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<?php |
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declare(strict_types=1); |
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namespace Yiisoft\Yii\Web\RateLimiter; |
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use Psr\SimpleCache\CacheInterface; |
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/** |
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* Counter implements generic сell rate limit algorithm (GCRA) that ensures that after reaching the limit futher |
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* requests are distributed equally. |
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* |
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* @link https://en.wikipedia.org/wiki/Generic_cell_rate_algorithm |
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*/ |
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final class Counter implements CounterInterface |
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{ |
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public const ID_PREFIX = 'rate-limiter-'; |
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private const MILLISECONDS_PER_SECOND = 1000; |
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private int $period; |
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private int $limit; |
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private ?string $id = null; |
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private CacheInterface $storage; |
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private int $arrivalTime; |
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public function __construct(int $limit, int $period, CacheInterface $storage) |
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{ |
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if ($limit < 1) { |
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throw new \InvalidArgumentException('The limit must be a positive value.'); |
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} |
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if ($period < 1) { |
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throw new \InvalidArgumentException('The period must be a positive value.'); |
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} |
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$this->limit = $limit; |
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$this->period = $period * self::MILLISECONDS_PER_SECOND; |
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$this->storage = $storage; |
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} |
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public function setId(string $id): void |
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{ |
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$this->id = self::ID_PREFIX . $id; |
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} |
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public function incrementAndGetResult(): CounterStatistics |
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{ |
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if ($this->id === null) { |
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throw new \LogicException('The counter id not set'); |
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} |
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$this->arrivalTime = $this->getArrivalTime(); |
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$theoreticalArrivalTime = $this->calculateTheoreticalArrivalTime($this->getStorageValue()); |
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$remaining = $this->getRemaining($theoreticalArrivalTime); |
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if ($remaining < 1) { |
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return new CounterStatistics($this->limit, 0, $this->getResetAfter($theoreticalArrivalTime)); |
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} |
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$this->setStorageValue($theoreticalArrivalTime); |
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return new CounterStatistics($this->limit, (int)$remaining, $this->getResetAfter($theoreticalArrivalTime)); |
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} |
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private function getEmissionInterval(): float |
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{ |
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return (float)($this->period / $this->limit); |
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} |
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private function calculateTheoreticalArrivalTime(float $theoreticalArrivalTime): float |
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{ |
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return max($this->arrivalTime, $theoreticalArrivalTime) + $this->getEmissionInterval(); |
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} |
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private function getRemaining(float $theoreticalArrivalTime): float |
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{ |
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$allowAt = $theoreticalArrivalTime - $this->period; |
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return (floor($this->arrivalTime - $allowAt) / $this->getEmissionInterval()) + 0.5; |
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} |
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private function getStorageValue(): float |
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{ |
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return $this->storage->get($this->id, (float)$this->arrivalTime); |
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} |
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private function setStorageValue(float $theoreticalArrivalTime): void |
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{ |
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$this->storage->set($this->id, $theoreticalArrivalTime); |
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} |
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private function getArrivalTime(): int |
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{ |
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return time() * self::MILLISECONDS_PER_SECOND; |
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} |
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private function getResetAfter(float $theoreticalArrivalTime): int |
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{ |
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return (int)($theoreticalArrivalTime - $this->arrivalTime); |
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} |
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} |
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yiisoft /
yii-web
