[PR] Use ThreadLocalRandom for thread selection in OrderedExecutor [bookkeeper]

["merlimat (via GitHub)" <gi...@apache.org>]

merlimat opened a new pull request, #4832:
URL: https://github.com/apache/bookkeeper/pull/4832

   ### Motivation
   
   `OrderedExecutor.chooseThread()` — the path behind the keyless `submit()`/`execute()` overloads and `chooseThread(null)` — picks a thread using a single shared `java.util.Random` instance. `Random.nextInt()` is a CAS retry loop over one shared `AtomicLong` seed, so when many threads submit keyless tasks to a shared executor they all contend on the same cache line, purely to produce a thread index.
   
   ### Changes
   
   Use `ThreadLocalRandom.current().nextInt(...)` for the random routing (no shared state, no CAS contention) and remove the now-unused `rand` field.
   
   Verified with `TestOrderedExecutor` and `TestOrderedExecutorDecorators` (all pass) and module checkstyle.
   


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Re: [PR] Use ThreadLocalRandom for thread selection in OrderedExecutor [bookkeeper]

["merlimat (via GitHub)" <gi...@apache.org>]

merlimat merged PR #4832:
URL: https://github.com/apache/bookkeeper/pull/4832


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