Retries and backoff

import os
import random
import time

import requests

RETRY_STATUS = {429, 502, 503, 504}
NEVER_CODES = {"quota_exceeded", "rate_limit_exceeded"}


def error_code(r: requests.Response) -> str | None:
    try:
        body = r.json()
    except ValueError:
        return None
    return body.get("code") or (body.get("error") or {}).get("code")


def get_with_retry(session, url, params=None, attempts=5, base=0.5, cap=30.0):
    for n in range(attempts):
        last = n == attempts - 1
        try:
            r = session.get(url, params=params, timeout=10)
        except (requests.ConnectionError, requests.Timeout):
            if last:
                raise
            time.sleep(random.uniform(0, min(cap, base * 2 ** n)))
            continue
        if r.status_code not in RETRY_STATUS or error_code(r) in NEVER_CODES or last:
            r.raise_for_status()
            return r
        wait = random.uniform(0, min(cap, base * 2 ** n))
        retry_after = r.headers.get("Retry-After", "")
        if retry_after.isdigit():
            wait = max(wait, float(retry_after))
        time.sleep(min(wait, cap))
    raise RuntimeError("unreachable")


session = requests.Session()
session.headers["X-Api-Key"] = os.environ["DANADRESSE_API_KEY"]
r = get_with_retry(session, "https://api.danadresse.dk/autocomplete",
                   params={"q": "Rådhuspladsen 1", "per_side": 1})
print(r.json()[0]["forslagstekst"])

const RETRY_STATUS = new Set([429, 502, 503, 504]);
const NEVER_CODES = new Set(["quota_exceeded", "rate_limit_exceeded"]);
const sleep = (ms) => new Promise((r) => setTimeout(r, ms));

async function errorCode(res) {
  try {
    const body = await res.clone().json();
    return body.code ?? body.error?.code ?? null;
  } catch {
    return null;
  }
}

export async function fetchWithRetry(url, init = {}, { attempts = 5, base = 500, cap = 30000 } = {}) {
  for (let n = 0; n < attempts; n++) {
    const last = n === attempts - 1;
    let res;
    try {
      res = await fetch(url, { ...init, signal: AbortSignal.timeout(10000) });
    } catch (err) {
      if (last) throw err;
      await sleep(Math.random() * Math.min(cap, base * 2 ** n));
      continue;
    }
    if (!RETRY_STATUS.has(res.status) || NEVER_CODES.has(await errorCode(res)) || last) {
      if (!res.ok) throw new Error(`HTTP ${res.status}: ${await res.text()}`);
      return res;
    }
    let wait = Math.random() * Math.min(cap, base * 2 ** n);
    const retryAfter = Number(res.headers.get("retry-after"));
    if (retryAfter > 0) wait = Math.max(wait, retryAfter * 1000);
    await sleep(Math.min(wait, cap));
  }
  throw new Error("unreachable");
}

const url = new URL("https://api.danadresse.dk/autocomplete");
url.search = new URLSearchParams({ q: "Rådhuspladsen 1", per_side: "1" });
const res = await fetchWithRetry(url, { headers: { "X-Api-Key": process.env.DANADRESSE_API_KEY } });
console.log((await res.json())[0].forslagstekst);

<?php
function getWithRetry(string $url, string $apiKey, int $attempts = 5, float $base = 0.5, float $cap = 30.0): array
{
    for ($n = 0; $n < $attempts; $n++) {
        $last = $n === $attempts - 1;
        $retryAfter = null;
        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT => 10,
            CURLOPT_HTTPHEADER => ["X-Api-Key: $apiKey"],
            CURLOPT_HEADERFUNCTION => function ($ch, $line) use (&$retryAfter) {
                if (stripos($line, 'Retry-After:') === 0) {
                    $retryAfter = (int) trim(substr($line, 12));
                }
                return strlen($line);
            },
        ]);
        $body = curl_exec($ch);
        $status = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
        $networkError = curl_errno($ch) !== 0;
        curl_close($ch);

        $jitter = mt_rand() / mt_getrandmax() * min($cap, $base * 2 ** $n);
        if ($networkError) {
            if ($last) {
                throw new RuntimeException('Network error');
            }
            usleep((int) ($jitter * 1e6));
            continue;
        }
        $data = json_decode($body, true) ?? [];
        $code = $data['code'] ?? ($data['error']['code'] ?? null);
        $retry = in_array($status, [429, 502, 503, 504], true)
            && !in_array($code, ['quota_exceeded', 'rate_limit_exceeded'], true);
        if (!$retry || $last) {
            if ($status >= 400) {
                throw new RuntimeException("HTTP $status: $body");
            }
            return $data;
        }
        $wait = max($jitter, (float) ($retryAfter ?? 0));
        usleep((int) (min($wait, $cap) * 1e6));
    }
    throw new RuntimeException('unreachable');
}

$data = getWithRetry(
    'https://api.danadresse.dk/autocomplete?q=' . rawurlencode('Rådhuspladsen 1') . '&per_side=1',
    getenv('DANADRESSE_API_KEY')
);
echo $data[0]['forslagstekst'], PHP_EOL;