32. Rate limiting and retries

Public and even paid RPC providers rate-limit requests. A robust client backs off and retries transient failures (timeouts, 429s, 5xx) with increasing delay, instead of hammering the endpoint or failing on the first blip.

js
async function withRetry(fn, { attempts = 5, baseDelay = 200 } = {}) {
  for (let i = 0; i < attempts; i++) {
    try {
      return await fn();
    } catch (err) {
      if (i === attempts - 1) throw err;
      const delay = baseDelay * 2 ** i; // exponential backoff
      await new Promise((r) => setTimeout(r, delay));
    }
  }
}

const block = await withRetry(() => rpcCall(url, "eth_blockNumber"));

Exponential backoff (doubling the delay each retry) spreads out retries so a temporary outage doesn't turn into a thundering herd of simultaneous retries the instant service resumes.

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