Host: notify separately for new heads and new validated heads

go/common/host/services.go

@@ -118,14 +118,20 @@ type L1Publisher interface {
 
 // L2BatchRepository provides an interface for the host to request L2 batch data (live-streaming and historical)
 type L2BatchRepository interface {
-	// Subscribe will register a batch handler to receive new batches as they arrive
-	Subscribe(handler L2BatchHandler) func()
+	// SubscribeNewBatches will register a handler to receive new batches from the publisher as they arrive at the host
+	SubscribeNewBatches(handler L2BatchHandler) func()
+
+	// SubscribeValidatedBatches will register a handler to receive batches that have been validated by the enclave
+	SubscribeValidatedBatches(handler L2BatchHandler) func()
 
 	FetchBatchBySeqNo(background context.Context, seqNo *big.Int) (*common.ExtBatch, error)
 
 	// AddBatch is used to notify the repository of a new batch, e.g. from the enclave when seq produces one or a rollup is consumed
 	// Note: it is fine to add batches that the repo already has, it will just ignore them
 	AddBatch(batch *common.ExtBatch) error
+
+	// NotifyNewValidatedHead - called after an enclave validates a batch, to update the repo's validated head and notify subscribers
+	NotifyNewValidatedHead(batch *common.ExtBatch)
 }
 
 // L2BatchHandler is an interface for receiving new batches from the publisher as they arrive

go/host/enclave/guardian.go

@@ -128,7 +128,7 @@ func (g *Guardian) Start() error {
 
 	// note: not keeping the unsubscribe functions because the lifespan of the guardian is the same as the host
 	g.sl.L1Repo().Subscribe(g)
-	g.sl.L2Repo().Subscribe(g)
+	g.sl.L2Repo().SubscribeNewBatches(g)
 
 	// start streaming data from the enclave
 	go g.streamEnclaveData()
@@ -659,8 +659,10 @@ func (g *Guardian) streamEnclaveData() {
 						g.logger.Error("Failed to broadcast batch", log.BatchHashKey, resp.Batch.Hash(), log.ErrKey, err)
 					}
 				} else {
-					g.logger.Debug("Received batch from enclave", log.BatchSeqNoKey, resp.Batch.Header.SequencerOrderNo, log.BatchHashKey, resp.Batch.Hash())
+					g.logger.Debug("Received validated batch from enclave", log.BatchSeqNoKey, resp.Batch.Header.SequencerOrderNo, log.BatchHashKey, resp.Batch.Hash())
 				}
+				// Notify the L2 repo that an enclave has validated a batch, so it can update its validated head and notify subscribers
+				g.sl.L2Repo().NotifyNewValidatedHead(resp.Batch)
 				g.state.OnProcessedBatch(resp.Batch.Header.SequencerOrderNo)
 			}
 

go/host/host.go

@@ -97,7 +97,7 @@ func NewHost(config *config.HostConfig, hostServices *ServicesRegistry, p2p host
 	l2Repo := l2.NewBatchRepository(config, hostServices, hostStorage, logger)
 	subsService := events.NewLogEventManager(hostServices, logger)
 
-	l2Repo.Subscribe(batchListener{newHeads: host.newHeads})
+	l2Repo.SubscribeValidatedBatches(batchListener{newHeads: host.newHeads})
 	hostServices.RegisterService(hostcommon.P2PName, p2p)
 	hostServices.RegisterService(hostcommon.L1BlockRepositoryName, l1Repo)
 	maxWaitForL1Receipt := 6 * config.L1BlockTime   // wait ~10 blocks to see if tx gets published before retrying

go/host/l2/batchrepository.go

@@ -36,7 +36,8 @@ type batchRepoServiceLocator interface {
 // Repository is responsible for storing and retrieving batches from the database
 // If it can't find a batch it will request it from peers. It also subscribes for batch requests from peers and responds to them.
 type Repository struct {
-	batchSubscribers *subscription.Manager[host.L2BatchHandler]
+	batchSubscribers          *subscription.Manager[host.L2BatchHandler] // notified when a new batch is added to the repository
+	validatedBatchSubscribers *subscription.Manager[host.L2BatchHandler] // notified when a new batch is validated by the enclave
 
 	sl          batchRepoServiceLocator
 	storage     storage.Storage
@@ -46,6 +47,10 @@ type Repository struct {
 	latestBatchSeqNo *big.Int
 	latestSeqNoMutex sync.Mutex
 
+	// high watermark for batch sequence numbers validated by our enclave so far.
+	latestValidatedSeqNo *big.Int
+	latestValidatedMutex sync.Mutex
+
 	// The repository requests batches from peers asynchronously, we don't want to repeatedly spam out requests if we
 	// haven't received a response yet, but we also don't want to wait forever if there's no response.
 	// So we keep track of the last request time and what was requested, using a mutex to avoid concurrent access errors on them
@@ -59,13 +64,15 @@ type Repository struct {
 
 func NewBatchRepository(cfg *config.HostConfig, hostService batchRepoServiceLocator, storage storage.Storage, logger gethlog.Logger) *Repository {
 	return &Repository{
-		batchSubscribers: subscription.NewManager[host.L2BatchHandler](),
-		sl:               hostService,
-		storage:          storage,
-		isSequencer:      cfg.NodeType == common.Sequencer,
-		latestBatchSeqNo: big.NewInt(0),
-		running:          atomic.Bool{},
-		logger:           logger,
+		batchSubscribers:          subscription.NewManager[host.L2BatchHandler](),
+		validatedBatchSubscribers: subscription.NewManager[host.L2BatchHandler](),
+		sl:                        hostService,
+		storage:                   storage,
+		isSequencer:               cfg.NodeType == common.Sequencer,
+		latestBatchSeqNo:          big.NewInt(0),
+		latestValidatedSeqNo:      big.NewInt(0),
+		running:                   atomic.Bool{},
+		logger:                    logger,
 	}
 }
 
@@ -144,11 +151,15 @@ func (r *Repository) HandleBatchRequest(requesterID string, fromSeqNo *big.Int)
 	}
 }
 
-// Subscribe registers a handler to be notified of new head batches as they arrive, returns unsubscribe func
-func (r *Repository) Subscribe(handler host.L2BatchHandler) func() {
+// SubscribeNewBatches registers a handler to be notified of new head batches as they arrive, returns unsubscribe func
+func (r *Repository) SubscribeNewBatches(handler host.L2BatchHandler) func() {
 	return r.batchSubscribers.Subscribe(handler)
 }
 
+func (r *Repository) SubscribeValidatedBatches(handler host.L2BatchHandler) func() {
+	return r.validatedBatchSubscribers.Subscribe(handler)
+}
+
 func (r *Repository) FetchBatchBySeqNo(ctx context.Context, seqNo *big.Int) (*common.ExtBatch, error) {
 	b, err := r.storage.FetchBatchBySeqNo(seqNo.Uint64())
 	if err != nil {
@@ -190,6 +201,19 @@ func (r *Repository) AddBatch(batch *common.ExtBatch) error {
 	return nil
 }
 
+// NotifyNewValidatedHead - called after an enclave validates a batch, to update the repo's validated head and notify subscribers
+func (r *Repository) NotifyNewValidatedHead(batch *common.ExtBatch) {
+	r.latestValidatedMutex.Lock()
+	defer r.latestValidatedMutex.Unlock()
+	if batch.SeqNo().Cmp(r.latestValidatedSeqNo) > 0 {
+		r.latestValidatedSeqNo = batch.SeqNo()
+	}
+	// notify validated batch subscribers, a new batch has been successfully processed by an enclave
+	for _, subscriber := range r.validatedBatchSubscribers.Subscribers() {
+		go subscriber.HandleBatch(batch)
+	}
+}
+
 func (r *Repository) fetchBatchFallbackToEnclave(ctx context.Context, seqNo *big.Int) (*common.ExtBatch, error) {
 	b, err := r.sl.Enclaves().LookupBatchBySeqNo(ctx, seqNo)
 	if err != nil {