| 1 | /** |
| 2 | * One run's model spend, as a Durable Object named by its model session. |
| 3 | * |
| 4 | * Why an object per run: the count must agree across every isolate the |
| 5 | * run's requests reach, at once, or an agent that sends many requests in |
| 6 | * parallel spends the cap once per isolate. A per-isolate count written |
| 7 | * back now and then has exactly that hole, and the proxy has no database |
| 8 | * of its own to count in (billing's token count is written after each |
| 9 | * answer, for usage views, and read nowhere near this fast). One object |
| 10 | * per run is the natural unit: a run is one model session, its object sees |
| 11 | * every one of its requests in order, and it costs two short requests per |
| 12 | * model answer (admit and settle) plus one storage write, far below what |
| 13 | * the answer itself costs. The object forgets the run a while after its |
| 14 | * session has lapsed. |
| 15 | */ |
| 16 | import { DurableObject } from "cloudflare:workers"; |
| 17 | |
| 18 | import { type Admission, SpendTally } from "./spend.ts"; |
| 19 | |
| 20 | /** How long after its first answer a run's count is kept: longer than a model session lives (3 hours). */ |
| 21 | const FORGET_MS = 4 * 60 * 60_000; |
| 22 | |
| 23 | export class RunSpend extends DurableObject<object> { |
| 24 | private tally = new SpendTally(); |
| 25 | |
| 26 | constructor(ctx: DurableObjectState, env: object) { |
| 27 | super(ctx, env); |
| 28 | void ctx.blockConcurrencyWhile(async () => { |
| 29 | this.tally = new SpendTally((await ctx.storage.get<number>("spent")) ?? 0); |
| 30 | }); |
| 31 | } |
| 32 | |
| 33 | /** Whether the run may start another answer under `cap`, in millionths of a dollar. */ |
| 34 | async admit(cap: number): Promise<Admission> { |
| 35 | const admission = this.tally.admit(cap, Date.now()); |
| 36 | if (admission.ok && admission.spent === 0 && (await this.ctx.storage.getAlarm()) === null) { |
| 37 | await this.ctx.storage.setAlarm(Date.now() + FORGET_MS); |
| 38 | } |
| 39 | return admission; |
| 40 | } |
| 41 | |
| 42 | /** An answer has ended, costing `micros`. Returns what the run has spent. */ |
| 43 | async settle(ticket: string, micros: number): Promise<number> { |
| 44 | const before = this.tally.spent; |
| 45 | const spent = this.tally.settle(ticket, micros); |
| 46 | if (spent !== before) await this.ctx.storage.put("spent", spent); |
| 47 | return spent; |
| 48 | } |
| 49 | |
| 50 | override async alarm(): Promise<void> { |
| 51 | await this.ctx.storage.deleteAll(); |
| 52 | this.tally = new SpendTally(); |
| 53 | } |
| 54 | } |