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Amends 0103: the lock package gains fencing, renewal and a decorator.

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Context

0103 set named server-side locks behind a driver. The owner’s locking answer LK1 (mem L868, 2026-10-20) says the default is a Postgres advisory lock, that Valkey is optional, and that locks must have a TTL, renew themselves, carry fencing tokens and be easy to use.

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Decision

  1. The default driver is a Postgres advisory lock. Valkey is an optional driver.
  2. Every lock has a TTL and renews automatically while its holder is alive.
  3. Every lock carries a fencing token, so a stale holder cannot write after its lock has expired and moved on.
  4. @WithLock takes a lock around a method, so authors do not call acquire and release by hand.
  5. Locks emit metrics.

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Consequences

  • A stale worker cannot overwrite a newer write, because the store rejects a lower fencing token.
  • Locks need no extra infrastructure on-prem, because Postgres is always there.

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Enforcement

planned — the lock conformance suite checks TTL expiry, renewal and the fencing rule on each driver.

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Alternatives

  • Valkey as the default: not chosen; it is optional.
  • Locks without fencing: rejected, a lock alone cannot stop a stale write.

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Supersedes and sources

Supersedes: none. Amends: 0103. Sources: owner locking answer LK1 (stackra-decisions-2026-10-19.md L868, 2026-10-20).