OAK-12341 adding cache for service lookup

[pat-lego]

The use of a service cache will prevent the need to perform service tracker requests lowering the chances of a blocking permission lookup

[anchela]

hi @pat-lego , thanks a lot for the contribution. would you be able to also add one or multiple test cases that illustrates the issue? that's needed for us to merge the PR.

[Amoratinos]

Looks good to me 👍

Regarding the test it helps to understand the topic but I do not see too much value to add it to the test set as it will add more delay on test execution and not sure if it could be a bit flaky depending on the environment is executed. wdyt @anchela

[jsedding]

For the stacktrace shared in the JIRA ticket, I believe it would be sufficient to change the isEnabled() method to the following. The rationale being that ServiceTracker.getServiceReference() reads the cached value from a volatile field, i.e. no synchronization overhead.

    boolean isEnabled() {
        return getServiceReference() != null;
    }

Now, the question is whether we see contention with different stack traces as well.

[jsedding]

Note, PR #3072 proposes the alternative fix mentioned above.

[jsedding]

I have closed #3072 because it looks like we need to speed up not only the isEnabled() code-path, but also the retrieval of references.

@pat-lego could you consider taking e7ab1d6 from my PR over? It would speed up the unit-tests. Feel free to adjust, based on @rishabhdaim 's comments over there.

[pat-lego]

@jsedding added the test with 50 ms polling let me know if there are any other points on this if not perhaps we can move towards resolving this issue.