10000 [RateLimiter] Fix SlidingWindow calculations by Jeroeny · Pull Request #47557 · symfony/symfony · GitHub
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[RateLimiter] Fix SlidingWindow calculations #47557

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[RateLimiter] Fix SlidingWindow calculations #47557

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calculateTimeForTokens for SlidingWindow
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@Jeroeny
Jeroeny committed Nov 30, 2022
commit e3906cfde91ec418bd77488696c61b354dc82d3f
21 changes: 21 additions & 0 deletions src/Symfony/Component/RateLimiter/Policy/SlidingWindow.php
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,27 @@ public function getRetryAfter(): \DateTimeImmutable
return \DateTimeImmutable::createFromFormat('U.u', sprintf('%.6F', $this->windowEndAt));
}

public function calculateTimeForTokens(int $maxSize, int $tokens): int
{
$remaining = $maxSize - $this->getHitCount();
if ($remaining >= $tokens) {
return 0;
}

$startOfWindow = $this->windowEndAt - $this->intervalInSeconds;
$percentOfCurrentTimeFrame = min((microtime(true) - $startOfWindow) / $this->intervalInSeconds, 1);
$releasable = $maxSize - floor($this->hitCountForLastWindow * (1 - $percentOfCurrentTimeFrame));
$remainingWindow = (microtime(true) - $startOfWindow) - $this->intervalInSeconds;
$timePerToken = $remainingWindow / $releasable;
$needed = $tokens - $remaining;

if ($releasable <= $needed) {
return (int) ceil($needed * $timePerToken);
}

return (int) (($this->windowEndAt - microtime(true)) + ceil(($needed - $releasable) * ($this->intervalInSeconds / $maxSize)));
}

public function __serialize(): array
{
return [
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42 changes: 31 additions & 11 deletions src/Symfony/Component/RateLimiter/Policy/SlidingWindowLimiter.php
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Expand Up @@ -12,7 +12,7 @@
namespace Symfony\Component\RateLimiter\Policy;

use Symfony\Component\Lock\LockInterface;
use Symfony\Component\RateLimiter\Exception\ReserveNotSupportedException;
use Symfony\Component\RateLimiter\Exception\MaxWaitDurationExceededException;
use Symfony\Component\RateLimiter\LimiterInterface;
use Symfony\Component\RateLimiter\RateLimit;
use Symfony\Component\RateLimiter\Reservation;
Expand Down Expand Up @@ -48,11 +48,10 @@ public function __construct(string $id, int $limit, \DateInterval $interval, Sto

public function reserve(int $tokens = 1, float $maxTime = null): Reservation
{
throw new ReserveNotSupportedException(__CLASS__);
}
if ($tokens > $this->limit) {
throw new \InvalidArgumentException(sprintf('Cannot reserve more tokens (%d) than the size of the rate limiter (%d).', $tokens, $this->limit));
}

public function consume(int $tokens = 1): RateLimit
{
$this->lock?->acquire(true);

try {
Expand All @@ -63,22 +62,43 @@ public function consume(int $tokens = 1): RateLimit
$window = SlidingWindow::createFromPreviousWindow($window, $this->interval);
}

$now = microtime(true);
$hitCount = $window->getHitCount();
$availableTokens = $this->getAvailableTokens($hitCount);
if ($availableTokens < $tokens) {
return new RateLimit($availableTokens, $window->getRetryAfter(), false, $this->limit);
}
if ($availableTokens >= $tokens) {
$window->add($tokens);

$window->add($tokens);
$reservation = new Reservation($now, new RateLimit($this->getAvailableTokens($window->getHitCount()), \DateTimeImmutable::createFromFormat('U', floor($now)), true, $this->limit));
} else {
$waitDuration = $window->calculateTimeForTokens($this->limit, max(1, $tokens));

if (null !== $maxTime && $waitDuration > $maxTime) {
// process needs to wait longer than set interval
throw new MaxWaitDurationExceededException(sprintf('The rate limiter wait time ("%d" seconds) is longer than the provided maximum time ("%d" seconds).', $waitDuration, $maxTime), new RateLimit($this->getAvailableTokens($window->getHitCount()), \DateTimeImmutable::createFromFormat('U', floor($now + $waitDuration)), false, $this->limit));
}

$window->add($tokens);

$reservation = new Reservation($now + $waitDuration, new RateLimit($this->getAvailableTokens($window->getHitCount()), \DateTimeImmutable::createFromFormat('U', floor($now + $waitDuration)), false, $this->limit));
}

if (0 < $tokens) {
$this->storage->save($window);
}

return new RateLimit($this->getAvailableTokens($window->getHitCount()), $window->getRetryAfter(), true, $this->limit);
} finally {
$this->lock?->release();
}

return $reservation;
}

public function consume(int $tokens = 1): RateLimit
{
try {
return $this->reserve($tokens, 0)->getRateLimit();
} catch (MaxWaitDurationExceededException $e) {
return $e->getRateLimit();
}
}

private function getAvailableTokens(int $hitCount): int
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10 changes: 6 additions & 4 deletions src/Symfony/Component/RateLimiter/Tests/Policy/SlidingWindowLimiterTest.php
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Expand Up @@ -13,7 +13,6 @@

use PHPUnit\Framework\TestCase;
use Symfony\Bridge\PhpUnit\ClockMock;
use Symfony\Component\RateLimiter\Exception\ReserveNotSupportedException;
use Symfony\Component\RateLimiter\Policy\SlidingWindowLimiter;
use Symfony\Component\RateLimiter\RateLimit;
use Symfony\Component\RateLimiter\Storage\InMemoryStorage;
Expand Down Expand Up @@ -66,14 +65,17 @@ public function testWaitIntervalOnConsumeOverLimit()

$start = microtime(true);
$rateLimit->wait(); // wait 12 seconds
$this->assertEqualsWithDelta($start + 12, microtime(true), 1);
$this->assertEqualsWithDelta($start + (12 / 5), microtime(true), 1);
$this->assertTrue($limiter->consume()->isAccepted());
}

public function testReserve()
{
$this->expectException(ReserveNotSupportedException::class);
$limiter = $this->createLimiter();
$limiter->consume(8);

$this->createLimiter()->reserve();
// 2 over the limit, causing the WaitDuration to become 2/10th of the 12s interval
$this->assertEqualsWithDelta(12 / 5, $limiter->reserve(4)->getWaitDuration(), 1);
}

public function testPeekConsume()
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0