Could we avoid attributes merge in HttpServerMetrics.onEnd?

[wgy035]

Is your feature request related to a problem? Please describe.

While conducting a performance test, I discovered through flame graph analysis that the merge operation in the HttpServerMetrics.onEnd() causes performance overhead.

The startAttributes is generated by HttpCommonAttributesExtractor.onStart() and all attributes are extracted from request, could we move the attributes extract into HttpCommonAttributesExtractor.onEnd() to avoid merge in the HttpServerMetrics.onEnd()? I have reviewed the tracking code, the request will not be changed.

Describe the solution you'd like

I would like HttpCommonAttributesExtractor to extract attributes onEnd, so that it can be used in HttpServerMetrics directly. And startAttributes().toBuilder().putAll(endAttributes).build() is no longer needed.

Describe alternatives you've considered

No response

Additional context

No response

[knarfli]

looked interesting, I want to take a look into it.

[wgy035]

I audited and tested most of AttributeExtractor.onEnd implementations, in each scenario, whether the attribute extract is executed in onStart or onEnd, the test results are the same.