Github user franz1981 commented on the issue:
https://github.com/apache/activemq-artemis/pull/1263
@michaelandrepearce Good work and great findings!
My 2 cents on it, the new map is great but:
1) it has a slightly different behaviour about atomic operations (eg
[ConcurrentHashMap::compute
javadoc](https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentHashMap.html#compute-K-java.util.function.BiFunction-))
hence please checks if there are callers relying on such behaviours
2) it doesn't shrink/grow like the vanilla ConcurrentHashMap -> when it
grows it is not incremental by little chuncks, but could put a lot of pressure
on Humongous Allocations hurting the heap allocations of byte[] performed
during message translations
3) JournalCompactor in JournalImpl::compac is using a keySet from it
(producing the unwanted Longs
So it is important to make sure that the common usage do not make them
happen or at least , that the benefits are well balanced by these drawbacks
Anyway, the PR is great and I'm pretty happy about it :)
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