fix(nvsnap): do not treat an empty manifest as an existing capture - #960
fix(nvsnap): do not treat an empty manifest as an existing capture#960balajinvda wants to merge 2 commits into
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Backend is a chain (Local -> ConfigMap -> PerCapturePVC) and Stat answers from the first tier that claims a hash, so the tiers can disagree. A per-capture PVC left behind by an earlier capture claims a hash whose manifest tier is gone and returns a manifest describing no content. Capture treated any successful Stat as "already captured", so it skipped the work and the watcher logged capture skipped: hash already exists capture committed for pod files=0 size_mib=0 both at info. The pod is recorded as captured and cannot be restored, and nothing says so. On a 70B TP=4 workload this turned a stale artifact into a silent 60-minute wait for a manifest that was never going to be written. Treat a manifest with no files or no bytes as unusable: warn that the tiers are inconsistent for that hash, and re-capture. A workload that genuinely captured nothing is then re-captured every pass rather than skipped -- cheap, since there is nothing to copy, and better than caching something restore cannot use. This makes the inconsistency loud, not impossible. Converging the tiers, or requiring the manifest tier specifically since restore needs it, is a larger change left for #959. Closes #959 Co-Authored-By: Balaji Ganesan <bganesan@nvidia.com>
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ChangesCapture validation
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: ⚪ Minimal · up to This change re-captures incomplete stored captures instead of treating them as restorable, with focused unit coverage and no actionable merge-blocking risk remaining beyond normal checks and review. Sequence Diagram(s)sequenceDiagram
participant Capture
participant Backend
participant Manifest
Capture->>Backend: Stat(hash)
Backend-->>Capture: Return manifest
Capture->>Manifest: Check file count and total bytes
alt Content is present
Capture-->>Capture: Skip recapture
else Content is absent
Capture-->>Capture: Warn and recapture
end
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Actionable comments posted: 1
🔇 Additional comments (5)
src/compute-plane-services/nvsnap/internal/rootfsonly/orchestrator.go (3)
224-232: 🗄️ Data Integrity & Integration
⚠️ Unverified finding
Sandbox verification was unavailable.Verify that re-capture can replace an unusable claimed hash.
If
Backend.PutreturnsErrExistsfor the same unusable claim, the existingErrExistspath re-reads and returns that unusable manifest. Confirm that the backend chain repairs or replaces this state, or thatErrExistscan only represent a concurrent usable capture. Add a Capture-level test for this backend sequence.
216-232: 📐 Maintainability & Code QualityConfirm diagram impact.
Confirm whether the capture-tier architecture or sequence diagram must show the new revalidation and re-capture path after
Backend.Stat.As per coding guidelines: "When a change modifies runtime behavior, data flow, or component interactions, ask whether architecture or sequence diagrams need updating."
Source: Coding guidelines
646-655: LGTM!src/compute-plane-services/nvsnap/internal/rootfsonly/empty_capture_test.go (1)
34-92: LGTM!src/compute-plane-services/nvsnap/internal/rootfsonly/BUILD.bazel (1)
37-37: LGTM!
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Inline comments:
In `@src/compute-plane-services/nvsnap/internal/rootfsonly/empty_capture_test.go`:
- Around line 31-33: Remove the workload-specific incident description and
quoted log excerpts from the comment near empty_capture_test.go, while retaining
the general failure mechanism described immediately above.
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…ment The comment carried workload-specific debugging context and log excerpts from the run that surfaced this, which an external reader of the public repo cannot access and does not need. Keep the mechanism -- tiers can disagree, the skip is logged as a successful commit, nothing downstream can tell -- and drop the rest. Co-Authored-By: Balaji Ganesan <bganesan@nvidia.com>
2 participants
Why
When the backend tiers disagree about a hash, the agent skips the capture and reports success, leaving the pod recorded as captured but unrestorable.
Observed on a 70B TP=4 workload:
Both lines are
info, so it reads as success. The e2e then sat for 60 minutes waiting for a manifest that was never going to be written.Backendis a chain (Local -> ConfigMap -> PerCapturePVC) andStatanswers from the first tier that claims the hash. A per-capture PVC left behind by an earlier capture claims a hash whose manifest tier is gone, and returns a manifest describing no content.Capturetreated any successfulStatas "already captured" and returned it unchanged, so a partially-removed capture was indistinguishable from a complete one.Anything that removes one tier without the others reproduces this: manifest GC, partial cleanup, a failed promote.
What changed
Treat a manifest with no files or no bytes as not a usable capture: log at
warnthat the tiers are inconsistent for that hash, and re-capture.Customer Release Notes
A pod whose stored capture is incomplete is now re-captured instead of being silently recorded as captured-but-unrestorable.
Plan Summary
Not applicable.
Usage
Not applicable.
Testing
New unit tests cover the decision this turns on: a real capture still short-circuits, and each shape of empty manifest (no files, no bytes, neither) does not.
go build ./...clean,internal/...andcmd/...pass. The new test file is registered inBUILD.bazelso the generated-files check stays green.Not reproduced end to end on a cluster: doing so means deliberately deleting one tier of a real capture and waiting out a capture cycle. The production occurrence is quoted above, and the unit tests pin the decision that caused it.
Notes
Two limits worth stating rather than glossing:
FileCount/TotalSizeBytesare the only emptiness signal available at that point, so a workload that genuinely captured nothing is re-captured on every pass instead of skipped. That is cheap -- there is nothing to copy -- and preferable to caching something restore cannot use.References
Closes #959
Related Pull Requests
Found while validating #945; independent of it. #945 changes behaviour only for workloads with runtime directories, this changes when any capture is considered to exist -- kept separate so they can be reviewed and reverted independently.
Dependencies
None
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