Can we make RestTemplate async instrumentation simpler

[ayumiono]

now, we enhance spring web resttemplate by add interceptors for AsyncRestTemplate.doExecute, org.springframework.web.client.AsyncRestTemplate$ResponseExtractorFuture.addCallback( which dependent on SuccessCallbackInstrumentation and FailureCallbackInstrumentation) and get method, it comes out that we can not capture the real time cost of a http request cause RestExecuteInterceptor stop the span as soon as doExecute exit, we can not capture the response status code also. so I wonder if we can make RestExecuteInterceptor#afterMethod simpler like below:

[wu-sheng]

Async span is open for this usage, as you coded.
But notice, async span would not vring trace context to the new thread. If we need to continue trace in the callback context, we need more than async span, we should use capture/continue APIs to create local span for callback.

[ayumiono]

thanks for your reply, what i mean "make simpler" is that do we really need tracing callback function. in most scene, what we care is just the request duration and response status code right? i think introducing local spans named "future/successCallback:" or "future/failureCallback:" making thing complex

[wu-sheng]

These are two things. As I replied, making async span to track async http call makes sense to me.
The question around local span is about, whether there is custom callback executing after this? If so, you need that to continue the trace.

[ayumiono]

ok, i got it. thanks