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nicolas-grekasnicolas-grekas
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bug #44354 [RateLimiter] Make RateLimiter resilient to timeShifting (jderusse)
This PR was merged into the 5.3 branch. Discussion ---------- [RateLimiter] Make RateLimiter resilient to timeShifting | Q | A | ------------- | --- | Branch? | 5.3 | Bug fix? | yes | New feature? | no | Deprecations? | no | Tickets | - | License | MIT | Doc PR | - When 2 servers use the FixedWindowLimiter and do not have the exact same clock (with microsecond precision) the `Window` might return 0 available tokens. Commits ------- 6918a21 Make RateLimiter resilient to timeShifting
2 parents fdc61b4 + 6918a21 commit 9b1dcc5

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6 files changed

+34
-11
lines changed

6 files changed

+34
-11
lines changed

‎src/Symfony/Component/RateLimiter/Policy/FixedWindowLimiter.php

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -66,7 +66,7 @@ public function reserve(int $tokens = 1, float $maxTime = null): Reservation
6666
$now = microtime(true);
6767
$availableTokens = $window->getAvailableTokens($now);
6868
if ($availableTokens >= $tokens) {
69-
$window->add($tokens);
69+
$window->add($tokens, $now);
7070

7171
$reservation = new Reservation($now, new RateLimit($window->getAvailableTokens($now), \DateTimeImmutable::createFromFormat('U', floor($now)), true, $this->limit));
7272
} else {
@@ -77,7 +77,7 @@ public function reserve(int $tokens = 1, float $maxTime = null): Reservation
7777
throw new MaxWaitDurationExceededException(sprintf('The rate limiter wait time ("%d" seconds) is longer than the provided maximum time ("%d" seconds).', $waitDuration, $maxTime), new RateLimit($window->getAvailableTokens($now), \DateTimeImmutable::createFromFormat('U', floor($now + $waitDuration)), false, $this->limit));
7878
}
7979

80-
$window->add($tokens);
80+
$window->add($tokens, $now);
8181

8282
$reservation = new Reservation($now + $waitDuration, new RateLimit($window->getAvailableTokens($now), \DateTimeImmutable::createFromFormat('U', floor($now + $waitDuration)), false, $this->limit));
8383
}

‎src/Symfony/Component/RateLimiter/Policy/TokenBucket.php

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -82,7 +82,7 @@ public function setTokens(int $tokens): void
8282

8383
public function getAvailableTokens(float $now): int
8484
{
85-
$elapsed = $now - $this->timer;
85+
$elapsed = max(0, $now - $this->timer);
8686

8787
return min($this->burstSize, $this->tokens + $this->rate->calculateNewTokensDuringInterval($elapsed));
8888
}

‎src/Symfony/Component/RateLimiter/Policy/TokenBucketLimiter.php

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -88,10 +88,10 @@ public function reserve(int $tokens = 1, float $maxTime = null): Reservation
8888

8989
// at $now + $waitDuration all tokens will be reserved for this process,
9090
// so no tokens are left for other processes.
91-
$bucket->setTokens(0);
92-
$bucket->setTimer($now + $waitDuration);
91+
$bucket->setTokens($availableTokens - $tokens);
92+
$bucket->setTimer($now);
9393

94-
$reservation = new Reservation($bucket->getTimer(), new RateLimit(0, \DateTimeImmutable::createFromFormat('U', floor($now + $waitDuration)), false, $this->maxBurst));
94+
$reservation = new Reservation($now + $waitDuration, new RateLimit(0, \DateTimeImmutable::createFromFormat('U', floor($now + $waitDuration)), false, $this->maxBurst));
9595
}
9696

9797
$this->storage->save($bucket);

‎src/Symfony/Component/RateLimiter/Policy/Window.php

Lines changed: 0 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -68,11 +68,6 @@ public function getHitCount(): int
6868

6969
public function getAvailableTokens(float $now)
7070
{
71-
// if timer is in future, there are no tokens available anymore
72-
if ($this->timer > $now) {
73-
return 0;
74-
}
75-
7671
// if now is more than the window interval in the past, all tokens are available
7772
if (($now - $this->timer) > $this->intervalInSeconds) {
7873
return $this->maxSize;

‎src/Symfony/Component/RateLimiter/Tests/Policy/FixedWindowLimiterTest.php

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -14,6 +14,7 @@
1414
use PHPUnit\Framework\TestCase;
1515
use Symfony\Bridge\PhpUnit\ClockMock;
1616
use Symfony\Component\RateLimiter\Policy\FixedWindowLimiter;
17+
use Symfony\Component\RateLimiter\Policy\Window;
1718
use Symfony\Component\RateLimiter\RateLimit;
1819
use Symfony\Component\RateLimiter\Storage\InMemoryStorage;
1920
use Symfony\Component\RateLimiter\Tests\Resources\DummyWindow;
@@ -90,6 +91,19 @@ public function testWrongWindowFromCache()
9091
$this->assertEquals(9, $rateLimit->getRemainingTokens());
9192
}
9293

94+
public function testWindowResilientToTimeShifting()
95+
{
96+
$serverOneClock = microtime(true) - 1;
97+
$serverTwoClock = microtime(true) + 1;
98+
$window = new Window('id', 300, 100, $serverTwoClock);
99+
$this->assertSame(100, $window->getAvailableTokens($serverTwoClock));
100+
$this->assertSame(100, $window->getAvailableTokens($serverOneClock));
101+
102+
$window = new Window('id', 300, 100, $serverOneClock);
103+
$this->assertSame(100, $window->getAvailableTokens($serverTwoClock));
104+
$this->assertSame(100, $window->getAvailableTokens($serverOneClock));
105+
}
106+
93107
private function createLimiter(): FixedWindowLimiter
94108
{
95109
return new FixedWindowLimiter('test', 10, new \DateInterval('PT1M'), $this->storage);

‎src/Symfony/Component/RateLimiter/Tests/Policy/TokenBucketLimiterTest.php

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -114,6 +114,20 @@ public function testWrongWindowFromCache()
114114
$this->assertEquals(9, $rateLimit->getRemainingTokens());
115115
}
116116

117+
public function testBucketResilientToTimeShifting()
118+
{
119+
$serverOneClock = microtime(true) - 1;
120+
$serverTwoClock = microtime(true) + 1;
121+
122+
$bucket = new TokenBucket('id', 100, new Rate(\DateInterval::createFromDateString('5 minutes'), 10), $serverTwoClock);
123+
$this->assertSame(100, $bucket->getAvailableTokens($serverTwoClock));
124+
$this->assertSame(100, $bucket->getAvailableTokens($serverOneClock));
125+
126+
$bucket = new TokenBucket('id', 100, new Rate(\DateInterval::createFromDateString('5 minutes'), 10), $serverOneClock);
127+
$this->assertSame(100, $bucket->getAvailableTokens($serverTwoClock));
128+
$this->assertSame(100, $bucket->getAvailableTokens($serverOneClock));
129+
}
130+
117131
private function createLimiter($initialTokens = 10, Rate $rate = null)
118132
{
119133
return new TokenBucketLimiter('test', $initialTokens, $rate ?? Rate::perSecond(10), $this->storage);

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