Apache Kafka: Delivery Guarantees

Apache Kafka is a distributed event streaming platform that is widely used for building real-time data pipelines and streaming applications. One of the key features of Kafka is its ability to provide robust and flexible delivery guarantees to ensure that messages are delivered to consumers in a reliable and timely manner. In this article, we’ll take a closer look at the various delivery guarantees offered by Apache Kafka and how they can be used to meet the specific needs of your application.

What are Delivery Guarantees in Apache Kafka?

Delivery guarantees refer to the level of reliability and consistency that Apache Kafka provides when delivering messages from producers to consumers. These guarantees ensure that messages are delivered in a timely and accurate manner, even in the face of failures and network outages.

There are several different delivery guarantees offered by Apache Kafka, including:

• At least once delivery
• At most once delivery
• Exactly once delivery

Each of these guarantees offers a different level of reliability and consistency, and it’s important to understand the trade-offs between them in order to make the best choice for your application.

It’s important to choose the delivery guarantee that best meets the specific needs of your application. For example, if duplicates are unacceptable and message loss is a concern, you may choose exactly once delivery. On the other hand, if efficiency is a priority, you may choose at most once delivery.

At Least Once Delivery

At least once delivery is the most basic delivery guarantee offered by Apache Kafka. It ensures that each message sent by a producer will be delivered to a consumer at least once. This guarantee is achieved by storing all messages sent by producers on disk and allowing consumers to read from those messages multiple times if necessary.

For example, consider a scenario where a producer sends a message to a topic and the consumer acknowledges the receipt of that message. If the consumer crashes or fails before processing the message, the message will be redelivered to the consumer the next time it comes online. This ensures that the message is delivered at least once, even if the consumer crashes or fails during processing.

However, there is a trade-off with this delivery guarantee. Since messages are delivered multiple times, it is possible for consumers to process the same message multiple times, which can lead to duplicates in your data. To prevent this, you’ll need to implement deduplication logic within your consumer application.

At Most Once Delivery

At most once delivery is a more efficient delivery guarantee than at least once delivery, as it eliminates the need for duplicates in your data. With this delivery guarantee, each message sent by a producer will be delivered to a consumer exactly once.

To achieve this guarantee, consumers must acknowledge the receipt of each message immediately after processing it. If the consumer crashes or fails before sending the acknowledgment, the message will be lost and will not be redelivered.

This delivery guarantee is useful in scenarios where duplicates are not acceptable and you need to ensure that each message is delivered exactly once. However, there is a risk that messages will be lost if the consumer crashes or fails before acknowledging receipt.

Exactly Once Delivery

Exactly once delivery is the most reliable and consistent delivery guarantee offered by Apache Kafka. With this guarantee, each message sent by a producer will be delivered to a consumer exactly once, without the risk of duplicates or message loss.

This delivery guarantee is achieved by using a combination of transactions and idempotent writes. Producers can use transactions to ensure that a message is written to the topic only once, even if the producer crashes or fails during the process. Consumers can use idempotent writes to ensure that messages are processed exactly once, even if the consumer crashes or fails during processing.

Exactly once delivery is the most complex and resource-intensive delivery guarantee, but it is also the most reliable and consistent. It is ideal for applications where accuracy and reliability are of the utmost importance, such as financial transactions or mission