The token bucket algorithm can be used for controlling the usage rate
of a resource. The scope of that rate is determined by the underlying
storage.
Example:
use bandwidthThrottle\tokenBucket\Rate;
use bandwidthThrottle\tokenBucket\TokenBucket;
use bandwidthThrottle\tokenBucket\storage\FileStorage;
$storage = new FileStorage(__DIR__ . "/api.bucket");
$rate = new Rate(10, Rate::SECOND);
$bucket = new TokenBucket(10, $rate, $storage);
$bucket->bootstrap(10);
if (!$bucket->consume(1, $seconds)) {
http_response_code(429);
header(sprintf("Retry-After: %d", floor($seconds)));
exit();
}
/**
* Initialize the a new token bucket, then proload that bucket with tokens
* @param string $bucketName The name of the bucket to create
* @param Rate $fillRate Rate Object used to define fill rate
* @return TokenBucket The initialized bucket
* @access private
*/
private function initializeBucket($bucketName, Rate $fillRate)
{
$storage = new PHPRedisStorage($bucketName, $this->redisObj);
$bucket = new TokenBucket(self::MAXBUCKETSIZE, $fillRate, $storage);
$bucket->bootstrap(self::MAXBUCKETSIZE);
return $bucket;
}
/**
* Test the capacity limit of the bucket
*
* @test
*/
public function testCapacity()
{
$rate = new Rate(1, Rate::SECOND);
$tokenBucket = new TokenBucket(10, $rate, new SingleProcessStorage());
$tokenBucket->bootstrap();
sleep(11);
$this->assertTrue($tokenBucket->consume(10));
$this->assertFalse($tokenBucket->consume(1));
}
/**
* Tests traffic shapping filtering.
*
* @param float $expectedDuration The expected duration in seconds.
* @param int[] $bytes The amount of bytes to write.
*
* @test
* @dataProvider provideTestFilterShapesTraffic
*/
public function testFilterShapesTraffic($expectedDuration, array $bytes)
{
$stream = fopen("php://memory", "w");
$bucket = new TokenBucket(10, new Rate(1, Rate::SECOND), new SingleProcessStorage());
$bucket->bootstrap();
stream_filter_register("test", TokenBucketFilter::class);
$this->filter = stream_filter_append($stream, "test", STREAM_FILTER_WRITE, $bucket);
$time = microtime(true);
foreach ($bytes as $byte) {
fwrite($stream, str_repeat(" ", $byte));
}
fclose($stream);
$this->assertLessThan(0.001, abs(microtime(true) - $time - $expectedDuration));
}
/**
* Throttles a stream to the given rate.
*
* This registers a filter to the given stream which does the traffic
* shaping. After that any stream operation is throttled.
*
* The stream can be an input or an output stream.
*
* This object can throttle only one stream at a time. If you want to
* call throttle() again, make either sure you called {@link unthrottle()}
* before or use a new instance.
*
* @param resource $stream The stream.
*
* @throws BandwidthThrottleException Error during throtteling the stream.
* @throws \LengthException The initial burst size was greater than the burst size.
*/
public function throttle($stream)
{
try {
if (is_resource($this->filter)) {
throw new BandwidthThrottleException("This throttle is still attached to a stream. Call unthrottle() or use a new instance.");
}
$this->registerOnce();
$capacity = empty($this->capacity) ? $this->rate->getTokensPerSecond() : $this->capacity;
$bucket = new TokenBucket($capacity, $this->rate, $this->storage);
$bucket->bootstrap($this->initialTokens);
$this->filter = stream_filter_append($stream, self::FILTER_NAME, $this->filterMode, $bucket);
if (!is_resource($this->filter)) {
throw new BandwidthThrottleException("Could not throttle the stream.");
}
} catch (StorageException $e) {
throw new BandwidthThrottleException("Could not initialize token bucket.", 0, $e);
}
}
/**
* Tests consume() won't sleep less than one millisecond.
*
* @test
*/
public function testMinimumSleep()
{
$rate = new Rate(10, Rate::MILLISECOND);
$bucket = new TokenBucket(1, $rate, new SingleProcessStorage());
$bucket->bootstrap();
$consumer = new BlockingConsumer($bucket);
$time = microtime(true);
$consumer->consume(1);
$this->assertLessThan(1.0E-5, abs(microtime(true) - $time - 0.001));
}
/**
* After waiting longer than the complete refill period on an empty bucket,
* getTokens() should return the capacity of the bucket.
*
* @test
*/
public function getTokensShouldReturnCapacityAfterWaitingLongerThanRefillPeriod()
{
$rate = new Rate(1, Rate::SECOND);
$bucket = new TokenBucket(10, $rate, new SingleProcessStorage());
$bucket->bootstrap(0);
sleep(11);
$this->assertEquals(10, $bucket->getTokens());
}
