package routing import ( "sync" "time" "github.com/lightningnetwork/lnd/channeldb" ) const ( // vertexDecay is the decay period of colored vertexes added to // missionControl. Once vertexDecay passes after an entry has been // added to the prune view, it is garbage collected. This value is // larger than edgeDecay as an edge failure typical indicates an // unbalanced channel, while a vertex failure indicates a node is not // online and active. vertexDecay = time.Duration(time.Minute * 5) // edgeDecay is the decay period of colored edges added to // missionControl. Once edgeDecay passed after an entry has been added, // it is garbage collected. This value is smaller than vertexDecay as // an edge related failure during payment sending typically indicates // that a channel was unbalanced, a condition which may quickly change. // // TODO(roasbeef): instead use random delay on each? edgeDecay = time.Duration(time.Second * 5) ) // missionControl contains state which summarizes the past attempts of HTLC // routing by external callers when sending payments throughout the network. // missionControl remembers the outcome of these past routing attempts (success // and failure), and is able to provide hints/guidance to future HTLC routing // attempts. missionControl maintains a decaying network view of the // edges/vertexes that should be marked as "pruned" during path finding. This // graph view acts as a shared memory during HTLC payment routing attempts. // With each execution, if an error is encountered, based on the type of error // and the location of the error within the route, an edge or vertex is added // to the view. Later sending attempts will then query the view for all the // vertexes/edges that should be ignored. Items in the view decay after a set // period of time, allowing the view to be dynamic w.r.t network changes. type missionControl struct { // failedEdges maps a short channel ID to be pruned, to the time that // it was added to the prune view. Edges are added to this map if a // caller reports to missionControl a failure localized to that edge // when sending a payment. failedEdges map[uint64]time.Time // failedVertexes maps a node's public key that should be pruned, to // the time that it was added to the prune view. Vertexes are added to // this map if a caller reports to missionControl a failure localized // to that particular vertex. failedVertexes map[vertex]time.Time graph *channeldb.ChannelGraph selfNode *channeldb.LightningNode sync.Mutex // TODO(roasbeef): further counters, if vertex continually unavailable, // add to another generation // TODO(roasbeef): also add favorable metrics for nodes } // newMissionControl returns a new instance of missionControl. // // TODO(roasbeef): persist memory func newMissionControl(g *channeldb.ChannelGraph, s *channeldb.LightningNode) *missionControl { return &missionControl{ graph: g, selfNode: s, failedEdges: make(map[uint64]time.Time), failedVertexes: make(map[vertex]time.Time), } } // ReportVertexFailure adds a vertex to the graph prune view after a client // reports a routing failure localized to the vertex. The time the vertex was // added is noted, as it'll be pruned from the view after a period of // vertexDecay. func (m *missionControl) ReportVertexFailure(v vertex) { log.Debugf("Reporting vertex %v failure to Mission Control", v) m.Lock() m.failedVertexes[v] = time.Now() m.Unlock() } // ReportChannelFailure adds a channel to the graph prune view. The time the // channel was added is noted, as it'll be pruned from the view after a period // of edgeDecay. // // TODO(roasbeef): also add value attempted to send and capacity of channel func (m *missionControl) ReportChannelFailure(e uint64) { log.Debugf("Reporting edge %v failure to Mission Control", e) m.Lock() m.failedEdges[e] = time.Now() m.Unlock() } // RequestRoute returns a route which is likely to be capable for successfully // routing the specified HTLC payment to the target node. Initially the first // set of paths returned from this method may encounter routing failure along // the way, however as more payments are sent, mission control will start to // build an up to date view of the network itself. With each payment a new area // will be explored, which feeds into the recommendations made for routing. // // NOTE: This function is safe for concurrent access. func (m *missionControl) RequestRoute(payment *LightningPayment, height uint32) (*Route, error) { // First, we'll query mission control for it's current recommendation // on the edges/vertexes to ignore during path finding. pruneView := m.GraphPruneView() // TODO(roasbeef): sync logic amongst dist sys // Taking into account this prune view, we'll attempt to locate a path // to our destination, respecting the recommendations from // missionControl. path, err := findPath(nil, m.graph, m.selfNode, payment.Target, pruneView.vertexes, pruneView.edges, payment.Amount) if err != nil { return nil, err } // With the next candidate path found, we'll attempt to turn this into // a route by applying the time-lock and fee requirements. sourceVertex := newVertex(m.selfNode.PubKey) route, err := newRoute(payment.Amount, sourceVertex, path, height) if err != nil { // TODO(roasbeef): return which edge/vertex didn't work // out return nil, err } return route, err } // GraphPruneView returns a new graphPruneView instance which is to be // consulted during path finding. If a vertex/edge is found within the returned // prune view, it is to be ignored as a goroutine has had issues routing // through it successfully. Within this method the main view of the // missionControl is garbage collected as entires are detected to be "stale". func (m *missionControl) GraphPruneView() *graphPruneView { // First, we'll grab the current time, this value will be used to // determine if an entry is stale or not. now := time.Now() m.Lock() // For each of the vertexes that have been added to the prune view, if // it is now "stale", then we'll ignore it and avoid adding it to the // view we'll return. vertexes := make(map[vertex]struct{}) for vertex, pruneTime := range m.failedVertexes { if now.Sub(pruneTime) >= vertexDecay { log.Tracef("Pruning decayed failure report for vertex %v "+ "from Mission Control", vertex) delete(m.failedVertexes, vertex) continue } vertexes[vertex] = struct{}{} } // We'll also do the same for edges, but use the edgeDecay this time // rather than the decay for vertexes. edges := make(map[uint64]struct{}) for edge, pruneTime := range m.failedEdges { if now.Sub(pruneTime) >= edgeDecay { log.Tracef("Pruning decayed failure report for edge %v "+ "from Mission Control", edge) delete(m.failedEdges, edge) continue } edges[edge] = struct{}{} } m.Unlock() log.Debugf("Mission Control returning prune view of %v edges, %v "+ "vertexes", len(edges), len(vertexes)) return &graphPruneView{ edges: edges, vertexes: vertexes, } } // graphPruneView is a filter of sorts that path finding routines should // consult during the execution. Any edges or vertexes within the view should // be ignored during path finding. The contents of the view reflect the current // state of the wider network from the PoV of mission control compiled via HTLC // routing attempts in the past. type graphPruneView struct { edges map[uint64]struct{} vertexes map[vertex]struct{} } // ResetHistory resets the history of missionControl returning it to a state as // if no payment attempts have been made. func (m *missionControl) ResetHistory() { m.Lock() m.failedEdges = make(map[uint64]time.Time) m.failedVertexes = make(map[vertex]time.Time) m.Unlock() }