Br Optimistic Locking

Better Route optimistic locking

Use optimistic locking on updates or deletes where overwriting a newer state is unsafe. Resolve the current version from storage while the critical section is held.

use BetterRoute\Middleware\Write\CallbackOptimisticLockVersionResolver;
use BetterRoute\Middleware\Write\OptimisticLockMiddleware;
use BetterRoute\Middleware\Write\WpdbOptimisticLockCriticalSection;

$lock = new OptimisticLockMiddleware(
    versionResolver: new CallbackOptimisticLockVersionResolver(
        static function ($context): string|int|null {
            $id = (int) $context->request->get_param('id');
            return my_current_record_version($id);
        }
    ),
    required: true,
    headerName: 'if-match',
    paramName: 'version',
    criticalSection: new WpdbOptimisticLockCriticalSection(timeoutSeconds: 2)
);

$router->patch('/records/(?P<id>\d+)', $handler)
    ->middleware([$auth, $lock])
    ->protectedByMiddleware('bearerAuth');

The middleware prefers If-Match, then falls back to the configured request parameter. It accepts quoted or weak ETag-like values by normalizing W/"value" to value; numeric values become strings. * accepts any available current version.

Response contract

• Missing precondition with required: true returns 428 Precondition Required.
• A supplied version that differs from current storage returns 412 optimistic_lock_failed with expected/current details.
• An unavailable current version returns 409 version_unavailable.
• Lock acquisition failure throws and becomes an internal failure unless the application maps it deliberately.
• On success, context attribute optimisticLock contains expected, current, and atomic: true.

Atomicity boundary

The default WpdbOptimisticLockCriticalSection derives a MySQL named lock from route path plus canonicalized URL parameters. It holds that lock around both the current-version read and the downstream handler. Concurrent Better Route writers using the same route identity cannot both pass the same stale check.

This is a cooperative lock, not a database-wide compare-and-swap:

• External writers, direct SQL, background jobs, and different routes can still race unless they use the identical lock discipline.
• Route parameters must uniquely and consistently identify the stored resource. A write identity hidden only in body/query data is not included by the default lock name.
• The handler must actually advance the version after a successful mutation.
• MySQL named locks are connection-scoped. Keep the protected handler bounded and never perform slow remote I/O inside it.

For storage shared with uncontrolled writers, implement a true conditional update such as UPDATE ... WHERE id = ? AND version = ? and verify one affected row, or provide a custom OptimisticLockCriticalSectionInterface aligned with that storage.

Checks

• Send no precondition, a matching version, a stale version, weak/quoted versions, and *.
• Run two concurrent requests with the same version and assert only one mutation succeeds.
• Verify two different resource IDs do not share a lock and equivalent parameter ordering does.
• Exercise lock timeout and handler exceptions; the named lock must release in finally.
• Verify every mutation path, including jobs and alternate endpoints, follows the chosen concurrency contract.

Source references: src/Middleware/Write/OptimisticLockMiddleware.php, src/Middleware/Write/WpdbOptimisticLockCriticalSection.php, src/Middleware/Write/CallbackOptimisticLockVersionResolver.php.

References

• Official documentation: https://lonsdale201.github.io/better-docs/docs/better-route/agents