Guzzle4: Recording the time of an API Call

[J Cobb]

I'd like to be able to record the amount of time that it takes for an API Call to be sent and the full response to be received.

I was thinking this should be an Event Listener or Subscriber but I am having trouble figuring out how to attach one since I am also using a ClientFactory with a Service Description and all of the examples of adding subscribers/listeners seem to do so directly on the $client and I can't figure out how to access the client when using the Service Description. Additionally, I'm not sure how I would access the elapsed time after the call is complete.

Here is what I had started with, but I was unable to figure out how to actually get everything working. Any help is appreciated.

class RequestTimer implements SubscriberInterface

{

    /** @var float Used to measure API call execution time */

    protected $_timeStart;

    protected $_timeEnd;

    public function __construct(Configuration $config)

    {

        $this->config = $config;

    }

    public function getEvents()

    {

        return [

            'before' => ['_startTimer', (RequestEvents::SIGN_REQUEST - 1)],

            'after'  => ['_endTimer', (RequestEvents::EARLY + 1),

                '_getElapsedTime', (RequestEvents::EARLY + 2)],

        ];

    }

    protected function _startTimer(BeforeEvent $event)

    {

        $this->_timeStart = microtime(true);

    }

    protected function _endTimer(CompleteEvent $event)

    {

        $this->_timeEnd = microtime(true);

    }

    protected function _getElapsedTime()

    {

        try {

            return $this->_timeEnd - $this->_timeStart;

        } catch (\Exception $e) {

            return false;

        }

    }

}