HDDS-14834. Fix race condition between DeadNodeHandler and HealthyReadOnlyNodeHandler on NetworkTopology#9926
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ivandika3 wants to merge 1 commit intoapache:masterfrom
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HDDS-14834. Fix race condition between DeadNodeHandler and HealthyReadOnlyNodeHandler on NetworkTopology#9926ivandika3 wants to merge 1 commit intoapache:masterfrom
ivandika3 wants to merge 1 commit intoapache:masterfrom
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…dOnlyNodeHandler on NetworkTopology DeadNodeHandler and HealthyReadOnlyNodeHandler run on separate SingleThreadExecutors, which can lead to a race condition where a resurrected datanode is removed from the NetworkTopology after being re-added. This leaves the node reachable but invisible to the placement policy. Fix: DeadNodeHandler now checks the current node state before removing it from the topology, skipping removal if the node is no longer DEAD. HealthyReadOnlyNodeHandler uses unconditional add (idempotent) instead of a contains-then-add check, closing the TOCTOU gap. Made-with: Cursor
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What changes were proposed in this pull request?
DeadNodeHandler and HealthyReadOnlyNodeHandler run on separate SingleThreadExecutors, which can lead to a race condition where a resurrected datanode is removed from the NetworkTopology after being re-added. This leaves the node reachable but invisible to the placement policy.
Fix: DeadNodeHandler now checks the current node state before removing it from the topology, skipping removal if the node is no longer DEAD. HealthyReadOnlyNodeHandler uses unconditional add (idempotent) instead of a contains-then-add check, closing the TOCTOU gap.
Made-with: Cursor
There is still a very small chance that race condition might still happen since there is no synchronization method (i.e. lock), but the chance is reduced compared to the previous implementation.
Alternative considered approaches
SingleThreadExecutorfor bothDeadNodeHandler: This requires a large change in the SCM eventframework and might delay event processing
What is the link to the Apache JIRA
https://issues.apache.org/jira/browse/HDDS-14834
How was this patch tested?
UT (Clean CI: https://github.com/ivandika3/ozone/actions/runs/23047544006)