.Context, blk blocks.Block) error {
 
 // TODO(brian): handle errors
 func (bs *bitswap) ReceiveMessage(ctx context.Context, p *peer.Peer, incoming bsmsg.BitSwapMessage) (
-	*peer.Peer, bsmsg.BitSwapMessage, error) {
+	*peer.Peer, bsmsg.BitSwapMessage) {
 	u.DOut("ReceiveMessage from %v\n", p.Key().Pretty())
 
 	if p == nil {
-		return nil, nil, errors.New("Received nil Peer")
+		// TODO propagate the error upward
+		return nil, nil
 	}
 	if incoming == nil {
-		return nil, nil, errors.New("Received nil Message")
+		// TODO propagate the error upward
+		return nil, nil
 	}
 
 	bs.strategy.MessageReceived(p, incoming) // FIRST
@@ -157,7 +157,12 @@ func (bs *bitswap) ReceiveMessage(ctx context.Context, p *peer.Peer, incoming bs
 		}
 	}
 	defer bs.strategy.MessageSent(p, message)
-	return p, message, nil
+	return p, message
+}
+
+func (bs *bitswap) ReceiveError(err error) {
+	// TODO log the network error
+	// TODO bubble the network error up to the parent context/error logger
 }
 
 // send strives to ensure that accounting is always performed when a message is

network/interface.go

@@ -33,7 +33,9 @@ type Adapter interface {
 type Receiver interface {
 	ReceiveMessage(
 		ctx context.Context, sender *peer.Peer, incoming bsmsg.BitSwapMessage) (
-		destination *peer.Peer, outgoing bsmsg.BitSwapMessage, err error)
+		destination *peer.Peer, outgoing bsmsg.BitSwapMessage)
+
+	ReceiveError(error)
 }
 
 // TODO(brian): move this to go-ipfs/net package

network/net_message_adapter.go

 package network
 
 import (
-	"errors"
-
 	context "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
 
 	bsmsg "github.com/jbenet/go-ipfs/exchange/bitswap/message"
@@ -34,18 +32,16 @@ func (adapter *impl) HandleMessage(
 	ctx context.Context, incoming netmsg.NetMessage) (netmsg.NetMessage, error) {
 
 	if adapter.receiver == nil {
-		return nil, errors.New("No receiver. NetMessage dropped")
+		return nil, nil
 	}
 
 	received, err := bsmsg.FromNet(incoming)
 	if err != nil {
-		return nil, err
+		adapter.receiver.ReceiveError(err)
+		return nil, nil
 	}
 
-	p, bsmsg, err := adapter.receiver.ReceiveMessage(ctx, incoming.Peer(), received)
-	if err != nil {
-		return nil, err
-	}
+	p, bsmsg := adapter.receiver.ReceiveMessage(ctx, incoming.Peer(), received)
 
 	// TODO(brian): put this in a helper function
 	if bsmsg == nil || p == nil {
@@ -54,7 +50,8 @@ func (adapter *impl) HandleMessage(
 
 	outgoing, err := bsmsg.ToNet(p)
 	if err != nil {
-		return nil, err
+		adapter.receiver.ReceiveError(err)
+		return nil, nil
 	}
 
 	return outgoing, nil

testnet/network.go

@@ -76,18 +76,7 @@ func (n *network) deliver(
 		return errors.New("Invalid input")
 	}
 
-	nextPeer, nextMsg, err := r.ReceiveMessage(context.TODO(), from, message)
-	if err != nil {
-
-		// TODO should this error be returned across network boundary?
-
-		// TODO this raises an interesting question about network contract. How
-		// can the network be expected to behave under different failure
-		// conditions? What if peer is unreachable? Will we know if messages
-		// aren't delivered?
-
-		return err
-	}
+	nextPeer, nextMsg := r.ReceiveMessage(context.TODO(), from, message)
 
 	if (nextPeer == nil && nextMsg != nil) || (nextMsg == nil && nextPeer != nil) {
 		return errors.New("Malformed client request")
@@ -119,15 +108,12 @@ func (n *network) SendRequest(
 	if !ok {
 		return nil, errors.New("Cannot locate peer on network")
 	}
-	nextPeer, nextMsg, err := r.ReceiveMessage(context.TODO(), from, message)
-	if err != nil {
-		return nil, err
-		// TODO return nil, NoResponse
-	}
+	nextPeer, nextMsg := r.ReceiveMessage(context.TODO(), from, message)
 
 	// TODO dedupe code
 	if (nextPeer == nil && nextMsg != nil) || (nextMsg == nil && nextPeer != nil) {
-		return nil, errors.New("Malformed client request")
+		r.ReceiveError(errors.New("Malformed client request"))
+		return nil, nil
 	}
 
 	// TODO dedupe code
@@ -144,7 +130,7 @@ func (n *network) SendRequest(
 			}
 			n.deliver(nextReceiver, nextPeer, nextMsg)
 		}()
-		return nil, NoResponse
+		return nil, nil
 	}
 	return nextMsg, nil
 }

testnet/network_test.go

@@ -26,7 +26,7 @@ func TestSendRequestToCooperativePeer(t *testing.T) {
 		ctx context.Context,
 		from *peer.Peer,
 		incoming bsmsg.BitSwapMessage) (
-		*peer.Peer, bsmsg.BitSwapMessage, error) {
+		*peer.Peer, bsmsg.BitSwapMessage) {
 
 		t.Log("Recipient received a message from the network")
 
@@ -35,7 +35,7 @@ func TestSendRequestToCooperativePeer(t *testing.T) {
 		m := bsmsg.New()
 		m.AppendBlock(testutil.NewBlockOrFail(t, expectedStr))
 
-		return from, m, nil
+		return from, m
 	}))
 
 	t.Log("Build a message and send a synchronous request to recipient")
@@ -74,19 +74,19 @@ func TestSendMessageAsyncButWaitForResponse(t *testing.T) {
 		ctx context.Context,
 		fromWaiter *peer.Peer,
 		msgFromWaiter bsmsg.BitSwapMessage) (
-		*peer.Peer, bsmsg.BitSwapMessage, error) {
+		*peer.Peer, bsmsg.BitSwapMessage) {
 
 		msgToWaiter := bsmsg.New()
 		msgToWaiter.AppendBlock(testutil.NewBlockOrFail(t, expectedStr))
 
-		return fromWaiter, msgToWaiter, nil
+		return fromWaiter, msgToWaiter
 	}))
 
 	waiter.SetDelegate(lambda(func(
 		ctx context.Context,
 		fromResponder *peer.Peer,
 		msgFromResponder bsmsg.BitSwapMessage) (
-		*peer.Peer, bsmsg.BitSwapMessage, error) {
+		*peer.Peer, bsmsg.BitSwapMessage) {
 
 		// TODO assert that this came from the correct peer and that the message contents are as expected
 		ok := false
@@ -101,7 +101,7 @@ func TestSendMessageAsyncButWaitForResponse(t *testing.T) {
 			t.Fatal("Message not received from the responder")
 
 		}
-		return nil, nil, nil
+		return nil, nil
 	}))
 
 	messageSentAsync := bsmsg.New()
@@ -116,7 +116,7 @@ func TestSendMessageAsyncButWaitForResponse(t *testing.T) {
 }
 
 type receiverFunc func(ctx context.Context, p *peer.Peer,
-	incoming bsmsg.BitSwapMessage) (*peer.Peer, bsmsg.BitSwapMessage, error)
+	incoming bsmsg.BitSwapMessage) (*peer.Peer, bsmsg.BitSwapMessage)
 
 // lambda returns a Receiver instance given a receiver function
 func lambda(f receiverFunc) bsnet.Receiver {
@@ -126,13 +126,16 @@ func lambda(f receiverFunc) bsnet.Receiver {
 }
 
 type lambdaImpl struct {
-	f func(ctx context.Context, p *peer.Peer,
-		incoming bsmsg.BitSwapMessage) (
-		*peer.Peer, bsmsg.BitSwapMessage, error)
+	f func(ctx context.Context, p *peer.Peer, incoming bsmsg.BitSwapMessage) (
+		*peer.Peer, bsmsg.BitSwapMessage)
 }
 
 func (lam *lambdaImpl) ReceiveMessage(ctx context.Context,
 	p *peer.Peer, incoming bsmsg.BitSwapMessage) (
-	*peer.Peer, bsmsg.BitSwapMessage, error) {
+	*peer.Peer, bsmsg.BitSwapMessage) {
 	return lam.f(ctx, p, incoming)
 }
+
+func (lam *lambdaImpl) ReceiveError(err error) {
+	// TODO log error
+}