| 1 | /** |
| 2 | * Running a part's check: each request it makes, all at once, with a short |
| 3 | * timeout. The answer's body is never read. |
| 4 | */ |
| 5 | import type { Check, Step } from "./components.ts"; |
| 6 | |
| 7 | /** A check's raw outcome. */ |
| 8 | export type ProbeResult = { |
| 9 | ok: boolean; |
| 10 | /** How long it took, in milliseconds: the slowest of its requests. */ |
| 11 | ms: number; |
| 12 | /** Why it failed, in a few words: "timed out", "HTTP 502". */ |
| 13 | error?: string; |
| 14 | }; |
| 15 | |
| 16 | /** No request waits longer than this. */ |
| 17 | export const TIMEOUT_MS = 5000; |
| 18 | |
| 19 | export const USER_AGENT = "g1t-status (+https://status.g1t.sh)"; |
| 20 | |
| 21 | type Fetch = (url: string, init: RequestInit) => Promise<Response>; |
| 22 | |
| 23 | class Timeout extends Error {} |
| 24 | |
| 25 | /** Runs `work`, timing it, and failing it after `timeoutMs`. */ |
| 26 | export async function timed( |
| 27 | work: (signal: AbortSignal) => Promise<true | string>, |
| 28 | timeoutMs = TIMEOUT_MS, |
| 29 | now: () => number = Date.now, |
| 30 | ): Promise<ProbeResult> { |
| 31 | const started = now(); |
| 32 | const controller = new AbortController(); |
| 33 | let timer: ReturnType<typeof setTimeout> | undefined; |
| 34 | const deadline = new Promise<never>((_, reject) => { |
| 35 | timer = setTimeout(() => { |
| 36 | controller.abort(); |
| 37 | reject(new Timeout()); |
| 38 | }, timeoutMs); |
| 39 | }); |
| 40 | try { |
| 41 | const outcome = await Promise.race([work(controller.signal), deadline]); |
| 42 | const ms = now() - started; |
| 43 | return outcome === true ? { ok: true, ms } : { ok: false, ms, error: outcome }; |
| 44 | } catch (error) { |
| 45 | const ms = now() - started; |
| 46 | return { ok: false, ms, error: error instanceof Timeout ? "timed out" : "could not connect" }; |
| 47 | } finally { |
| 48 | clearTimeout(timer); |
| 49 | } |
| 50 | } |
| 51 | |
| 52 | /** One request, answered with the status that means it works. */ |
| 53 | export function step(fetcher: Fetch, { url, headers = {}, expect }: Step, timeoutMs = TIMEOUT_MS): Promise<ProbeResult> { |
| 54 | return timed(async (signal) => { |
| 55 | const response = await fetcher(url, { |
| 56 | signal, |
| 57 | redirect: "manual", |
| 58 | headers: { "user-agent": USER_AGENT, "cache-control": "no-cache", ...headers }, |
| 59 | }); |
| 60 | await response.body?.cancel().catch(() => undefined); |
| 61 | const good = expect == null ? response.ok : response.status === expect; |
| 62 | return good || `HTTP ${response.status}`; |
| 63 | }, timeoutMs); |
| 64 | } |
| 65 | |
| 66 | /** A check's requests together: it works when every one does, and takes as long as the slowest. */ |
| 67 | export function combine(results: ProbeResult[]): ProbeResult { |
| 68 | const ms = Math.max(0, ...results.map((r) => r.ms)); |
| 69 | const failed = results.find((r) => !r.ok); |
| 70 | return failed ? { ok: false, ms, error: failed.error ?? "no answer" } : { ok: true, ms }; |
| 71 | } |
| 72 | |
| 73 | /** What runs a check. `billing` is null when there is no binding to it. */ |
| 74 | export type Probers = { |
| 75 | fetch: Fetch; |
| 76 | billing: (() => Promise<unknown>) | null; |
| 77 | timeoutMs?: number; |
| 78 | }; |
| 79 | |
| 80 | /** Runs one part's check. Null for a part with no check. */ |
| 81 | export async function runCheck(check: Check, probers: Probers): Promise<ProbeResult | null> { |
| 82 | const timeoutMs = probers.timeoutMs ?? TIMEOUT_MS; |
| 83 | switch (check.kind) { |
| 84 | case "http": |
| 85 | return combine(await Promise.all(check.steps.map((s) => step(probers.fetch, s, timeoutMs)))); |
| 86 | case "billing": { |
| 87 | const billing = probers.billing; |
| 88 | if (!billing) return null; |
| 89 | return timed(async () => ((await billing()) ? true : "no price book"), timeoutMs); |
| 90 | } |
| 91 | case "none": |
| 92 | return null; |
| 93 | } |
| 94 | } |