typescript 51 lines · 8 steps

Retrying HTTP requests with backoff

A generic wrapper that retries failed requests on transient errors using exponential backoff with jitter.

Explained by highlit

Intermediate retry exponential-backoff error-handling generics async

1type RetryableRequest<T> = () => Promise<T>;
2 
3interface RetryOptions {
4  maxAttempts?: number;
5  baseDelayMs?: number;
6  retryOnStatus?: number[];
7}
8 
9class HttpError extends Error {
10  constructor(public readonly status: number, message: string) {
11    super(message);
12    this.name = "HttpError";
13  }
14}
15 
16const isHttpError = (err: unknown): err is HttpError =>
17  err instanceof HttpError;
18 
19const sleep = (ms: number) => new Promise((r) => setTimeout(r, ms));
20 
21export async function withRetry<T>(
22  request: RetryableRequest<T>,
23  options: RetryOptions = {},
24): Promise<T> {
25  const {
26    maxAttempts = 3,
27    baseDelayMs = 200,
28    retryOnStatus = [429, 502, 503, 504],
29  } = options;
30 
31  let lastError: unknown;
32 
33  for (let attempt = 1; attempt <= maxAttempts; attempt++) {
34    try {
35      return await request();
36    } catch (err) {
37      lastError = err;
38 
39      const retryable = isHttpError(err) && retryOnStatus.includes(err.status);
40      if (!retryable || attempt === maxAttempts) {
41        throw err;
42      }
43 
44      const jitter = Math.random() * baseDelayMs;
45      const delay = baseDelayMs * 2 ** (attempt - 1) + jitter;
46      await sleep(delay);
47    }
48  }
49 
50  throw lastError;
51}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Only retry on transient failures — inspect the error type and status before deciding to try again.
2Exponential backoff with random jitter spreads out retries and avoids synchronized thundering-herd load.
3A generic wrapper keeps retry logic reusable across any promise-returning request without coupling to a specific client.

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