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[cr-test] sbx-mgr: end an artifact backup whose artifact a newer suspend replaced - #1482
A suspend publishes over the sandbox's one canonical snapshot directory. When a backup's synchronous handoff did not submit and a newer suspend published before the durable worker did, the worker pushed the newer suspend's files under the old attempt. Either its rootfs send was then refused on the old retained-source identity on every retry, ending in artifact_backup_failed with the queued uploads orphaned, or, with the old send already queued, the old attempt finalized ready from mixed artifacts.
For a suspend-origin upload from the canonical directory, submission now checks the sidecar's local_artifact_id before the first transfer and after the last. A sidecar naming another artifact returns a typed Superseded error; only that is evidence. A missing sidecar proves nothing yet: a publication can be between its renames. Submission continues; a source still missing fails it as retriable, and the check after the last transfer catches a publication that completed meanwhile. After the last transfer a missing sidecar fails the attempt, also as retriable. Publication is an atomic rename and volume-manager stages each source at submit, so a sidecar still naming this artifact proves every staged file was its.
An imported artifact keeps the exporter's sidecar, and its backup adopts a fresh id. The payload records sidecar_artifact_id: the id the sidecar names while the directory holds the artifact. That is the upload's id when preparation rewrote the sidecar, or what the sidecar named when it staged the uploaded metadata elsewhere. Every payload this binary writes carries the field, so its absence marks one an earlier binary wrote:
An earlier binary's queued transfers are checked before they are polled: a sidecar naming this artifact continues and is recorded, one naming another ends the attempt superseded, and a missing one retries.
Deferred btrfs-send capture, the default, always stages metadata. For an earlier binary's staged payload, the sidecar left in place also names the retained source the upload was prepared from. An import shares that source, and a newer suspend's capture has a new one. The upload is superseded only when both the artifact and the source differ, so a pre-upgrade import still submits.
The worker treats Superseded as permanent unless the handoff already persisted this attempt's transfers, which it rejoins. Otherwise it closes the cluster row failed and emits artifact_backup_failed with reason=artifact_superseded, documented in crates/libs/events/README.md.
The rootfs send, the only transfer volume-manager can refuse on identity, is now submitted first, and its refusal stops submission. Transfer ids keep artifact order.
submit_artifact_backup refuses, with FAILED_PRECONDITION and before preparing anything, a suspend artifact in the canonical directory that the row does not pin. A suspend's own handoff is exempt, because the row pins its capture only once that suspend commits. Only EnqueueArtifactBackup by local_artifact_id can be refused; node-drain promotion sends that and retries on its next tick.
Validation
At this head, cargo nextest run -p pplx-space-sbx-mgr -p pplx-space-sbx-mgr-store: 1979 passed, 1 skipped. Clippy -D warnings and cargo fmt --check are clean.
Fail without their fix: submission_ends_with_the_sidecar_naming_the_upload, imported_artifact_is_superseded_only_by_a_newer_publication, durable_artifact_backup_persists_the_submitted_artifact_identity, sidecar_identity_decides_a_deferred_submission, upload_of_a_replaced_artifact_rejoins_the_transfers_its_handoff_staged, sidecar_identity_supersedes_only_a_canonical_suspend_upload; upload_prepared_before_a_newer_publication_queues_no_transfer and upload_of_a_replaced_artifact_fails_permanently_without_a_transfer fail on main.
Fail at 4af23850, the head before the upgrade handling and admission check: transfers_an_earlier_binary_queued_are_checked_before_polling, transfers_an_earlier_binary_queued_for_the_named_artifact_are_polled, staged_import_an_earlier_binary_prepared_is_superseded_only_by_a_newer_capture, backup_of_a_replaced_suspend_artifact_is_refused_at_admission.
Kind at e8cc21d3: a failed handoff, a wake, a marker write and a newer suspend. Retained capture 4/4 and staged capture 3/3: the old attempt ended artifact_superseded with no refusal; the newer backup completed and restored the newer marker. Merge base fails both (retry_budget_exhausted; orphaned transfers).
Kind at this head, across an upgrade: shapes built on the merge-base binary under an object-store outage and a closed volume-manager socket, then the images rebuilt at this head. In 2 of 2 trials a replaced pre-upgrade attempt ended artifact_superseded with no transfer queued; the merge base queued the newer files under it and exhausted its retries. Persisted transfer ids and an import-shaped sidecar finalized ready (2/2); at 4af23850 the import shape ended superseded.
Typed smokes pass at this head: ecw.command_round_trip, ecw.pause_connect, ecw.sandbox_delete, native.resident_pause, native_contract.command_wakes_idle_suspended_sandbox, local.suspend_restore_cross_node_from_object_storage, local.deferred_btrfs_send_capture_restores_cross_node, local.suspend_snapshot_rows_are_per_attempt, local.cold_sandbox_eviction_wake_round_trip, local.pending_backup_census_reports_blocked_upload.
Severity and risk
Severity: medium. A repeated suspend after a failed handoff could fail a backup noisily or finalize one from mixed artifacts, including for backups queued before an upgrade.
Risk: each suspend-origin submission from the canonical directory reads the sidecar twice. A canonical directory moved away between the last submission and the second read, by a wake that consumes the checkpoint or by a sandbox deleted mid-upload, now fails that try. The moved files cannot be staged again, so the backup ends failed where main finished it ready. The window is one file read; a move during submission already fails the backup on main. An earlier binary's transfers that all queued before a newer suspend published end superseded. A by-id backup of a canonical artifact the row does not pin is refused, including a rolled-back capture, whose own job still uploads it. Consumers counting artifact_backup_failed without filtering on reason count superseded attempts. Roll back by reverting the four commits.
Rollout
No drain is needed. Payloads from an earlier binary are recognized by the absent field and checked before they are polled or submitted. An earlier binary ignores the field, and drops it when it rewrites a payload, which then reads as an earlier binary's again.
When Superseded ends an attempt, the transfers already queued, in that try or an earlier one, run under the failed attempt, and their objects stay there until the sandbox is deleted, because snapshot retention prunes only ready snapshots.
A suspend that fails after publishing over the canonical directory rolls the row back to its predecessor (rollback_suspending_to_paused), while the directory holds the newer capture's complete files. A by-id backup of the predecessor then uploads that capture under the predecessor's id, as on main. The files are one consistent capture, not the mixture this PR prevents. The row and directory disagreeing is a rollback problem, so it is fixed separately, at the rollback.
Kind can't reach two shapes through public operations, so unit tests cover them. The control plane refuses a wake while a backup is in flight, which rules out persisted ids followed by a newer suspend. A wake retires the replaced artifact's row, so a by-id request of it gets "not published" before admission. Real imports are simulated by a sidecar rewrite.
AI assistance: Claude Code drafted the code, tests and this description, and ran the Kind validation.
Why: This change makes suspend backups stop when a newer suspend has replaced their artifact, and it changes how backup uploads are submitted and retried. It is well tested, but it touches backup admission, submission ordering, and failure handling, so owners should confirm the failure-mode tradeoffs before merging. Those tradeoffs are attempts that fail if the canonical directory moves mid-submission, and queued transfers that remain until sandbox deletion.
Commit: c82c6303acdc.
Walkthrough
Backup submission now checks whether a canonical suspend artifact is still pinned and preserves artifact identity in upload payloads. Upload submission checks the canonical sidecar before and after transfer submission. The worker handles superseded uploads, including handoffs with already-staged transfers and payloads from earlier binaries. Tests cover replacement, imported artifacts, transfer ordering, and worker outcomes.
Possibly related PRs
perplexityai/SPACE#1241: Implements related artifact-supersession behavior in backup submission and upload handling.
Merge Risk: Moderate · up to c82c6
This change makes suspend backups stop when a newer suspend has replaced their artifact, and it changes how backup uploads are submitted and retried. It is well tested, but it touches backup admission, submission ordering, and failure handling, so owners should confirm the failure-mode tradeoffs before merging. Those tradeoffs are attempts that fail if the canonical directory moves mid-submission, and queued transfers that remain until sandbox deletion.
Security architecture risk: Moderate · up to c82c6
The change strengthens backup identity checks, but rejecting an upload after transfers have started can leave sensitive backup data retained until its sandbox is deleted. Existing retry safeguards limit duplicate work. Broader access or privilege expansion was not established.
Retained concerns
Medium · security · inferred: The new post-submission rejection path expands the cases in which uploaded snapshot contents remain under a terminal failed attempt rather than entering normal ready-snapshot retention. Submission can queue every transfer and then discard the locally collected handles when the final identity check reports supersession. The worker reloads handles persisted by a concurrent handoff, but otherwise ends the attempt with failed-state convergence and local metadata cleanup only. The documented outcome is that remote objects remain until sandbox deletion. Unlike the base's successful-submission path, which could incorrectly finalize mixed contents as ready, the head correctly refuses readiness but leaves the rejected data without bounded remote cleanup in this lifecycle. Transfer deduplication limits repeated work, not accumulation across distinct failed attempts. This is an inferred sensitive-data lifecycle and resource-containment concern; no cross-tenant disclosure is established.
Security review details
Security Blast Radius
inferred — The supported concern is bounded to snapshot contents and storage consumption under affected backup-attempt prefixes in the sandbox's configured destination. Repeated distinct attempts can accumulate rejected contents under the documented retention behavior. No cross-tenant access, credential gain, or infrastructure-authority expansion was demonstrated.
Security Findings and Attack Paths
inferred — A newer publication during submission can cause an already queued upload set to become a terminal failed backup whose objects remain retained. This is a data-lifecycle consequence, not a verified unauthorized-read exploit. Its retention duration follows the documented contract; the production retention and deletion implementations remain unverified in this review.
Trust Boundaries and Controls
observed — The inspected volume-manager entrypoints authenticate permitted service peers and authorize the sandbox subject before accepting transfer requests. File staging and retained-source identity provide separate controls below the new backup-side identity checks.
Resilience and Maintainability Implications
observed — Volume-manager retains durable transfer ownership even when the backup job does not record returned handles. Immutable snapshot pushes can reuse completed work, and unused duplicate staging files are removed. These controls substantially narrow the concern to failed-attempt cleanup rather than generalized retry amplification.
Hardening Proposals
proposed — Give rejected transfer sets an explicit durable cleanup owner. Preserve their handles or provide failed-attempt prefix reclamation, ensuring transfers are terminal or fenced before deletion so late completion cannot recreate deleted objects. Keep readiness refusal independent from cleanup completion.
Pre-merge checks: 4 · 1
Failed checks: 1 warning
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Title check
The title describes the change, but it starts with the extra prefix "[cr-test]" instead of the changed area. The required area prefix is "sbx-mgr:".
Rename the pull request to "sbx-mgr: end an artifact backup whose artifact a newer suspend replaced".
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Description Follows The Pr Template
The description includes all required sections with real content: ## Summary explains the change, ## Validation names commands and results, ## Severity and risk states medium severity and specif…
Bug Fixes Name A Regression Test
The pull request fixes application behavior under crates/. Its Validation section names regression tests that fail without the fix, including submission_ends_with_the_sidecar_naming_the_upload, `u…
Weakened Safeguards Are Justified
No weakened safeguard is introduced. The diff changes source, documentation, and tests only; it does not modify CI, nextest, lint, allowlists, baselines, or test attributes. The deleted lines are help…
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The changed files and PR text contain no credentials, tokens, private keys, private URLs or tracker links, cloud account IDs/ARNs, personal workstation paths, raw production logs, or undisclosed secur…
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The description includes all required sections with real content: ## Summary explains the change, ## Validation names commands and results, ## Severity and risk states medium severity and specific risks, and AI assistance: identifies Claude Code and the drafted or changed parts.
Full details: Bug Fixes Name A Regression Test
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The pull request fixes application behavior under crates/. Its Validation section names regression tests that fail without the fix, including submission_ends_with_the_sidecar_naming_the_upload, upload_prepared_before_a_newer_publication_queues_no_transfer, and upload_of_a_replaced_artifact_fails_permanently_without_a_transfer. The section also reports 1,979 package tests passed at the reviewed head. The changed test files contain these tests.
Full details: Weakened Safeguards Are Justified
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No weakened safeguard is introduced. The diff changes source, documentation, and tests only; it does not modify CI, nextest, lint, allowlists, baselines, or test attributes. The deleted lines are helper comments, replaced submission logic, and moved fixture setup. No test or assertion is removed. The diff adds tests and assertions for the new behavior.
Full details: Public-Safe Content
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The changed files and PR text contain no credentials, tokens, private keys, private URLs or tracker links, cloud account IDs/ARNs, personal workstation paths, raw production logs, or undisclosed security vulnerability details. The reported Kind trials and issue references are test and public-repository context.
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Summary
A suspend publishes over the sandbox's one canonical snapshot directory. When a backup's synchronous handoff did not submit and a newer suspend published before the durable worker did, the worker pushed the newer suspend's files under the old attempt. Either its rootfs send was then refused on the old retained-source identity on every retry, ending in
artifact_backup_failedwith the queued uploads orphaned, or, with the old send already queued, the old attempt finalized ready from mixed artifacts.For a suspend-origin upload from the canonical directory, submission now checks the sidecar's
local_artifact_idbefore the first transfer and after the last. A sidecar naming another artifact returns a typedSupersedederror; only that is evidence. A missing sidecar proves nothing yet: a publication can be between its renames. Submission continues; a source still missing fails it as retriable, and the check after the last transfer catches a publication that completed meanwhile. After the last transfer a missing sidecar fails the attempt, also as retriable. Publication is an atomic rename and volume-manager stages each source at submit, so a sidecar still naming this artifact proves every staged file was its.An imported artifact keeps the exporter's sidecar, and its backup adopts a fresh id. The payload records
sidecar_artifact_id: the id the sidecar names while the directory holds the artifact. That is the upload's id when preparation rewrote the sidecar, or what the sidecar named when it staged the uploaded metadata elsewhere. Every payload this binary writes carries the field, so its absence marks one an earlier binary wrote:The worker treats
Supersededas permanent unless the handoff already persisted this attempt's transfers, which it rejoins. Otherwise it closes the cluster row failed and emitsartifact_backup_failedwithreason=artifact_superseded, documented incrates/libs/events/README.md.The rootfs send, the only transfer volume-manager can refuse on identity, is now submitted first, and its refusal stops submission. Transfer ids keep artifact order.
submit_artifact_backuprefuses, withFAILED_PRECONDITIONand before preparing anything, a suspend artifact in the canonical directory that the row does not pin. A suspend's own handoff is exempt, because the row pins its capture only once that suspend commits. OnlyEnqueueArtifactBackupbylocal_artifact_idcan be refused; node-drain promotion sends that and retries on its next tick.Validation
cargo nextest run -p pplx-space-sbx-mgr -p pplx-space-sbx-mgr-store: 1979 passed, 1 skipped. Clippy-D warningsandcargo fmt --checkare clean.submission_ends_with_the_sidecar_naming_the_upload,imported_artifact_is_superseded_only_by_a_newer_publication,durable_artifact_backup_persists_the_submitted_artifact_identity,sidecar_identity_decides_a_deferred_submission,upload_of_a_replaced_artifact_rejoins_the_transfers_its_handoff_staged,sidecar_identity_supersedes_only_a_canonical_suspend_upload;upload_prepared_before_a_newer_publication_queues_no_transferandupload_of_a_replaced_artifact_fails_permanently_without_a_transferfail on main.4af23850, the head before the upgrade handling and admission check:transfers_an_earlier_binary_queued_are_checked_before_polling,transfers_an_earlier_binary_queued_for_the_named_artifact_are_polled,staged_import_an_earlier_binary_prepared_is_superseded_only_by_a_newer_capture,backup_of_a_replaced_suspend_artifact_is_refused_at_admission.e8cc21d3: a failed handoff, a wake, a marker write and a newer suspend. Retained capture 4/4 and staged capture 3/3: the old attempt endedartifact_supersededwith no refusal; the newer backup completed and restored the newer marker. Merge base fails both (retry_budget_exhausted; orphaned transfers).artifact_supersededwith no transfer queued; the merge base queued the newer files under it and exhausted its retries. Persisted transfer ids and an import-shaped sidecar finalized ready (2/2); at4af23850the import shape ended superseded.ecw.command_round_trip,ecw.pause_connect,ecw.sandbox_delete,native.resident_pause,native_contract.command_wakes_idle_suspended_sandbox,local.suspend_restore_cross_node_from_object_storage,local.deferred_btrfs_send_capture_restores_cross_node,local.suspend_snapshot_rows_are_per_attempt,local.cold_sandbox_eviction_wake_round_trip,local.pending_backup_census_reports_blocked_upload.Severity and risk
Severity: medium. A repeated suspend after a failed handoff could fail a backup noisily or finalize one from mixed artifacts, including for backups queued before an upgrade.
Risk: each suspend-origin submission from the canonical directory reads the sidecar twice. A canonical directory moved away between the last submission and the second read, by a wake that consumes the checkpoint or by a sandbox deleted mid-upload, now fails that try. The moved files cannot be staged again, so the backup ends failed where main finished it ready. The window is one file read; a move during submission already fails the backup on main. An earlier binary's transfers that all queued before a newer suspend published end superseded. A by-id backup of a canonical artifact the row does not pin is refused, including a rolled-back capture, whose own job still uploads it. Consumers counting
artifact_backup_failedwithout filtering onreasoncount superseded attempts. Roll back by reverting the four commits.Rollout
No drain is needed. Payloads from an earlier binary are recognized by the absent field and checked before they are polled or submitted. An earlier binary ignores the field, and drops it when it rewrites a payload, which then reads as an earlier binary's again.
Not covered
submit_prepared_snapshot. Whichever merges second carries over the send-first order, the transfer-id re-sort,Superseded, bothcheck_prepared_artifactcalls,sidecar_artifact_idand its recording, the worker's rejoin and its pre-poll check. Both checks belong insubmit_prepared_snapshot_with_context, which Fix autosuspend stranding during volume-manager handoff #1121's hand-off calls directly. Keeping Fix autosuspend stranding during volume-manager handoff #1121's body drops both checks without a compile error.Supersededends an attempt, the transfers already queued, in that try or an earlier one, run under the failed attempt, and their objects stay there until the sandbox is deleted, because snapshot retention prunes only ready snapshots.rollback_suspending_to_paused), while the directory holds the newer capture's complete files. A by-id backup of the predecessor then uploads that capture under the predecessor's id, as on main. The files are one consistent capture, not the mixture this PR prevents. The row and directory disagreeing is a rollback problem, so it is fixed separately, at the rollback.AI assistance: Claude Code drafted the code, tests and this description, and ran the Kind validation.