Dont log errors when the transfer event queue is full

transport/httptransport/http_transport.go

@@ -140,7 +140,7 @@ func (h *httpTransport) Execute(ctx context.Context, transportInfo []byte, dealI
 
 	cleanupFns := []func(){
 		cancel,
-		func() { close(t.eventCh) },
+		func() { t.closeEventChannel(tctx) },
 	}
 	cleanup := func() {
 		for _, fn := range cleanupFns {
@@ -178,12 +178,7 @@ func (h *httpTransport) Execute(ctx context.Context, transportInfo []byte, dealI
 	if fileSize == dealInfo.DealSize {
 		defer cleanup()
 
-		if err := t.emitEvent(tctx, types.TransportEvent{
-			NBytesReceived: fileSize,
-		}, dealInfo.DealUuid); err != nil {
-			return nil, fmt.Errorf("failed to publish transfer completion event, id: %s, err: %w", t.dealInfo.DealUuid, err)
-		}
-
+		t.emitEvent(types.TransportEvent{NBytesReceived: fileSize})
 		h.dl.Infow(duuid, "file size is already equal to deal size, returning")
 		return t, nil
 	}
@@ -195,11 +190,7 @@ func (h *httpTransport) Execute(ctx context.Context, transportInfo []byte, dealI
 		defer cleanup()
 
 		if err := t.execute(tctx); err != nil {
-			if err := t.emitEvent(tctx, types.TransportEvent{
-				Error: err,
-			}, dealInfo.DealUuid); err != nil {
-				t.dl.LogError(duuid, "failed to publish transport error", err)
-			}
+			t.emitEvent(types.TransportEvent{Error: err})
 		}
 	}()
 
@@ -212,6 +203,7 @@ type transfer struct {
 	cancel    context.CancelFunc
 
 	eventCh chan types.TransportEvent
+	lastEvt *types.TransportEvent
 
 	tInfo    *types.HttpRequest
 	dealInfo *types.TransportDealInfo
@@ -226,15 +218,6 @@ type transfer struct {
 	dl     *logs.DealLogger
 }
 
-func (t *transfer) emitEvent(ctx context.Context, evt types.TransportEvent, id uuid.UUID) error {
-	select {
-	case t.eventCh <- evt:
-		return nil
-	default:
-		return fmt.Errorf("dropping event %+v as channel is full for deal id %s", evt, id)
-	}
-}
-
 func (t *transfer) execute(ctx context.Context) error {
 	duuid := t.dealInfo.DealUuid
 	for {
@@ -387,11 +370,7 @@ func (t *transfer) doHttp(ctx context.Context, req *http.Request, dst io.Writer,
 			t.nBytesReceived = t.nBytesReceived + int64(nw)
 
 			// emit event updating the number of bytes received
-			if err := t.emitEvent(ctx, types.TransportEvent{
-				NBytesReceived: t.nBytesReceived,
-			}, t.dealInfo.DealUuid); err != nil {
-				t.dl.LogError(duid, "failed to publish transport event", err)
-			}
+			t.emitEvent(types.TransportEvent{NBytesReceived: t.nBytesReceived})
 		}
 		// the http stream we're reading from has sent us an EOF, nothing to do here.
 		if readErr == io.EOF {
@@ -420,3 +399,28 @@ func (t *transfer) Close() {
 func (t *transfer) Sub() chan types.TransportEvent {
 	return t.eventCh
 }
+
+func (t *transfer) emitEvent(evt types.TransportEvent) {
+	t.lastEvt = nil
+	select {
+	case t.eventCh <- evt:
+	default:
+		// If it wasn't possible to send the event because the channel is full,
+		// save it so that we can ensure it gets sent before the channel is closed.
+		// A new event always supersedes an older event, so if there is another
+		// event after this one, it will simply over-write this one.
+		t.lastEvt = &evt
+	}
+}
+
+func (t *transfer) closeEventChannel(ctx context.Context) {
+	// If there was an event that wasn't sent because the channel was full,
+	// ensure that it gets sent before close
+	if t.lastEvt != nil {
+		select {
+		case <-ctx.Done():
+		case t.eventCh <- *t.lastEvt:
+		}
+	}
+	close(t.eventCh)
+}