Apa sing dimaksud idempotency lan apa alasane penting ing sistem terdistribusi?

Question

Accepted Answer

**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

```text
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

```text
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.
```

## Nyukupi idempotency

```text
✓ IDEMPOTENCY KEYS → client sends a unique key per operation; the server processes each
  key only ONCE (dedupe) → retries with the same key are safe (common for payments/APIs)
✓ Design operations to be naturally idempotent (set vs increment; upsert)
✓ Track processed message/request IDs → skip duplicates
✓ Make consumers handle duplicate messages safely (since queues deliver at-least-once)
```

## Alasane penting

Paham idempotency isih berharga amergi iki **penting banget kanggo ketelitian ing sistem terdistribusi**, ngendi retry lan duplikat mesthi ana, mula penting sekali kabar sistem design.

Idempotency — operasi ngasilake asil sing sama menawa dilakoni saiji utawa akeh kali — penting banget amerga ing sistem terdistribusi, **retry lan pesan duplikat mesthi ana**: request bisa timeout lan diulang maneh nalika asline wis sukses (nglakoni operasi loro kali — kadang bisa ngisi bayaran loro kali utawa nggawe order duplikat!), message queue asring njamin paling-kurang-saiji delivery (nyebabake duplikat), lan masalah jaringan nyebabake retry.

Menawa operasi **idempotent, duplikat lan retry dadi aman** (diulang ora merugike), iki penting banget kanggo ketelitian — lan paham iki kabar penting kanggo nggawe sistem terdistribusi sing dipercaya.

Paham pabedane ("set balance 100" idempotent; "tambah 100" ora — pabeda kritis, amergi versi non-idempotent nyebabake asil salah menawa duplikat) lan HTTP method endi sing idempotent (GET, PUT, DELETE vs POST) nggawe konsep iki jelas.

Paham cara **nyukupi idempotency** — nggunakake **idempotency keys** (client ngirim key unik saben operasi sing server proses mung saiji, deduplikasi — pola umum lan penting banget kanggo bayaran lan API), desain operasi sing asli idempotent (set vs increment, upsert), catat ID request/message sing wis diproses kanggo skip duplikat, lan konsumen handle pesan duplikat kanthi aman — iki kabar praktis penting kanggo retry aman lan sistem terdistribusi sing bener.

Sebab retry lan duplikat mesthi ana ing sistem terdistribusi lan idempotency nggawe aman (nyegah bug ketelitian serius kaya double-charging sing duplikat sebabe), lan sebab paham idempotency lan cara nyukupinya (idempotency keys, desain asli idempotent) penting banget kanggo sistem terdistribusi sing bener, paham idempotency iki kabar design sistem sing berharga, praktis-penting — penting kanggo ketelitian ing sistem terdistribusi ngendi retry lan duplikat mesthi ana, nyegah bug serius kaya double-processing, lan konsep kunci (luwih-luwih idempotency keys) kanggo nggawe sistem sing dipercaya kanthi retry aman.