الأقفال الموزّعة وحدودها

في هذا الدرس

know when a lock is safe and when it is only an optimization.

الموضوعات المخطط لها

• A lock on a database row or a lock service (ZooKeeper, etcd) is useful for efficiency: avoid duplicate work.
• Unsafe scenario: instance A takes a lease, pauses (GC, network stall), the lease expires, B takes over, A wakes and still writes.
• A Redis SET NX PX lock gives no safety guarantee under pauses and failover; do not use it alone for correctness.
• Keep critical sections short and make the work idempotent.
• ShedLock provides database-backed single-run scheduling and is meant for efficiency, not strict mutual exclusion.