This topic describes how to use the SDK for Java to connect to an endpoint of a Message Queue for Apache Kafka instance to send and receive messages.

Prerequisites

Install the Java dependency library

Add the following dependencies to the pom.xml file:
<dependency>
    <groupId>org.apache.kafka</groupId>
    <artifactId>kafka-clients</artifactId>
    <version>2.4.0</version>
</dependency>
<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.7.6</version>
</dependency>
Note We recommend that you make sure that the version of your client library is same as the major version of your Message Queue for Apache Kafka instance. You can view the major version of the Message Queue for Apache Kafka instance on the Instance Details page in the Message Queue for Apache Kafka console.

Preparations

  1. Optional:Download the SSL root certificate. If you are connecting to an SSL endpoint, you must download this certificate.
  2. Go to the aliware-kafka-demos page, download the demo project to your on-premises machine, and then decompress the package of the demo project.
  3. In the decompressed demo project, find the kafka-java-demo folder and import this file to IntelliJ IDEA.
  4. Optional:If the instance uses an SSL endpoint or SASL endpoint, modify the configuration file kafka_client_jaas.conf.
    KafkaClient {
      org.apache.kafka.common.security.plain.PlainLoginModule required
      username="xxxx"
      password="xxxx";
    }; 
    Enter the username and password of the instance in username and password.
    • If the access control list (ACL) feature is disabled for the instance, you can obtain the default username and password in the Configuration Information section on the Instance Details page in the Message Queue for Apache Kafka console.
    • If ACL is enabled for the instance, make sure that the SASL user to be used is of the PLAIN type and that the user is authorized to send and consume messages. For more information, see Grant permissions to SASL users.
  5. Modify the configuration file kafka.properties.
    ##==============================common configuration parameters==============================
    bootstrap.servers=xxxxxxxxxxxxxxxxxxxxx
    topic=xxx
    group.id=xxx
    ##=======================Configure the following parameters to their actual values.========================
    ## For an SSL endpoint, configure:
    ssl.truststore.location=/xxxx/kafka.client.truststore.jks
    java.security.auth.login.config=/xxxx/kafka_client_jaas.conf
    ## For an SASL endpoint and the PLAIN mechanism, configure:
    java.security.auth.login.config.plain=/xxxx/kafka_client_jaas_plain.conf
    ## For an SASL access point and the SCRAM mechanism, configure:
    java.security.auth.login.config.scram=/xxxx/kafka_client_jaas_scram.conf
    Parameter Description
    bootstrap.servers The information about the endpoint. You can obtain the information in the Endpoint Information section of the Instance Details page in the Message Queue for Apache Kafka console.
    topic The topics that you created in the instance. You can obtain the names of the topics on the Topics page in the Message Queue for Apache Kafka console.
    group.id The Group of the instance. You can obtain the IDs of the consumer groups on the Groups page in the Message Queue for Apache Kafka console.
    Note If the client runs producer.go to send messages, this parameter is optional. If the client runs consumer.go to subscribe to messages, this parameter is required.
    ssl.truststore.location The path of the SSL root certificate. Replace xxxx with the actual value, for example, /home/doc/project/kafka-java-demo/ssl/src/main/resources/kafka.client.truststore.jks.
    Note If the default endpoint or an SASL endpoint is used, this parameter is not required. If an SSL endpoint is used, this parameter is required.
    kafka_client_jaas.conf The path where the JAAS configuration file is saved. Replace xxxx with the actual value, for example, /home/doc/project/kafka-java-demo/ssl/src/main/resources/kafka_client_jaas_scram.conf.
    Note If the default endpoint is used, this parameter is not required. If an SSL endpoint or an SASL endpoint is used, this parameter is required.

Send messages

Compile and run KafkaProducerDemo.java to send messages.

Sample code
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import java.util.concurrent.Future;
// If the instance uses an SSL endpoint or SASL endpoint, comment out the first line of the following code: 
import java.util.concurrent.TimeUnit;
import org.apache.kafka.clients.CommonClientConfigs;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.clients.producer.RecordMetadata;
/*
* If the instance uses an SSL endpoint or SASL endpoint, uncomment the following two lines of code: 
import org.apache.kafka.common.config.SaslConfigs;
import org.apache.kafka.common.config.SslConfigs;
*/

public class KafkaProducerDemo {

    public static void main(String args[]) {
          
       /*
        * If the instance uses an SSL endpoint, uncomment the following line of code: 
        Specify the path of the JAAS configuration file. 
        JavaKafkaConfigurer.configureSasl();
        */
         
       /*
        * If the instance uses an SASL endpoint and the PLAIN mechanism, uncomment the following line of code: 
        Specify the path of the JAAS configuration file. 
        JavaKafkaConfigurer.configureSaslPlain();
        */
       
       /*
        * If the instance uses an SASL endpoint and the SCRAM mechanism, uncomment the following line of code: 
        Specify the path of the JAAS configuration file. 
        JavaKafkaConfigurer.configureSaslScram();
        */

        // Load kafka.properties. 
        Properties kafkaProperties =  JavaKafkaConfigurer.getKafkaProperties();

        Properties props = new Properties();
        // Specify an endpoint. Obtain the endpoint of the corresponding topic in the Message Queue for Apache Kafka console. 
        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, kafkaProperties.getProperty("bootstrap.servers"));
         
       /*
        * If the instance uses an SSL endpoint, uncomment the following four lines of code: 
        * Do not compress this file into a JAR package. 
        props.put(SslConfigs.SSL_TRUSTSTORE_LOCATION_CONFIG, kafkaProperties.getProperty("ssl.truststore.location"));
        * The password of the truststore in the root certificate store. Use the default value. 
        props.put(SslConfigs.SSL_TRUSTSTORE_PASSWORD_CONFIG, "KafkaOnsClient");
        * Specify the access protocol. Set the value to SASL_SSL. 
        props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SASL_SSL");
        * Specify the SASL authentication method. Use the default value. 
        props.put(SaslConfigs.SASL_MECHANISM, "PLAIN");
        */

       /*
        * If the instance uses an SASL endpoint and the PLAIN mechanism, uncomment the following two lines of code: 
        * The access protocol. 
        props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SASL_PLAINTEXT");
        * The PLAIN mechanism. 
        props.put(SaslConfigs.SASL_MECHANISM, "PLAIN");
        */

       /*
        * If the instance uses an SASL endpoint and the SCRAM mechanism, uncomment the following two lines of code: 
        * The access protocol. 
        props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SASL_PLAINTEXT");
        * The SCRAM mechanism. 
        props.put(SaslConfigs.SASL_MECHANISM, "SCRAM-SHA-256");
        */

        // Specify the message serialization format used by Message Queue for Apache Kafka. 
        props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");
        props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");
        // Set the maximum time to wait for a request. 
        props.put(ProducerConfig.MAX_BLOCK_MS_CONFIG, 30 * 1000);
        // Set the maximum number of retries allowed for the client. 
        props.put(ProducerConfig.RETRIES_CONFIG, 5);
        // Set the interval between two consecutive retries for the client. 
        props.put(ProducerConfig.RETRY_BACKOFF_MS_CONFIG, 3000);
         
       /*
        * If the instance uses an SSL endpoint, uncomment the following line of code: 
        * Set the algorithm for hostname verification to an empty value. 
        props.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
        */

        // Create a thread-safe producer object. One producer object can serve one process. 
        // To improve performance, you can create multiple objects. We recommend that you create no more than five objects. 
        KafkaProducer<String, String> producer = new KafkaProducer<String, String>(props);

        // Create a Message Queue for Apache Kafka message. 
        String topic = kafkaProperties.getProperty("topic"); // The topic of the message. Enter the topic that you created in the Message Queue for Apache Kafka console. 
        String value = "this is the message's value"; // The content of the message. 

        try {
            // To improve efficiency, obtain multiple future objects at a time. Do not obtain a large number of future objects at a time. 
            List<Future<RecordMetadata>> futures = new ArrayList<Future<RecordMetadata>>(128);
            for (int i =0; i < 100; i++) {
                // Send the message and obtain a future object. 
                ProducerRecord<String, String> kafkaMessage =  new ProducerRecord<String, String>(topic, value + ": " + i);
                Future<RecordMetadata> metadataFuture = producer.send(kafkaMessage);
                futures.add(metadataFuture);

            }
            producer.flush();
            for (Future<RecordMetadata> future: futures) {
                // Synchronize the future object. 
                try {
                    RecordMetadata recordMetadata = future.get();
                    System.out.println("Produce ok:" + recordMetadata.toString());
                } catch (Throwable t) {
                    t.printStackTrace();
                }
            }
        } catch (Exception e) {
            // If the message still fails to be sent after retries, troubleshoot the error. 
            System.out.println("error occurred");
            e.printStackTrace();
        }
    }
}

Subscribe to messages

You can consume messages by using one of the following methods:
  • Use a single consumer to consume messages. Compile and run KafkaConsumerDemo.java to send messages.
    Sample code
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Properties;
    
    
    import org.apache.kafka.clients.consumer.ConsumerConfig;
    import org.apache.kafka.clients.consumer.ConsumerRecord;
    import org.apache.kafka.clients.consumer.ConsumerRecords;
    import org.apache.kafka.clients.consumer.KafkaConsumer;
    import org.apache.kafka.clients.producer.ProducerConfig;
    /*
    * If the instance uses an SSL endpoint, uncomment the following three lines of code. If the instance uses an SASL endpoint, uncomment the first two lines of the following code: 
    import org.apache.kafka.clients.CommonClientConfigs;
    import org.apache.kafka.common.config.SaslConfigs;
    import org.apache.kafka.common.config.SslConfigs;
    */
    
    public class KafkaConsumerDemo {
    
        public static void main(String args[]) {
    
            // Specify the path of the JAAS configuration file. 
            /*
             * If the instance uses an SSL endpoint, uncomment the following line of code: 
            JavaKafkaConfigurer.configureSasl();
             */
                            
            /*
             * If the instance uses an SASL endpoint and the PLAIN mechanism, uncomment the following line of code: 
            JavaKafkaConfigurer.configureSaslPlain();
             */
                            
            /*
            * If the instance uses an SASL endpoint and the SCRAM mechanism, uncomment the following line of code: 
            JavaKafkaConfigurer.configureSaslScram();
            */
    
            // Load kafka.properties.
            Properties kafkaProperties =  JavaKafkaConfigurer.getKafkaProperties();
    
            Properties props = new Properties();
            // Specify an endpoint. Obtain the endpoint of the corresponding topic in the Message Queue for Apache Kafka console. 
            props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, kafkaProperties.getProperty("bootstrap.servers"));
    
            * If the instance uses an SSL endpoint, uncomment the first line of the following code: 
            // Specify the session timeout period. If the consumer does not return a heartbeat before the session times out, the broker determines that the consumer is not alive. Then the broker removes the consumer from the consumer group and triggers rebalancing. The default value is 30s. 
            props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 30000);
            /*
             * If the instance uses an SSL endpoint, uncomment the following six lines of code: 
             * Specify the path of the SSL root certificate. Replace XXX with the actual path. 
             * Do not compress the certificate file into a JAR package. 
             props.put(SslConfigs.SSL_TRUSTSTORE_LOCATION_CONFIG, kafkaProperties.getProperty("ssl.truststore.location"));
             * Specify the password of the truststore in the root certificate store. Use the default value. 
             props.put(SslConfigs.SSL_TRUSTSTORE_PASSWORD_CONFIG, "KafkaOnsClient");
             * Specify the access protocol. Set the value to SASL_SSL. 
             props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SASL_SSL");
             * Specify the SASL authentication method. Use the default value. 
             props.put(SaslConfigs.SASL_MECHANISM, "PLAIN");
             * Set the maximum interval between two consecutive polling cycles. 
             * The default interval is 30s. If the consumer does not return a heartbeat message within the interval, the broker determines that the consumer is not alive. In this case, the broker removes the consumer from the consumer group and triggers load balancing. 
             props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 30000);
             * Set the maximum message size allowed for a single poll operation. This parameter has a significant effect if data is transmitted over the Internet. 
             props.put(ConsumerConfig.MAX_PARTITION_FETCH_BYTES_CONFIG, 32000);
             props.put(ConsumerConfig.FETCH_MAX_BYTES_CONFIG, 32000);
             */
    
            // If the instance uses an SASL endpoint and the PLAIN mechanism, uncomment the following line of code: 
           // Specify the session timeout period. If the consumer does not return a heartbeat before the session times out, the broker determines that the consumer is not alive. Then the broker removes the consumer from the consumer group and triggers rebalancing. The default value is 30s. 
            props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 30000);
            /*
             * If the instance uses an SASL endpoint and the PLAIN mechanism, uncomment the following three lines of code: 
             * The access protocol. 
             props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SASL_PLAINTEXT");
             * The PLAIN mechanism. 
             props.put(SaslConfigs.SASL_MECHANISM, "PLAIN");
             * Set the maximum interval between two consecutive polling cycles. 
             * The default interval is 30s. If the consumer does not return a heartbeat message within the interval, the broker determines that the consumer is not alive. In this case, the broker removes the consumer from the consumer group and triggers load balancing. 
             props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 30000);
             */
    
            * If the instance uses an SASL endpoint and the SCRAM mechanism, uncomment the following line of code: 
           // The session timeout period. If the consumer does not return a heartbeat before the session times out, the broker determines that the consumer is not alive. Then, the broker removes the consumer from the consumer group and triggers rebalancing. The default value is 30s.
            props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 30000);
            /*
             * If the instance uses an SASL endpoint and the SCRAM mechanism, uncomment the following four lines of code: 
             * The access protocol. 
             props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SASL_PLAINTEXT");
             * The SCRAM mechanism. 
             props.put(SaslConfigs.SASL_MECHANISM, "SCRAM-SHA-256");
             * Set the maximum interval between two consecutive polling cycles. 
             * The default interval is 30s. If the consumer does not return a heartbeat message within the interval, the broker determines that the consumer is not alive. In this case, the broker removes the consumer from the consumer group and triggers load balancing. 
             props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 30000);
             props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 30000);
             */
    
            // Specify the maximum number of messages that can be polled at a time. 
            // Do not set this parameter to an excessively large value. If polled messages are not all consumed before the next poll starts, load balancing is triggered and performance may deteriorate. 
            props.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG, 30);
            // The deserialization format of the message.
            props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
            props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
            // Specify the consumer group of the current consumer. You must create the consumer group in the Message Queue for Apache Kafka console. 
            // The consumers in a consumer group consume messages in load balancing mode. 
            props.put(ConsumerConfig.GROUP_ID_CONFIG, kafkaProperties.getProperty("group.id"));
            
            * If the instance uses an SSL endpoint, uncomment the following line of code: 
            // Set the algorithm for hostname verification to an empty value. 
            //props.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
    
            // Construct a message object, which is a consumer instance. 
            KafkaConsumer<String, String> consumer = new org.apache.kafka.clients.consumer.KafkaConsumer<String, String>(props);
            // Specify one or more topics to which the consumer group subscribes. 
            // We recommend that you configure consumers with the same GROUP_ID_CONFIG value to subscribe to the same topics. 
            List<String> subscribedTopics =  new ArrayList<String>();
            
            // If the instance uses an SSL endpoint, comment out the first five lines and uncomment the sixth line of the following code: 
            // If you want to subscribe to multiple topics, add them here. 
            // You must create the topics in the Message Queue for Apache Kafka console in advance. 
            String topicStr = kafkaProperties.getProperty("topic");
            String[] topics = topicStr.split(",");
            for (String topic: topics) {
                subscribedTopics.add(topic.trim());
            }
            //subscribedTopics.add(kafkaProperties.getProperty("topic"));
            consumer.subscribe(subscribedTopics);
    
            // Consume messages in a loop. 
            while (true){
                try {
                    ConsumerRecords<String, String> records = consumer.poll(1000);
                    // All messages must be consumed before the next polling cycle starts. The total duration cannot exceed the timeout interval specified by SESSION_TIMEOUT_MS_CONFIG. 
                    // We recommend that you create a separate thread pool to consume messages and then asynchronously return the results. 
                    for (ConsumerRecord<String, String> record : records) {
                        System.out.println(String.format("Consume partition:%d offset:%d", record.partition(), record.offset()));
                    }
                } catch (Exception e) {
                    try {
                        Thread.sleep(1000);
                    } catch (Throwable ignore) {
    
                    }
                    // See Client errors when you use Message Queue for Apache Kafka.
                    e.printStackTrace();
                }
            }
        }
    }
  • Use multiple consumers to consume messages: Compile and run KafkaConsumerDemo.java.
    Sample code
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Properties;
    import java.util.concurrent.atomic.AtomicBoolean;
    // If the instance uses an SSL endpoint or SASL endpoint, comment out the first line of the following code: 
    
    import org.apache.kafka.clients.consumer.ConsumerConfig;
    import org.apache.kafka.clients.consumer.ConsumerRecord;
    import org.apache.kafka.clients.consumer.ConsumerRecords;
    import org.apache.kafka.clients.consumer.KafkaConsumer;
    import org.apache.kafka.clients.producer.ProducerConfig;
    /*
    * If the instance uses an SSL endpoint, uncomment the first three lines of the following code. If the instance uses an SASL endpoint, uncomment the first two lines of the following code: 
    import org.apache.kafka.clients.CommonClientConfigs;
    import org.apache.kafka.common.config.SaslConfigs;
    import org.apache.kafka.common.config.SslConfigs;
    */
    import org.apache.kafka.common.errors.WakeupException;
    
    /**
     * This tutorial shows you how to use multiple consumers to simultaneously consume messages in one process. 
     * Make sure that the total number of consumers in the environment does not exceed the number of partitions of the topics to which the consumers subscribe. 
     */
    public class KafkaMultiConsumerDemo {
    
        public static void main(String args[]) throws InterruptedException {
            
            // Specify the path of the JAAS configuration file. 
            /* 
             * If the instance uses an SSL endpoint, uncomment the following line of code: 
             JavaKafkaConfigurer.configureSasl();
             */
                                
            /* 
             * If the instance uses an SASL endpoint and the PLAIN mechanism, uncomment the following line of code: 
             JavaKafkaConfigurer.configureSaslPlain(); 
             */
                                
            /* 
             * If the instance uses an SASL endpoint and the SCRAM mechanism, uncomment the following line of code: 
             JavaKafkaConfigurer.configureSaslScram();
             */
    
    
            // Load kafka.properties. 
            Properties kafkaProperties = JavaKafkaConfigurer.getKafkaProperties();
    
            Properties props = new Properties();
            // Specify an endpoint. Obtain the endpoint of the corresponding topic in the Message Queue for Apache Kafka console. 
            props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, kafkaProperties.getProperty("bootstrap.servers"));
            
            /*
             * If the instance uses an SSL endpoint, uncomment the following four lines of code: 
             * Do not compress the certificate file into a JAR package. 
             props.put(SslConfigs.SSL_TRUSTSTORE_LOCATION_CONFIG, kafkaProperties.getProperty("ssl.truststore.location"));
             * Specify the password of the truststore in the root certificate store. Use the default value. 
             props.put(SslConfigs.SSL_TRUSTSTORE_PASSWORD_CONFIG, "KafkaOnsClient");
             * Specify the access protocol. Set the value to SASL_SSL. 
             props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SASL_SSL");
             * Specify the SASL authentication method. Use the default value. 
             props.put(SaslConfigs.SASL_MECHANISM, "PLAIN");
             */
            
            /*
             * If the instance uses an SASL endpoint and the PLAIN mechanism, uncomment the following two lines of code: 
             * The access protocol. 
             props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SASL_PLAINTEXT");
             * The PLAIN mechanism. 
             props.put(SaslConfigs.SASL_MECHANISM, "PLAIN");
             */
    
            /* 
             * If the instance uses an SASL endpoint and the SCRAM mechanism, uncomment the following two lines of code: 
             * The access protocol. 
             props.put(CommonClientConfigs.SECURITY_PROTOCOL_CONFIG, "SASL_PLAINTEXT");
             * The SCRAM mechanism. 
             props.put(SaslConfigs.SASL_MECHANISM, "SCRAM-SHA-256");
             */
    
            // Set the maximum interval between two consecutive polling cycles. 
            // The default interval is 30s. If the consumer does not return a heartbeat message within the interval, the broker determines that the consumer is not alive. In this case, the broker removes the consumer from the consumer group and triggers load balancing. 
            props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 30000);
            // Set the maximum number of messages that can be polled at a time. 
            // Do not set this parameter to an excessively large value. If the messages polled are not all consumed before the next polling cycle starts, load balancing is triggered and performance may deteriorate. 
            props.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG, 30);
            // Set the method for deserializing messages. 
            props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
            props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
            // Specify the consumer group of the current consumer. You must create the consumer group in the Message Queue for Apache Kafka console. 
            // The consumers in a consumer group consume messages in load balancing mode. 
            props.put(ConsumerConfig.GROUP_ID_CONFIG, kafkaProperties.getProperty("group.id"));
    
            /* 
             * If the instance uses an SSL endpoint, uncomment the following line of code: 
             * Construct a consumer object, which is a consumer instance. 
             * Set the algorithm for hostname verification to an empty value. 
             props.put(SslConfigs.SSL_ENDPOINT_IDENTIFICATION_ALGORITHM_CONFIG, "");
             */
    
            int consumerNum = 2;
            Thread[] consumerThreads = new Thread[consumerNum];
            for (int i = 0; i < consumerNum; i++) {
                KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props);
    
                List<String> subscribedTopics = new ArrayList<String>();
                subscribedTopics.add(kafkaProperties.getProperty("topic"));
                consumer.subscribe(subscribedTopics);
    
                KafkaConsumerRunner kafkaConsumerRunner = new KafkaConsumerRunner(consumer);
                consumerThreads[i] = new Thread(kafkaConsumerRunner);
            }
    
            for (int i = 0; i < consumerNum; i++) {
                consumerThreads[i].start();
            }
    
            for (int i = 0; i < consumerNum; i++) {
                consumerThreads[i].join();
            }
        }
    
        static class KafkaConsumerRunner implements Runnable {
            private final AtomicBoolean closed = new AtomicBoolean(false);
            private final KafkaConsumer consumer;
    
            KafkaConsumerRunner(KafkaConsumer consumer) {
                this.consumer = consumer;
            }
    
            @Override
            public void run() {
                try {
                    while (!closed.get()) {
                        try {
                            ConsumerRecords<String, String> records = consumer.poll(1000);
                            // All messages must be consumed before the next polling cycle starts. The total duration cannot exceed the interval specified by SESSION_TIMEOUT_MS_CONFIG. 
                            for (ConsumerRecord<String, String> record : records) {
                                System.out.println(String.format("Thread:%s Consume partition:%d offset:%d", Thread.currentThread().getName(), record.partition(), record.offset()));
                            }
                        } catch (Exception e) {
                            try {
                                Thread.sleep(1000);
                            } catch (Throwable ignore) {
    
                            }
                            e.printStackTrace();
                        }
                    }
                } catch (WakeupException e) {
                    // If the consumer is shut down, ignore the exception. 
                    if (!closed.get()) {
                        throw e;
                    }
                } finally {
                    consumer.close();
                }
            }
            // Implement a shutdown hook that can be called by another thread. 
            public void shutdown() {
                closed.set(true);
                consumer.wakeup();
            }
        }
    }