Goldpath.Locking 0.1.0-preview.8

Goldpath.Locking

Ring B distributed locking: Medallion DistributedLock composed behind manifest-driven provider selection — Redis (RedLock), Postgres (advisory locks) or SQL Server (sp_getapplock) — with tenant-scoped lock names and acquire metrics.

Honest scope: locks reduce duplicate work; they are NOT correctness fences (no fencing tokens — a paused holder can outlive its lock). Correctness comes from the Idempotency module; the two compose.

Getting started

builder.AddGoldpathLocking();                       // provider per manifest

public sealed class SettlementJob(IDistributedLockProvider locks, GoldpathLockNames names)
{
    public async Task RunAsync(CancellationToken ct)
    {
        await using var handle = await locks.TryAcquireLockAsync(
            names.For("settlement"), TimeSpan.FromSeconds(5), ct);
        if (handle is null) return;            // another instance holds it — that's the point
        // ... exactly one instance runs this ...
    }
}

IDistributedLockProvider is Medallion's own interface — no Goldpath wrapper; the full acquire API (wait, try-with-timeout, sync/async) is the library's, documented not rewritten.

Configuration

"Goldpath": {
  "DistributedLocking": {
    "Provider": "Redis",                       // Redis | Postgres | SqlServer
    "ConnectionName": "redis"                  // db providers: point at the app db → ZERO new infra
  }
}

Advanced

• Names are tenant-scoped and fail-closed: names.For("nightly-report") → goldpath:{tenant}:lock:nightly-report; with NO ambient tenant it THROWS (a silent cross-tenant lock collision is a correctness bug). Background flows either pin a tenant with GoldpathTenant.Use(...) or declare GoldpathLockNames.Global("name") — explicit and greppable.
• Metrics via a decorator over the same interface (composition, not a wrapper abstraction): goldpath_lock_acquire_total{outcome} and goldpath_lock_wait_seconds flow into Ring A OTel.
• Provider swap is behavior-neutral — the same contract test runs against real Redis AND real Postgres in CI (LockContractTests).
• Timeout semantics: TryAcquire* returns null on contention (no exception); Acquire* waits and throws TimeoutException — pick by intent.

Providers

Redis (reuses the caching L2 connection by default) · Postgres advisory locks · SQL Server sp_getapplock. ZooKeeper/etcd deferred until a project demands them (RFC).