gistfile1.txt

<?php

namespace App\Services;

use Psr\Http\Message\RequestInterface;
use Zipkin\Propagation\RequestHeaders;
use Zipkin\Tracing;

class ZipkinGuzzleMiddleware {

    /**
     * ZipkinGuzzleMiddleware constructor.
     */
    public function __construct(Tracing $tracing)
    {
        $this->tracing = $tracing;
    }

    /**
     * @param callable $handler
     * @return \Closure
     */
    function __invoke(callable $handler)
    {
        return function (RequestInterface $request, array $options) use ($handler) {
            $injector = $this->tracing->getPropagation()->getInjector(new RequestHeaders());

            $context = $this->tracing->getTracer()->getCurrentSpan()->getContext();
            $injector($context, $request);

            return $handler($request, $options);
        };
    }
}