4.0.11: Add RW locking to better manage concurrency #8999
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* Add RW locking to better manage concurrency Signed-off-by: Tim Quinn <tim.quinn@oracle.com> * Address review comments --------- Signed-off-by: Tim Quinn <tim.quinn@oracle.com>
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Jul 17, 2024
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Description
Backport of #8997 to 4.0.11
Resolves #8980
The Helidon metrics implementation which uses Micrometer involves several interrelated data structures. Updates to these have always been protected by a lock, but the referenced issue reveals an oversight: read-only operations (which did not participate in locking) could fail in odd ways because the backing data structure for a returned list or set could change.
This PR enhances the locking scheme to use a
ReadWriteReentrantLock.Notable points:
getOrCreate, starts with a read lock and "promotes" to the write lock as needed. Of courseRWRLdoes not itself support that but the changes togetOrCreatedo. See the comments in the revision to the code for details.Documentation
No impact