Idempotency tegese operasi ngasilake asil sing sama menawa dilakoni saiji utawa kaping-kaping. Iki penting banget ing sistem terdistribusi amergi retry lan pesan duplikat mesthi ana — operasi idempotent nggawe iki aman.
Apa sing dimaksud idempotency
An operation is IDEMPOTENT if doing it MULTIPLE times has the SAME effect as doing it ONCE:
→ "set balance to 100" → idempotent (same result however many times)
→ "add 100 to balance" → NOT idempotent (each call changes it → wrong if duplicated!)
→ in HTTP: GET, PUT, DELETE are idempotent; POST typically is NOT
Alasane penting ing sistem terdistribusi
Retries and duplicates are INEVITABLE in distributed systems:
→ a request times out → the client RETRIES → but the original may have succeeded →
the operation runs TWICE (e.g. a payment charged twice! an order placed twice!)
→ message queues often guarantee AT-LEAST-ONCE delivery → duplicates happen
→ network issues, failures → operations get retried
→ if operations are IDEMPOTENT, duplicates/retries are SAFE (no harm from repeating)
→ this is essential for correctness and safe retries.
