Kafka: Delete idle consumer group id

Question

In some cases, I use Kafka-stream to model a small in memory (hashmap) projection of a topic. The K,V cache does require some manipulations, so it is not a good case for a GlobalKTable. In such a “caching” scenario, I want all my sibling instances to have the same cache, so I need to bypass the consumer-group mechanism.

To enable this, I normally simply start my apps with a randomly generated application Id, so each app will reload the topic each time it restarts. The only caveat to that is that I end up with some consumer group orphaned on the kafka brokers up to the offsets.retention.minutes which is not ideal for our operational monitoring tools. Any idea how to workaround this?

• Can we configure the applicationId to be ephemeral in order to have it disappeared once the app dies?
• Or could we force the consumer to manage its offset only locally?
• Or is there some java adminApi I could use to clean up my consumer-group-id when gracefully shutting down the app?

Thanks

Answer 1

There is a Java API in the AdminClient called deleteConsumerGroups which can be used to delete individual ConsumerGroups.

You can use it as shown below with Kafka 2.5.0.

import java.util.Arrays;
import java.util.Properties;
import java.util.concurrent.ExecutionException;

import org.apache.kafka.clients.admin.*;
import org.apache.kafka.common.KafkaFuture;

public class DeleteConsumerGroups {
  public static void main(String[] args) {
    System.out.println("*** Starting AdminClient to delete a Consumer Group ***");

    final Properties properties = new Properties();
    properties.put(AdminClientConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
    properties.put(AdminClientConfig.REQUEST_TIMEOUT_MS_CONFIG, "1000");
    properties.put(AdminClientConfig.DEFAULT_API_TIMEOUT_MS_CONFIG, "5000");

    AdminClient adminClient = AdminClient.create(properties);
    String consumerGroupToBeDeleted = "console-consumer-65092";
    DeleteConsumerGroupsResult deleteConsumerGroupsResult = adminClient.deleteConsumerGroups(Arrays.asList(consumerGroupToBeDeleted));

    KafkaFuture<Void> resultFuture = deleteConsumerGroupsResult.all();
    try {
      resultFuture.get();
    } catch (InterruptedException e) {
      e.printStackTrace();
    } catch (ExecutionException e) {
      e.printStackTrace();
    }

    adminClient.close();
  }
}

ConsumerGroups List before running the code above

$ kafka-consumer-groups --bootstrap-server localhost:9092 --list
console-consumer-65092
console-consumer-53268

ConsumerGroups List after running the code above

$ kafka-consumer-groups --bootstrap-server localhost:9092 --list
console-consumer-53268