Apache Kafka Guide #29 Idempotent Producer

Apache Kafka Guide Idempotent Producer

Hi, this is Paul, and welcome to the #29 part of my Apache Kafka guide. Today we will discuss how works prevent message duplication in Apache Kafka using Idempotent Producer.

Apache Kafka At the Gates of Mastery: Kafka Core

Problem of Non- Idempotent Producer

Let’s discuss what an idempotent producer is. An idempotent producer is involved when sending data to Apache Kafka, and there’s a potential for duplicate messages due to network errors. For instance, consider a successful transaction: The producer sends data to Apache Kafka, which then commits this data to its log and acknowledges the operation back to the producer. Up to this point, everything operates smoothly.

However, issues arise with bad or duplicate requests. When a producer sends data, Apache Kafka commits the messages to the log and acknowledges the operation. But suppose this acknowledgment fails to reach the producer due to a network error. In that case, the producer, unaware of the successful commit, might find the lack of acknowledgment odd and decide to resend the data, thanks to a retry setting. Consequently, Kafka treats this as a fresh request, committing duplicate messages. From the producer’s standpoint, it appears that only one request was successfully acknowledged by Kafka, even though Kafka has committed two instances of the message.

Non-Idempotent Kafka Producer

Idempotent Producer

To leverage the capabilities of an idempotent producer, we start with an older version of Kafka. The key advantage of using an idempotent producer is its ability to prevent the introduction of duplicate messages in the event of network errors. This is possible because, for a successful request, the operation proceeds as normal. However, in cases where a duplicate request is made — due to an acknowledgment (ack) not being received by the producer and the request being retried — Kafka is equipped to recognize this situation. It identifies the request as a potential duplicate and decides not to commit it a second time. Nevertheless, Kafka still sends back an acknowledgment to the producer, giving the impression that the request was successfully processed. This functionality underscores the significant benefit of using an idempotent producer in Kafka.

• Kafka ≥ 0.11 you can define Idempotent Producer which does not introduce duplicated:

Idempotent Kafka Producer

How to Enable Idempotent Producer

Ensuring a stable and secure pipeline is essential. Since the release of Kafka 3.0, there has been a significant evolution from version 0.11 to 3.0, making certain features the new default. It is strongly advised to utilize these features, which, despite not being default in versions before 3.0, have now become standard. With the configuration of an idempotent producer, the retry settings automatically adjust to their maximum value. The maximum number of in-flight requests is limited to one for Kafka version 0.11 and increases to five for version 1.0. Additionally, even when the maximum in-flight requests are set to five, order preservation is ensured.

For those interested in the technical specifics, searching for “Kafka 5494” will provide detailed insights. Another important automatic setting is that acknowledgments acks=all enhance reliability. These adjustments are applied automatically upon the initiation of your producer unless manually configured otherwise. In your producer's code, simply setting producerProps.put("enable.idempotence", true);is sufficient for activation.

Understanding these defaults is crucial, as they reflect Kafka’s evolving standards aimed at enhancing performance. For users not yet on Kafka 3.0, manually setting these configurations is recommended to ensure your producer adheres to the most effective practices.

• Default for Kafka ≥ v3.0
• retries=Integer.MAX_VALUE (2³¹-1)
• max.in.flight.requests=1 (Kafka = v0.11)
• max.in.flight.requests=5 (Kafka ≥ v1.0 higher performance and keep ordering)

All this will be enabled after the set:

producerProps.put("enable.idempotence", true);

Thank you for reading until the end. Before you go:

Apache Kafka At the Gates of Mastery: Kafka Core

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