Idempotent

In Apache Kafka, idempotence ensures that duplicate message processing or delivery does not affect the final system state. An operation is idempotent when executing it multiple times has the same effect as executing it once.

Producer Idempotence

• Enabled using enable.idempotence=true
• Prevents network-induced duplicates
• Automatically configures:
  • Proper retries
  • Appropriate acknowledgment settings
  • Safe in-flight request limits

How It Works

1. Producer assigns sequence numbers to messages
2. Broker tracks sequence numbers per producer session
3. Duplicate messages are automatically detected and discarded
4. Provides exactly-once delivery semantics within a partition

Use Cases

• Financial transactions
• Event counting systems
• State-changing operations
• Any scenario where duplicates are problematic

Best Practices

1. Enable producer idempotence for critical data flows
2. Combine with acks=all for strongest guarantees
3. Monitor producer metrics for retry rates
4. Implement proper error handling for non-retriable errors

Limitations

• Small performance impact
• Requires compatible broker version
• Only prevents duplicates from network issues
• Does not prevent application-level duplicates

Related Concepts

• Exactly Once Delivery
• Producer Configuration for Reliability
• At Least Once Delivery

References