How do you implement message acknowledgments in Kafka consumer implementation using Java?

In Kafka, message acknowledgments are used to ensure that a message has been successfully processed by a consumer before it is removed from the topic. Here’s how you can implement message acknowledgments in a Kafka consumer implementation using Java:

1. Enable auto-commit: By default, Kafka consumers automatically commit offsets after processing messages. You can enable this feature by setting the “enable.auto.commit” property to “true”.

2. Disable auto-commit: If you want to control when offsets are committed, you can disable the auto-commit feature by setting the “enable.auto.commit” property to “false”. This allows you to manually commit offsets after processing messages.

3. Manual offset management: When you disable auto-commit, you can manually manage offsets by calling the commitSync or commitAsync methods of the Kafka consumer. These methods take an OffsetAndMetadata object that specifies the offset of the last processed message.

4. Implement message acknowledgments: To implement message acknowledgments, you can set the “acks” property to “all” when producing messages to Kafka. This ensures that the producer will wait for acknowledgments from all in-sync replicas before considering the message as successfully processed.

5. Error handling: It’s important to handle errors that may occur during message processing and offset management. You can catch and handle exceptions such as “CommitFailedException” or “RetriableCommitFailedException” and implement appropriate error handling and retry strategies as needed.

Here’s an example of how to implement message acknowledgments in a Kafka consumer implementation using Java:

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("group.id", "my_group");
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("enable.auto.commit", "false");

KafkaConsumer consumer = new KafkaConsumer<>(props);
consumer.subscribe(Collections.singletonList("my_topic"));

while (true) {
    ConsumerRecords records = consumer.poll(Duration.ofMillis(100));
    for (ConsumerRecord record : records) {
        // Process the message here
    }
    consumer.commitSync();
}

consumer.close();

In this example, we have defined the properties for the Kafka consumer and disabled auto-commit by setting the “enable.auto.commit” property to “false”. This allows us to manually manage offsets using the commitSync method.

When messages are received, they are processed in the same way as in the previous examples. Finally, we have used the commitSync method to commit the offsets of the processed messages.

By implementing message acknowledgments in a Kafka consumer implementation using Java, you can ensure that messages are processed reliably and that offsets are managed effectively, even in the face of failures or errors.