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<?php
namespace Jaeger\Sampler;
use OutOfBoundsException;
use const Jaeger\SAMPLER_PARAM_TAG_KEY;
use const Jaeger\SAMPLER_TYPE_PROBABILISTIC;
use const Jaeger\SAMPLER_TYPE_TAG_KEY;
/**
* A sampler that randomly samples a certain percentage of traces specified
* by the samplingRate, in the range between 0.0 and 1.0.
*
* @package Jaeger\Sampler
*/
class ProbabilisticSampler implements SamplerInterface
{
/**
* The sampling rate rate between 0.0 and 1.0.
*
* @var float
*/
private $rate;
/**
* A list of the sampler tags.
*
* @var array
*/
private $tags = [];
/**
* The boundary of the sample sampling rate.
*
* @var float
*/
private $boundary;
/**
* ProbabilisticSampler constructor.
*
* @param float $rate
* @throws OutOfBoundsException
*/
public function __construct(float $rate)
{
$this->tags = [
SAMPLER_TYPE_TAG_KEY => SAMPLER_TYPE_PROBABILISTIC,
SAMPLER_PARAM_TAG_KEY => $rate,
];
if ($rate < 0.0 || $rate > 1.0) {
throw new OutOfBoundsException('Sampling rate must be between 0.0 and 1.0.');
}
$this->rate = $rate;
if ($rate < 0.5) {
$this->boundary = (int)($rate * PHP_INT_MAX);
} else {
// more precise calculation due to int and float having different precision near PHP_INT_MAX
$this->boundary = PHP_INT_MAX - (int)((1 - $rate) * PHP_INT_MAX);
}
}
/**
* {@inheritdoc}
*
* @param string $traceId The traceId on the span.
* @param string $operation The operation name set on the span.
* @return array
*/
public function isSampled(string $traceId, string $operation = ''): array
{
return [($traceId < $this->boundary), $this->tags];
}
/**
* {@inheritdoc}
*
* Only implemented to satisfy the sampler interface.
*
* @return void
*/
public function close()
{
// nothing to do
}
}
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