dosubot[bot] commented on issue #3162: URL: https://github.com/apache/hugegraph/issues/3162#issuecomment-5315166379
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Here's what's happening: In [`SnapshotHandler.onSnapshotSave`](https://github.com/apache/hugegraph/blob/9126c80e414c073b60fc074361b211cfb409e0eb/hugegraph-store/hg-store-core/src/main/java/org/apache/hugegraph/store/snapshot/SnapshotHandler.java#L93-L100), when `state == doing` (i.e. compaction is in progress), the method silently returns without writing the `data/` directory or throwing an exception: ```java if (state != null && state.get() == BusinessHandler.doing) { return; // ← exits silently without writing data/ or throwing } ``` The caller in [`PartitionStateMachine.onSnapshotSave`](https://github.com/apache/hugegraph/blob/9126c80e414c073b60fc074361b211cfb409e0eb/hugegraph-store/hg-store-core/src/main/java/org/apache/hugegraph/store/raft/PartitionStateMachine.java#L192-L206) always calls `done.run(Status.OK())` on normal return, since the early return doesn't throw: ```java snapshotHandler.onSnapshotSave(writer); // may return early silently done.run(Status.OK()); // ← always OK on no exception ``` The `doing` state is set in [`BusinessHandlerImpl.dbCompaction`](https://github.com/apache/hugegraph/blob/9126c80e414c073b60fc074361b211cfb409e0eb/hugegraph-store/hg-store-core/src/main/java/org/apache/hugegraph/store/business/BusinessHandlerImpl.java#L1368-L1373) before `op.compactRange()` blocks, and only transitions to `compactionDone` after `compactRange()` completes — so the race window during a long compaction is wide. Two additional observations that make the failure worse: - The `should_not_load` marker is written only at the [end of the happy path](https://github.com/apache/hugegraph/blob/9126c80e414c073b60fc074361b211cfb409e0eb/hugegraph-store/hg-store-core/src/main/java/org/apache/hugegraph/store/snapshot/SnapshotHandler.java#L125), so an early-return snapshot directory lacks both `data/` and `should_not_load`. - On load, `onSnapshotLoad` [calls `businessHandler.loadSnapshot` unconditionally](https://github.com/apache/hugegraph/blob/9126c80e414c073b60fc074361b211cfb409e0eb/hugegraph-store/hg-store-core/src/main/java/org/apache/hugegraph/store/snapshot/SnapshotHandler.java#L169-L183) when `should_not_load` is absent, which will fail or produce undefined behavior when `data/` doesn't exist. - The deprecated [`HgSnapshotHandler`](https://github.com/apache/hugegraph/blob/9126c80e414c073b60fc074361b211cfb409e0eb/hugegraph-store/hg-store-core/src/main/java/org/apache/hugegraph/store/snapshot/HgSnapshotHandler.java#L93-L123) does not have this early-return path — it always proceeds to write `data/` — so this bug is specific to the active `SnapshotHandler`. **The fix** is straightforward: `onSnapshotSave` should throw an `HgStoreException` instead of silently returning when `state == doing`, so `PartitionStateMachine` calls `done.run(new Status(RaftError.EBUSY, ...))` rather than `Status.OK()`. This causes JRaft to skip committing the snapshot metadata for that round: ```java if (state != null && state.get() == BusinessHandler.doing) { throw new HgStoreException("Snapshot skipped: compaction in progress for group " + groupId); } ``` A defensive guard in `onSnapshotLoad` — checking for the existence of `data/` before attempting to load — would also provide a safety net against any corrupt snapshot that slips through. <!-- Dosu Comment Footer --> *To reply, just mention [@dosu](<https://go.dosu.dev/dosubot?utm_source=github&utm_medium=bot-comment&utm_campaign=github-comment-footer-20260415&utm_content=reply-with-mention&utm_term=apache%2Fhugegraph>).* --- Share context across your team and agents. Try [Dosu](https://dosu.dev?utm_source=github&utm_medium=bot-comment&utm_campaign=github-comment-footer-20260415&utm_content=knowledge-infrastructure-tagline&utm_term=apache%2Fhugegraph). 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