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<?php |
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namespace ZoiloMora\ElasticAPM\Helper; |
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final class DistributedTracing |
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{ |
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/** |
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* Supporting Elastic's Traceparent Header until W3C goes GA |
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* |
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* @link https://www.w3.org/TR/trace-context/#header-name |
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*/ |
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const HEADER_NAME = 'ELASTIC-APM-TRACEPARENT'; |
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/** |
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* @link https://www.w3.org/TR/trace-context/#version |
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*/ |
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const VERSION = '00'; |
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/** |
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* @var DistributedTracing |
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*/ |
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private static $fakeDistributedTracing; |
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/** |
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* @var string |
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*/ |
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private $traceId; |
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/** |
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* @var string |
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*/ |
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private $parentId; |
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/** |
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* @var string |
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*/ |
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private $traceFlags; |
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/** |
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* @param DistributedTracing|null $fakeDistributedTracing |
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* |
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* @return void |
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*/ |
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public static function fakeDistributedTracing(DistributedTracing $fakeDistributedTracing = null) |
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{ |
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self::$fakeDistributedTracing = $fakeDistributedTracing; |
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} |
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/** |
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* @param string $traceId |
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* @param string $parentId |
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* @param string $traceFlags |
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*/ |
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public function __construct($traceId, $parentId, $traceFlags = '00') |
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{ |
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$this->traceId = $traceId; |
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$this->parentId = $parentId; |
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$this->traceFlags = $traceFlags; |
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} |
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/** |
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* @return string |
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*/ |
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public function traceId() |
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{ |
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return $this->traceId; |
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} |
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/** |
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* @return string |
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*/ |
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public function parentId() |
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{ |
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return $this->parentId; |
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} |
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/** |
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* @return string |
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*/ |
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public function traceFlags() |
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{ |
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return $this->traceFlags; |
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} |
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/** |
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* @return DistributedTracing|null |
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* |
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* @throws \Exception |
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*/ |
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public static function discoverDistributedTracing() |
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{ |
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if (null !== self::$fakeDistributedTracing) { |
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return self::$fakeDistributedTracing; |
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} |
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$traceHeader = self::traceHeader(); |
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if (null === $traceHeader) { |
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return null; |
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} |
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return self::createFromHeader($traceHeader); |
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} |
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/** |
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* @return string|null |
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*/ |
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private static function traceHeader() |
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{ |
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$key = sprintf( |
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'HTTP_%s', |
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str_replace( |
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'-', |
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'_', |
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self::HEADER_NAME |
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) |
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); |
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if (false === array_key_exists($key, $_SERVER)) { |
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return null; |
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} |
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return (string) $_SERVER[$key]; |
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} |
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/** |
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* Check if the Header Value is valid |
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* |
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* @link https://www.w3.org/TR/trace-context/#version-format |
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* |
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* @param string $header |
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* |
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* @return bool |
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*/ |
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private static function isValidHeader($header) |
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{ |
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return 1 === preg_match( |
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'/^' . self::VERSION . '-[\da-f]{32}-[\da-f]{16}-[\da-f]{2}$/', |
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$header |
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); |
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} |
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/** |
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* @param string $header |
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* |
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* @return DistributedTracing |
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* |
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* @throws \Exception |
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*/ |
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private static function createFromHeader($header) |
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{ |
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if (false === self::isValidHeader($header)) { |
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throw new \Exception('Invalid distributed trace header.'); |
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} |
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$parsed = explode('-', $header); |
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return new self($parsed[1], $parsed[2], $parsed[3]); |
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} |
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/** |
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* Get Distributed Tracing Id |
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* |
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* @return string |
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*/ |
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public function __toString() |
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{ |
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return sprintf( |
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'%s-%s-%s-%s', |
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self::VERSION, |
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$this->traceId, |
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$this->parentId, |
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$this->traceFlags |
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); |
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} |
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} |
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