[opentelemetry-php-contrib] [opentelemetry-auto-symfony] http.route uses route name instead of route template path

[Apoorva64]

Describe your environment

• PHP version: 8.4
• open-telemetry/opentelemetry-auto-symfony: ^1.1.1
• Symfony: 8
• OS: Linux

Steps to reproduce

1. Create a Symfony application with a route that has path parameters:

<?php
#[Route('/v1/payments/{paymentId}/capture', name: 'api_payments_capture', methods: ['POST'])]
public function capture(string $paymentId): Response
{
    return new JsonResponse(['id' => $paymentId]);
}

2. Make a request to POST /v1/payments/abc123/capture
3. Inspect the generated span in your tracing backend (Jaeger, etc.) in http.route will be "api_payments_capture"

What is the expected behavior?
Per OpenTelemetry HTTP semantic conventions, http.route should be "the matched route template for the request. This MUST be low-cardinality and include all static path segments, with dynamic path segments represented with placeholders"

• http.route: /v1/payments/{paymentId}/capture

What is the actual behavior?
The instrumentation uses the Symfony route name from $request->attributes->get('_route'):

• http.route: api_payments_capture

Additional context
Current workaround is to use an event subscriber that modifies _route before the instrumentation reads it, but this is fragile and could affect other application logic that depends on the route name.

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[Apoorva64]

current subscriber workaround

<?php

namespace App\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\Event\ControllerEvent;
use Symfony\Component\HttpKernel\KernelEvents;
use Symfony\Component\Routing\RouterInterface;

/**
 * Replaces the _route attribute with the route template path for OpenTelemetry.
 * 
 * The opentelemetry-auto-symfony instrumentation uses $_route for http.route,
 * but OpenTelemetry semantic conventions require the matched route template
 * (low-cardinality) with placeholders, not logical route names.
 * 
 * This subscriber runs after the router but before the auto-instrumentation
 * reads the _route attribute, replacing the route name with the template path.
 */
class OpenTelemetryRouteSubscriber implements EventSubscriberInterface
{
    public function __construct(
        private RouterInterface $router,
    ) {
    }

    public static function getSubscribedEvents(): array
    {
        // Run after RouterListener (priority 32) resolves the route
        return [
            KernelEvents::CONTROLLER => ['onKernelController', 0],
        ];
    }

    public function onKernelController(ControllerEvent $event): void
    {
        if (!$event->isMainRequest()) {
            return;
        }

        $request = $event->getRequest();
        $routeName = $request->attributes->get('_route');
        
        if (!$routeName) {
            return;
        }

        // Get the route template (path with placeholders)
        try {
            $routeCollection = $this->router->getRouteCollection();
            $route = $routeCollection->get($routeName);
            
            if ($route) {
                $routeTemplate = $route->getPath();
                
                // Replace _route with the template path so the auto-instrumentation
                // picks it up correctly when it sets http.route
                $request->attributes->set('_route', $routeTemplate);
            }
        } catch (\Throwable $e) {
            // Silently ignore - don't break the request for telemetry
        }
    }
}