Issue #3455: ability to customize micrometer observation

[nvervelle]

PR to show possible implementation for #3455

[pivotal-cla]

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[chemicL]

@nvervelle can you please add some tests depicting the intended usage and enrich the documentation around https://projectreactor.io/docs/core/release/reference/#_observation and https://projectreactor.io/docs/core/release/reference/#micrometer-details-observation to reflect the possibilities this creates? Thanks!

[nvervelle]

Hi @chemicL , I've added documentation and test about this feature. I hope it's ok

[chemicL]

Thanks for adding the test and documenting the feature. Some minor comments and good from my side :)

[nvervelle]

@OlegDokuka and @chemicL : I tried reproducing locally the problems in the checks, and I didn't succeed to properly run them.

I'm using a JDK 17, so I had to disable a few tasks like blockHoundTest because each test is failing with a java.lang.NoClassDefFoundError: Could not initialize class reactor.core.scheduler.ReactorBlockHoundIntegrationTest or other error message.

And when I switched back to a JDK 8, ./gradlew :reactor-core:blockHoundTest gives no error.

Any advice on how to proceed ?

[chemicL]

@OlegDokuka and @chemicL : I tried reproducing locally the problems in the checks, and I didn't succeed to properly run them.

I'm not sure what exact problems there were, but it's fair to say we still have a few flaky tests. Last week @OlegDokuka reported them as issues, some are being fixed in other PRs. Don't worry about them, the last re-run passed fine and the functionality you introduced is well-behaved :)

[chemicL]

@nvervelle thanks for all the work you put into this so far! I was about to merge it, but I have one last request for you. This week we created 3.5.x branch, which was the previous main. Current main became the 3.6.0 Milestone branch. Please sync your fork with upstream and rebase this branch onto 3.5.x:

git rebase --onto 3.5.x main issue-3455-customize-observation

[nvervelle]

Please sync your fork with upstream and rebase this branch onto 3.5.x:

Hi @chemicL , this should be done, this PR is now targeting branch 3.5.x

[reactorbot]

@chemicL this PR seems to have been merged on a maintenance branch, please ensure the change is merge-forwarded to intermediate maintenance branches and up to main 🙇