v2: Updates

* Simplifies & beautifies everything
* Introduces a new Class system.
* Errors are defaulted to AWS's handler.
* New function names & more efficient handling.
* Should fix a majority of the errors.

Please read the README for more!

aws/Aws/Retry/RateLimiter.php

@@ -0,0 +1,182 @@
+<?php
+namespace Aws\Retry;
+
+
+/**
+ * @internal
+ */
+class RateLimiter
+{
+    // User-configurable constants
+    private $beta;
+    private $minCapacity;
+    private $minFillRate;
+    private $scaleConstant;
+    private $smooth;
+
+    // Optional callable time provider
+    private $timeProvider;
+
+    // Pre-set state variables
+    private $currentCapacity = 0;
+    private $enabled = false;
+    private $lastMaxRate = 0;
+    private $measuredTxRate = 0;
+    private $requestCount = 0;
+
+    // Other state variables
+    private $fillRate;
+    private $lastThrottleTime;
+    private $lastTimestamp;
+    private $lastTxRateBucket;
+    private $maxCapacity;
+    private $timeWindow;
+
+    public function __construct($options = [])
+    {
+        $this->beta = isset($options['beta'])
+            ? $options['beta']
+            : 0.7;
+        $this->minCapacity = isset($options['min_capacity'])
+            ? $options['min_capacity']
+            : 1;
+        $this->minFillRate = isset($options['min_fill_rate'])
+            ? $options['min_fill_rate']
+            : 0.5;
+        $this->scaleConstant = isset($options['scale_constant'])
+            ? $options['scale_constant']
+            : 0.4;
+        $this->smooth = isset($options['smooth'])
+            ? $options['smooth']
+            : 0.8;
+        $this->timeProvider = isset($options['time_provider'])
+            ? $options['time_provider']
+            : null;
+
+        $this->lastTxRateBucket = floor($this->time());
+        $this->lastThrottleTime = $this->time();
+    }
+
+    public function isEnabled()
+    {
+        return $this->enabled;
+    }
+
+    public function getSendToken()
+    {
+        $this->acquireToken(1);
+    }
+
+    public function updateSendingRate($isThrottled)
+    {
+        $this->updateMeasuredRate();
+
+        if ($isThrottled) {
+            if (!$this->isEnabled()) {
+                $rateToUse = $this->measuredTxRate;
+            } else {
+                $rateToUse = min($this->measuredTxRate, $this->fillRate);
+            }
+
+            $this->lastMaxRate = $rateToUse;
+            $this->calculateTimeWindow();
+            $this->lastThrottleTime = $this->time();
+            $calculatedRate = $this->cubicThrottle($rateToUse);
+            $this->enableTokenBucket();
+        } else {
+            $this->calculateTimeWindow();
+            $calculatedRate = $this->cubicSuccess($this->time());
+        }
+        $newRate = min($calculatedRate, 2 * $this->measuredTxRate);
+        $this->updateTokenBucketRate($newRate);
+        return $newRate;
+    }
+
+    private function acquireToken($amount)
+    {
+        if (!$this->enabled) {
+            return true;
+        }
+
+        $this->refillTokenBucket();
+
+        if ($amount > $this->currentCapacity) {
+            usleep(1000000 * ($amount - $this->currentCapacity) / $this->fillRate);
+        }
+
+        $this->currentCapacity -= $amount;
+        return true;
+    }
+
+    private function calculateTimeWindow()
+    {
+        $this->timeWindow = pow(($this->lastMaxRate * (1 - $this->beta) / $this->scaleConstant), 0.333);
+    }
+
+    private function cubicSuccess($timestamp)
+    {
+        $dt = $timestamp - $this->lastThrottleTime;
+        return $this->scaleConstant * pow($dt - $this->timeWindow, 3) + $this->lastMaxRate;
+    }
+
+    private function cubicThrottle($rateToUse)
+    {
+        return $rateToUse * $this->beta;
+    }
+
+    private function enableTokenBucket()
+    {
+        $this->enabled = true;
+    }
+
+    private function refillTokenBucket()
+    {
+        $timestamp = $this->time();
+        if (!isset($this->lastTimestamp)) {
+            $this->lastTimestamp = $timestamp;
+            return;
+        }
+        $fillAmount = ($timestamp - $this->lastTimestamp) * $this->fillRate;
+        $this->currentCapacity = $this->currentCapacity + $fillAmount;
+        if (!is_null($this->maxCapacity)) {
+            $this->currentCapacity = min(
+                $this->maxCapacity,
+                $this->currentCapacity
+            );
+        }
+
+        $this->lastTimestamp = $timestamp;
+    }
+
+    private function time()
+    {
+        if (is_callable($this->timeProvider)) {
+            $provider = $this->timeProvider;
+            $time = $provider();
+            return $time;
+        }
+        return microtime(true);
+    }
+
+    private function updateMeasuredRate()
+    {
+        $timestamp = $this->time();
+        $timeBucket = floor(round($timestamp, 3) * 2) / 2;
+        $this->requestCount++;
+        if ($timeBucket > $this->lastTxRateBucket) {
+            $currentRate = $this->requestCount / ($timeBucket - $this->lastTxRateBucket);
+            $this->measuredTxRate = ($currentRate * $this->smooth)
+                + ($this->measuredTxRate * (1 - $this->smooth));
+            $this->requestCount = 0;
+            $this->lastTxRateBucket = $timeBucket;
+        }
+    }
+
+    private function updateTokenBucketRate($newRps)
+    {
+        $this->refillTokenBucket();
+        $this->fillRate = max($newRps, $this->minFillRate);
+        $this->maxCapacity = max($newRps, $this->minCapacity);
+        $this->currentCapacity = min($this->currentCapacity, $this->maxCapacity);
+    }
+}