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package routing
import (
"errors"
"sort"
"strconv"
"sync"
"sync/atomic"
"aigw/internal/catalog"
"aigw/internal/domain"
"aigw/internal/providerhealth"
)
var (
ErrNoRoute = errors.New("no compatible upstream route")
ErrNoHealthyRoute = errors.New("all compatible upstream routes have open circuits")
ErrProviderNotFound = errors.New("requested provider is not configured for this model and protocol")
)
type Router struct {
catalog *catalog.Catalog
health *providerhealth.Tracker
counters sync.Map
}
const (
adaptiveMinimumAvailabilitySamples = 5
adaptiveMinimumTTFTSamples = 3
adaptiveExplorationInterval = 20
adaptivePreferenceThreshold = 0.90
)
func New(catalog *catalog.Catalog, trackers ...*providerhealth.Tracker) *Router {
router := &Router{catalog: catalog}
if len(trackers) > 0 {
router.health = trackers[0]
}
return router
}
func (r *Router) Plan(modelID string, protocol domain.Protocol) ([]domain.Route, error) {
return r.plan(modelID, protocol, "")
}
func (r *Router) PlanProvider(modelID string, protocol domain.Protocol, providerSlug string) ([]domain.Route, error) {
return r.plan(modelID, protocol, providerSlug)
}
func (r *Router) plan(modelID string, protocol domain.Protocol, providerSlug string) ([]domain.Route, error) {
model, err := r.catalog.Model(modelID)
if err != nil {
return nil, err
}
routes := make([]domain.Route, 0, len(model.Routes))
compatible := 0
matched := 0
for _, route := range model.Routes {
if protocolCompatible(route.Provider, protocol) {
compatible++
if providerSlug != "" && route.Provider.EffectiveSlug() != providerSlug {
continue
}
matched++
if r.health != nil && r.health.CircuitOpen(providerhealth.RouteKey{ModelID: model.ID, ProviderID: route.Provider.ID, WireAPI: route.Provider.EffectiveWireAPI()}) {
continue
}
routes = append(routes, route)
}
}
if len(routes) == 0 {
if providerSlug != "" && matched == 0 {
return nil, ErrProviderNotFound
}
if compatible > 0 {
return nil, ErrNoHealthyRoute
}
return nil, ErrNoRoute
}
sort.SliceStable(routes, func(i, j int) bool { return routes[i].Priority < routes[j].Priority })
result := make([]domain.Route, 0, len(routes))
for start := 0; start < len(routes); {
end := start + 1
for end < len(routes) && routes[end].Priority == routes[start].Priority {
end++
}
result = append(result, r.rotate(modelID, protocol, routes[start:end])...)
start = end
}
return result, nil
}
func protocolCompatible(provider domain.Provider, requestProtocol domain.Protocol) bool {
switch requestProtocol {
case domain.ProtocolOpenAI:
return provider.Protocol == domain.ProtocolOpenAI && provider.EffectiveWireAPI() == "chat_completions"
case domain.ProtocolOpenAIResponses:
return provider.Protocol == domain.ProtocolOpenAI && provider.EffectiveWireAPI() == "responses"
case domain.ProtocolOpenAIEmbeddings:
return provider.Protocol == domain.ProtocolOpenAI && provider.EffectiveWireAPI() == "embeddings"
case domain.ProtocolAnthropic:
return provider.Protocol == domain.ProtocolAnthropic && provider.EffectiveWireAPI() == "messages"
default:
return false
}
}
func (r *Router) rotate(modelID string, protocol domain.Protocol, routes []domain.Route) []domain.Route {
if len(routes) < 2 {
return append([]domain.Route(nil), routes...)
}
key := modelID + "\x00" + string(protocol) + "\x00" + strconv.Itoa(routes[0].Priority)
counterValue, _ := r.counters.LoadOrStore(key, &atomic.Uint64{})
counter := counterValue.(*atomic.Uint64).Add(1) - 1
indices := make([]int, len(routes))
for index := range routes {
indices[index] = index
}
primaryPool := indices
if r.health != nil && counter%adaptiveExplorationInterval != adaptiveExplorationInterval-1 {
if preferred := r.preferredRoutes(modelID, routes); len(preferred) > 0 && len(preferred) < len(routes) {
indices = append(preferred, difference(indices, preferred)...)
primaryPool = preferred
}
}
selectedPosition := weightedPosition(routes, primaryPool, counter)
selected := primaryPool[selectedPosition]
result := make([]domain.Route, 0, len(routes))
result = append(result, routes[selected])
for _, index := range indices {
if index != selected {
result = append(result, routes[index])
}
}
return result
}
func (r *Router) preferredRoutes(modelID string, routes []domain.Route) []int {
type measuredRoute struct {
qualified bool
status providerhealth.Status
}
measured := make([]measuredRoute, len(routes))
fastestTTFT := int64(0)
for index, route := range routes {
status, exists := r.health.StatusFor(providerhealth.RouteKey{ModelID: modelID, ProviderID: route.Provider.ID, WireAPI: route.Provider.EffectiveWireAPI()})
if !exists {
continue
}
qualified := status.RecentSamples >= adaptiveMinimumAvailabilitySamples || status.TTFTSamples >= adaptiveMinimumTTFTSamples
measured[index] = measuredRoute{qualified: qualified, status: status}
if status.TTFTSamples >= adaptiveMinimumTTFTSamples && status.TTFTEWMA > 0 && (fastestTTFT == 0 || status.TTFTEWMA < fastestTTFT) {
fastestTTFT = status.TTFTEWMA
}
}
scores := make([]float64, len(routes))
best := 0.0
hasQualified := false
for index, item := range measured {
score := 1.0
if item.qualified {
hasQualified = true
if item.status.RecentSamples >= adaptiveMinimumAvailabilitySamples {
availability := item.status.AvailabilityPercent / 100
if availability < 0.05 {
availability = 0.05
}
score *= availability
}
if fastestTTFT > 0 && item.status.TTFTSamples >= adaptiveMinimumTTFTSamples && item.status.TTFTEWMA > 0 {
latencyFactor := float64(fastestTTFT) / float64(item.status.TTFTEWMA)
if latencyFactor < 0.10 {
latencyFactor = 0.10
}
score *= latencyFactor
}
}
scores[index] = score
if score > best {
best = score
}
}
if !hasQualified {
return nil
}
result := make([]int, 0, len(routes))
for index, score := range scores {
if score >= best*adaptivePreferenceThreshold {
result = append(result, index)
}
}
return result
}
func difference(all, selected []int) []int {
included := make(map[int]struct{}, len(selected))
for _, index := range selected {
included[index] = struct{}{}
}
result := make([]int, 0, len(all)-len(selected))
for _, index := range all {
if _, exists := included[index]; !exists {
result = append(result, index)
}
}
return result
}
func weightedPosition(routes []domain.Route, indices []int, counter uint64) int {
totalWeight := 0
for _, index := range indices {
totalWeight += routes[index].Weight
}
position := int(counter % uint64(totalWeight))
for positionIndex, routeIndex := range indices {
if position < routes[routeIndex].Weight {
return positionIndex
}
position -= routes[routeIndex].Weight
}
return 0
}
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