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kafka消费积压

如果生产者发送消息的速度过快，或者是消费者处理消息的速度太慢，那么就会有越来越多的消息无法及时消费，也就是消费积压。

消费积压时，

(1) 可以增加Topic的分区数，并且增加消费组的消费者数量，让消费者数等于分区数。
(2) 还可以使用多线程消费，提高消费速度。

kafka多线程消费的代码：

public class ThirdMultiConsumerThreadDemo {public static final String BROKER_LIST = "localhost:9092";public static final String TOPIC = "myTopic1";public static final String GROUP_ID = "group.demo";public static void main(String[] args) {Properties props = initConfig();KafkaConsumerThread consumerThread = new KafkaConsumerThread(props, TOPIC,Runtime.getRuntime().availableProcessors());consumerThread.start();}/**** kafka配置* @return*/public static Properties initConfig() {Properties props = new Properties();props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG,StringDeserializer.class.getName());props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG,StringDeserializer.class.getName());props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, BROKER_LIST);props.put(ConsumerConfig.GROUP_ID_CONFIG, GROUP_ID);props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, true);return props;}/*** kafka消费者线程*/public static class KafkaConsumerThread extends Thread {private KafkaConsumer<String, String> kafkaConsumer;private ExecutorService executorService;private int threadNumber;public KafkaConsumerThread(Properties props, String topic, int threadNumber) {kafkaConsumer = new KafkaConsumer<>(props);kafkaConsumer.subscribe(Collections.singletonList(topic));this.threadNumber = threadNumber;executorService = new ThreadPoolExecutor(threadNumber, threadNumber,0L, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<>(1000),new ThreadPoolExecutor.CallerRunsPolicy());}@Overridepublic void run() {try {while (true) {ConsumerRecords<String, String> records =kafkaConsumer.poll(Duration.ofMillis(100));if (!records.isEmpty()) {executorService.submit(new RecordsHandler(records));}}} catch (Exception e) {log.error("run error", e);} finally {kafkaConsumer.close();}}}/*** 处理消息*/public static class RecordsHandler extends Thread {public final ConsumerRecords<String, String> records;public RecordsHandler(ConsumerRecords<String, String> records) {this.records = records;}@Overridepublic void run() {//处理records.for (ConsumerRecord<String, String> record : records) {System.out.println("==========>record:"+record.value() + ",thread:" + Thread.currentThread().getName());}}}}

发送消息后，使用多线程消息，运行结果如下：

==========>record:{"id":"1234","name":"lin"},thread:pool-1-thread-1
==========>record:{"id":"5678","name":"chen"},thread:pool-1-thread-2
==========>record:{"id":"91011","name":"wu"},thread:pool-1-thread-3

参考资料：

《深入理解Kafka：核心设计与实践原理》