channeldb+routing: htlcs are pruned on settle

routing/control_tower.go

@@ -19,6 +19,11 @@ type ControlTower interface {
 	// hash.
 	InitPayment(lntypes.Hash, *channeldb.PaymentCreationInfo) error
 
+	// DeleteFailedAttempts removes all failed HTLCs from the db. It should
+	// be called for a given payment whenever all inflight htlcs are
+	// completed, and the payment has reached a final settled state.
+	DeleteFailedAttempts(lntypes.Hash) error
+
 	// RegisterAttempt atomically records the provided HTLCAttemptInfo.
 	RegisterAttempt(lntypes.Hash, *channeldb.HTLCAttemptInfo) error
 
@@ -125,6 +130,12 @@ func (p *controlTower) InitPayment(paymentHash lntypes.Hash,
 	return p.db.InitPayment(paymentHash, info)
 }
 
+// DeleteFailedAttempts deletes all failed htlcs if the payment was
+// successfully settled.
+func (p *controlTower) DeleteFailedAttempts(paymentHash lntypes.Hash) error {
+	return p.db.DeleteFailedAttempts(paymentHash)
+}
+
 // RegisterAttempt atomically records the provided HTLCAttemptInfo to the
 // DB.
 func (p *controlTower) RegisterAttempt(paymentHash lntypes.Hash,

routing/mock_test.go

@@ -309,6 +309,32 @@ func (m *mockControlTowerOld) InitPayment(phash lntypes.Hash,
 	return nil
 }
 
+func (m *mockControlTowerOld) DeleteFailedAttempts(phash lntypes.Hash) error {
+	p, ok := m.payments[phash]
+	if !ok {
+		return channeldb.ErrPaymentNotInitiated
+	}
+
+	var inFlight bool
+	for _, a := range p.attempts {
+		if a.Settle != nil {
+			continue
+		}
+
+		if a.Failure != nil {
+			continue
+		}
+
+		inFlight = true
+	}
+
+	if inFlight {
+		return channeldb.ErrPaymentInFlight
+	}
+
+	return nil
+}
+
 func (m *mockControlTowerOld) RegisterAttempt(phash lntypes.Hash,
 	a *channeldb.HTLCAttemptInfo) error {
 
@@ -665,6 +691,11 @@ func (m *mockControlTower) InitPayment(phash lntypes.Hash,
 	return args.Error(0)
 }
 
+func (m *mockControlTower) DeleteFailedAttempts(phash lntypes.Hash) error {
+	args := m.Called(phash)
+	return args.Error(0)
+}
+
 func (m *mockControlTower) RegisterAttempt(phash lntypes.Hash,
 	a *channeldb.HTLCAttemptInfo) error {
 

routing/payment_lifecycle.go

@@ -186,9 +186,21 @@ lifecycle:
 			// Find the first successful shard and return
 			// the preimage and route.
 			for _, a := range payment.HTLCs {
-				if a.Settle != nil {
-					return a.Settle.Preimage, &a.Route, nil
+				if a.Settle == nil {
+					continue
 				}
+
+				err := p.router.cfg.Control.
+					DeleteFailedAttempts(
+						p.identifier)
+				if err != nil {
+					log.Errorf("Error deleting failed "+
+						"payment attempts for "+
+						"payment %v: %v", p.identifier,
+						err)
+				}
+
+				return a.Settle.Preimage, &a.Route, nil
 			}
 
 			// Payment failed.

routing/router_test.go

@@ -3571,6 +3571,7 @@ func TestSendMPPaymentSucceed(t *testing.T) {
 			}
 		}
 	})
+	controlTower.On("DeleteFailedAttempts", identifier).Return(nil)
 
 	// Call the actual method SendPayment on router. This is place inside a
 	// goroutine so we can set a timeout for the whole test, in case
@@ -3782,6 +3783,7 @@ func TestSendMPPaymentSucceedOnExtraShards(t *testing.T) {
 			return
 		}
 	})
+	controlTower.On("DeleteFailedAttempts", identifier).Return(nil)
 
 	// Call the actual method SendPayment on router. This is place inside a
 	// goroutine so we can set a timeout for the whole test, in case