HDFS-17850. Reject append() when newGS equals current generation stamp.#8320
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balodesecurity wants to merge 1 commit intoapache:trunkfrom
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HDFS-17850. Reject append() when newGS equals current generation stamp.#8320balodesecurity wants to merge 1 commit intoapache:trunkfrom
balodesecurity wants to merge 1 commit intoapache:trunkfrom
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Previously FsDatasetImpl.append() only threw IOException when newGS < replica.getGenerationStamp(), allowing a client bug that reuses the same GS to silently succeed and corrupt replica state. Change the check to newGS <= getGenerationStamp() so that equal-GS appends are rejected with a clear error message, consistent with the invariant that every append must strictly bump the generation stamp. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
Fixes a subtle bug where
FsDatasetImpl.append()accepted anewGSequal to the replica's current generation stamp. The invariant for any append is that the new generation stamp must be strictly greater than the existing one; allowingnewGS == currentGSpermits a misbehaving client to re-use the same GS and corrupt replica state silently.Changes
FsDatasetImpl.java: ChangenewGS < b.getGenerationStamp()tonewGS <= b.getGenerationStamp()(one character change).TestFsDatasetImpl.java: AddtestAppendRejectsSameGenerationStampwhich asserts:newGS == currentGSthrows IOExceptionnewGS < currentGSthrows IOException (pre-existing behavior)newGS > currentGSsucceeds (pre-existing behavior)Test plan
TestFsDatasetImpl#testAppendRejectsSameGenerationStamppasses locally ✅mvn package -pl hadoop-hdfs-project/hadoop-hdfs -am -DskipTests) ✅