chainntnfs: allow clients to pass in best block

Clients can optionally pass their best block known into RegisterBlockEpochNtfn. This enables the notifiers to catch up clients on blocks they may have missed.

chainntnfs/bitcoindnotify/bitcoind.go

@@ -805,6 +805,10 @@ type blockEpochRegistration struct {
 
 	epochQueue *chainntnfs.ConcurrentQueue
 
+	bestBlock *chainntnfs.BlockEpoch
+
+	errorChan chan error
+
 	cancelChan chan struct{}
 
 	wg sync.WaitGroup
@@ -818,13 +822,18 @@ type epochCancel struct {
 
 // RegisterBlockEpochNtfn returns a BlockEpochEvent which subscribes the
 // caller to receive notifications, of each new block connected to the main
-// chain.
-func (b *BitcoindNotifier) RegisterBlockEpochNtfn() (*chainntnfs.BlockEpochEvent, error) {
+// chain. Clients have the option of passing in their best known block, which
+// the notifier uses to check if they are behind on blocks and catch them up.
+func (b *BitcoindNotifier) RegisterBlockEpochNtfn(
+	bestBlock *chainntnfs.BlockEpoch) (*chainntnfs.BlockEpochEvent, error) {
+
 	reg := &blockEpochRegistration{
 		epochQueue: chainntnfs.NewConcurrentQueue(20),
 		epochChan:  make(chan *chainntnfs.BlockEpoch, 20),
 		cancelChan: make(chan struct{}),
 		epochID:    atomic.AddUint64(&b.epochClientCounter, 1),
+		bestBlock:  bestBlock,
+		errorChan:  make(chan error, 1),
 	}
 	reg.epochQueue.Start()
 

chainntnfs/btcdnotify/btcd.go

@@ -16,7 +16,6 @@ import (
 )
 
 const (
-
 	// notifierType uniquely identifies this concrete implementation of the
 	// ChainNotifier interface.
 	notifierType = "btcd"
@@ -857,6 +856,10 @@ type blockEpochRegistration struct {
 
 	epochQueue *chainntnfs.ConcurrentQueue
 
+	bestBlock *chainntnfs.BlockEpoch
+
+	errorChan chan error
+
 	cancelChan chan struct{}
 
 	wg sync.WaitGroup
@@ -870,13 +873,18 @@ type epochCancel struct {
 
 // RegisterBlockEpochNtfn returns a BlockEpochEvent which subscribes the
 // caller to receive notifications, of each new block connected to the main
-// chain.
-func (b *BtcdNotifier) RegisterBlockEpochNtfn() (*chainntnfs.BlockEpochEvent, error) {
+// chain. Clients have the option of passing in their best known block, which
+// the notifier uses to check if they are behind on blocks and catch them up.
+func (b *BtcdNotifier) RegisterBlockEpochNtfn(
+	bestBlock *chainntnfs.BlockEpoch) (*chainntnfs.BlockEpochEvent, error) {
+
 	reg := &blockEpochRegistration{
 		epochQueue: chainntnfs.NewConcurrentQueue(20),
 		epochChan:  make(chan *chainntnfs.BlockEpoch, 20),
 		cancelChan: make(chan struct{}),
 		epochID:    atomic.AddUint64(&b.epochClientCounter, 1),
+		bestBlock:  bestBlock,
+		errorChan:  make(chan error, 1),
 	}
 	reg.epochQueue.Start()
 

chainntnfs/interface.go

@@ -59,7 +59,12 @@ type ChainNotifier interface {
 	// new block connected to the tip of the main chain. The returned
 	// BlockEpochEvent struct contains a channel which will be sent upon
 	// for each new block discovered.
-	RegisterBlockEpochNtfn() (*BlockEpochEvent, error)
+	//
+	// Clients have the option of passing in their best known block.
+	// If they specify a block, the ChainNotifier checks whether the client
+	// is behind on blocks. If they are, the ChainNotifier sends a backlog
+	// of block notifications for the missed blocks.
+	RegisterBlockEpochNtfn(*BlockEpoch) (*BlockEpochEvent, error)
 
 	// Start the ChainNotifier. Once started, the implementation should be
 	// ready, and able to receive notification registrations from clients.

chainntnfs/neutrinonotify/neutrino.go

@@ -20,7 +20,6 @@ import (
 )
 
 const (
-
 	// notifierType uniquely identifies this concrete implementation of the
 	// ChainNotifier interface.
 	notifierType = "neutrino"
@@ -781,6 +780,10 @@ type blockEpochRegistration struct {
 
 	cancelChan chan struct{}
 
+	bestBlock *chainntnfs.BlockEpoch
+
+	errorChan chan error
+
 	wg sync.WaitGroup
 }
 
@@ -790,14 +793,20 @@ type epochCancel struct {
 	epochID uint64
 }
 
-// RegisterBlockEpochNtfn returns a BlockEpochEvent which subscribes the caller
-// to receive notifications, of each new block connected to the main chain.
-func (n *NeutrinoNotifier) RegisterBlockEpochNtfn() (*chainntnfs.BlockEpochEvent, error) {
+// RegisterBlockEpochNtfn returns a BlockEpochEvent which subscribes the
+// caller to receive notifications, of each new block connected to the main
+// chain. Clients have the option of passing in their best known block, which
+// the notifier uses to check if they are behind on blocks and catch them up.
+func (n *NeutrinoNotifier) RegisterBlockEpochNtfn(
+	bestBlock *chainntnfs.BlockEpoch) (*chainntnfs.BlockEpochEvent, error) {
+
 	reg := &blockEpochRegistration{
 		epochQueue: chainntnfs.NewConcurrentQueue(20),
 		epochChan:  make(chan *chainntnfs.BlockEpoch, 20),
 		cancelChan: make(chan struct{}),
 		epochID:    atomic.AddUint64(&n.epochClientCounter, 1),
+		bestBlock:  bestBlock,
+		errorChan:  make(chan error, 1),
 	}
 	reg.epochQueue.Start()