onFinishRequest affects performance

In the onFinishRequest the module only ends the request span:

  public function onFinishRequest(FinishRequestEvent $event): void {
    if (!$this->isSpanInitialized) {
      return;
    }
    $this->requestSpan->end();
  }

without any uploading or additional actions, so this should be executed almost instantly.

All trace info uploading is done in the OpentelemetryService::onTerminate() event subscriber, which executes after finishing sending the request to the client browser, so should not affect the request response time at all.

Please recheck the exact stage of the request in which this 600-700ms delay happens.

It is true that both finishRequest and onTerminate increases the response time

1. I i feel, in onRequest method should only work for http kernel::MAIN_REQUEST
2. Is it possible to use BatchSpanProcessor instead of SimpleSpanProcessor
https://docs.newrelic.com/docs/more-integrations/open-source-telemetry-i...
https://github.com/open-telemetry/opentelemetry-collector/blob/main/proc...

Yeah, using BatchSpanProcessor should improve the performance, so I'll prepare an MR with this change.

Tested the MR - works well, so committing and closing.