Ensure chain notifier is started before accessed.

The use case comes from the RPC layer that is ready before the
chain notifier which is used in the sub server.

chainntnfs/bitcoindnotify/bitcoind.go

@@ -35,6 +35,7 @@ type BitcoindNotifier struct {
 	epochClientCounter uint64 // To be used atomically.
 
 	start   sync.Once
+	active  int32 // To be used atomically.
 	stopped int32 // To be used atomically.
 
 	chainConn   *chain.BitcoindClient
@@ -130,6 +131,11 @@ func (b *BitcoindNotifier) Stop() error {
 	return nil
 }
 
+// Started returns true if this instance has been started, and false otherwise.
+func (b *BitcoindNotifier) Started() bool {
+	return atomic.LoadInt32(&b.active) != 0
+}
+
 func (b *BitcoindNotifier) startNotifier() error {
 	// Connect to bitcoind, and register for notifications on connected,
 	// and disconnected blocks.
@@ -158,6 +164,10 @@ func (b *BitcoindNotifier) startNotifier() error {
 	b.wg.Add(1)
 	go b.notificationDispatcher()
 
+	// Set the active flag now that we've completed the full
+	// startup.
+	atomic.StoreInt32(&b.active, 1)
+
 	return nil
 }
 

chainntnfs/btcdnotify/btcd.go

@@ -54,6 +54,7 @@ type BtcdNotifier struct {
 	epochClientCounter uint64 // To be used atomically.
 
 	start   sync.Once
+	active  int32 // To be used atomically.
 	stopped int32 // To be used atomically.
 
 	chainConn   *rpcclient.Client
@@ -141,6 +142,11 @@ func (b *BtcdNotifier) Start() error {
 	return startErr
 }
 
+// Started returns true if this instance has been started, and false otherwise.
+func (b *BtcdNotifier) Started() bool {
+	return atomic.LoadInt32(&b.active) != 0
+}
+
 // Stop shutsdown the BtcdNotifier.
 func (b *BtcdNotifier) Stop() error {
 	// Already shutting down?
@@ -212,6 +218,10 @@ func (b *BtcdNotifier) startNotifier() error {
 	b.wg.Add(1)
 	go b.notificationDispatcher()
 
+	// Set the active flag now that we've completed the full
+	// startup.
+	atomic.StoreInt32(&b.active, 1)
+
 	return nil
 }
 

chainntnfs/interface.go

@@ -139,6 +139,9 @@ type ChainNotifier interface {
 	// ready, and able to receive notification registrations from clients.
 	Start() error
 
+	// Started returns true if this instance has been started, and false otherwise.
+	Started() bool
+
 	// Stops the concrete ChainNotifier. Once stopped, the ChainNotifier
 	// should disallow any future requests from potential clients.
 	// Additionally, all pending client notifications will be canceled

chainntnfs/neutrinonotify/neutrino.go

@@ -40,6 +40,7 @@ type NeutrinoNotifier struct {
 	epochClientCounter uint64 // To be used atomically.
 
 	start   sync.Once
+	active  int32 // To be used atomically.
 	stopped int32 // To be used atomically.
 
 	bestBlockMtx sync.RWMutex
@@ -144,6 +145,11 @@ func (n *NeutrinoNotifier) Stop() error {
 	return nil
 }
 
+// Started returns true if this instance has been started, and false otherwise.
+func (n *NeutrinoNotifier) Started() bool {
+	return atomic.LoadInt32(&n.active) != 0
+}
+
 func (n *NeutrinoNotifier) startNotifier() error {
 	// Start our concurrent queues before starting the rescan, to ensure
 	// onFilteredBlockConnected and onRelavantTx callbacks won't be
@@ -200,6 +206,10 @@ func (n *NeutrinoNotifier) startNotifier() error {
 	n.wg.Add(1)
 	go n.notificationDispatcher()
 
+	// Set the active flag now that we've completed the full
+	// startup.
+	atomic.StoreInt32(&n.active, 1)
+
 	return nil
 }
 

contractcourt/chain_watcher_test.go

@@ -43,6 +43,10 @@ func (m *mockNotifier) Start() error {
 	return nil
 }
 
+func (m *mockNotifier) Started() bool {
+	return true
+}
+
 func (m *mockNotifier) Stop() error {
 	return nil
 }

discovery/gossiper_test.go

@@ -453,6 +453,10 @@ func (m *mockNotifier) Start() error {
 	return nil
 }
 
+func (m *mockNotifier) Started() bool {
+	return true
+}
+
 func (m *mockNotifier) Stop() error {
 	return nil
 }

fundingmanager_test.go

@@ -131,6 +131,10 @@ func (m *mockNotifier) Start() error {
 	return nil
 }
 
+func (m *mockNotifier) Started() bool {
+	return true
+}
+
 func (m *mockNotifier) Stop() error {
 	return nil
 }

htlcswitch/mock.go

@@ -931,6 +931,10 @@ func (m *mockNotifier) Start() error {
 	return nil
 }
 
+func (m *mockNotifier) Started() bool {
+	return true
+}
+
 func (m *mockNotifier) Stop() error {
 	return nil
 }

lnrpc/chainrpc/chainnotifier_server.go

@@ -63,6 +63,11 @@ var (
 	// has been shut down.
 	ErrChainNotifierServerShuttingDown = errors.New("chain notifier RPC " +
 		"subserver shutting down")
+
+	// ErrChainNotifierServerNotActive indicates that the chain notifier hasn't
+	// finished the startup process.
+	ErrChainNotifierServerNotActive = errors.New("chain notifier RPC is" +
+		"still in the process of starting")
 )
 
 // fileExists reports whether the named file or directory exists.
@@ -196,6 +201,10 @@ func (s *Server) RegisterWithRootServer(grpcServer *grpc.Server) error {
 func (s *Server) RegisterConfirmationsNtfn(in *ConfRequest,
 	confStream ChainNotifier_RegisterConfirmationsNtfnServer) error {
 
+	if !s.cfg.ChainNotifier.Started() {
+		return ErrChainNotifierServerNotActive
+	}
+
 	// We'll start by reconstructing the RPC request into what the
 	// underlying ChainNotifier expects.
 	var txid chainhash.Hash
@@ -292,6 +301,10 @@ func (s *Server) RegisterConfirmationsNtfn(in *ConfRequest,
 func (s *Server) RegisterSpendNtfn(in *SpendRequest,
 	spendStream ChainNotifier_RegisterSpendNtfnServer) error {
 
+	if !s.cfg.ChainNotifier.Started() {
+		return ErrChainNotifierServerNotActive
+	}
+
 	// We'll start by reconstructing the RPC request into what the
 	// underlying ChainNotifier expects.
 	var op *wire.OutPoint
@@ -399,6 +412,10 @@ func (s *Server) RegisterSpendNtfn(in *SpendRequest,
 func (s *Server) RegisterBlockEpochNtfn(in *BlockEpoch,
 	epochStream ChainNotifier_RegisterBlockEpochNtfnServer) error {
 
+	if !s.cfg.ChainNotifier.Started() {
+		return ErrChainNotifierServerNotActive
+	}
+
 	// We'll start by reconstructing the RPC request into what the
 	// underlying ChainNotifier expects.
 	var hash chainhash.Hash

mock.go

@@ -112,6 +112,10 @@ func (m *mockNotfier) Start() error {
 	return nil
 }
 
+func (m *mockNotfier) Started() bool {
+	return true
+}
+
 func (m *mockNotfier) Stop() error {
 	return nil
 }

sweep/test_utils.go

@@ -200,6 +200,11 @@ func (m *MockNotifier) Start() error {
 	return nil
 }
 
+// Started checks if started
+func (m *MockNotifier) Started() bool {
+	return true
+}
+
 // Stop the notifier.
 func (m *MockNotifier) Stop() error {
 	return nil