alkstore/tasks/sqlite-engine-locks.md

id, name, status, depends_on, scope, risk, impact, level, tags

id	name	status	depends_on	scope	risk	impact	level	tags
sqlite-engine-locks	SQLite engine — named locks (`try_lock`, `Lock` handle, duration guards)	pending	sqlite-engine-seam-tx	narrow	low	component	implementation	wave-3 sqlite-engine

Description

Implement Store::try_lock and the Lock trait over the substrate's lock ops (lock_acquire, lock_release, lock_renew):

• try_lock(name, owner, ttl) — validated entry point (name: shared-namespace rules; owner: non-empty only); None = someone holds it (no-work is a value). Returns the boxed Lock handle.
• Duration guard (ADR-023 §2): ttl <= 0 is a rejection — Err, opaque Database shape — enforced at the trait-impl entry, before the substrate. The substrate's lock_renew already guards ttl_s <= 0 (its message preserved in the source chain where it fires); lock_acquire does not — the engine guards both call sites uniformly so the rule is contract-side, not substrate-side (the pg engine implements the same rule with no inherited guard at all).
• Lock::renew(ttl) — same duration guard; a new full TTL window from now; false = lost it (expired and re-acquired elsewhere).
• Lock::release(self) — consuming; true = was held; false = already expired/re-acquired (no-op, not an error).
• Exclusion lapses silently at TTL expiry (no revocation event) — the substrate's expired-row delete on next acquire is the mechanism; pin the lapse-then-reacquire shape in tests.

Acceptance Criteria

• try_lock grants exclusively (second acquirer gets None); release makes it acquirable again
• Duration guards: try_lock/renew with ttl <= 0 return opaque Err (Database) — never a granted lock, never a panic; substrate guard message preserved in the source chain on renew — pinned per ADR-023 §2's backlog row
• renew extends from now (full window, not additive); foreign owner cannot renew; false on lapsed/re-acquired
• release removes only the owner's row; false = no-op shape
• TTL lapse: after expiry, another owner acquires (silent lapse)
• cargo test -p alkstore-sqlite, clippy -D warnings, fmt clean

References

• docs/architecture/core-contract.md (locks section, numeric-domain rules)
• docs/architecture/decisions/008-contract-v1-pinning.md §7
• docs/architecture/decisions/019-mechanism-handle-surfaces.md §1
• docs/architecture/decisions/023-fourth-review-round.md §2
• alkstore-sqlite/src/substrate/ops.rs (lock_* fns)

Notes

To be filled by implementation agent

Summary

To be filled on completion