Event-driven architecture allows microservices to communicate asynchronously without synchronous HTTP blocking. Learn how Apache Kafka manages commit logs, topic partitioning, partition rebalancing, and exactly-once processing guarantees (EOS).
1. Kafka Topic Partitioning & Producer Hashing
// Java Spring Kafka Producer with Record Keys
@Service
public class OrderEventProducer {
private final KafkaTemplate<String, OrderEvent> kafkaTemplate;
public OrderEventProducer(KafkaTemplate<String, OrderEvent> kafkaTemplate) {
this.kafkaTemplate = kafkaTemplate;
}
public void publishOrderEvent(String orderId, OrderEvent event) {
// Murmur2 Hash of orderId determines exact Partition assignment
kafkaTemplate.send("order-events-topic", orderId, event);
}
}2. Concurrent Consumer Group Listener
@Component
public class OrderEventListener {
@KafkaListener(topics = "order-events-topic", groupId = "inventory-group", concurrency = "3")
public void handleOrderEvent(ConsumerRecord<String, OrderEvent> record, Acknowledgment ack) {
log.info("Received event key={} from partition={}", record.key(), record.partition());
// Process event & commit offset manually
ack.acknowledge();
}
}