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missioncontrol.go
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missioncontrol.go
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package routing
import (
"fmt"
"sync"
"time"
"github.com/btcsuite/btcd/btcec"
"github.com/coreos/bbolt"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/lightningnetwork/lnd/lnwire"
)
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
queryBandwidth func(*channeldb.ChannelEdgeInfo) lnwire.MilliSatoshi
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, selfNode *channeldb.LightningNode,
qb func(*channeldb.ChannelEdgeInfo) lnwire.MilliSatoshi) *missionControl {
return &missionControl{
failedEdges: make(map[uint64]time.Time),
failedVertexes: make(map[Vertex]time.Time),
selfNode: selfNode,
queryBandwidth: qb,
graph: g,
}
}
// 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{}
}
// 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 entries 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,
}
}
// paymentSession is used during an HTLC routings session to prune the local
// chain view in response to failures, and also report those failures back to
// missionControl. The snapshot copied for this session will only ever grow,
// and will now be pruned after a decay like the main view within mission
// control. We do this as we want to avoid the case where we continually try a
// bad edge or route multiple times in a session. This can lead to an infinite
// loop if payment attempts take long enough. An additional set of edges can
// also be provided to assist in reaching the payment's destination.
type paymentSession struct {
pruneViewSnapshot graphPruneView
additionalEdges map[Vertex][]*channeldb.ChannelEdgePolicy
bandwidthHints map[uint64]lnwire.MilliSatoshi
mc *missionControl
haveRoutes bool
preBuiltRoutes []*Route
}
// NewPaymentSession creates a new payment session backed by the latest prune
// view from Mission Control. An optional set of routing hints can be provided
// in order to populate additional edges to explore when finding a path to the
// payment's destination.
func (m *missionControl) NewPaymentSession(routeHints [][]HopHint,
target *btcec.PublicKey) (*paymentSession, error) {
viewSnapshot := m.GraphPruneView()
edges := make(map[Vertex][]*channeldb.ChannelEdgePolicy)
// Traverse through all of the available hop hints and include them in
// our edges map, indexed by the public key of the channel's starting
// node.
for _, routeHint := range routeHints {
// If multiple hop hints are provided within a single route
// hint, we'll assume they must be chained together and sorted
// in forward order in order to reach the target successfully.
for i, hopHint := range routeHint {
// In order to determine the end node of this hint,
// we'll need to look at the next hint's start node. If
// we've reached the end of the hints list, we can
// assume we've reached the destination.
endNode := &channeldb.LightningNode{}
if i != len(routeHint)-1 {
endNode.AddPubKey(routeHint[i+1].NodeID)
} else {
endNode.AddPubKey(target)
}
// Finally, create the channel edge from the hop hint
// and add it to list of edges corresponding to the node
// at the start of the channel.
edge := &channeldb.ChannelEdgePolicy{
Node: endNode,
ChannelID: hopHint.ChannelID,
FeeBaseMSat: lnwire.MilliSatoshi(
hopHint.FeeBaseMSat,
),
FeeProportionalMillionths: lnwire.MilliSatoshi(
hopHint.FeeProportionalMillionths,
),
TimeLockDelta: hopHint.CLTVExpiryDelta,
}
v := NewVertex(hopHint.NodeID)
edges[v] = append(edges[v], edge)
}
}
// We'll also obtain a set of bandwidthHints from the lower layer for
// each of our outbound channels. This will allow the path finding to
// skip any links that aren't active or just don't have enough
// bandwidth to carry the payment.
sourceNode, err := m.graph.SourceNode()
if err != nil {
return nil, err
}
bandwidthHints, err := generateBandwidthHints(
sourceNode, m.queryBandwidth,
)
if err != nil {
return nil, err
}
return &paymentSession{
pruneViewSnapshot: viewSnapshot,
additionalEdges: edges,
bandwidthHints: bandwidthHints,
mc: m,
}, nil
}
// NewPaymentSessionFromRoutes creates a new paymentSession instance that will
// skip all path finding, and will instead utilize a set of pre-built routes.
// This constructor allows callers to specify their own routes which can be
// used for things like channel rebalancing, and swaps.
func (m *missionControl) NewPaymentSessionFromRoutes(routes []*Route) *paymentSession {
return &paymentSession{
pruneViewSnapshot: m.GraphPruneView(),
haveRoutes: true,
preBuiltRoutes: routes,
mc: m,
}
}
// generateBandwidthHints is a helper function that's utilized the main
// findPath function in order to obtain hints from the lower layer w.r.t to the
// available bandwidth of edges on the network. Currently, we'll only obtain
// bandwidth hints for the edges we directly have open ourselves. Obtaining
// these hints allows us to reduce the number of extraneous attempts as we can
// skip channels that are inactive, or just don't have enough bandwidth to
// carry the payment.
func generateBandwidthHints(sourceNode *channeldb.LightningNode,
queryBandwidth func(*channeldb.ChannelEdgeInfo) lnwire.MilliSatoshi) (map[uint64]lnwire.MilliSatoshi, error) {
// First, we'll collect the set of outbound edges from the target
// source node.
var localChans []*channeldb.ChannelEdgeInfo
err := sourceNode.ForEachChannel(nil, func(tx *bolt.Tx,
edgeInfo *channeldb.ChannelEdgeInfo,
_, _ *channeldb.ChannelEdgePolicy) error {
localChans = append(localChans, edgeInfo)
return nil
})
if err != nil {
return nil, err
}
// Now that we have all of our outbound edges, we'll populate the set
// of bandwidth hints, querying the lower switch layer for the most up
// to date values.
bandwidthHints := make(map[uint64]lnwire.MilliSatoshi)
for _, localChan := range localChans {
bandwidthHints[localChan.ChannelID] = queryBandwidth(localChan)
}
return bandwidthHints, nil
}
// 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 shared view after a period of
// vertexDecay. However, the vertex will remain pruned for the *local* session.
// This ensures we don't retry this vertex during the payment attempt.
func (p *paymentSession) ReportVertexFailure(v Vertex) {
log.Debugf("Reporting vertex %v failure to Mission Control", v)
// First, we'll add the failed vertex to our local prune view snapshot.
p.pruneViewSnapshot.vertexes[v] = struct{}{}
// With the vertex added, we'll now report back to the global prune
// view, with this new piece of information so it can be utilized for
// new payment sessions.
p.mc.Lock()
p.mc.failedVertexes[v] = time.Now()
p.mc.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 global view after a
// period of edgeDecay. However, the edge will remain pruned for the duration
// of the *local* session. This ensures that we don't flap by continually
// retrying an edge after its pruning has expired.
//
// TODO(roasbeef): also add value attempted to send and capacity of channel
func (p *paymentSession) ReportChannelFailure(e uint64) {
log.Debugf("Reporting edge %v failure to Mission Control", e)
// First, we'll add the failed edge to our local prune view snapshot.
p.pruneViewSnapshot.edges[e] = struct{}{}
// With the edge added, we'll now report back to the global prune view,
// with this new piece of information so it can be utilized for new
// payment sessions.
p.mc.Lock()
p.mc.failedEdges[e] = time.Now()
p.mc.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 (p *paymentSession) RequestRoute(payment *LightningPayment,
height uint32, finalCltvDelta uint16) (*Route, error) {
switch {
// If we have a set of pre-built routes, then we'll just pop off the
// next route from the queue, and use it directly.
case p.haveRoutes && len(p.preBuiltRoutes) > 0:
nextRoute := p.preBuiltRoutes[0]
p.preBuiltRoutes[0] = nil // Set to nil to avoid GC leak.
p.preBuiltRoutes = p.preBuiltRoutes[1:]
return nextRoute, nil
// If we were instantiated with a set of pre-built routes, and we've
// run out, then we'll return a terminal error.
case p.haveRoutes && len(p.preBuiltRoutes) == 0:
return nil, fmt.Errorf("pre-built routes exhausted")
}
// Otherwise we actually need to perform path finding, so we'll obtain
// our current prune view snapshot. This view will only ever grow
// during the duration of this payment session, never shrinking.
pruneView := p.pruneViewSnapshot
log.Debugf("Mission Control session using prune view of %v "+
"edges, %v vertexes", len(pruneView.edges),
len(pruneView.vertexes))
// 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, p.mc.graph, p.additionalEdges, p.mc.selfNode,
payment.Target, pruneView.vertexes, pruneView.edges,
payment.Amount, payment.FeeLimit, p.bandwidthHints,
)
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 := Vertex(p.mc.selfNode.PubKeyBytes)
route, err := newRoute(
payment.Amount, payment.FeeLimit, sourceVertex, path, height,
finalCltvDelta,
)
if err != nil {
// TODO(roasbeef): return which edge/vertex didn't work
// out
return nil, err
}
return route, err
}
// 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()
}