ExponentialBackoff.php

<?php

namespace SchulzeFelix\AdWords;

/**
 * Exponential backoff implementation.
 */
class ExponentialBackoff
{
    const MAX_DELAY_MICROSECONDS = 120000000;

    /**
     * @var int
     */
    private $retries;

    /**
     * @var callable
     */
    private $retryFunction;

    /**
     * @var callable
     */
    private $delayFunction;

    /**
     * @param int $retries [optional] Number of retries for a failed request.
     * @param callable $retryFunction [optional] returns bool for whether or not to retry
     */
    public function __construct($retries = null, callable $retryFunction = null)
    {
        $this->retries = $retries !== null ? (int) $retries : 3;
        $this->retryFunction = $retryFunction;
        $this->delayFunction = function ($delay) {
            usleep($delay);
        };
    }

    /**
     * Executes the retry process.
     *
     * @param callable $function
     * @param array $arguments [optional]
     * @return mixed
     * @throws \Exception The last exception caught while retrying.
     */
    public function execute(callable $function, array $arguments = [])
    {
        $delayFunction = $this->delayFunction;
        $retryAttempt = 0;
        $exception = null;

        while (true) {
            try {
                return call_user_func_array($function, $arguments);
            } catch (\Exception $exception) {
                if ($this->retryFunction) {
                    if (! call_user_func($this->retryFunction, $exception)) {
                        throw $exception;
                    }
                }

                if (in_array($exception->getCode(), [0, 400, 403])) {
                    break;
                }


                if ($retryAttempt >= $this->retries) {
                    break;
                }

                $delayFunction($this->calculateDelay($retryAttempt));
                $retryAttempt++;
            }
        }

        throw $exception;
    }

    /**
     * @param callable $delayFunction
     * @return void
     */
    public function setDelayFunction(callable $delayFunction)
    {
        $this->delayFunction = $delayFunction;
    }

    /**
     * Calculates exponential delay.
     *
     * @param int $attempt
     * @return int
     */
    private function calculateDelay($attempt)
    {
        return min(
            mt_rand(0, 1000000) + (pow(2, $attempt) * 1000000),
            self::MAX_DELAY_MICROSECONDS
        );
    }
}