298 lines
9.4 KiB
Go
298 lines
9.4 KiB
Go
package routing
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import (
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"sync"
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"github.com/lightningnetwork/lnd/channeldb"
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"github.com/lightningnetwork/lnd/lntypes"
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"github.com/lightningnetwork/lnd/multimutex"
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"github.com/lightningnetwork/lnd/queue"
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)
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// ControlTower tracks all outgoing payments made, whose primary purpose is to
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// prevent duplicate payments to the same payment hash. In production, a
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// persistent implementation is preferred so that tracking can survive across
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// restarts. Payments are transitioned through various payment states, and the
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// ControlTower interface provides access to driving the state transitions.
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type ControlTower interface {
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// This method checks that no suceeded payment exist for this payment
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// hash.
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InitPayment(lntypes.Hash, *channeldb.PaymentCreationInfo) error
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// RegisterAttempt atomically records the provided HTLCAttemptInfo.
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RegisterAttempt(lntypes.Hash, *channeldb.HTLCAttemptInfo) error
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// SettleAttempt marks the given attempt settled with the preimage. If
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// this is a multi shard payment, this might implicitly mean the the
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// full payment succeeded.
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//
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// After invoking this method, InitPayment should always return an
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// error to prevent us from making duplicate payments to the same
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// payment hash. The provided preimage is atomically saved to the DB
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// for record keeping.
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SettleAttempt(lntypes.Hash, uint64, *channeldb.HTLCSettleInfo) (
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*channeldb.HTLCAttempt, error)
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// FailAttempt marks the given payment attempt failed.
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FailAttempt(lntypes.Hash, uint64, *channeldb.HTLCFailInfo) (
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*channeldb.HTLCAttempt, error)
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// FetchPayment fetches the payment corresponding to the given payment
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// hash.
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FetchPayment(paymentHash lntypes.Hash) (*channeldb.MPPayment, error)
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// Fail transitions a payment into the Failed state, and records the
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// ultimate reason the payment failed. Note that this should only be
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// called when all active active attempts are already failed. After
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// invoking this method, InitPayment should return nil on its next call
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// for this payment hash, allowing the user to make a subsequent
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// payment.
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Fail(lntypes.Hash, channeldb.FailureReason) error
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// FetchInFlightPayments returns all payments with status InFlight.
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FetchInFlightPayments() ([]*channeldb.MPPayment, error)
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// SubscribePayment subscribes to updates for the payment with the given
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// hash. A first update with the current state of the payment is always
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// sent out immediately.
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SubscribePayment(paymentHash lntypes.Hash) (*ControlTowerSubscriber,
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error)
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}
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// ControlTowerSubscriber contains the state for a payment update subscriber.
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type ControlTowerSubscriber struct {
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// Updates is the channel over which *channeldb.MPPayment updates can be
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// received.
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Updates <-chan interface{}
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queue *queue.ConcurrentQueue
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quit chan struct{}
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}
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// newControlTowerSubscriber instantiates a new subscriber state object.
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func newControlTowerSubscriber() *ControlTowerSubscriber {
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// Create a queue for payment updates.
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queue := queue.NewConcurrentQueue(20)
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queue.Start()
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return &ControlTowerSubscriber{
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Updates: queue.ChanOut(),
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queue: queue,
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quit: make(chan struct{}),
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}
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}
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// Close signals that the subscriber is no longer interested in updates.
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func (s *ControlTowerSubscriber) Close() {
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// Close quit channel so that any pending writes to the queue are
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// cancelled.
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close(s.quit)
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// Stop the queue goroutine so that it won't leak.
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s.queue.Stop()
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}
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// controlTower is persistent implementation of ControlTower to restrict
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// double payment sending.
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type controlTower struct {
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db *channeldb.PaymentControl
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subscribers map[lntypes.Hash][]*ControlTowerSubscriber
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subscribersMtx sync.Mutex
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// paymentsMtx provides synchronization on the payment level to ensure
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// that no race conditions occur in between updating the database and
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// sending a notification.
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paymentsMtx *multimutex.HashMutex
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}
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// NewControlTower creates a new instance of the controlTower.
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func NewControlTower(db *channeldb.PaymentControl) ControlTower {
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return &controlTower{
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db: db,
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subscribers: make(map[lntypes.Hash][]*ControlTowerSubscriber),
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paymentsMtx: multimutex.NewHashMutex(),
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}
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}
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// InitPayment checks or records the given PaymentCreationInfo with the DB,
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// making sure it does not already exist as an in-flight payment. Then this
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// method returns successfully, the payment is guranteeed to be in the InFlight
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// state.
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func (p *controlTower) InitPayment(paymentHash lntypes.Hash,
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info *channeldb.PaymentCreationInfo) error {
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return p.db.InitPayment(paymentHash, info)
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}
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// RegisterAttempt atomically records the provided HTLCAttemptInfo to the
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// DB.
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func (p *controlTower) RegisterAttempt(paymentHash lntypes.Hash,
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attempt *channeldb.HTLCAttemptInfo) error {
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p.paymentsMtx.Lock(paymentHash)
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defer p.paymentsMtx.Unlock(paymentHash)
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payment, err := p.db.RegisterAttempt(paymentHash, attempt)
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if err != nil {
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return err
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}
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// Notify subscribers of the attempt registration.
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p.notifySubscribers(paymentHash, payment)
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return nil
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}
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// SettleAttempt marks the given attempt settled with the preimage. If
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// this is a multi shard payment, this might implicitly mean the the
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// full payment succeeded.
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func (p *controlTower) SettleAttempt(paymentHash lntypes.Hash,
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attemptID uint64, settleInfo *channeldb.HTLCSettleInfo) (
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*channeldb.HTLCAttempt, error) {
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p.paymentsMtx.Lock(paymentHash)
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defer p.paymentsMtx.Unlock(paymentHash)
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payment, err := p.db.SettleAttempt(paymentHash, attemptID, settleInfo)
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if err != nil {
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return nil, err
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}
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// Notify subscribers of success event.
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p.notifySubscribers(paymentHash, payment)
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return payment.GetAttempt(attemptID)
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}
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// FailAttempt marks the given payment attempt failed.
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func (p *controlTower) FailAttempt(paymentHash lntypes.Hash,
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attemptID uint64, failInfo *channeldb.HTLCFailInfo) (
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*channeldb.HTLCAttempt, error) {
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p.paymentsMtx.Lock(paymentHash)
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defer p.paymentsMtx.Unlock(paymentHash)
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payment, err := p.db.FailAttempt(paymentHash, attemptID, failInfo)
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if err != nil {
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return nil, err
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}
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// Notify subscribers of failed attempt.
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p.notifySubscribers(paymentHash, payment)
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return payment.GetAttempt(attemptID)
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}
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// FetchPayment fetches the payment corresponding to the given payment hash.
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func (p *controlTower) FetchPayment(paymentHash lntypes.Hash) (
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*channeldb.MPPayment, error) {
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return p.db.FetchPayment(paymentHash)
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}
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// Fail transitions a payment into the Failed state, and records the reason the
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// payment failed. After invoking this method, InitPayment should return nil on
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// its next call for this payment hash, allowing the switch to make a
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// subsequent payment.
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func (p *controlTower) Fail(paymentHash lntypes.Hash,
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reason channeldb.FailureReason) error {
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p.paymentsMtx.Lock(paymentHash)
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defer p.paymentsMtx.Unlock(paymentHash)
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payment, err := p.db.Fail(paymentHash, reason)
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if err != nil {
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return err
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}
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// Notify subscribers of fail event.
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p.notifySubscribers(paymentHash, payment)
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return nil
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}
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// FetchInFlightPayments returns all payments with status InFlight.
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func (p *controlTower) FetchInFlightPayments() ([]*channeldb.MPPayment, error) {
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return p.db.FetchInFlightPayments()
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}
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// SubscribePayment subscribes to updates for the payment with the given hash. A
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// first update with the current state of the payment is always sent out
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// immediately.
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func (p *controlTower) SubscribePayment(paymentHash lntypes.Hash) (
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*ControlTowerSubscriber, error) {
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// Take lock before querying the db to prevent missing or duplicating an
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// update.
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p.paymentsMtx.Lock(paymentHash)
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defer p.paymentsMtx.Unlock(paymentHash)
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payment, err := p.db.FetchPayment(paymentHash)
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if err != nil {
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return nil, err
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}
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subscriber := newControlTowerSubscriber()
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// Always write current payment state to the channel.
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subscriber.queue.ChanIn() <- payment
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// Payment is currently in flight. Register this subscriber for further
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// updates. Otherwise this update is the final update and the incoming
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// channel can be closed. This will close the queue's outgoing channel
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// when all updates have been written.
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if payment.Status == channeldb.StatusInFlight {
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p.subscribersMtx.Lock()
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p.subscribers[paymentHash] = append(
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p.subscribers[paymentHash], subscriber,
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)
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p.subscribersMtx.Unlock()
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} else {
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close(subscriber.queue.ChanIn())
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}
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return subscriber, nil
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}
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// notifySubscribers sends a final payment event to all subscribers of this
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// payment. The channel will be closed after this. Note that this function must
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// be executed atomically (by means of a lock) with the database update to
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// guarantuee consistency of the notifications.
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func (p *controlTower) notifySubscribers(paymentHash lntypes.Hash,
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event *channeldb.MPPayment) {
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// Get all subscribers for this payment.
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p.subscribersMtx.Lock()
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list, ok := p.subscribers[paymentHash]
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if !ok {
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p.subscribersMtx.Unlock()
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return
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}
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// If the payment reached a terminal state, the subscriber list can be
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// cleared. There won't be any more updates.
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terminal := event.Status != channeldb.StatusInFlight
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if terminal {
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delete(p.subscribers, paymentHash)
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}
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p.subscribersMtx.Unlock()
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// Notify all subscribers of the event.
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for _, subscriber := range list {
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select {
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case subscriber.queue.ChanIn() <- event:
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// If this event is the last, close the incoming channel
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// of the queue. This will signal the subscriber that
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// there won't be any more updates.
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if terminal {
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close(subscriber.queue.ChanIn())
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}
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// If subscriber disappeared, skip notification. For further
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// notifications, we'll keep skipping over this subscriber.
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case <-subscriber.quit:
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}
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}
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}
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