13414831183

Committed 19 Feb 2025 02:22PM UTC coverage: 58.821% (+0.03%) from 58.794%

Build # 13414831183

Build Type

Pull #9529

github

Committed by

ellemouton

Commit Message

graph/db: move Topology client management to ChannelGraph

Pull Request Pull Request #9529: [Concept ACK 🙏 ] graph: move graph cache out of CRUD layer & move topology change subscription

Run Details

2730 of 3482 new or added lines in 9 files covered. (78.4%)

43 existing lines in 11 files now uncovered.

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86.24

/graph/db/graph.go

package graphdb

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

        "github.com/btcsuite/btcd/chaincfg/chainhash"
        "github.com/btcsuite/btcd/wire"
        "github.com/lightningnetwork/lnd/batch"
        "github.com/lightningnetwork/lnd/graph/db/models"
        "github.com/lightningnetwork/lnd/kvdb"
        "github.com/lightningnetwork/lnd/lnutils"
        "github.com/lightningnetwork/lnd/lnwire"
        "github.com/lightningnetwork/lnd/routing/route"
)

// ErrChanGraphShuttingDown indicates that the ChannelGraph has shutdown or is
// busy shutting down.
var ErrChanGraphShuttingDown = fmt.Errorf("ChannelGraph shutting down")

// Config is a struct that holds all the necessary dependencies for a
// ChannelGraph.
type Config struct {
        // KVDB is the kvdb.Backend that will be used for initializing the
        // KVStore CRUD layer.
        KVDB kvdb.Backend

        // KVStoreOpts is a list of functional options that will be used when
        // initializing the KVStore.
        KVStoreOpts []KVStoreOptionModifier
}

// ChannelGraph is a layer above the graph's CRUD layer.
//
// NOTE: currently, this is purely a pass-through layer directly to the backing
// KVStore. Upcoming commits will move the graph cache out of the KVStore and
// into this layer so that the KVStore is only responsible for CRUD operations.
type ChannelGraph struct {
        started atomic.Bool
        stopped atomic.Bool

        graphCache *GraphCache

        *KVStore

        ntfnClientCounter atomic.Uint64

        // topologyUpdate is a channel that carries new topology updates
        // messages from outside the ChannelGraph to be processed by the
        // networkHandler.
        topologyUpdate chan any

        // 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 ChannelGraph. Updates either
        // add a new notification client, or cancel notifications for an
        // existing client.
        ntfnClientUpdates chan *topologyClientUpdate

        quit chan struct{}
        wg   sync.WaitGroup
}

// NewChannelGraph creates a new ChannelGraph instance with the given backend.
func NewChannelGraph(cfg *Config, options ...ChanGraphOption) (*ChannelGraph,
        error) {

        opts := defaultChanGraphOptions()
        for _, o := range options {
                o(opts)
        }

        store, err := NewKVStore(cfg.KVDB, cfg.KVStoreOpts...)
        if err != nil {
                return nil, err
        }

        g := &ChannelGraph{
                KVStore:           store,
                topologyUpdate:    make(chan any),
                topologyClients:   &lnutils.SyncMap[uint64, *topologyClient]{},
                ntfnClientUpdates: make(chan *topologyClientUpdate),
                quit:              make(chan struct{}),
        }

        // The graph cache can be turned off (e.g. for mobile users) for a
        // speed/memory usage tradeoff.
        if opts.useGraphCache {
                g.graphCache = NewGraphCache(opts.preAllocCacheNumNodes)
        }

        return g, nil
}

// Start kicks off any goroutines required for the ChannelGraph to function.
// If the graph cache is enabled, then it will be populated with the contents of
// the database.
func (c *ChannelGraph) Start() error {
        if !c.started.CompareAndSwap(false, true) {
                return nil
        }
        log.Debugf("ChannelGraph starting")
        defer log.Debug("ChannelGraph started")

        if c.graphCache != nil {
                if err := c.populateCache(); err != nil {
                        return fmt.Errorf("could not populate the graph "+
                                "cache: %w", err)
                }
        }

        c.wg.Add(1)
        go c.handleTopologySubscriptions()

        return nil
}

// Stop signals any active goroutines for a graceful closure.
func (c *ChannelGraph) Stop() error {
        if !c.stopped.CompareAndSwap(false, true) {
                return nil
        }

        log.Debugf("ChannelGraph shutting down...")
        defer log.Debug("Builder shutdown complete")

        close(c.quit)
        c.wg.Wait()

        return nil
}

// handleTopologySubscriptions ensures that topology client subscriptions,
// subscription cancellations and topology notifications are handled
// synchronously.
//
// NOTE: this MUST be run in a goroutine.
func (c *ChannelGraph) handleTopologySubscriptions() {
        defer c.wg.Done()

        for {
                select {
                // A new fully validated topology update has just arrived.
                // We'll notify any registered clients.
                case update := <-c.topologyUpdate:
                        c.wg.Add(1)
                        go c.handleTopologyUpdate(update)

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

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

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

                                        close(client.ntfnChan)
                                }

                                continue
                        }

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

                case <-c.quit:
                        return
                }
        }
}

// populateCache loads the entire channel graph into the in-memory graph cache.
//
// NOTE: This should only be called if the graphCache has been constructed.
func (c *ChannelGraph) populateCache() error {
        startTime := time.Now()
        log.Debugf("Populating in-memory channel graph, this might take a " +
                "while...")

        err := c.KVStore.ForEachNodeCacheable(func(node route.Vertex,
                features *lnwire.FeatureVector) error {

                c.graphCache.AddNodeFeatures(node, features)

                return nil
        })
        if err != nil {
                return err
        }

        err = c.KVStore.ForEachChannel(func(info *models.ChannelEdgeInfo,
                policy1, policy2 *models.ChannelEdgePolicy) error {

                c.graphCache.AddChannel(info, policy1, policy2)

                return nil
        })
        if err != nil {
                return err
        }

        log.Debugf("Finished populating in-memory channel graph (took %v, %s)",
                time.Since(startTime), c.graphCache.Stats())

        return nil
}

// ForEachNodeDirectedChannel iterates through all channels of a given node,
// executing the passed callback on the directed edge representing the channel
// and its incoming policy. If the callback returns an error, then the iteration
// is halted with the error propagated back up to the caller. If the graphCache
// is available, then it will be used to retrieve the node's channels instead
// of the database.
//
// Unknown policies are passed into the callback as nil values.
//
// NOTE: this is part of the graphdb.NodeTraverser interface.
func (c *ChannelGraph) ForEachNodeDirectedChannel(node route.Vertex,
        cb func(channel *DirectedChannel) error) error {

        if c.graphCache != nil {
                return c.graphCache.ForEachChannel(node, cb)
        }

        return c.KVStore.ForEachNodeDirectedChannel(node, cb)
}

// FetchNodeFeatures returns the features of the given node. If no features are
// known for the node, an empty feature vector is returned.
// If the graphCache is available, then it will be used to retrieve the node's
// features instead of the database.
//
// NOTE: this is part of the graphdb.NodeTraverser interface.
func (c *ChannelGraph) FetchNodeFeatures(node route.Vertex) (
        *lnwire.FeatureVector, error) {

        if c.graphCache != nil {
                return c.graphCache.GetFeatures(node), nil
        }

        return c.KVStore.FetchNodeFeatures(node)
}

// GraphSession will provide the call-back with access to a NodeTraverser
// instance which can be used to perform queries against the channel graph. If
// the graph cache is not enabled, then the call-back will  be provided with
// access to the graph via a consistent read-only transaction.
func (c *ChannelGraph) GraphSession(cb func(graph NodeTraverser) error) error {
        if c.graphCache != nil {
                return cb(c)
        }

        return c.KVStore.GraphSession(cb)
}

// ForEachNodeCached iterates through all the stored vertices/nodes in the
// graph, executing the passed callback with each node encountered.
//
// NOTE: The callback contents MUST not be modified.
func (c *ChannelGraph) ForEachNodeCached(cb func(node route.Vertex,
        chans map[uint64]*DirectedChannel) error) error {

        if c.graphCache != nil {
                return c.graphCache.ForEachNode(cb)
        }

        return c.KVStore.ForEachNodeCached(cb)
}

// AddLightningNode adds a vertex/node to the graph database. If the node is not
// in the database from before, this will add a new, unconnected one to the
// graph. If it is present from before, this will update that node's
// information. Note that this method is expected to only be called to update an
// already present node from a node announcement, or to insert a node found in a
// channel update.
func (c *ChannelGraph) AddLightningNode(node *models.LightningNode,
        op ...batch.SchedulerOption) error {

        err := c.KVStore.AddLightningNode(node, op...)
        if err != nil {
                return err
        }

        if c.graphCache != nil {
                c.graphCache.AddNodeFeatures(
                        node.PubKeyBytes, node.Features,
                )
        }

        // No need to send topology updates for shell nodes.
        if !node.HaveNodeAnnouncement {
                return nil
        }

        select {
        case c.topologyUpdate <- node:
        case <-c.quit:
                return ErrChanGraphShuttingDown
        }

        return nil
}

// DeleteLightningNode starts a new database transaction to remove a vertex/node
// from the database according to the node's public key.
func (c *ChannelGraph) DeleteLightningNode(nodePub route.Vertex) error {
        err := c.KVStore.DeleteLightningNode(nodePub)
        if err != nil {
                return err
        }

        if c.graphCache != nil {
                c.graphCache.RemoveNode(nodePub)
        }

        return nil
}

// AddChannelEdge adds a new (undirected, blank) edge to the graph database. An
// undirected edge from the two target nodes are created. The information stored
// denotes the static attributes of the channel, such as the channelID, the keys
// involved in creation of the channel, and the set of features that the channel
// supports. The chanPoint and chanID are used to uniquely identify the edge
// globally within the database.
func (c *ChannelGraph) AddChannelEdge(edge *models.ChannelEdgeInfo,
        op ...batch.SchedulerOption) error {

        err := c.KVStore.AddChannelEdge(edge, op...)
        if err != nil {
                return err
        }

        if c.graphCache != nil {
                c.graphCache.AddChannel(edge, nil, nil)
        }

        select {
        case c.topologyUpdate <- edge:
        case <-c.quit:
                return ErrChanGraphShuttingDown
        }

        return nil
}

// MarkEdgeLive clears an edge from our zombie index, deeming it as live.
// If the cache is enabled, the edge will be added back to the graph cache if
// we still have a record of this channel in the DB.
func (c *ChannelGraph) MarkEdgeLive(chanID uint64) error {
        err := c.KVStore.MarkEdgeLive(chanID)
        if err != nil {
                return err
        }

        if c.graphCache != nil {
                // We need to add the channel back into our graph cache,
                // otherwise we won't use it for path finding.
                infos, err := c.KVStore.FetchChanInfos([]uint64{chanID})
                if err != nil {
                        return err
                }

                if len(infos) == 0 {
                        return nil
                }

                info := infos[0]

                c.graphCache.AddChannel(info.Info, info.Policy1, info.Policy2)
        }

        return nil
}

// DeleteChannelEdges removes edges with the given channel IDs from the
// database and marks them as zombies. This ensures that we're unable to re-add
// it to our database once again. If an edge does not exist within the
// database, then ErrEdgeNotFound will be returned. If strictZombiePruning is
// true, then when we mark these edges as zombies, we'll set up the keys such
// that we require the node that failed to send the fresh update to be the one
// that resurrects the channel from its zombie state. The markZombie bool
// denotes whether or not to mark the channel as a zombie.
func (c *ChannelGraph) DeleteChannelEdges(strictZombiePruning, markZombie bool,
        chanIDs ...uint64) error {

        infos, err := c.KVStore.DeleteChannelEdges(
                strictZombiePruning, markZombie, chanIDs...,
        )
        if err != nil {
                return err
        }

        if c.graphCache != nil {
                for _, info := range infos {
                        c.graphCache.RemoveChannel(
                                info.NodeKey1Bytes, info.NodeKey2Bytes,
                                info.ChannelID,
                        )
                }
        }

        return err
}

// DisconnectBlockAtHeight is used to indicate that the block specified
// by the passed height has been disconnected from the main chain. This
// will "rewind" the graph back to the height below, deleting channels
// that are no longer confirmed from the graph. The prune log will be
// set to the last prune height valid for the remaining chain.
// Channels that were removed from the graph resulting from the
// disconnected block are returned.
func (c *ChannelGraph) DisconnectBlockAtHeight(height uint32) (
        []*models.ChannelEdgeInfo, error) {

        edges, err := c.KVStore.DisconnectBlockAtHeight(height)
        if err != nil {
                return nil, err
        }

        if c.graphCache != nil {
                for _, edge := range edges {
                        c.graphCache.RemoveChannel(
                                edge.NodeKey1Bytes, edge.NodeKey2Bytes,
                                edge.ChannelID,
                        )
                }
        }

        return edges, nil
}

// PruneGraph prunes newly closed channels from the channel graph in response
// to a new block being solved on the network. Any transactions which spend the
// funding output of any known channels within he graph will be deleted.
// Additionally, the "prune tip", or the last block which has been used to
// prune the graph is stored so callers can ensure the graph is fully in sync
// with the current UTXO state. A slice of channels that have been closed by
// the target block are returned if the function succeeds without error.
func (c *ChannelGraph) PruneGraph(spentOutputs []*wire.OutPoint,
        blockHash *chainhash.Hash, blockHeight uint32) (
        []*models.ChannelEdgeInfo, error) {

        edges, err := c.KVStore.PruneGraph(spentOutputs, blockHash, blockHeight)
        if err != nil {
                return nil, err
        }

        // Now that the graph has been pruned, we'll also attempt to
        // prune any nodes that have had a channel closed within the
        // latest block.
        nodes, err := c.KVStore.PruneGraphNodes()
        if err != nil {
                return nil, err
        }

        if c.graphCache != nil {
                for _, edge := range edges {
                        c.graphCache.RemoveChannel(
                                edge.NodeKey1Bytes, edge.NodeKey2Bytes,
                                edge.ChannelID,
                        )
                }

                for _, node := range nodes {
                        c.graphCache.RemoveNode(node)
                }

                log.Debugf("Pruned graph, cache now has %s",
                        c.graphCache.Stats())
        }

        if len(edges) != 0 {
                // Notify all currently registered clients of the newly closed
                // channels.
                closeSummaries := createCloseSummaries(
                        blockHeight, edges...,
                )
                c.notifyTopologyChange(&TopologyChange{
                        ClosedChannels: closeSummaries,
                })
        }

        return edges, nil
}

// PruneGraphNodes is a garbage collection method which attempts to prune out
// any nodes from the channel graph that are currently unconnected. This ensure
// that we only maintain a graph of reachable nodes. In the event that a pruned
// node gains more channels, it will be re-added back to the graph.
func (c *ChannelGraph) PruneGraphNodes() error {
        nodes, err := c.KVStore.PruneGraphNodes()
        if err != nil {
                return err
        }

        if c.graphCache != nil {
                for _, node := range nodes {
                        c.graphCache.RemoveNode(node)
                }
        }

        return nil
}

// FilterKnownChanIDs takes a set of channel IDs and return the subset of chan
// ID's that we don't know and are not known zombies of the passed set. In other
// words, we perform a set difference of our set of chan ID's and the ones
// passed in. This method can be used by callers to determine the set of
// channels another peer knows of that we don't.
func (c *ChannelGraph) FilterKnownChanIDs(chansInfo []ChannelUpdateInfo,
        isZombieChan func(time.Time, time.Time) bool) ([]uint64, error) {

        unknown, knownZombies, err := c.KVStore.FilterKnownChanIDs(chansInfo)
        if err != nil {
                return nil, err
        }

        for _, info := range knownZombies {
                // TODO(ziggie): Make sure that for the strict pruning case we
                // compare the pubkeys and whether the right timestamp is not
                // older than the `ChannelPruneExpiry`.
                //
                // NOTE: The timestamp data has no verification attached to it
                // in the `ReplyChannelRange` msg so we are trusting this data
                // at this point. However it is not critical because we are just
                // removing the channel from the db when the timestamps are more
                // recent. During the querying of the gossip msg verification
                // happens as usual. However we should start punishing peers
                // when they don't provide us honest data ?
                isStillZombie := isZombieChan(
                        info.Node1UpdateTimestamp, info.Node2UpdateTimestamp,
                )

                if isStillZombie {
                        continue
                }

                // If we have marked it as a zombie but the latest update
                // timestamps could bring it back from the dead, then we mark it
                // alive, and we let it be added to the set of IDs to query our
                // peer for.
                err := c.KVStore.MarkEdgeLive(
                        info.ShortChannelID.ToUint64(),
                )
                // Since there is a chance that the edge could have been marked
                // as "live" between the FilterKnownChanIDs call and the
                // MarkEdgeLive call, we ignore the error if the edge is already
                // marked as live.
                if err != nil && !errors.Is(err, ErrZombieEdgeNotFound) {
                        return nil, err
                }
        }

        return unknown, nil
}

// MarkEdgeZombie attempts to mark a channel identified by its channel ID as a
// zombie. This method is used on an ad-hoc basis, when channels need to be
// marked as zombies outside the normal pruning cycle.
func (c *ChannelGraph) MarkEdgeZombie(chanID uint64,
        pubKey1, pubKey2 [33]byte) error {

        err := c.KVStore.MarkEdgeZombie(chanID, pubKey1, pubKey2)
        if err != nil {
                return err
        }

        if c.graphCache != nil {
                c.graphCache.RemoveChannel(pubKey1, pubKey2, chanID)
        }

        return nil
}

// UpdateEdgePolicy updates the edge routing policy for a single directed edge
// within the database for the referenced channel. The `flags` attribute within
// the ChannelEdgePolicy determines which of the directed edges are being
// updated. If the flag is 1, then the first node's information is being
// updated, otherwise it's the second node's information. The node ordering is
// determined by the lexicographical ordering of the identity public keys of the
// nodes on either side of the channel.
func (c *ChannelGraph) UpdateEdgePolicy(edge *models.ChannelEdgePolicy,
        op ...batch.SchedulerOption) error {

        from, to, err := c.KVStore.UpdateEdgePolicy(edge, op...)
        if err != nil {
                return err
        }

        if c.graphCache != nil {
                var isUpdate1 bool
                if edge.ChannelFlags&lnwire.ChanUpdateDirection == 0 {
                        isUpdate1 = true
                }

                c.graphCache.UpdatePolicy(edge, from, to, isUpdate1)
        }

        select {
        case c.topologyUpdate <- edge:
        case <-c.quit:
                return ErrChanGraphShuttingDown
        }

        return nil
}

lightningnetwork / lnd / 13414831183

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