Continuing tracing with other systems

Using Open Telemetry, a trace can start and stop on different systems. For example, imagine a request handled by a webserver, triggering a job on a different queue server. Another example might be if you're building a microservice, an incoming request might already be part of an ongoing trace. The package is able to handle this.

##Accepting a trace from another system to your Laravel app

If your Laravel app is used in a bigger system, where one of the other apps started a trace, your Laravel app might get called by that other apps with a traceparent header. This header contains the ID of the trace that was previously started on another system.

To automatically discover and use this parent trace ID, you can use the ContinueTrace middleware. This middleware will look for incoming requests that have a traceparent header and use the given trace ID when available.

To use the ContinueTrace middleware, register it in your HTTP kernel.

namespace App\Http\Middleware;

use Spatie\OpenTelemetry\Http\Middleware\ContinueTrace;

class Kernel extends HttpKernel
{
    protected $middleware = [
        ContinueTrace::class,
        
        // other middleware
    ];
}

##Sending trace information from your Laravel app to another system

If your app uses Laravel's built-in Http client to call another system, you can call the withTrace() method to automatically add a traceparent header to the request for the current trace.

use Illuminate\Support\Facades\Http;

Http::withTrace()->post('https://example.com');