Kafkaacks=all yêu cầu leader đợi tất cả ISR (In-Sync Replicas) ghi xong mới acknowledge producer. min.insync.replicas (broker/topic config, default=1) quy định số replica tối thiểu trong ISR để accept write. Kết hợp tối ưu: replication.factor=3, min.insync.replicas=2, acks=all → message chỉ acknowledged khi ít nhất 2 replica ghi xong → chịu được 1 broker failure mà không mất data. NotEnoughReplicasException xảy ra khi ISR size < min.insync.replicas — ví dụ 2 trong 3 broker down, ISR chỉ còn 1 nhưng min.insync.replicas=2 → producer bị reject.
- Đây là trade-off giữa availability và durability.
- Nếu muốn availability hơn durability: giảm
min.insync.replicas=1(có thể mất data nếu leader fail trước follower sync). - Trong production tài chính:
replication.factor=3,min.insync.replicas=2,acks=alllà cấu hình bắt buộc.
acks=all requires the leader to wait for all ISR (In-Sync Replicas) to write before acknowledging the producer. min.insync.replicas (a broker/topic config, default=1) specifies the minimum number of replicas that must be in the ISR to accept a write. Optimal combination: replication.factor=3, min.insync.replicas=2, acks=all → a message is only acknowledged once at least 2 replicas have written it → tolerates 1 broker failure without data loss. NotEnoughReplicasException occurs when the ISR size drops below min.insync.replicas — e.g., 2 of 3 brokers are down, leaving ISR size=1 while min.insync.replicas=2 → the producer write is rejected.
- This is a deliberate availability vs durability trade-off.
- If you prefer availability over durability: lower
min.insync.replicas=1(risks data loss if the leader fails before a follower syncs). - For financial production systems:
replication.factor=3,min.insync.replicas=2,acks=allis a mandatory configuration.