distributed-locking

Distributed Lock for Safe Concurrent Resource Updates

Two services trying to update the same resource simultaneously can corrupt it. Without a lock, both read the current value, apply their change, and the second write silently overwrites the first. This workflow acquires a distributed lock with a TTL, executes the critical operation within the lock, and releases it afterward -- ensuring only one writer accesses the resource at a time.

Workflow

resourceId, operation, ttlSeconds
              |
              v
+---------------------+     +------------------------+     +---------------------+
| dl_acquire_lock     | --> | dl_execute_critical    | --> | dl_release_lock     |
+---------------------+     +------------------------+     +---------------------+
  lockToken: LOCK-...         result: "updated"              released: true
  acquired: true              version: 5

Workers

AcquireLockWorker -- Acquires a lock on resourceId with ttlSeconds. Returns lockToken: "LOCK-{timestamp}", acquired: true.

ExecuteCriticalWorker -- Executes the operation on resourceId within the lock. Returns result: "updated", version: 5.

ReleaseLockWorker -- Releases the lock using lockToken, freeing the resource for other callers. Returns released: true.

Tests

6 unit tests cover lock acquisition, critical section execution, and lock release. The lock token is timestamp-based for uniqueness across concurrent requests.

Running

See ../../RUNNING.md for setup and execution instructions.