【Kafka】broker -副本与ISR设计

### Kafka Acknowledgment Modes Explained In Apache Kafka, the producer sends messages to brokers and expects an acknowledgment (ack) from them. There are three main ack modes that dictate how acknowledgments work: #### 0: No Acknowledgment Required When setting `acks=0`, the producer does not wait for any acknowledgment from the broker after sending a message. This mode offers the highest throughput but provides no guarantee that the message has been successfully written to the log[^1]. ```python producer.send('topic', key=b'key', value=b'value').add_callback( lambda resp: print(f'Successfully sent message at offset {resp.offset}') ).add_errback(lambda err: print(f'Message delivery failed due to error: {err}')) ``` This example demonstrates sending without waiting for acknowledgment. #### 1: Wait for Leader Acknowledgment Setting `acks=1` means the producer waits until it receives an acknowledgment only from the leader partition replica. Once this happens, the leader considers the write successful even if followers have yet to replicate data. While offering better reliability than `acks=0`, some risk remains as unreplicated writes can be lost upon leader failure. #### All (-1): Wait for Full Replication Acknowledgment By configuring `acks=all` or `-1`, producers ensure all in-sync replicas acknowledge receipt before considering send operations complete. Although slower compared with other settings, this option guarantees maximum durability since committed records will remain available despite potential failures affecting fewer than half of configured ISR nodes.