Simple retry strategy for Guzzle 7 when encountering "429 Too Many Requests" errors

README.md

Simple retry strategy for Guzzle 7

APIs might implement rate limiting, and if they do your clients might experience 429 Too Many Requests responses with a Retry-After header, informing your client how long it should wait before making the next request. And being good internet citizens we should all implement support for this in our API clients.

Guzzle includes a retry middleware class that can be used to handle this.

The implementation in this gist is a PoC, so feel free to build upon it, and comment if you think something should be added / removed.

client.php

<?php declare(strict_types=1);
require 'vendor/autoload.php';

use Psr\Http\Message\{RequestInterface, ResponseInterface};
use GuzzleHttp\{Client, HandlerStack, Middleware, RetryMiddleware};

$maxRetries = 3;

$decider = function(int $retries, RequestInterface $request, ResponseInterface $response = null) use ($maxRetries) : bool {
    return 
        $retries < $maxRetries
        && null !== $response 
        && 429 === $response->getStatusCode();
};

$delay = function(int $retries, ResponseInterface $response) : int {
    if (!$response->hasHeader('Retry-After')) {
        return RetryMiddleware::exponentialDelay($retries);
    }

    $retryAfter = $response->getHeaderLine('Retry-After');

    if (!is_numeric($retryAfter)) {
        $retryAfter = (new DateTime($retryAfter))->getTimestamp() - time();
    }

    return (int) $retryAfter * 1000;
};

$stack = HandlerStack::create();
$stack->push(Middleware::retry($decider, $delay));

$client = new Client(['handler'  => $stack]);

// ...

composer.json

{
  "require": {
    "guzzlehttp/guzzle": "^7.1",
  }
}

Works great. There's a small bug:
The return RetryMiddleware::exponentialDelay($retries);
should be return RetryMiddleware::exponentialDelay($retries) * 1000;

@ignas2526 The exponentialDelay method does that itself:

https://github.com/guzzle/guzzle/blob/82ca75f0b1f130f018febdda29af13086da5dbac/src/RetryMiddleware.php#L55-L58

Thanks for your quick gist

Appreciate the gist! Thanks