13412100018

Committed 19 Feb 2025 12:05PM UTC coverage: 44.914% (-13.9%) from 58.794%

Build # 13412100018

Build Type

Pull #9521

github

Committed by

web-flow

Commit Message

Merge 861d6970e into 0e8786348

Pull Request Pull Request #9521: unit: remove GOACC, use Go 1.20 native coverage functionality

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69.68

/graph/builder.go

package graph

import (
        "fmt"
        "sync"
        "sync/atomic"
        "time"

        "github.com/btcsuite/btcd/btcec/v2"
        "github.com/btcsuite/btcd/wire"
        "github.com/go-errors/errors"
        "github.com/lightningnetwork/lnd/batch"
        "github.com/lightningnetwork/lnd/chainntnfs"
        graphdb "github.com/lightningnetwork/lnd/graph/db"
        "github.com/lightningnetwork/lnd/graph/db/models"
        "github.com/lightningnetwork/lnd/kvdb"
        "github.com/lightningnetwork/lnd/lnutils"
        "github.com/lightningnetwork/lnd/lnwallet"
        "github.com/lightningnetwork/lnd/lnwire"
        "github.com/lightningnetwork/lnd/multimutex"
        "github.com/lightningnetwork/lnd/netann"
        "github.com/lightningnetwork/lnd/routing/chainview"
        "github.com/lightningnetwork/lnd/routing/route"
        "github.com/lightningnetwork/lnd/ticker"
)

const (
        // DefaultChannelPruneExpiry is the default duration used to determine
        // if a channel should be pruned or not.
        DefaultChannelPruneExpiry = time.Hour * 24 * 14

        // DefaultFirstTimePruneDelay is the time we'll wait after startup
        // before attempting to prune the graph for zombie channels. We don't
        // do it immediately after startup to allow lnd to start up without
        // getting blocked by this job.
        DefaultFirstTimePruneDelay = 30 * time.Second

        // defaultStatInterval governs how often the router will log non-empty
        // stats related to processing new channels, updates, or node
        // announcements.
        defaultStatInterval = time.Minute
)

var (
        // ErrGraphBuilderShuttingDown is returned if the graph builder is in
        // the process of shutting down.
        ErrGraphBuilderShuttingDown = fmt.Errorf("graph builder shutting down")
)

// Config holds the configuration required by the Builder.
type Config struct {
        // SelfNode is the public key of the node that this channel router
        // belongs to.
        SelfNode route.Vertex

        // Graph is the channel graph that the ChannelRouter will use to gather
        // metrics from and also to carry out path finding queries.
        Graph DB

        // Chain is the router's source to the most up-to-date blockchain data.
        // All incoming advertised channels will be checked against the chain
        // to ensure that the channels advertised are still open.
        Chain lnwallet.BlockChainIO

        // ChainView is an instance of a FilteredChainView which is used to
        // watch the sub-set of the UTXO set (the set of active channels) that
        // we need in order to properly maintain the channel graph.
        ChainView chainview.FilteredChainView

        // Notifier is a reference to the ChainNotifier, used to grab
        // the latest blocks if the router is missing any.
        Notifier chainntnfs.ChainNotifier

        // ChannelPruneExpiry is the duration used to determine if a channel
        // should be pruned or not. If the delta between now and when the
        // channel was last updated is greater than ChannelPruneExpiry, then
        // the channel is marked as a zombie channel eligible for pruning.
        ChannelPruneExpiry time.Duration

        // GraphPruneInterval is used as an interval to determine how often we
        // should examine the channel graph to garbage collect zombie channels.
        GraphPruneInterval time.Duration

        // FirstTimePruneDelay is the time we'll wait after startup before
        // attempting to prune the graph for zombie channels. We don't do it
        // immediately after startup to allow lnd to start up without getting
        // blocked by this job.
        FirstTimePruneDelay time.Duration

        // AssumeChannelValid toggles whether the builder will prune channels
        // based on their spentness vs using the fact that they are considered
        // zombies.
        AssumeChannelValid bool

        // StrictZombiePruning determines if we attempt to prune zombie
        // channels according to a stricter criteria. If true, then we'll prune
        // a channel if only *one* of the edges is considered a zombie.
        // Otherwise, we'll only prune the channel when both edges have a very
        // dated last update.
        StrictZombiePruning bool

        // IsAlias returns whether a passed ShortChannelID is an alias. This is
        // only used for our local channels.
        IsAlias func(scid lnwire.ShortChannelID) bool
}

// Builder builds and maintains a view of the Lightning Network graph.
type Builder struct {
        started atomic.Bool
        stopped atomic.Bool

        ntfnClientCounter atomic.Uint64
        bestHeight        atomic.Uint32

        cfg *Config

        // newBlocks is a channel in which new blocks connected to the end of
        // the main chain are sent over, and blocks updated after a call to
        // UpdateFilter.
        newBlocks <-chan *chainview.FilteredBlock

        // staleBlocks is a channel in which blocks disconnected from the end
        // of our currently known best chain are sent over.
        staleBlocks <-chan *chainview.FilteredBlock

        // networkUpdates is a channel that carries new topology updates
        // messages from outside the Builder to be processed by the
        // networkHandler.
        networkUpdates chan *routingMsg

        // topologyClients maps a client's unique notification ID to a
        // topologyClient client that contains its notification dispatch
        // channel.
        topologyClients *lnutils.SyncMap[uint64, *topologyClient]

        // ntfnClientUpdates is a channel that's used to send new updates to
        // topology notification clients to the Builder. Updates either
        // add a new notification client, or cancel notifications for an
        // existing client.
        ntfnClientUpdates chan *topologyClientUpdate

        // channelEdgeMtx is a mutex we use to make sure we process only one
        // ChannelEdgePolicy at a time for a given channelID, to ensure
        // consistency between the various database accesses.
        channelEdgeMtx *multimutex.Mutex[uint64]

        // statTicker is a resumable ticker that logs the router's progress as
        // it discovers channels or receives updates.
        statTicker ticker.Ticker

        // stats tracks newly processed channels, updates, and node
        // announcements over a window of defaultStatInterval.
        stats *builderStats

        quit chan struct{}
        wg   sync.WaitGroup
}

// A compile time check to ensure Builder implements the
// ChannelGraphSource interface.
var _ ChannelGraphSource = (*Builder)(nil)

// NewBuilder constructs a new Builder.
func NewBuilder(cfg *Config) (*Builder, error) {
        return &Builder{
                cfg:               cfg,
                networkUpdates:    make(chan *routingMsg),
                topologyClients:   &lnutils.SyncMap[uint64, *topologyClient]{},
                ntfnClientUpdates: make(chan *topologyClientUpdate),
                channelEdgeMtx:    multimutex.NewMutex[uint64](),
                statTicker:        ticker.New(defaultStatInterval),
                stats:             new(builderStats),
                quit:              make(chan struct{}),
        }, nil
}

// Start launches all the goroutines the Builder requires to carry out its
// duties. If the builder has already been started, then this method is a noop.
func (b *Builder) Start() error {
        if !b.started.CompareAndSwap(false, true) {
                return nil
        }

        log.Info("Builder starting")

        bestHash, bestHeight, err := b.cfg.Chain.GetBestBlock()
        if err != nil {
                return err
        }

        // If the graph has never been pruned, or hasn't fully been created yet,
        // then we don't treat this as an explicit error.
        if _, _, err := b.cfg.Graph.PruneTip(); err != nil {
                switch {
                case errors.Is(err, graphdb.ErrGraphNeverPruned):
                        fallthrough

                case errors.Is(err, graphdb.ErrGraphNotFound):
                        // If the graph has never been pruned, then we'll set
                        // the prune height to the current best height of the
                        // chain backend.
                        _, err = b.cfg.Graph.PruneGraph(
                                nil, bestHash, uint32(bestHeight),
                        )
                        if err != nil {
                                return err
                        }

                default:
                        return err
                }
        }

        // If AssumeChannelValid is present, then we won't rely on pruning
        // channels from the graph based on their spentness, but whether they
        // are considered zombies or not. We will start zombie pruning after a
        // small delay, to avoid slowing down startup of lnd.
        if b.cfg.AssumeChannelValid { //nolint:nestif
                time.AfterFunc(b.cfg.FirstTimePruneDelay, func() {
                        select {
                        case <-b.quit:
                                return
                        default:
                        }

                        log.Info("Initial zombie prune starting")
                        if err := b.pruneZombieChans(); err != nil {
                                log.Errorf("Unable to prune zombies: %v", err)
                        }
                })
        } else {
                // Otherwise, we'll use our filtered chain view to prune
                // channels as soon as they are detected as spent on-chain.
                if err := b.cfg.ChainView.Start(); err != nil {
                        return err
                }

                // Once the instance is active, we'll fetch the channel we'll
                // receive notifications over.
                b.newBlocks = b.cfg.ChainView.FilteredBlocks()
                b.staleBlocks = b.cfg.ChainView.DisconnectedBlocks()

                // Before we perform our manual block pruning, we'll construct
                // and apply a fresh chain filter to the active
                // FilteredChainView instance.  We do this before, as otherwise
                // we may miss on-chain events as the filter hasn't properly
                // been applied.
                channelView, err := b.cfg.Graph.ChannelView()
                if err != nil && !errors.Is(
                        err, graphdb.ErrGraphNoEdgesFound,
                ) {

                        return err
                }

                log.Infof("Filtering chain using %v channels active",
                        len(channelView))

                if len(channelView) != 0 {
                        err = b.cfg.ChainView.UpdateFilter(
                                channelView, uint32(bestHeight),
                        )
                        if err != nil {
                                return err
                        }
                }

                // The graph pruning might have taken a while and there could be
                // new blocks available.
                _, bestHeight, err = b.cfg.Chain.GetBestBlock()
                if err != nil {
                        return err
                }
                b.bestHeight.Store(uint32(bestHeight))

                // Before we begin normal operation of the router, we first need
                // to synchronize the channel graph to the latest state of the
                // UTXO set.
                if err := b.syncGraphWithChain(); err != nil {
                        return err
                }

                // Finally, before we proceed, we'll prune any unconnected nodes
                // from the graph in order to ensure we maintain a tight graph
                // of "useful" nodes.
                err = b.cfg.Graph.PruneGraphNodes()
                if err != nil &&
                        !errors.Is(err, graphdb.ErrGraphNodesNotFound) {

                        return err
                }
        }

        b.wg.Add(1)
        go b.networkHandler()

        log.Debug("Builder started")

        return nil
}

// Stop signals to the Builder that it should halt all routines. This method
// will *block* until all goroutines have excited. If the builder has already
// stopped then this method will return immediately.
func (b *Builder) Stop() error {
        if !b.stopped.CompareAndSwap(false, true) {
                return nil
        }

        log.Info("Builder shutting down...")

        // Our filtered chain view could've only been started if
        // AssumeChannelValid isn't present.
        if !b.cfg.AssumeChannelValid {
                if err := b.cfg.ChainView.Stop(); err != nil {
                        return err
                }
        }

        close(b.quit)
        b.wg.Wait()

        log.Debug("Builder shutdown complete")

        return nil
}

// syncGraphWithChain attempts to synchronize the current channel graph with
// the latest UTXO set state. This process involves pruning from the channel
// graph any channels which have been closed by spending their funding output
// since we've been down.
func (b *Builder) syncGraphWithChain() error {
        // First, we'll need to check to see if we're already in sync with the
        // latest state of the UTXO set.
        bestHash, bestHeight, err := b.cfg.Chain.GetBestBlock()
        if err != nil {
                return err
        }
        b.bestHeight.Store(uint32(bestHeight))

        pruneHash, pruneHeight, err := b.cfg.Graph.PruneTip()
        if err != nil {
                switch {
                // If the graph has never been pruned, or hasn't fully been
                // created yet, then we don't treat this as an explicit error.
                case errors.Is(err, graphdb.ErrGraphNeverPruned):
                case errors.Is(err, graphdb.ErrGraphNotFound):
                default:
                        return err
                }
        }

        log.Infof("Prune tip for Channel Graph: height=%v, hash=%v",
                pruneHeight, pruneHash)

        switch {
        // If the graph has never been pruned, then we can exit early as this
        // entails it's being created for the first time and hasn't seen any
        // block or created channels.
        case pruneHeight == 0 || pruneHash == nil:
                return nil

        // If the block hashes and heights match exactly, then we don't need to
        // prune the channel graph as we're already fully in sync.
        case bestHash.IsEqual(pruneHash) && uint32(bestHeight) == pruneHeight:
                return nil
        }

        // If the main chain blockhash at prune height is different from the
        // prune hash, this might indicate the database is on a stale branch.
        mainBlockHash, err := b.cfg.Chain.GetBlockHash(int64(pruneHeight))
        if err != nil {
                return err
        }

        // While we are on a stale branch of the chain, walk backwards to find
        // first common block.
        for !pruneHash.IsEqual(mainBlockHash) {
                log.Infof("channel graph is stale. Disconnecting block %v "+
                        "(hash=%v)", pruneHeight, pruneHash)
                // Prune the graph for every channel that was opened at height
                // >= pruneHeight.
                _, err := b.cfg.Graph.DisconnectBlockAtHeight(pruneHeight)
                if err != nil {
                        return err
                }

                pruneHash, pruneHeight, err = b.cfg.Graph.PruneTip()
                switch {
                // If at this point the graph has never been pruned, we can exit
                // as this entails we are back to the point where it hasn't seen
                // any block or created channels, alas there's nothing left to
                // prune.
                case errors.Is(err, graphdb.ErrGraphNeverPruned):
                        return nil

                case errors.Is(err, graphdb.ErrGraphNotFound):
                        return nil

                case err != nil:
                        return err

                default:
                }

                mainBlockHash, err = b.cfg.Chain.GetBlockHash(
                        int64(pruneHeight),
                )
                if err != nil {
                        return err
                }
        }

        log.Infof("Syncing channel graph from height=%v (hash=%v) to "+
                "height=%v (hash=%v)", pruneHeight, pruneHash, bestHeight,
                bestHash)

        // If we're not yet caught up, then we'll walk forward in the chain
        // pruning the channel graph with each new block that hasn't yet been
        // consumed by the channel graph.
        var spentOutputs []*wire.OutPoint
        for nextHeight := pruneHeight + 1; nextHeight <= uint32(bestHeight); nextHeight++ { //nolint:ll
                // Break out of the rescan early if a shutdown has been
                // requested, otherwise long rescans will block the daemon from
                // shutting down promptly.
                select {
                case <-b.quit:
                        return ErrGraphBuilderShuttingDown
                default:
                }

                // Using the next height, request a manual block pruning from
                // the chainview for the particular block hash.
                log.Infof("Filtering block for closed channels, at height: %v",
                        int64(nextHeight))
                nextHash, err := b.cfg.Chain.GetBlockHash(int64(nextHeight))
                if err != nil {
                        return err
                }
                log.Tracef("Running block filter on block with hash: %v",
                        nextHash)
                filterBlock, err := b.cfg.ChainView.FilterBlock(nextHash)
                if err != nil {
                        return err
                }

                // We're only interested in all prior outputs that have been
                // spent in the block, so collate all the referenced previous
                // outpoints within each tx and input.
                for _, tx := range filterBlock.Transactions {
                        for _, txIn := range tx.TxIn {
                                spentOutputs = append(spentOutputs,
                                        &txIn.PreviousOutPoint)
                        }
                }
        }

        // With the spent outputs gathered, attempt to prune the channel graph,
        // also passing in the best hash+height so the prune tip can be updated.
        closedChans, err := b.cfg.Graph.PruneGraph(
                spentOutputs, bestHash, uint32(bestHeight),
        )
        if err != nil {
                return err
        }

        log.Infof("Graph pruning complete: %v channels were closed since "+
                "height %v", len(closedChans), pruneHeight)

        return nil
}

// isZombieChannel takes two edge policy updates and determines if the
// corresponding channel should be considered a zombie. The first boolean is
// true if the policy update from node 1 is considered a zombie, the second
// boolean is that of node 2, and the final boolean is true if the channel
// is considered a zombie.
func (b *Builder) isZombieChannel(e1,
        e2 *models.ChannelEdgePolicy) (bool, bool, bool) {

        chanExpiry := b.cfg.ChannelPruneExpiry

        e1Zombie := e1 == nil || time.Since(e1.LastUpdate) >= chanExpiry
        e2Zombie := e2 == nil || time.Since(e2.LastUpdate) >= chanExpiry

        var e1Time, e2Time time.Time
        if e1 != nil {
                e1Time = e1.LastUpdate
        }
        if e2 != nil {
                e2Time = e2.LastUpdate
        }

        return e1Zombie, e2Zombie, b.IsZombieChannel(e1Time, e2Time)
}

// IsZombieChannel takes the timestamps of the latest channel updates for a
// channel and returns true if the channel should be considered a zombie based
// on these timestamps.
func (b *Builder) IsZombieChannel(updateTime1,
        updateTime2 time.Time) bool {

        chanExpiry := b.cfg.ChannelPruneExpiry

        e1Zombie := updateTime1.IsZero() ||
                time.Since(updateTime1) >= chanExpiry

        e2Zombie := updateTime2.IsZero() ||
                time.Since(updateTime2) >= chanExpiry

        // If we're using strict zombie pruning, then a channel is only
        // considered live if both edges have a recent update we know of.
        if b.cfg.StrictZombiePruning {
                return e1Zombie || e2Zombie
        }

        // Otherwise, if we're using the less strict variant, then a channel is
        // considered live if either of the edges have a recent update.
        return e1Zombie && e2Zombie
}

// pruneZombieChans is a method that will be called periodically to prune out
// any "zombie" channels. We consider channels zombies if *both* edges haven't
// been updated since our zombie horizon. If AssumeChannelValid is present,
// we'll also consider channels zombies if *both* edges are disabled. This
// usually signals that a channel has been closed on-chain. We do this
// periodically to keep a healthy, lively routing table.
func (b *Builder) pruneZombieChans() error {
        chansToPrune := make(map[uint64]struct{})
        chanExpiry := b.cfg.ChannelPruneExpiry

        log.Infof("Examining channel graph for zombie channels")

        // A helper method to detect if the channel belongs to this node
        isSelfChannelEdge := func(info *models.ChannelEdgeInfo) bool {
                return info.NodeKey1Bytes == b.cfg.SelfNode ||
                        info.NodeKey2Bytes == b.cfg.SelfNode
        }

        // First, we'll collect all the channels which are eligible for garbage
        // collection due to being zombies.
        filterPruneChans := func(info *models.ChannelEdgeInfo,
                e1, e2 *models.ChannelEdgePolicy) error {

                // Exit early in case this channel is already marked to be
                // pruned
                _, markedToPrune := chansToPrune[info.ChannelID]
                if markedToPrune {
                        return nil
                }

                // We'll ensure that we don't attempt to prune our *own*
                // channels from the graph, as in any case this should be
                // re-advertised by the sub-system above us.
                if isSelfChannelEdge(info) {
                        return nil
                }

                e1Zombie, e2Zombie, isZombieChan := b.isZombieChannel(e1, e2)

                if e1Zombie {
                        log.Tracef("Node1 pubkey=%x of chan_id=%v is zombie",
                                info.NodeKey1Bytes, info.ChannelID)
                }

                if e2Zombie {
                        log.Tracef("Node2 pubkey=%x of chan_id=%v is zombie",
                                info.NodeKey2Bytes, info.ChannelID)
                }

                // If either edge hasn't been updated for a period of
                // chanExpiry, then we'll mark the channel itself as eligible
                // for graph pruning.
                if !isZombieChan {
                        return nil
                }

                log.Debugf("ChannelID(%v) is a zombie, collecting to prune",
                        info.ChannelID)

                // TODO(roasbeef): add ability to delete single directional edge
                chansToPrune[info.ChannelID] = struct{}{}

                return nil
        }

        // If AssumeChannelValid is present we'll look at the disabled bit for
        // both edges. If they're both disabled, then we can interpret this as
        // the channel being closed and can prune it from our graph.
        if b.cfg.AssumeChannelValid {
                disabledChanIDs, err := b.cfg.Graph.DisabledChannelIDs()
                if err != nil {
                        return fmt.Errorf("unable to get disabled channels "+
                                "ids chans: %v", err)
                }

                disabledEdges, err := b.cfg.Graph.FetchChanInfos(
                        disabledChanIDs,
                )
                if err != nil {
                        return fmt.Errorf("unable to fetch disabled channels "+
                                "edges chans: %v", err)
                }

                // Ensuring we won't prune our own channel from the graph.
                for _, disabledEdge := range disabledEdges {
                        if !isSelfChannelEdge(disabledEdge.Info) {
                                chansToPrune[disabledEdge.Info.ChannelID] =
                                        struct{}{}
                        }
                }
        }

        startTime := time.Unix(0, 0)
        endTime := time.Now().Add(-1 * chanExpiry)
        oldEdges, err := b.cfg.Graph.ChanUpdatesInHorizon(startTime, endTime)
        if err != nil {
                return fmt.Errorf("unable to fetch expired channel updates "+
                        "chans: %v", err)
        }

        for _, u := range oldEdges {
                err = filterPruneChans(u.Info, u.Policy1, u.Policy2)
                if err != nil {
                        return fmt.Errorf("error filtering channels to "+
                                "prune: %w", err)
                }
        }

        log.Infof("Pruning %v zombie channels", len(chansToPrune))
        if len(chansToPrune) == 0 {
                return nil
        }

        // With the set of zombie-like channels obtained, we'll do another pass
        // to delete them from the channel graph.
        toPrune := make([]uint64, 0, len(chansToPrune))
        for chanID := range chansToPrune {
                toPrune = append(toPrune, chanID)
                log.Tracef("Pruning zombie channel with ChannelID(%v)", chanID)
        }
        err = b.cfg.Graph.DeleteChannelEdges(
                b.cfg.StrictZombiePruning, true, toPrune...,
        )
        if err != nil {
                return fmt.Errorf("unable to delete zombie channels: %w", err)
        }

        // With the channels pruned, we'll also attempt to prune any nodes that
        // were a part of them.
        err = b.cfg.Graph.PruneGraphNodes()
        if err != nil && !errors.Is(err, graphdb.ErrGraphNodesNotFound) {
                return fmt.Errorf("unable to prune graph nodes: %w", err)
        }

        return nil
}

// handleNetworkUpdate is responsible for processing the update message and
// notifies topology changes, if any.
//
// NOTE: must be run inside goroutine.
func (b *Builder) handleNetworkUpdate(update *routingMsg) {
        defer b.wg.Done()

        // Process the routing update to determine if this is either a new
        // update from our PoV or an update to a prior vertex/edge we
        // previously accepted.
        var err error
        switch msg := update.msg.(type) {
        case *models.LightningNode:
                err = b.addNode(msg, update.op...)

        case *models.ChannelEdgeInfo:
                err = b.addEdge(msg, update.op...)

        case *models.ChannelEdgePolicy:
                err = b.updateEdge(msg, update.op...)

        default:
                err = errors.Errorf("wrong routing update message type")
        }
        update.err <- err

        // If the error is not nil here, there's no need to send topology
        // change.
        if err != nil {
                // Log as a debug message if this is not an error we need to be
                // concerned about.
                if IsError(err, ErrIgnored, ErrOutdated) {
                        log.Debugf("process network updates got: %v", err)
                } else {
                        log.Errorf("process network updates got: %v", err)
                }

                return
        }

        // Otherwise, we'll send off a new notification for the newly accepted
        // update, if any.
        topChange := &TopologyChange{}
        err = addToTopologyChange(b.cfg.Graph, topChange, update.msg)
        if err != nil {
                log.Errorf("unable to update topology change notification: %v",
                        err)
                return
        }

        if !topChange.isEmpty() {
                b.notifyTopologyChange(topChange)
        }
}

// networkHandler is the primary goroutine for the Builder. The roles of
// this goroutine include answering queries related to the state of the
// network, pruning the graph on new block notification, applying network
// updates, and registering new topology clients.
//
// NOTE: This MUST be run as a goroutine.
func (b *Builder) networkHandler() {
        defer b.wg.Done()

        graphPruneTicker := time.NewTicker(b.cfg.GraphPruneInterval)
        defer graphPruneTicker.Stop()

        defer b.statTicker.Stop()

        b.stats.Reset()

        for {
                // If there are stats, resume the statTicker.
                if !b.stats.Empty() {
                        b.statTicker.Resume()
                }

                select {
                // A new fully validated network update has just arrived. As a
                // result we'll modify the channel graph accordingly depending
                // on the exact type of the message.
                case update := <-b.networkUpdates:
                        b.wg.Add(1)
                        go b.handleNetworkUpdate(update)

                        // TODO(roasbeef): remove all unconnected vertexes
                        // after N blocks pass with no corresponding
                        // announcements.

                case chainUpdate, ok := <-b.staleBlocks:
                        // If the channel has been closed, then this indicates
                        // the daemon is shutting down, so we exit ourselves.
                        if !ok {
                                return
                        }

                        // Since this block is stale, we update our best height
                        // to the previous block.
                        blockHeight := chainUpdate.Height
                        b.bestHeight.Store(blockHeight - 1)

                        // Update the channel graph to reflect that this block
                        // was disconnected.
                        _, err := b.cfg.Graph.DisconnectBlockAtHeight(
                                blockHeight,
                        )
                        if err != nil {
                                log.Errorf("unable to prune graph with stale "+
                                        "block: %v", err)
                                continue
                        }

                        // TODO(halseth): notify client about the reorg?

                // A new block has arrived, so we can prune the channel graph
                // of any channels which were closed in the block.
                case chainUpdate, ok := <-b.newBlocks:
                        // If the channel has been closed, then this indicates
                        // the daemon is shutting down, so we exit ourselves.
                        if !ok {
                                return
                        }

                        // We'll ensure that any new blocks received attach
                        // directly to the end of our main chain. If not, then
                        // we've somehow missed some blocks. Here we'll catch
                        // up the chain with the latest blocks.
                        currentHeight := b.bestHeight.Load()
                        switch {
                        case chainUpdate.Height == currentHeight+1:
                                err := b.updateGraphWithClosedChannels(
                                        chainUpdate,
                                )
                                if err != nil {
                                        log.Errorf("unable to prune graph "+
                                                "with closed channels: %v", err)
                                }

                        case chainUpdate.Height > currentHeight+1:
                                log.Errorf("out of order block: expecting "+
                                        "height=%v, got height=%v",
                                        currentHeight+1, chainUpdate.Height)

                                err := b.getMissingBlocks(
                                        currentHeight, chainUpdate,
                                )
                                if err != nil {
                                        log.Errorf("unable to retrieve missing"+
                                                "blocks: %v", err)
                                }

                        case chainUpdate.Height < currentHeight+1:
                                log.Errorf("out of order block: expecting "+
                                        "height=%v, got height=%v",
                                        currentHeight+1, chainUpdate.Height)

                                log.Infof("Skipping channel pruning since "+
                                        "received block height %v was already"+
                                        " processed.", chainUpdate.Height)
                        }

                // A new notification client update has arrived. We're either
                // gaining a new client, or cancelling notifications for an
                // existing client.
                case ntfnUpdate := <-b.ntfnClientUpdates:
                        clientID := ntfnUpdate.clientID

                        if ntfnUpdate.cancel {
                                client, ok := b.topologyClients.LoadAndDelete(
                                        clientID,
                                )
                                if ok {
                                        close(client.exit)
                                        client.wg.Wait()

                                        close(client.ntfnChan)
                                }

                                continue
                        }

                        b.topologyClients.Store(clientID, &topologyClient{
                                ntfnChan: ntfnUpdate.ntfnChan,
                                exit:     make(chan struct{}),
                        })

                // The graph prune ticker has ticked, so we'll examine the
                // state of the known graph to filter out any zombie channels
                // for pruning.
                case <-graphPruneTicker.C:
                        if err := b.pruneZombieChans(); err != nil {
                                log.Errorf("Unable to prune zombies: %v", err)
                        }

                // Log any stats if we've processed a non-empty number of
                // channels, updates, or nodes. We'll only pause the ticker if
                // the last window contained no updates to avoid resuming and
                // pausing while consecutive windows contain new info.
                case <-b.statTicker.Ticks():
                        if !b.stats.Empty() {
                                log.Infof(b.stats.String())
                        } else {
                                b.statTicker.Pause()
                        }
                        b.stats.Reset()

                // The router has been signalled to exit, to we exit our main
                // loop so the wait group can be decremented.
                case <-b.quit:
                        return
                }
        }
}

// getMissingBlocks walks through all missing blocks and updates the graph
// closed channels accordingly.
func (b *Builder) getMissingBlocks(currentHeight uint32,
        chainUpdate *chainview.FilteredBlock) error {

        outdatedHash, err := b.cfg.Chain.GetBlockHash(int64(currentHeight))
        if err != nil {
                return err
        }

        outdatedBlock := &chainntnfs.BlockEpoch{
                Height: int32(currentHeight),
                Hash:   outdatedHash,
        }

        epochClient, err := b.cfg.Notifier.RegisterBlockEpochNtfn(
                outdatedBlock,
        )
        if err != nil {
                return err
        }
        defer epochClient.Cancel()

        blockDifference := int(chainUpdate.Height - currentHeight)

        // We'll walk through all the outdated blocks and make sure we're able
        // to update the graph with any closed channels from them.
        for i := 0; i < blockDifference; i++ {
                var (
                        missingBlock *chainntnfs.BlockEpoch
                        ok           bool
                )

                select {
                case missingBlock, ok = <-epochClient.Epochs:
                        if !ok {
                                return nil
                        }

                case <-b.quit:
                        return nil
                }

                filteredBlock, err := b.cfg.ChainView.FilterBlock(
                        missingBlock.Hash,
                )
                if err != nil {
                        return err
                }

                err = b.updateGraphWithClosedChannels(
                        filteredBlock,
                )
                if err != nil {
                        return err
                }
        }

        return nil
}

// updateGraphWithClosedChannels prunes the channel graph of closed channels
// that are no longer needed.
func (b *Builder) updateGraphWithClosedChannels(
        chainUpdate *chainview.FilteredBlock) error {

        // Once a new block arrives, we update our running track of the height
        // of the chain tip.
        blockHeight := chainUpdate.Height

        b.bestHeight.Store(blockHeight)
        log.Infof("Pruning channel graph using block %v (height=%v)",
                chainUpdate.Hash, blockHeight)

        // We're only interested in all prior outputs that have been spent in
        // the block, so collate all the referenced previous outpoints within
        // each tx and input.
        var spentOutputs []*wire.OutPoint
        for _, tx := range chainUpdate.Transactions {
                for _, txIn := range tx.TxIn {
                        spentOutputs = append(spentOutputs,
                                &txIn.PreviousOutPoint)
                }
        }

        // With the spent outputs gathered, attempt to prune the channel graph,
        // also passing in the hash+height of the block being pruned so the
        // prune tip can be updated.
        chansClosed, err := b.cfg.Graph.PruneGraph(spentOutputs,
                &chainUpdate.Hash, chainUpdate.Height)
        if err != nil {
                log.Errorf("unable to prune routing table: %v", err)
                return err
        }

        log.Infof("Block %v (height=%v) closed %v channels", chainUpdate.Hash,
                blockHeight, len(chansClosed))

        if len(chansClosed) == 0 {
                return err
        }

        // Notify all currently registered clients of the newly closed channels.
        closeSummaries := createCloseSummaries(blockHeight, chansClosed...)
        b.notifyTopologyChange(&TopologyChange{
                ClosedChannels: closeSummaries,
        })

        return nil
}

// assertNodeAnnFreshness returns a non-nil error if we have an announcement in
// the database for the passed node with a timestamp newer than the passed
// timestamp. ErrIgnored will be returned if we already have the node, and
// ErrOutdated will be returned if we have a timestamp that's after the new
// timestamp.
func (b *Builder) assertNodeAnnFreshness(node route.Vertex,
        msgTimestamp time.Time) error {

        // If we are not already aware of this node, it means that we don't
        // know about any channel using this node. To avoid a DoS attack by
        // node announcements, we will ignore such nodes. If we do know about
        // this node, check that this update brings info newer than what we
        // already have.
        lastUpdate, exists, err := b.cfg.Graph.HasLightningNode(node)
        if err != nil {
                return errors.Errorf("unable to query for the "+
                        "existence of node: %v", err)
        }
        if !exists {
                return NewErrf(ErrIgnored, "Ignoring node announcement"+
                        " for node not found in channel graph (%x)",
                        node[:])
        }

        // If we've reached this point then we're aware of the vertex being
        // advertised. So we now check if the new message has a new time stamp,
        // if not then we won't accept the new data as it would override newer
        // data.
        if !lastUpdate.Before(msgTimestamp) {
                return NewErrf(ErrOutdated, "Ignoring outdated "+
                        "announcement for %x", node[:])
        }

        return nil
}

// MarkZombieEdge adds a channel that failed complete validation into the zombie
// index so we can avoid having to re-validate it in the future.
func (b *Builder) MarkZombieEdge(chanID uint64) error {
        // If the edge fails validation we'll mark the edge itself as a zombie
        // so we don't continue to request it. We use the "zero key" for both
        // node pubkeys so this edge can't be resurrected.
        var zeroKey [33]byte
        err := b.cfg.Graph.MarkEdgeZombie(chanID, zeroKey, zeroKey)
        if err != nil {
                return fmt.Errorf("unable to mark spent chan(id=%v) as a "+
                        "zombie: %w", chanID, err)
        }

        return nil
}

// routingMsg couples a routing related routing topology update to the
// error channel.
type routingMsg struct {
        msg interface{}
        op  []batch.SchedulerOption
        err chan error
}

// ApplyChannelUpdate validates a channel update and if valid, applies it to the
// database. It returns a bool indicating whether the updates were successful.
func (b *Builder) ApplyChannelUpdate(msg *lnwire.ChannelUpdate1) bool {
        ch, _, _, err := b.GetChannelByID(msg.ShortChannelID)
        if err != nil {
                log.Errorf("Unable to retrieve channel by id: %v", err)
                return false
        }

        var pubKey *btcec.PublicKey

        switch msg.ChannelFlags & lnwire.ChanUpdateDirection {
        case 0:
                pubKey, _ = ch.NodeKey1()

        case 1:
                pubKey, _ = ch.NodeKey2()
        }

        // Exit early if the pubkey cannot be decided.
        if pubKey == nil {
                log.Errorf("Unable to decide pubkey with ChannelFlags=%v",
                        msg.ChannelFlags)
                return false
        }

        err = netann.ValidateChannelUpdateAnn(pubKey, ch.Capacity, msg)
        if err != nil {
                log.Errorf("Unable to validate channel update: %v", err)
                return false
        }

        err = b.UpdateEdge(&models.ChannelEdgePolicy{
                SigBytes:                  msg.Signature.ToSignatureBytes(),
                ChannelID:                 msg.ShortChannelID.ToUint64(),
                LastUpdate:                time.Unix(int64(msg.Timestamp), 0),
                MessageFlags:              msg.MessageFlags,
                ChannelFlags:              msg.ChannelFlags,
                TimeLockDelta:             msg.TimeLockDelta,
                MinHTLC:                   msg.HtlcMinimumMsat,
                MaxHTLC:                   msg.HtlcMaximumMsat,
                FeeBaseMSat:               lnwire.MilliSatoshi(msg.BaseFee),
                FeeProportionalMillionths: lnwire.MilliSatoshi(msg.FeeRate),
                ExtraOpaqueData:           msg.ExtraOpaqueData,
        })
        if err != nil && !IsError(err, ErrIgnored, ErrOutdated) {
                log.Errorf("Unable to apply channel update: %v", err)
                return false
        }

        return true
}

// AddNode is used to add information about a node to the router database. If
// the node with this pubkey is not present in an existing channel, it will
// be ignored.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) AddNode(node *models.LightningNode,
        op ...batch.SchedulerOption) error {

        rMsg := &routingMsg{
                msg: node,
                op:  op,
                err: make(chan error, 1),
        }

        select {
        case b.networkUpdates <- rMsg:
                select {
                case err := <-rMsg.err:
                        return err
                case <-b.quit:
                        return ErrGraphBuilderShuttingDown
                }
        case <-b.quit:
                return ErrGraphBuilderShuttingDown
        }
}

// addNode does some basic checks on the given LightningNode against what we
// currently have persisted in the graph, and then adds it to the graph. If we
// already know about the node, then we only update our DB if the new update
// has a newer timestamp than the last one we received.
func (b *Builder) addNode(node *models.LightningNode,
        op ...batch.SchedulerOption) error {

        // Before we add the node to the database, we'll check to see if the
        // announcement is "fresh" or not. If it isn't, then we'll return an
        // error.
        err := b.assertNodeAnnFreshness(node.PubKeyBytes, node.LastUpdate)
        if err != nil {
                return err
        }

        if err := b.cfg.Graph.AddLightningNode(node, op...); err != nil {
                return errors.Errorf("unable to add node %x to the "+
                        "graph: %v", node.PubKeyBytes, err)
        }

        log.Tracef("Updated vertex data for node=%x", node.PubKeyBytes)
        b.stats.incNumNodeUpdates()

        return nil
}

// AddEdge is used to add edge/channel to the topology of the router, after all
// information about channel will be gathered this edge/channel might be used
// in construction of payment path.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) AddEdge(edge *models.ChannelEdgeInfo,
        op ...batch.SchedulerOption) error {

        rMsg := &routingMsg{
                msg: edge,
                op:  op,
                err: make(chan error, 1),
        }

        select {
        case b.networkUpdates <- rMsg:
                select {
                case err := <-rMsg.err:
                        return err
                case <-b.quit:
                        return ErrGraphBuilderShuttingDown
                }
        case <-b.quit:
                return ErrGraphBuilderShuttingDown
        }
}

// addEdge does some validation on the new channel edge against what we
// currently have persisted in the graph, and then adds it to the graph. The
// Chain View is updated with the new edge if it is successfully added to the
// graph. We only persist the channel if we currently dont have it at all in
// our graph.
//
// TODO(elle): this currently also does funding-transaction validation. But this
// should be moved to the gossiper instead.
func (b *Builder) addEdge(edge *models.ChannelEdgeInfo,
        op ...batch.SchedulerOption) error {

        log.Debugf("Received ChannelEdgeInfo for channel %v", edge.ChannelID)

        // Prior to processing the announcement we first check if we
        // already know of this channel, if so, then we can exit early.
        _, _, exists, isZombie, err := b.cfg.Graph.HasChannelEdge(
                edge.ChannelID,
        )
        if err != nil && !errors.Is(err, graphdb.ErrGraphNoEdgesFound) {
                return errors.Errorf("unable to check for edge existence: %v",
                        err)
        }
        if isZombie {
                return NewErrf(ErrIgnored, "ignoring msg for zombie chan_id=%v",
                        edge.ChannelID)
        }
        if exists {
                return NewErrf(ErrIgnored, "ignoring msg for known chan_id=%v",
                        edge.ChannelID)
        }

        if err := b.cfg.Graph.AddChannelEdge(edge, op...); err != nil {
                return fmt.Errorf("unable to add edge: %w", err)
        }

        b.stats.incNumEdgesDiscovered()

        // If AssumeChannelValid is present, of if the SCID is an alias, then
        // the gossiper would not have done the expensive work of fetching
        // a funding transaction and validating it. So we won't have the channel
        // capacity nor the funding script. So we just log and return here.
        scid := lnwire.NewShortChanIDFromInt(edge.ChannelID)
        if b.cfg.AssumeChannelValid || b.cfg.IsAlias(scid) {
                log.Tracef("New channel discovered! Link connects %x and %x "+
                        "with ChannelID(%v)", edge.NodeKey1Bytes,
                        edge.NodeKey2Bytes, edge.ChannelID)

                return nil
        }

        log.Debugf("New channel discovered! Link connects %x and %x with "+
                "ChannelPoint(%v): chan_id=%v, capacity=%v", edge.NodeKey1Bytes,
                edge.NodeKey2Bytes, edge.ChannelPoint, edge.ChannelID,
                edge.Capacity)

        // Otherwise, then we expect the funding script to be present on the
        // edge since it would have been fetched when the gossiper validated the
        // announcement.
        fundingPkScript, err := edge.FundingScript.UnwrapOrErr(fmt.Errorf(
                "expected the funding transaction script to be set",
        ))
        if err != nil {
                return err
        }

        // As a new edge has been added to the channel graph, we'll update the
        // current UTXO filter within our active FilteredChainView so we are
        // notified if/when this channel is closed.
        filterUpdate := []graphdb.EdgePoint{
                {
                        FundingPkScript: fundingPkScript,
                        OutPoint:        edge.ChannelPoint,
                },
        }

        err = b.cfg.ChainView.UpdateFilter(filterUpdate, b.bestHeight.Load())
        if err != nil {
                return errors.Errorf("unable to update chain "+
                        "view: %v", err)
        }

        return nil
}

// UpdateEdge is used to update edge information, without this message edge
// considered as not fully constructed.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) UpdateEdge(update *models.ChannelEdgePolicy,
        op ...batch.SchedulerOption) error {

        rMsg := &routingMsg{
                msg: update,
                op:  op,
                err: make(chan error, 1),
        }

        select {
        case b.networkUpdates <- rMsg:
                select {
                case err := <-rMsg.err:
                        return err
                case <-b.quit:
                        return ErrGraphBuilderShuttingDown
                }
        case <-b.quit:
                return ErrGraphBuilderShuttingDown
        }
}

// updateEdge validates the new edge policy against what we currently have
// persisted in the graph, and then applies it to the graph if the update is
// considered fresh enough and if we actually have a channel persisted for the
// given update.
func (b *Builder) updateEdge(policy *models.ChannelEdgePolicy,
        op ...batch.SchedulerOption) error {

        log.Debugf("Received ChannelEdgePolicy for channel %v",
                policy.ChannelID)

        // We make sure to hold the mutex for this channel ID, such that no
        // other goroutine is concurrently doing database accesses for the same
        // channel ID.
        b.channelEdgeMtx.Lock(policy.ChannelID)
        defer b.channelEdgeMtx.Unlock(policy.ChannelID)

        edge1Timestamp, edge2Timestamp, exists, isZombie, err :=
                b.cfg.Graph.HasChannelEdge(policy.ChannelID)
        if err != nil && !errors.Is(err, graphdb.ErrGraphNoEdgesFound) {
                return errors.Errorf("unable to check for edge existence: %v",
                        err)
        }

        // If the channel is marked as a zombie in our database, and
        // we consider this a stale update, then we should not apply the
        // policy.
        isStaleUpdate := time.Since(policy.LastUpdate) >
                b.cfg.ChannelPruneExpiry

        if isZombie && isStaleUpdate {
                return NewErrf(ErrIgnored, "ignoring stale update "+
                        "(flags=%v|%v) for zombie chan_id=%v",
                        policy.MessageFlags, policy.ChannelFlags,
                        policy.ChannelID)
        }

        // If the channel doesn't exist in our database, we cannot apply the
        // updated policy.
        if !exists {
                return NewErrf(ErrIgnored, "ignoring update (flags=%v|%v) for "+
                        "unknown chan_id=%v", policy.MessageFlags,
                        policy.ChannelFlags, policy.ChannelID)
        }

        log.Debugf("Found edge1Timestamp=%v, edge2Timestamp=%v",
                edge1Timestamp, edge2Timestamp)

        // As edges are directional edge node has a unique policy for the
        // direction of the edge they control. Therefore, we first check if we
        // already have the most up-to-date information for that edge. If this
        // message has a timestamp not strictly newer than what we already know
        // of we can exit early.
        switch policy.ChannelFlags & lnwire.ChanUpdateDirection {
        // A flag set of 0 indicates this is an announcement for the "first"
        // node in the channel.
        case 0:
                // Ignore outdated message.
                if !edge1Timestamp.Before(policy.LastUpdate) {
                        return NewErrf(ErrOutdated, "Ignoring "+
                                "outdated update (flags=%v|%v) for "+
                                "known chan_id=%v", policy.MessageFlags,
                                policy.ChannelFlags, policy.ChannelID)
                }

        // Similarly, a flag set of 1 indicates this is an announcement
        // for the "second" node in the channel.
        case 1:
                // Ignore outdated message.
                if !edge2Timestamp.Before(policy.LastUpdate) {
                        return NewErrf(ErrOutdated, "Ignoring "+
                                "outdated update (flags=%v|%v) for "+
                                "known chan_id=%v", policy.MessageFlags,
                                policy.ChannelFlags, policy.ChannelID)
                }
        }

        // Now that we know this isn't a stale update, we'll apply the new edge
        // policy to the proper directional edge within the channel graph.
        if err = b.cfg.Graph.UpdateEdgePolicy(policy, op...); err != nil {
                err := errors.Errorf("unable to add channel: %v", err)
                log.Error(err)
                return err
        }

        log.Tracef("New channel update applied: %v",
                lnutils.SpewLogClosure(policy))
        b.stats.incNumChannelUpdates()

        return nil
}

// CurrentBlockHeight returns the block height from POV of the router subsystem.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) CurrentBlockHeight() (uint32, error) {
        _, height, err := b.cfg.Chain.GetBestBlock()
        return uint32(height), err
}

// SyncedHeight returns the block height to which the router subsystem currently
// is synced to. This can differ from the above chain height if the goroutine
// responsible for processing the blocks isn't yet up to speed.
func (b *Builder) SyncedHeight() uint32 {
        return b.bestHeight.Load()
}

// GetChannelByID return the channel by the channel id.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) GetChannelByID(chanID lnwire.ShortChannelID) (
        *models.ChannelEdgeInfo,
        *models.ChannelEdgePolicy,
        *models.ChannelEdgePolicy, error) {

        return b.cfg.Graph.FetchChannelEdgesByID(chanID.ToUint64())
}

// FetchLightningNode attempts to look up a target node by its identity public
// key. graphdb.ErrGraphNodeNotFound is returned if the node doesn't exist
// within the graph.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) FetchLightningNode(
        node route.Vertex) (*models.LightningNode, error) {

        return b.cfg.Graph.FetchLightningNode(node)
}

// ForAllOutgoingChannels is used to iterate over all outgoing channels owned by
// the router.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) ForAllOutgoingChannels(cb func(*models.ChannelEdgeInfo,
        *models.ChannelEdgePolicy) error) error {

        return b.cfg.Graph.ForEachNodeChannel(b.cfg.SelfNode,
                func(_ kvdb.RTx, c *models.ChannelEdgeInfo,
                        e *models.ChannelEdgePolicy,
                        _ *models.ChannelEdgePolicy) error {

                        if e == nil {
                                return fmt.Errorf("channel from self node " +
                                        "has no policy")
                        }

                        return cb(c, e)
                },
        )
}

// AddProof updates the channel edge info with proof which is needed to
// properly announce the edge to the rest of the network.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) AddProof(chanID lnwire.ShortChannelID,
        proof *models.ChannelAuthProof) error {

        return b.cfg.Graph.AddEdgeProof(chanID, proof)
}

// IsStaleNode returns true if the graph source has a node announcement for the
// target node with a more recent timestamp.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) IsStaleNode(node route.Vertex,
        timestamp time.Time) bool {

        // If our attempt to assert that the node announcement is fresh fails,
        // then we know that this is actually a stale announcement.
        err := b.assertNodeAnnFreshness(node, timestamp)
        if err != nil {
                log.Debugf("Checking stale node %x got %v", node, err)
                return true
        }

        return false
}

// IsPublicNode determines whether the given vertex is seen as a public node in
// the graph from the graph's source node's point of view.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) IsPublicNode(node route.Vertex) (bool, error) {
        return b.cfg.Graph.IsPublicNode(node)
}

// IsKnownEdge returns true if the graph source already knows of the passed
// channel ID either as a live or zombie edge.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) IsKnownEdge(chanID lnwire.ShortChannelID) bool {
        _, _, exists, isZombie, _ := b.cfg.Graph.HasChannelEdge(
                chanID.ToUint64(),
        )

        return exists || isZombie
}

// IsZombieEdge returns true if the graph source has marked the given channel ID
// as a zombie edge.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) IsZombieEdge(chanID lnwire.ShortChannelID) (bool, error) {
        _, _, _, isZombie, err := b.cfg.Graph.HasChannelEdge(chanID.ToUint64())

        return isZombie, err
}

// IsStaleEdgePolicy returns true if the graph source has a channel edge for
// the passed channel ID (and flags) that have a more recent timestamp.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) IsStaleEdgePolicy(chanID lnwire.ShortChannelID,
        timestamp time.Time, flags lnwire.ChanUpdateChanFlags) bool {

        edge1Timestamp, edge2Timestamp, exists, isZombie, err :=
                b.cfg.Graph.HasChannelEdge(chanID.ToUint64())
        if err != nil {
                log.Debugf("Check stale edge policy got error: %v", err)
                return false
        }

        // If we know of the edge as a zombie, then we'll make some additional
        // checks to determine if the new policy is fresh.
        if isZombie {
                // When running with AssumeChannelValid, we also prune channels
                // if both of their edges are disabled. We'll mark the new
                // policy as stale if it remains disabled.
                if b.cfg.AssumeChannelValid {
                        isDisabled := flags&lnwire.ChanUpdateDisabled ==
                                lnwire.ChanUpdateDisabled
                        if isDisabled {
                                return true
                        }
                }

                // Otherwise, we'll fall back to our usual ChannelPruneExpiry.
                return time.Since(timestamp) > b.cfg.ChannelPruneExpiry
        }

        // If we don't know of the edge, then it means it's fresh (thus not
        // stale).
        if !exists {
                return false
        }

        // As edges are directional edge node has a unique policy for the
        // direction of the edge they control. Therefore, we first check if we
        // already have the most up-to-date information for that edge. If so,
        // then we can exit early.
        switch {
        // A flag set of 0 indicates this is an announcement for the "first"
        // node in the channel.
        case flags&lnwire.ChanUpdateDirection == 0:
                return !edge1Timestamp.Before(timestamp)

        // Similarly, a flag set of 1 indicates this is an announcement for the
        // "second" node in the channel.
        case flags&lnwire.ChanUpdateDirection == 1:
                return !edge2Timestamp.Before(timestamp)
        }

        return false
}

// MarkEdgeLive clears an edge from our zombie index, deeming it as live.
//
// NOTE: This method is part of the ChannelGraphSource interface.
func (b *Builder) MarkEdgeLive(chanID lnwire.ShortChannelID) error {
        return b.cfg.Graph.MarkEdgeLive(chanID.ToUint64())
}

lightningnetwork / lnd / 13412100018

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