Simplify enclave batch streaming and fix p2p batch requesting (#1400)

go/common/enclave.go

@@ -105,6 +105,9 @@ type Enclave interface {
 	// GetBatch - retrieve a batch if existing within the enclave db.
 	GetBatch(hash L2BatchHash) (*ExtBatch, error)
 
+	// GetBatchBySeqNo - retrieve batch by sequencer number if it's in the db
+	GetBatchBySeqNo(seqNo uint64) (*ExtBatch, error)
+
 	// CreateBatch - creates a new head batch extending the previous one for the latest known L1 head if the node is
 	// a sequencer. Will panic otherwise.
 	CreateBatch() SystemError
@@ -116,9 +119,9 @@ type Enclave interface {
 	// DebugTraceTransaction returns the trace of a transaction
 	DebugTraceTransaction(hash gethcommon.Hash, config *tracers.TraceConfig) (json.RawMessage, SystemError)
 
-	// StreamL2Updates - will stream the batches following the L2 batch hash given along with any newly created batches
-	// in the right order. All will be queued in the channel that has been returned
-	StreamL2Updates(*L2BatchHash) (chan StreamL2UpdatesResponse, func())
+	// StreamL2Updates - will stream any new batches as they are created/detected
+	// All will be queued in the channel that has been returned.
+	StreamL2Updates() (chan StreamL2UpdatesResponse, func())
 	// DebugEventLogRelevancy returns the logs of a transaction
 	DebugEventLogRelevancy(hash gethcommon.Hash) (json.RawMessage, SystemError)
 }

go/common/host/services.go

@@ -124,3 +124,11 @@ type L2BatchHandler interface {
 	// HandleBatch will be called in a new goroutine for each new batch as it arrives
 	HandleBatch(batch *common.ExtBatch)
 }
+
+// EnclaveService provides access to the host enclave(s), it monitors and manages the states of the enclaves, so it can
+// help with failover, gate-keeping (throttling/load-balancing) and circuit-breaking when the enclave is not available
+type EnclaveService interface {
+	// LookupBatchBySeqNo is used to fetch batch data from the enclave - it is only used as a fallback for the sequencer
+	// host if it's missing a batch (other host services should use L2Repo to fetch batch data)
+	LookupBatchBySeqNo(seqNo *big.Int) (*common.ExtBatch, error)
+}