[Bug] Fix TOCTOU race condition in ZookeeperClientManager.getInstance()#16211
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LiyunZhang10 wants to merge 1 commit intoapache:3.3from
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[Bug] Fix TOCTOU race condition in ZookeeperClientManager.getInstance()#16211LiyunZhang10 wants to merge 1 commit intoapache:3.3from
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ZookeeperClientManager.getInstance() uses a non-atomic check-then-act pattern (containsKey + put) on a ConcurrentHashMap. When multiple threads call getInstance() concurrently with the same ApplicationModel, each thread can create a separate ZookeeperClientManager instance and register duplicate destroy listeners, causing redundant Zookeeper client cleanup and potential resource waste. Fix: replace the containsKey/put pattern with computeIfAbsent to ensure exactly one manager instance and one destroy listener per ApplicationModel. Added testGetInstanceConcurrentRaceCondition to verify exactly 1 instance is created across concurrent threads. Made-with: Cursor
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What is the purpose of the change?
Fixes a Time-Of-Check to Time-Of-Use (TOCTOU) race condition in
ZookeeperClientManager.getInstance().In the current implementation,
getInstance(ApplicationModel)uses a non-atomic check-then-act pattern (containsKeyfollowed byput) on aConcurrentHashMap.When multiple threads call
getInstance()concurrently for the first time with the sameApplicationModel, each thread can bypass thecontainsKeycheck, create a separateZookeeperClientManagerinstance, and register duplicateaddDestroyListenercallbacks. The later threads will overwrite the earlier instances inmanagerMap, causing the overwritten instances to be lost but their destroy listeners to remain registered, which leads to redundant Zookeeper client cleanup operations and resource waste.What is changed?
containsKey+putpattern withmanagerMap.computeIfAbsent()to ensure that exactly one manager instance and exactly one destroy listener are created perApplicationModel, regardless of concurrency.testGetInstanceConcurrentRaceConditionto verify that concurrent calls safely return exactly 1 instance and create only 1 entry in the map.