HDFS-17639. hasStorageType() allocates array unnecessarily on every call#8316
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balodesecurity wants to merge 1 commit intoapache:trunkfrom
Open
HDFS-17639. hasStorageType() allocates array unnecessarily on every call#8316balodesecurity wants to merge 1 commit intoapache:trunkfrom
balodesecurity wants to merge 1 commit intoapache:trunkfrom
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Problem
DatanodeDescriptor.hasStorageType()delegates togetStorageInfos()which:storageMaplockDatanodeStorageInfo[]arrayhasStorageType()then iterates the returned array. This means every call allocates a new array and acquires the lock twice (the second time is reentrant since callers likeinjectStorage()already hold the lock). The same pattern exists ingetStorageTypes().On large clusters with many storages per DataNode,
hasStorageType()is called frequently — during block placement, heartbeat processing, and topology updates — making this allocation and double-lock pattern a measurable source of lock contention and GC pressure.Fix
In both
hasStorageType()andgetStorageTypes(), iteratestorageMap.values()directly under a singlesynchronized (storageMap)block, eliminating the array allocation entirely. Callers that already hold the lock (e.g.injectStorage(),updateStorage()) benefit from Java's reentrant semantics — a single lock acquisition instead of two.Testing
Added
TestDatanodeDescriptor#testHasStorageTypeAndGetStorageTypes:DatanodeDescriptorand verifies no type is present before any storage is injectedhasStorageType(DISK)returns true andhasStorageType(SSD)returns falsehasStorageType()andgetStorageTypes()