Add async support to MP metrics support for inferred @SimplyTimed

[tjquinno]

Environment Details

• Helidon Version: 2.x
• Helidon SE or Helidon MP MP
• JDK version:
• OS:
• Docker version (if applicable):

---

The MP spec contains an optional feature (which Helidon implements) for inferring a @SimplyTimed annotation on each JAX-RS endpoint.

The spec https://download.eclipse.org/microprofile/microprofile-metrics-2.3/microprofile-metrics-spec-2.3.html has a very brief reference to "async":

With an asynchronous request the timing that is tracked by the REST metric must incorporate the time spent by the asynchronous call.

Our implementation does not currently treat JAX-RS methods with @Suspended AsyncResponse parameters differently, although we pass the optional TCK.

The spec is slightly vague on this point; I've asked for clarification in the MP Google group and the MP metrics Gitter group.

[tjquinno]

Here is the Google groups conversation I started about this: https://groups.google.com/g/microprofile/c/pMiRRB4TJIk It confirms that, in this case, the metric data should include the entire operation, not simply the submission of it.