approval-engine/docs/storage-operations.md

Storage operations

Production uses one SQLite writer on persistent ReadWriteOnce storage. Production serve disables automatic migration and refuses schema drift or an in-memory database.

approval-engine migrate --db /data/approvals.sqlite
approval-engine verify --db /data/approvals.sqlite
approval-engine backup --db /data/approvals.sqlite --output /backup/approval.sqlite

Migration is repeatable and sets an explicit PRAGMA user_version. Backup uses SQLite's online backup API, verifies PRAGMA integrity_check, writes mode 0600, and refuses to overwrite a target.

Restore is a stopped-single-writer operation:

1. Stop the StatefulSet and confirm no approval-engine or migration process has the PVC open.
2. Preserve the failed database and its -wal/-shm companions for analysis.
3. Copy the verified backup to a new database path with owner 10001 and mode 0600. Do not merge a backup with old WAL files.
4. Run verify, then migrate if the release schema is newer, then verify again.
5. Start exactly one replica and prove approval/entry/outbox counts, readiness, claim retrieval, and idempotent audit drain before reopening callers.

Approval mutation and outbox insertion share BEGIN IMMEDIATE and one commit; a failed outbox insert rolls the mutation back. Delivery occurs afterward and does not roll back a committed mutation.

Schema v3 — declared PDP-path intent

GH-DEC-2026-008 added approvals.pdp_path (INTEGER NOT NULL DEFAULT 0). Migration is the usual additive ALTER TABLE; run approval-engine migrate before a production start, which refuses an unmigrated store.

Legacy rows default to 0. Intent is not back-filled from a recorded pdp_digest: an approval issued before the ruling was never declared for the PDP path, and inferring the declaration from an incidental digest would manufacture a statement nobody made. Such approvals stay usable by consumers in this engine's own vocabulary and are simply not usable on the PDP path — which is the ruling's intended cost, not a migration defect.

Schema v4 — recorded approver principal type

entries.principal_type (TEXT, nullable) records what kind of principal bound an approval, taken only from the verified token. Migration is the usual additive ALTER TABLE; run approval-engine migrate before a production start, which refuses an unmigrated store.

Legacy entries stay NULL and are not back-filled — the same reasoning as pdp_path in v3. An entry written before this column existed carries no verified statement about the principal that made it, and reading user:-shaped subject_id values as human would manufacture approver evidence nobody presented. A NULL here means unclassified, never human.

Downgrade is not supported: an older server refuses the store on the version check rather than reading the column, which is the intended direction. Restore from a v4 backup onto a v3 release requires re-pinning forward, not editing user_version.

Schema v5 — explicit human-control declaration

GH-DEC-2026-016 adds approvals.human_control, constrained to 0 or 1, with default 0. Existing objects remain undeclared regardless of recorded approver types; there is no retrospective declaration or change to their five-field binding digest. A successor inherits the declaration. Linking an existing successor with a different declaration conflicts and rolls back the parent transition.

New human-control entries require verified type human at the engine boundary. The declaration is retained on object/claim and audit events. Claim and consume also refuse inconsistent persisted human evidence. Tests cover a persistent v4 upgrade and preservation, signed API refusal, quorum and outbox rollback. Take and verify the existing backup before migration. The old v3 image must not serve a v5 database; rollback requires the matching pre-migration backup and the existing single-writer recovery procedure. No live database is migrated by the source test run.