Apa iku offset ing Kafka lan papaone cara kerjane?

Question

Accepted Answer

An **offset** is a unique, sequential ID for each event within a partition — marking its position. Consumers track and commit offsets to know what they've consumed, enabling resuming, replay, and reliable processing.

## Apa iku offset

```text
OFFSET → the position/ID of an event within a PARTITION:
  → each partition is an ordered log; events get incrementing offsets (0, 1, 2, ...)
  → an offset uniquely identifies an event's position in its partition
  → events are RETAINED → the log keeps events (offsets remain valid for the retention period)
```

## Papaone consumer nggunakake offset

```text
→ a consumer reads events in order and tracks its CURRENT offset (where it has read to)
→ COMMITTING an offset → records "I've processed up to here" → on restart, resume from
  the committed offset (don't reprocess everything)
→ consumers can SEEK to any offset → REPLAY old events, skip ahead, reprocess from a point
→ each consumer GROUP tracks its own offsets per partition (independent progress)
```

## Pamboyongan offset lan delivery semantics

```text
WHEN/HOW you commit offsets affects DELIVERY GUARANTEES:
  → commit AFTER processing → AT-LEAST-ONCE (a crash before commit → reprocess → duplicates;
    need idempotency)
  → commit BEFORE processing → AT-MOST-ONCE (a crash after commit but before processing →
    message lost)
  → EXACTLY-ONCE → requires more (transactions, idempotent processing)
→ auto-commit (periodic) vs manual commit (control) → choose based on guarantees needed
```

## Mengapa iki penting

Paham ing offset iku fundamental amarga iku **papaone Kafka nglacak kemajuan consumption lan ngaktifake kemampuan distinctifnya** (resuming, replay, delivery guarantees), dadi iki knowledge Kafka sing penting.

An offset — posisi saka event ing partition — pusat banget papaone consumer karo Kafka.

Paham **apa iku offset** (sequential IDs sing nandai posisi saka saben event ing partition's ordered log, karo event retained supaya offset tetep valid) iki foundation.

Paham **papaone consumer nggunakake offset** — nglacak current offset mereka (dene wis baca nganti kono), **nge-commit offset** supaya rekod kemajuan (dadi mereka bisa mulai maneh saka committed point pas restart tinimbang ngolah maneh kabeh), lan bisa **seek menyang saben offset supaya replay** event lawas utawa ngolah maneh saka point (Kafka's distinctive replay capability), karo saben consumer group nglacak offset mereka sendiri independently — iki essential supaya paham papaone Kafka consumption, resumption, lan replay kerjane.

Paling penting, paham **offset management lan delivery semantics** iki crucial: **kaping lan papaone e-commit offset pengaruhi delivery guarantees** — nge-commit sawise processing menehi **at-least-once** (crash sadurunge commit nyebabke ngolah maneh/duplicates, butuh idempotency), nge-commit sadurunge menehi **at-most-once** (crash sawise commit nanging sadurunge processing ilang message), lan **exactly-once** butuh luwih (transactions, idempotent processing).

Koneksi antarane offset management lan delivery guarantees iki key practical concept supaya mbangun reliable Kafka consumers.

Paham auto-commit versus manual commit (kontrol ing guarantees) ngrefleksi practical offset management.

Kambi offset iku papaone Kafka nglacak consumption progress lan ngaktifake kemampuan distinctifnya (resuming, replay) nalika pamboyongan offset mereka tentokake delivery guarantees (at-least-once, at-most-once, exactly-once), lan amarga paham offset iku essential supaya mbangun reliable consumers, paham offset ing Kafka iku essential, foundational knowledge — pusat banget papaone Kafka nglacak consumption lan ngaktifake replay, lan crucial dikeseling menyang delivery guarantees permimpin offset management, essential supaya mbangun reliable Kafka consumers lan core Kafka concept.