Introduce sequence cancelled callback to the Backend interface (#96)

.golangci.yml

@@ -352,7 +352,7 @@ linters-settings:
       - name: max-public-structs
         severity: warning
         disabled: false
-        arguments: [ 3 ]
+        arguments: [ 8 ]
       # https://github.com/mgechev/revive/blob/master/RULES_DESCRIPTIONS.md#modifies-parameter
       - name: modifies-parameter
         severity: warning

core/backend.go

@@ -55,15 +55,22 @@ type Verifier interface {
 	IsValidCommittedSeal(proposalHash []byte, committedSeal *messages.CommittedSeal) bool
 }
 
+// Notifier contains callback functions that notifies about consensus execution
+type Notifier interface {
+	// RoundStarts notifies the backend implementation whenever new round is about to start
+	RoundStarts(view *proto.View) error
+
+	// SequenceCancelled notifies the backend implementation whenever a sequence is cancelled
+	SequenceCancelled(view *proto.View) error
+}
+
 // Backend defines an interface all backend implementations
 // need to implement
 type Backend interface {
 	MessageConstructor
 	Verifier
 	ValidatorBackend
-
+	Notifier
-	// StartRound notifies the backend implementation whenever new round is about to start
-	StartRound(view *proto.View) error
 
 	// BuildProposal builds a new proposal for the given view (height and round)
 	BuildProposal(view *proto.View) []byte

core/ibft.go

@@ -323,8 +323,8 @@ func (i *IBFT) RunSequence(ctx context.Context, h uint64) {
 	for {
 		view := i.state.getView()
 
-		if err := i.backend.StartRound(view); err != nil {
+		if err := i.backend.RoundStarts(view); err != nil {
-			i.log.Error("failed to handle start round callback on backend", "round", view.Round, "err", err)
+			i.log.Error("failed to handle start round callback on backend", "view", view, "err", err)
 		}
 
 		i.log.Info("round started", "round", view.Round)
@@ -382,6 +382,11 @@ func (i *IBFT) RunSequence(ctx context.Context, h uint64) {
 			return
 		case <-ctxRound.Done():
 			teardown()
+
+			if err := i.backend.SequenceCancelled(view); err != nil {
+				i.log.Error("failed to handle sequence cancelled callback on backend", "view", view, "err", err)
+			}
+
 			i.log.Debug("sequence cancelled")
 
 			return

core/mock_test.go

@@ -64,7 +64,7 @@ type buildRoundChangeMessageDelegate func(
 type insertProposalDelegate func(*proto.Proposal, []*messages.CommittedSeal)
 type idDelegate func() []byte
 type getVotingPowerDelegate func(uint64) (map[string]*big.Int, error)
-type startRoundDelegate func(*proto.View) error
+type viewNotificationDelegate func(*proto.View) error
 
 var _ Backend = &mockBackend{}
 
@@ -84,7 +84,8 @@ type mockBackend struct {
 	insertProposalFn          insertProposalDelegate
 	idFn                      idDelegate
 	getVotingPowerFn          getVotingPowerDelegate
-	startRoundFn              startRoundDelegate
+	roundStartsFn             viewNotificationDelegate
+	sequenceCancelledFn       viewNotificationDelegate
 }
 
 func (m mockBackend) ID() []byte {
@@ -204,9 +205,17 @@ func (m mockBackend) GetVotingPowers(height uint64) (map[string]*big.Int, error)
 	return map[string]*big.Int{}, nil
 }
 
-func (m mockBackend) StartRound(view *proto.View) error {
+func (m mockBackend) RoundStarts(view *proto.View) error {
-	if m.startRoundFn != nil {
+	if m.roundStartsFn != nil {
-		return m.startRoundFn(view)
+		return m.roundStartsFn(view)
+	}
+
+	return nil
+}
+
+func (m mockBackend) SequenceCancelled(view *proto.View) error {
+	if m.sequenceCancelledFn != nil {
+		return m.sequenceCancelledFn(view)
 	}
 
 	return nil