Merge pull request #879 from bhandras/notification-manager-backoff-fixup

notifications: implement incremental backoff for invalid L402 tokens

Author: bhandras

notifications/manager.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/lightninglabs/aperture/l402"
 	"github.com/lightninglabs/loop/swapserverrpc"
+	"github.com/lightningnetwork/lnd/lntypes"
 	"google.golang.org/grpc"
 )
 
@@ -26,6 +27,13 @@ const (
 	NotificationTypeStaticLoopInSweepRequest
 )
 
+const (
+	// defaultMinAliveConnTime is the default minimum time that the
+	// connection to the server needs to be alive before we consider it a
+	// successful connection.
+	defaultMinAliveConnTime = time.Minute
+)
+
 // Client is the interface that the notification manager needs to implement in
 // order to be able to subscribe to notifications.
 type Client interface {
@@ -45,6 +53,10 @@ type Config struct {
 	// CurrentToken returns the token that is currently contained in the
 	// store or an l402.ErrNoToken error if there is none.
 	CurrentToken func() (*l402.Token, error)
+
+	// MinAliveConnTime is the minimum time that the connection to the
+	// server needs to be alive before we consider it a successful.
+	MinAliveConnTime time.Duration
 }
 
 // Manager is a manager for notifications that the swap server sends to the
@@ -60,6 +72,11 @@ type Manager struct {
 
 // NewManager creates a new notification manager.
 func NewManager(cfg *Config) *Manager {
+	// Set the default minimum alive connection time if it's not set.
+	if cfg.MinAliveConnTime == 0 {
+		cfg.MinAliveConnTime = defaultMinAliveConnTime
+	}
+
 	return &Manager{
 		cfg:         cfg,
 		subscribers: make(map[NotificationType][]subscriber),
@@ -128,13 +145,18 @@ func (m *Manager) SubscribeStaticLoopInSweepRequests(ctx context.Context,
 // close the readyChan to signal that the manager is ready.
 func (m *Manager) Run(ctx context.Context) error {
 	// Initially we want to immediately try to connect to the server.
-	waitTime := time.Duration(0)
+	var (
+		waitTime time.Duration
+		backoff  time.Duration
+		attempts int
+	)
 
 	// Start the notification runloop.
 	for {
-		timer := time.NewTimer(waitTime)
 		// Increase the wait time for the next iteration.
-		waitTime += time.Second * 1
+		backoff = waitTime + time.Duration(attempts)*time.Second
+		waitTime = 0
+		timer := time.NewTimer(backoff)
 
 		// Return if the context has been canceled.
 		select {
@@ -145,37 +167,66 @@ func (m *Manager) Run(ctx context.Context) error {
 		}
 
 		// In order to create a valid l402 we first are going to call
-		// the FetchL402 method. As a client might not have outbound capacity
-		// yet, we'll retry until we get a valid response.
+		// the FetchL402 method. As a client might not have outbound
+		// capacity yet, we'll retry until we get a valid response.
 		if !m.hasL402 {
-			_, err := m.cfg.CurrentToken()
+			token, err := m.cfg.CurrentToken()
 			if err != nil {
-				// We only log the error if it's not the case that we
-				// don't have a token yet to avoid spamming the logs.
+				// We only log the error if it's not the case
+				// that we don't have a token yet to avoid
+				// spamming the logs.
 				if err != l402.ErrNoToken {
-					log.Errorf("Error getting L402 from store: %v", err)
+					log.Errorf("Error getting L402 from "+
+						"the store: %v", err)
 				}
 				continue
 			}
-			m.hasL402 = true
-		}
 
-		connectedFunc := func() {
-			// Reset the wait time to 10 seconds.
-			waitTime = time.Second * 10
+			// If the preimage is empty, we don't have a valid L402
+			// yet so we'll continue to retry with the incremental
+			// backoff.
+			emptyPreimage := lntypes.Preimage{}
+			if token.Preimage == emptyPreimage {
+				attempts++
+				continue
+			}
+
+			attempts = 0
+			m.hasL402 = true
 		}
 
-		err := m.subscribeNotifications(ctx, connectedFunc)
+		connectAttempted := time.Now()
+		err := m.subscribeNotifications(ctx)
 		if err != nil {
-			log.Errorf("Error subscribing to notifications: %v", err)
+			log.Errorf("Error subscribing to notifications: %v",
+				err)
+		}
+		connectionAliveTime := time.Since(connectAttempted)
+
+		// Note that we may be able to connet to the stream but not
+		// able to use it if the client is unable to pay for their
+		// L402. In this case the subscription will fail on the first
+		// read immediately after connecting. We'll therefore only
+		// consider the connection successful if we were able to use
+		// the stream for at least the minimum alive connection time
+		// (which defaults to 1 minute).
+		if connectionAliveTime > m.cfg.MinAliveConnTime {
+			// Reset the backoff to 10 seconds and the connect
+			// attempts to zero if we were really connected for a
+			// considerable amount of time (1 minute).
+			waitTime = time.Second * 10
+			attempts = 0
+		} else {
+			// We either failed to connect or the stream
+			// disconnected immediately, so we just increase the
+			// backoff.
+			attempts++
 		}
 	}
 }
 
 // subscribeNotifications subscribes to the notifications from the server.
-func (m *Manager) subscribeNotifications(ctx context.Context,
-	connectedFunc func()) error {
-
+func (m *Manager) subscribeNotifications(ctx context.Context) error {
 	callCtx, cancel := context.WithCancel(ctx)
 	defer cancel()
 
@@ -186,8 +237,6 @@ func (m *Manager) subscribeNotifications(ctx context.Context,
 		return err
 	}
 
-	// Signal that we're connected to the server.
-	connectedFunc()
 	log.Debugf("Successfully subscribed to server notifications")
 
 	for {