TypeScript 97.5%
SQL 1.4%
Python 0.8%
1import type { ConcreteNetwork, GeoTarget, NetworkClass, Plan } from "@fetcha/core";2import { PLAN_LIMITS } from "@fetcha/core";3import type { ProviderId, ProviderRegistry, ProxyProvider } from "@fetcha/providers";4import type { CircuitBreaker } from "./circuit";56export type RouteKey = `${ProviderId}:${ConcreteNetwork}`;78export function routeKey(provider: ProviderId, network: ConcreteNetwork): RouteKey {9 return `${provider}:${network}`;10}1112/** Aggregated statistics for a domain, as stored in `domain_profiles.route_stats`. */13export type RouteStats = Record<string, { n: number; ok: number; blocked: number; lat: number; cost: number }>;1415export interface DomainKnowledge {16 domain: string;17 routeStats: RouteStats;18 policy?: { order?: string[]; force_network?: string; browser?: boolean } | null;19 /** Share of requests where the browser was needed after HTTP attempts were blocked. */20 browserRequiredRate?: number;21 /** Number of requests behind `browserRequiredRate`. */22 browserSamples?: number;23}2425export interface RoutingInput {26 domain: string;27 network: NetworkClass;28 geo: GeoTarget;29 plan: Plan;30 sessionRequired: boolean;31 browser: boolean;32 /** Override the max number of attempts (bounded by plan). */33 retries?: number;34 knowledge?: DomainKnowledge | null;35}3637export interface RouteCandidate {38 provider: ProxyProvider;39 network: ConcreteNetwork;40 score: number;41 reasons: string[];42 estimatedCostPerMb: number;43}4445export interface RoutingPlan {46 candidates: RouteCandidate[];47 maxAttempts: number;48 networksConsidered: ConcreteNetwork[];49}5051export const SCORE_WEIGHTS = {52 success: 0.35,53 cost: 0.2,54 latency: 0.15,55 health: 0.15,56 geo: 0.1,57 session: 0.05,58} as const;5960/** Escalation order for `auto`: cheap first, then more expensive/reliable classes. */61const AUTO_NETWORK_ORDER: ConcreteNetwork[] = ["datacenter", "isp", "residential", "mobile"];6263const NETWORK_BASE_SUCCESS: Record<ConcreteNetwork, number> = {64 datacenter: 0.7,65 isp: 0.85,66 residential: 0.93,67 mobile: 0.95,68};6970export class RoutingEngine {71 constructor(72 private readonly registry: ProviderRegistry,73 private readonly circuit: CircuitBreaker,74 ) {}7576 plan(input: RoutingInput): RoutingPlan {77 const limits = PLAN_LIMITS[input.plan];78 const maxAttempts = Math.min((input.retries ?? limits.max_retries) + 1, limits.max_retries + 1);7980 const networks: ConcreteNetwork[] =81 input.network === "auto"82 ? AUTO_NETWORK_ORDER.filter((n) => limits.networks.includes(n))83 : [input.network];8485 const forced = input.knowledge?.policy?.force_network as ConcreteNetwork | undefined;86 const consider = forced && input.network === "auto" ? [forced] : networks;8788 const candidates: RouteCandidate[] = [];89 for (const network of consider) {90 for (const provider of this.registry.available(network)) {91 if (!provider.supportsGeo(input.geo)) continue;92 const key = routeKey(provider.id, network);93 if (!this.circuit.allow(key)) continue;94 candidates.push(this.score(provider, network, input));95 }96 }9798 // Admin-pinned order for the domain wins over score, within the same network class.99 const pinned = input.knowledge?.policy?.order;100 if (pinned?.length) {101 const rank = new Map(pinned.map((k, i) => [k, i]));102 candidates.sort((a, b) => {103 const ra = rank.get(routeKey(a.provider.id, a.network)) ?? 999;104 const rb = rank.get(routeKey(b.provider.id, b.network)) ?? 999;105 return ra - rb || b.score - a.score;106 });107 } else if (input.network === "auto") {108 // Auto: escalate by class order, but inside a class order by score. If a domain has109 // strong evidence a cheaper class is blocked (>60% block rate), skip it entirely.110 const classRank = new Map(AUTO_NETWORK_ORDER.map((n, i) => [n, i]));111 const filtered = candidates.filter((c) => {112 const st = input.knowledge?.routeStats?.[routeKey(c.provider.id, c.network)];113 if (st && st.n >= 5 && st.blocked / st.n > 0.6 && c.network !== "residential") return false;114 return true;115 });116 const pool = filtered.length ? filtered : candidates;117 pool.sort((a, b) => (classRank.get(a.network)! - classRank.get(b.network)!) || b.score - a.score);118 return { candidates: dedupeProviders(pool, maxAttempts), maxAttempts, networksConsidered: consider };119 } else {120 candidates.sort((a, b) => b.score - a.score);121 }122 return { candidates: candidates.slice(0, Math.max(maxAttempts, 1)), maxAttempts, networksConsidered: consider };123 }124125 score(provider: ProxyProvider, network: ConcreteNetwork, input: RoutingInput): RouteCandidate {126 const key = routeKey(provider.id, network);127 const stats = input.knowledge?.routeStats?.[key];128 const reasons: string[] = [];129130 // 35% historical success (Bayesian-smoothed toward the network prior)131 const prior = NETWORK_BASE_SUCCESS[network];132 const n = stats?.n ?? 0;133 const ok = stats?.ok ?? 0;134 const success = (ok + prior * 5) / (n + 5);135 reasons.push(`success=${(success * 100).toFixed(0)}%${n ? ` (n=${n})` : " (prior)"}`);136137 // 20% cost efficiency: normalize against the most expensive class (~$15/GB)138 const pricePerGb = provider.pricePerGb(network);139 const cost = Math.max(0, 1 - pricePerGb / 15);140 reasons.push(`price=$${pricePerGb}/GB`);141142 // 15% latency: 300 ms → 1.0, 5 s → 0143 const lat = stats?.n ? stats.lat : network === "datacenter" ? 500 : 1200;144 const latency = Math.max(0, Math.min(1, 1 - (lat - 300) / 4700));145 reasons.push(`latency≈${Math.round(lat)}ms`);146147 // 15% provider health (circuit breaker window)148 const health = this.circuit.healthFactor(key);149 reasons.push(`health=${(health * 100).toFixed(0)}%`);150151 // 10% geography match152 const geo = input.geo.country ? (provider.supportsGeo(input.geo) ? 1 : 0) : 1;153154 // 5% session stability (all upstream residential networks support sticky sessions; direct does not)155 const session = input.sessionRequired ? (provider.id === "direct" ? 0 : 1) : 1;156157 const total =158 SCORE_WEIGHTS.success * success +159 SCORE_WEIGHTS.cost * cost +160 SCORE_WEIGHTS.latency * latency +161 SCORE_WEIGHTS.health * health +162 SCORE_WEIGHTS.geo * geo +163 SCORE_WEIGHTS.session * session;164165 return { provider, network, score: Math.round(total * 1000) / 1000, reasons, estimatedCostPerMb: pricePerGb / 1024 };166 }167}168169/** Keep escalation diversity: alternate providers before repeating the same one. */170function dedupeProviders(sorted: RouteCandidate[], max: number): RouteCandidate[] {171 const out: RouteCandidate[] = [];172 const seen = new Set<string>();173 for (const c of sorted) {174 const k = routeKey(c.provider.id, c.network);175 if (seen.has(k)) continue;176 seen.add(k);177 out.push(c);178 if (out.length >= max) break;179 }180 // Fewer distinct routes than the attempt budget: round-robin over them (each retry gets a new exit IP).181 const distinct = out.length;182 while (distinct > 0 && out.length < max) out.push(out[out.length % distinct]!);183 return out;184}185186/** Update aggregated route stats after an attempt (pure helper used by the persistence layer). */187export function foldRouteStat(stats: RouteStats, key: string, outcome: { ok: boolean; blocked: boolean; latencyMs: number; costUsd: number }): RouteStats {188 const cur = stats[key] ?? { n: 0, ok: 0, blocked: 0, lat: 0, cost: 0 };189 const n = cur.n + 1;190 stats[key] = {191 n,192 ok: cur.ok + (outcome.ok ? 1 : 0),193 blocked: cur.blocked + (outcome.blocked ? 1 : 0),194 lat: cur.lat + (outcome.latencyMs - cur.lat) / n,195 cost: cur.cost + outcome.costUsd,196 };197 return stats;198}199200export function preferredRoute(stats: RouteStats): { provider: ProviderId; network: ConcreteNetwork } | null {201 let best: { key: string; v: number } | null = null;202 for (const [key, s] of Object.entries(stats)) {203 if (s.n < 3) continue;204 const successRate = s.ok / s.n;205 const costPerSuccess = s.ok ? s.cost / s.ok : Infinity;206 const v = successRate - Math.min(costPerSuccess * 100, 0.5);207 if (!best || v > best.v) best = { key, v };208 }209 if (!best) return null;210 const [provider, network] = best.key.split(":") as [ProviderId, ConcreteNetwork];211 return { provider, network };212}213