add metric annotation instrumentation

[Duncan-tree-zhou]

refer to #7030
add metric annotation instrumentation

[steverao]

There are some CI failures, firstly you can solve them by referring to https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/docs/contributing/running-tests.md#troubleshooting-ci-test-failures

[Duncan-tree-zhou]

Hi @steverao, I found that there are lots of fails "to connect to localhost/127.0.0.1:4318". So I want to rerun the task, but I can't see the rerun button. Is it disabled for contributors?

[steverao]

Is it disabled for contributors?

Yes, you can fix the problems firstly and push relevant commits. It will trigger to rerun the CI tasks.

[Duncan-tree-zhou]

I mean I guest the failure is caused by the CI run time environment crush..... if it's able to rerun a task, It might save some time....

[Duncan-tree-zhou]

I turn it ready for reviewing, and get some questions for discuss:

1. the module naming of the @Counted and @Timed instrumentation.
   • I avoid using the opentelemetry-instrumentation-annotations prefix because it's already been used for @Withspan. I am not sure if using opentelemetry-instrumentation-annotations-coutned would cause some problem somewhere.
   • I have no idea if there is a better module naming rule for metrics annotations instrumentations.
2. I am not sure if we should put the instance of meter, LongCounter and DoubleHistogram in another module where can be loaded without javaagent?
3. I am doubted about allowing the return value to be an attributes because most of time the return value is unpredictable. would it be possible to design some static api to allow user to post the attributes to the metrics via threadlocal?

[brunobat]

I get the name, but I think it's too specific and long.
What else can it handle apart from ending a span?

[Duncan-tree-zhou]

I think it needs to handle the end of the timer and record the duration to the histogram metrics recorder.

[brunobat]

This is effectively an Instrumentation Callback... Why not call it that?
Something like InstrumenterCallback with an end() method...
I can imagine this also being useful to add attributes if later we add an addAttribute() method.

[Duncan-tree-zhou]

Hi @brunobat, I go through the code. The class Instrumentation is coupled with the implementation of the span's operations(here) and it's widely used. It's going far from the guide's suggestion(here). I think to create a new set of abstract operation for metrics instrumentation and update the guide would be an option. @laurit gave a good example of it. And what's your opinion about it...