PHP rate limiting client

Question

I use a variety of 3rd party web APIs, and many of them enforce rate limiting. It would be very useful to have a fairly generic PHP library that I could rate limit my calls with. I can think of a few ways to do it, perhaps by putting calls into a queue with a timestamp of when the call can be made, but I was hoping to avoid reinventing the wheel if someone else has already done this well.

Answer 1

I realize this is an old thread but thought I'd post my solution since it was based on something else I found on SE. I looked for a while for an answer myself but had trouble finding something good. It's based on the Python solution discussed here, but I've added support for variable-sized requests and turned it into a function generator using PHP closures.

function ratelimiter($rate = 5, $per = 8) {
  $last_check = microtime(True);
  $allowance = $rate;

  return function ($consumed = 1) use (
    &$last_check,
    &$allowance,
    $rate,
    $per
  ) {
    $current = microtime(True);
    $time_passed = $current - $last_check;
    $last_check = $current;

    $allowance += $time_passed * ($rate / $per);
    if ($allowance > $rate)
      $allowance = $rate;

    if ($allowance < $consumed) {
      $duration = ($consumed - $allowance) * ($per / $rate);
      $last_check += $duration;
      usleep($duration * 1000000);
      $allowance = 0;
    }
    else
      $allowance -= $consumed;

    return;
  };
}

It can be used to limit just about anything. Here's a stupid example that limits a simple statement at the default five "requests" per eight seconds:

$ratelimit = ratelimiter();
while (True) {
  $ratelimit();
  echo "foo".PHP_EOL;
}

Here's how I'm using it to limit batched requests against the Facebook Graph API at 600 requests per 600 seconds based on the size of the batch:

$ratelimit = ratelimiter(600, 600);
while (..) {
  ..

  $ratelimit(count($requests));
  $response = (new FacebookRequest(
    $session, 'POST', '/', ['batch' => json_encode($requests)]
  ))->execute();

  foreach ($response->..) {
    ..
  }
}

Hope this helps someone!

Answer 2

You can do rate limiting with the token bucket algorithm. I implemented that for you in PHP: bandwidth-throttle/token-bucket :

use bandwidthThrottle\tokenBucket\Rate;
use bandwidthThrottle\tokenBucket\TokenBucket;
use bandwidthThrottle\tokenBucket\storage\FileStorage;

$storage = new FileStorage(__DIR__ . "/api.bucket");
$rate    = new Rate(10, Rate::SECOND);
$bucket  = new TokenBucket(10, $rate, $storage);
$bucket->bootstrap(10);

if (!$bucket->consume(1, $seconds)) {
    http_response_code(429);
    header(sprintf("Retry-After: %d", floor($seconds)));
    exit();
}