Destination HTTP

1'use strict';
2
3// Per-call time limits: every destination HTTP call is bounded by an explicit
4// client-side timeout, and every wait goes through an injectable clock so the bounds can be
5// proven with a fake clock instead of real minutes.
6
7class CallTimeoutError extends Error {
8  constructor(timeoutMs) {
9    super(`request timed out after ${timeoutMs} ms`);
10    this.code = 'call_timeout';
11    this.timeoutMs = timeoutMs;
12  }
13}
14
15function realClock() {
16  return {
17    now: () => Date.now(),
18    // A cancelled timer never resolves; nothing waits on it after cancellation.
19    timer(ms) {
20      let handle = null;
21      const promise = new Promise((resolve) => {
22        handle = setTimeout(resolve, Math.max(0, ms));
23      });
24      return { promise, cancel() { clearTimeout(handle); } };
25    },
26    sleep(ms) { return this.timer(ms).promise; },
27  };
28}
29
30// One HTTP call: fetch plus body read, aborted at `timeoutMs`. Resolves to
31// `{ status, headers, text, json }` (json is null when the body is not JSON) or rejects with
32// CallTimeoutError (timeout) / the transport error (network). Never logs headers or bodies.
33async function boundedRequest({ fetch, clock }, url, init, timeoutMs) {
34  if (!(timeoutMs > 0)) throw new CallTimeoutError(0);
35  const controller = new AbortController();
36  const timer = clock.timer(timeoutMs);
37  let timedOut = false;
38  const timeout = timer.promise.then(() => {
39    timedOut = true;
40    controller.abort();
41    throw new CallTimeoutError(timeoutMs);
42  });
43  const call = (async () => {
44    const response = await fetch(url, { ...init, signal: controller.signal });
45    const text = await response.text();
46    let json = null;
47    try { json = text ? JSON.parse(text) : null; } catch { json = null; }
48    return {
49      status: response.status,
50      retryAfter: response.headers && typeof response.headers.get === 'function' ? response.headers.get('retry-after') : null,
51      text,
52      json,
53    };
54  })();
55  try {
56    return await Promise.race([call, timeout]);
57  } catch (error) {
58    if (timedOut) throw new CallTimeoutError(timeoutMs);
59    throw error;
60  } finally {
61    if (!timedOut) timer.cancel();
62    call.catch(() => {});
63    timeout.catch(() => {});
64  }
65}
66
67// Retry-After in seconds or an HTTP date; returns milliseconds or null.
68function retryAfterMs(value, nowMs) {
69  if (value === null || value === undefined || value === '') return null;
70  const text = String(value).trim();
71  if (/^\d+$/.test(text)) return Number(text) * 1000;
72  const date = Date.parse(text);
73  if (Number.isNaN(date)) return null;
74  return Math.max(0, date - nowMs);
75}
76
77function isTransientStatus(status) {
78  return status === 429 || (status >= 500 && status <= 599);
79}
80
81module.exports = { CallTimeoutError, boundedRequest, isTransientStatus, realClock, retryAfterMs };