Kafka विभिन्न delivery guarantees का समर्थन करता है — at-most-once, at-least-once और exactly-once — जो यह निर्धारित करते हैं कि messages खो सकते हैं या दोहराए जा सकते हैं। इन्हें और इन्हें कैसे प्राप्त करना है यह समझना विश्वसनीय systems बनाने के लिए महत्वपूर्ण है।
तीन delivery semantics
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AT-MOST-ONCE → messages may be LOST but never duplicated:
→ commit offset BEFORE processing → if processing fails, the message is skipped (lost)
→ for: when occasional loss is acceptable and duplicates are not (rare)
AT-LEAST-ONCE → messages are never lost but may be DUPLICATED:
→ commit offset AFTER processing → if a crash occurs before commit, the message is
reprocessed (duplicate) → requires IDEMPOTENT processing
→ the common default; safe (no loss) but handle duplicates
EXACTLY-ONCE → each message is processed exactly once (no loss, no duplicates):
→ the strongest, but hardest; requires Kafka transactions + idempotent producers