routing: extract probability estimator cfg and add validation

In preparation for allowing live update of mc config, we extract our
probability estimator cfg for easy update and add validation.

routing/integrated_routing_context_test.go

@@ -58,10 +58,12 @@ func newIntegratedRoutingContext(t *testing.T) *integratedRoutingContext {
 		finalExpiry: 40,
 
 		mcCfg: MissionControlConfig{
+			ProbabilityEstimatorCfg: ProbabilityEstimatorCfg{
 				PenaltyHalfLife:       30 * time.Minute,
 				AprioriHopProbability: 0.6,
 				AprioriWeight:         0.5,
 			},
+		},
 
 		pathFindingCfg: PathFindingConfig{
 			AttemptCost:    1000,

routing/missioncontrol.go

@@ -1,6 +1,7 @@
 package routing
 
 import (
+	"errors"
 	"fmt"
 	"sync"
 	"time"
@@ -58,6 +59,17 @@ const (
 	DefaultMinFailureRelaxInterval = time.Minute
 )
 
+var (
+	// ErrInvalidMcHistory is returned if we get a negative mission control
+	// history count.
+	ErrInvalidMcHistory = errors.New("mission control history must be " +
+		">= 0")
+
+	// ErrInvalidFailureInterval is returned if we get an invalid failure
+	// interval.
+	ErrInvalidFailureInterval = errors.New("failure interval must be >= 0")
+)
+
 // NodeResults contains previous results from a node to its peers.
 type NodeResults map[route.Vertex]TimedPairResult
 
@@ -99,33 +111,36 @@ type MissionControl struct {
 // MissionControlConfig defines parameters that control mission control
 // behaviour.
 type MissionControlConfig struct {
-	// PenaltyHalfLife defines after how much time a penalized node or
-	// channel is back at 50% probability.
-	PenaltyHalfLife time.Duration
-
-	// AprioriHopProbability is the assumed success probability of a hop in
-	// a route when no other information is available.
-	AprioriHopProbability float64
+	// ProbabilityEstimatorConfig is the config we will use for probability
+	// calculations.
+	ProbabilityEstimatorCfg
 
 	// MaxMcHistory defines the maximum number of payment results that are
 	// held on disk.
 	MaxMcHistory int
 
-	// AprioriWeight is a value in the range [0, 1] that defines to what
-	// extent historical results should be extrapolated to untried
-	// connections. Setting it to one will completely ignore historical
-	// results and always assume the configured a priori probability for
-	// untried connections. A value of zero will ignore the a priori
-	// probability completely and only base the probability on historical
-	// results, unless there are none available.
-	AprioriWeight float64
-
 	// MinFailureRelaxInterval is the minimum time that must have passed
 	// since the previously recorded failure before the failure amount may
 	// be raised.
 	MinFailureRelaxInterval time.Duration
 }
 
+func (c *MissionControlConfig) validate() error {
+	if err := c.ProbabilityEstimatorCfg.validate(); err != nil {
+		return err
+	}
+
+	if c.MaxMcHistory < 0 {
+		return ErrInvalidMcHistory
+	}
+
+	if c.MinFailureRelaxInterval < 0 {
+		return ErrInvalidFailureInterval
+	}
+
+	return nil
+}
+
 // String returns a string representation of a mission control config.
 func (c *MissionControlConfig) String() string {
 	return fmt.Sprintf("Penalty Half Life: %v, Apriori Hop "+
@@ -190,15 +205,17 @@ func NewMissionControl(db kvdb.Backend, self route.Vertex,
 
 	log.Debugf("Instantiating mission control with config: %v", cfg)
 
+	if err := cfg.validate(); err != nil {
+		return nil, err
+	}
+
 	store, err := newMissionControlStore(db, cfg.MaxMcHistory)
 	if err != nil {
 		return nil, err
 	}
 
 	estimator := &probabilityEstimator{
-		aprioriHopProbability:  cfg.AprioriHopProbability,
-		aprioriWeight:          cfg.AprioriWeight,
-		penaltyHalfLife:        cfg.PenaltyHalfLife,
+		ProbabilityEstimatorCfg: cfg.ProbabilityEstimatorCfg,
 		prevSuccessProbability:  prevSuccessProbability,
 	}
 

routing/missioncontrol_test.go

@@ -80,10 +80,12 @@ func (ctx *mcTestContext) restartMc() {
 	mc, err := NewMissionControl(
 		ctx.db, mcTestSelf,
 		&MissionControlConfig{
+			ProbabilityEstimatorCfg: ProbabilityEstimatorCfg{
 				PenaltyHalfLife:       testPenaltyHalfLife,
 				AprioriHopProbability: testAprioriHopProbability,
 				AprioriWeight:         testAprioriWeight,
 			},
+		},
 	)
 	if err != nil {
 		ctx.t.Fatal(err)

routing/probability_estimator.go

@@ -1,6 +1,7 @@
 package routing
 
 import (
+	"errors"
 	"math"
 	"time"
 
@@ -8,25 +9,61 @@ import (
 	"github.com/lightningnetwork/lnd/routing/route"
 )
 
-// probabilityEstimator returns node and pair probabilities based on historical
-// payment results.
-type probabilityEstimator struct {
-	// penaltyHalfLife defines after how much time a penalized node or
+var (
+	// ErrInvalidHalflife is returned when we get an invalid half life.
+	ErrInvalidHalflife = errors.New("penalty half life must be >= 0")
+
+	// ErrInvalidHopProbability is returned when we get an invalid hop
+	// probability.
+	ErrInvalidHopProbability = errors.New("hop probability must be in [0;1]")
+
+	// ErrInvalidAprioriWeight is returned when we get an apriori weight
+	// that is out of range.
+	ErrInvalidAprioriWeight = errors.New("apriori weight must be in [0;1]")
+)
+
+// ProbabilityEstimatorCfg contains configuration for our probability estimator.
+type ProbabilityEstimatorCfg struct {
+	// PenaltyHalfLife defines after how much time a penalized node or
 	// channel is back at 50% probability.
-	penaltyHalfLife time.Duration
+	PenaltyHalfLife time.Duration
 
-	// aprioriHopProbability is the assumed success probability of a hop in
+	// AprioriHopProbability is the assumed success probability of a hop in
 	// a route when no other information is available.
-	aprioriHopProbability float64
+	AprioriHopProbability float64
 
-	// aprioriWeight is a value in the range [0, 1] that defines to what
+	// AprioriWeight is a value in the range [0, 1] that defines to what
 	// extent historical results should be extrapolated to untried
 	// connections. Setting it to one will completely ignore historical
 	// results and always assume the configured a priori probability for
 	// untried connections. A value of zero will ignore the a priori
 	// probability completely and only base the probability on historical
 	// results, unless there are none available.
-	aprioriWeight float64
+	AprioriWeight float64
+}
+
+func (p ProbabilityEstimatorCfg) validate() error {
+	if p.PenaltyHalfLife < 0 {
+		return ErrInvalidHalflife
+	}
+
+	if p.AprioriHopProbability < 0 || p.AprioriHopProbability > 1 {
+		return ErrInvalidHopProbability
+	}
+
+	if p.AprioriWeight < 0 || p.AprioriWeight > 1 {
+		return ErrInvalidAprioriWeight
+	}
+
+	return nil
+}
+
+// probabilityEstimator returns node and pair probabilities based on historical
+// payment results.
+type probabilityEstimator struct {
+	// ProbabilityEstimatorCfg contains configuration options for our
+	// estimator.
+	ProbabilityEstimatorCfg
 
 	// prevSuccessProbability is the assumed probability for node pairs that
 	// successfully relayed the previous attempt.
@@ -41,14 +78,14 @@ func (p *probabilityEstimator) getNodeProbability(now time.Time,
 
 	// If the channel history is not to be taken into account, we can return
 	// early here with the configured a priori probability.
-	if p.aprioriWeight == 1 {
-		return p.aprioriHopProbability
+	if p.AprioriWeight == 1 {
+		return p.AprioriHopProbability
 	}
 
 	// If there is no channel history, our best estimate is still the a
 	// priori probability.
 	if len(results) == 0 {
-		return p.aprioriHopProbability
+		return p.AprioriHopProbability
 	}
 
 	// The value of the apriori weight is in the range [0, 1]. Convert it to
@@ -58,7 +95,7 @@ func (p *probabilityEstimator) getNodeProbability(now time.Time,
 	// the weighted average calculation below. When the apriori weight
 	// approaches 1, the apriori factor goes to infinity. It will heavily
 	// outweigh any observations that have been collected.
-	aprioriFactor := 1/(1-p.aprioriWeight) - 1
+	aprioriFactor := 1/(1-p.AprioriWeight) - 1
 
 	// Calculate a weighted average consisting of the apriori probability
 	// and historical observations. This is the part that incentivizes nodes
@@ -76,7 +113,7 @@ func (p *probabilityEstimator) getNodeProbability(now time.Time,
 	// effectively prunes all channels of the node forever. This is the most
 	// aggressive way in which we can penalize nodes and unlikely to yield
 	// good results in a real network.
-	probabilitiesTotal := p.aprioriHopProbability * aprioriFactor
+	probabilitiesTotal := p.AprioriHopProbability * aprioriFactor
 	totalWeight := aprioriFactor
 
 	for _, result := range results {
@@ -106,7 +143,7 @@ func (p *probabilityEstimator) getNodeProbability(now time.Time,
 // the result is fresh and asymptotically approaches zero over time. The rate at
 // which this happens is controlled by the penaltyHalfLife parameter.
 func (p *probabilityEstimator) getWeight(age time.Duration) float64 {
-	exp := -age.Hours() / p.penaltyHalfLife.Hours()
+	exp := -age.Hours() / p.PenaltyHalfLife.Hours()
 	return math.Pow(2, exp)
 }
 

routing/probability_estimator_test.go

@@ -40,9 +40,11 @@ func newEstimatorTestContext(t *testing.T) *estimatorTestContext {
 	return &estimatorTestContext{
 		t: t,
 		estimator: &probabilityEstimator{
-			aprioriHopProbability:  aprioriHopProb,
-			aprioriWeight:          aprioriWeight,
-			penaltyHalfLife:        time.Hour,
+			ProbabilityEstimatorCfg: ProbabilityEstimatorCfg{
+				AprioriHopProbability: aprioriHopProb,
+				AprioriWeight:         aprioriWeight,
+				PenaltyHalfLife:       time.Hour,
+			},
 			prevSuccessProbability: aprioriPrevSucProb,
 		},
 	}

routing/router_test.go

@@ -85,9 +85,11 @@ func createTestCtxFromGraphInstance(startingHeight uint32, graphInstance *testGr
 	}
 
 	mcConfig := &MissionControlConfig{
+		ProbabilityEstimatorCfg: ProbabilityEstimatorCfg{
 			PenaltyHalfLife:       time.Hour,
 			AprioriHopProbability: 0.9,
 			AprioriWeight:         0.5,
+		},
 	}
 
 	mc, err := NewMissionControl(

server.go

@@ -725,13 +725,17 @@ func newServer(cfg *Config, listenAddrs []net.Addr,
 	// servers, the mission control instance itself can be moved there too.
 	routingConfig := routerrpc.GetRoutingConfig(cfg.SubRPCServers.RouterRPC)
 
+	estimatorCfg := routing.ProbabilityEstimatorCfg{
+		AprioriHopProbability: routingConfig.AprioriHopProbability,
+		PenaltyHalfLife:       routingConfig.PenaltyHalfLife,
+		AprioriWeight:         routingConfig.AprioriWeight,
+	}
+
 	s.missionControl, err = routing.NewMissionControl(
 		remoteChanDB, selfNode.PubKeyBytes,
 		&routing.MissionControlConfig{
-			AprioriHopProbability:   routingConfig.AprioriHopProbability,
-			PenaltyHalfLife:         routingConfig.PenaltyHalfLife,
+			ProbabilityEstimatorCfg: estimatorCfg,
 			MaxMcHistory:            routingConfig.MaxMcHistory,
-			AprioriWeight:           routingConfig.AprioriWeight,
 			MinFailureRelaxInterval: routing.DefaultMinFailureRelaxInterval,
 		},
 	)