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<?php |
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|
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namespace Dudlewebs\WPMCS\s3\Aws\Retry; |
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|
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/** |
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* @internal |
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*/ |
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class RateLimiter |
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{ |
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// User-configurable constants |
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private $beta; |
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private $minCapacity; |
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private $minFillRate; |
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private $scaleConstant; |
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private $smooth; |
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// Optional callable time provider |
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private $timeProvider; |
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// Pre-set state variables |
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private $currentCapacity = 0; |
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private $enabled = \false; |
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private $lastMaxRate = 0; |
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private $measuredTxRate = 0; |
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private $requestCount = 0; |
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// Other state variables |
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private $fillRate; |
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private $lastThrottleTime; |
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private $lastTimestamp; |
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private $lastTxRateBucket; |
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private $maxCapacity; |
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private $timeWindow; |
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public function __construct($options = []) |
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{ |
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$this->beta = isset($options['beta']) ? $options['beta'] : 0.7; |
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$this->minCapacity = isset($options['min_capacity']) ? $options['min_capacity'] : 1; |
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$this->minFillRate = isset($options['min_fill_rate']) ? $options['min_fill_rate'] : 0.5; |
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$this->scaleConstant = isset($options['scale_constant']) ? $options['scale_constant'] : 0.4; |
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$this->smooth = isset($options['smooth']) ? $options['smooth'] : 0.8; |
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$this->timeProvider = isset($options['time_provider']) ? $options['time_provider'] : null; |
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$this->lastTxRateBucket = \floor($this->time()); |
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$this->lastThrottleTime = $this->time(); |
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} |
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public function isEnabled() |
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{ |
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return $this->enabled; |
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} |
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public function getSendToken() |
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{ |
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$this->acquireToken(1); |
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} |
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public function updateSendingRate($isThrottled) |
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{ |
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$this->updateMeasuredRate(); |
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if ($isThrottled) { |
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if (!$this->isEnabled()) { |
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$rateToUse = $this->measuredTxRate; |
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} else { |
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$rateToUse = \min($this->measuredTxRate, $this->fillRate); |
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} |
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$this->lastMaxRate = $rateToUse; |
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$this->calculateTimeWindow(); |
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$this->lastThrottleTime = $this->time(); |
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$calculatedRate = $this->cubicThrottle($rateToUse); |
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$this->enableTokenBucket(); |
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} else { |
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$this->calculateTimeWindow(); |
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$calculatedRate = $this->cubicSuccess($this->time()); |
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} |
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$newRate = \min($calculatedRate, 2 * $this->measuredTxRate); |
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$this->updateTokenBucketRate($newRate); |
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return $newRate; |
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} |
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private function acquireToken($amount) |
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{ |
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if (!$this->enabled) { |
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return \true; |
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} |
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$this->refillTokenBucket(); |
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if ($amount > $this->currentCapacity) { |
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\usleep((int) (1000000 * ($amount - $this->currentCapacity) / $this->fillRate)); |
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} |
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$this->currentCapacity -= $amount; |
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return \true; |
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} |
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private function calculateTimeWindow() |
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{ |
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$this->timeWindow = \pow($this->lastMaxRate * (1 - $this->beta) / $this->scaleConstant, 0.333); |
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} |
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private function cubicSuccess($timestamp) |
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{ |
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$dt = $timestamp - $this->lastThrottleTime; |
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return $this->scaleConstant * \pow($dt - $this->timeWindow, 3) + $this->lastMaxRate; |
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} |
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private function cubicThrottle($rateToUse) |
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{ |
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return $rateToUse * $this->beta; |
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} |
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private function enableTokenBucket() |
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{ |
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$this->enabled = \true; |
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} |
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private function refillTokenBucket() |
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{ |
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$timestamp = $this->time(); |
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if (!isset($this->lastTimestamp)) { |
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$this->lastTimestamp = $timestamp; |
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return; |
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} |
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$fillAmount = ($timestamp - $this->lastTimestamp) * $this->fillRate; |
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$this->currentCapacity = $this->currentCapacity + $fillAmount; |
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if (!\is_null($this->maxCapacity)) { |
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$this->currentCapacity = \min($this->maxCapacity, $this->currentCapacity); |
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} |
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$this->lastTimestamp = $timestamp; |
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} |
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private function time() |
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{ |
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if (\is_callable($this->timeProvider)) { |
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$provider = $this->timeProvider; |
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$time = $provider(); |
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return $time; |
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} |
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return \microtime(\true); |
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} |
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private function updateMeasuredRate() |
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{ |
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$timestamp = $this->time(); |
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$timeBucket = \floor(\round($timestamp, 3) * 2) / 2; |
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$this->requestCount++; |
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if ($timeBucket > $this->lastTxRateBucket) { |
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$currentRate = $this->requestCount / ($timeBucket - $this->lastTxRateBucket); |
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$this->measuredTxRate = $currentRate * $this->smooth + $this->measuredTxRate * (1 - $this->smooth); |
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$this->requestCount = 0; |
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$this->lastTxRateBucket = $timeBucket; |
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} |
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} |
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private function updateTokenBucketRate($newRps) |
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{ |
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$this->refillTokenBucket(); |
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$this->fillRate = \max($newRps, $this->minFillRate); |
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$this->maxCapacity = \max($newRps, $this->minCapacity); |
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$this->currentCapacity = \min($this->currentCapacity, $this->maxCapacity); |
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} |
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} |
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