HDFS-17777. Replace synchronized methods in ExcessRedundancyMap with ReentrantReadWriteLock#8325
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balodesecurity wants to merge 1 commit intoapache:trunkfrom
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HDFS-17777. Replace synchronized methods in ExcessRedundancyMap with ReentrantReadWriteLock#8325balodesecurity wants to merge 1 commit intoapache:trunkfrom
balodesecurity wants to merge 1 commit intoapache:trunkfrom
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…ReentrantReadWriteLock. ExcessRedundancyMap uses a single coarse-grained `synchronized` monitor for all operations. Because `contains()`, `getSize4Testing()`, and `getExcessRedundancyMap()` are read-only, they serialize unnecessarily against each other. Replace the monitor with a `ReentrantReadWriteLock`: read operations acquire the read lock (allowing concurrent reads), while mutating operations (`add`, `remove`, `clear`) acquire the write lock. The `size` counter is already an `AtomicLong` and needs no additional locking. Add TestExcessRedundancyMap with four unit tests covering basic semantics, clear(), concurrent-reader throughput, and concurrent-write correctness. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
ExcessRedundancyMapuses a single coarse-grainedsynchronizedmonitor for all operations. Becausecontains(),getSize4Testing(), andgetExcessRedundancyMap()are purely read-only, they unnecessarily serialize against each other under the block management write lock, reducing throughput on read-heavy workloads.Changes
synchronizedon every method with an explicitReentrantReadWriteLock:contains(),getSize4Testing(),getExcessRedundancyMap()add(),remove(),clear()sizecounter is already anAtomicLongand requires no additional locking.Test
Added
TestExcessRedundancyMapwith 4 unit tests:testAddContainsRemove— basic correctness of add/contains/removetestClear— clear resets map and size countertestConcurrentReads— 8 concurrent readers all complete within 10 s (no deadlock)testConcurrentWritesProduceCorrectSize— 10 concurrent writers produce a consistent final sizeAll 4 tests pass.
Test plan
TestExcessRedundancyMap(4 tests) — PASSblockmanagementtest suite (CI)