<parent>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-parent</artifactId>
   <version>2.1.0.RELEASE</version>
</parent>

<dependency>
   <groupId>org.springframework.kafka</groupId>
   <artifactId>spring-kafka</artifactId>
</dependency>

<dependency>
   <groupId>com.alibaba.boot</groupId>
   <artifactId>nacos-config-spring-boot-starter</artifactId>
   <version>0.2.1</version>
</dependency>

spring:
  kafka:
    bootstrap-servers: kafka-server:9092
    producer:
      acks: all
    consumer:
      group-id: node1-group #三個服務分別為node1 node2 node3
      enable-auto-commit: false
# 部署的nacos服務
nacos:
  config:
    server-addr: nacos-server:8848

@Configuration
@NacosPropertySource(dataId = "input", groupId = "node1-server", autoRefreshed = true)
// autoRefreshed=true指的是nacos中配置發(fā)生改變后會刷新，false代表只會使用服務啟動時候讀取到的值
@NacosPropertySource(dataId = "sink", groupId = "node1-server", autoRefreshed = true)
public class NacosConfig {

    @NacosValue(value = "${input:}", autoRefreshed = true)
    private String input;

    @NacosValue(value = "${sink:}", autoRefreshed = true)
    private String sink;
    
    public String getInput() {
        return input;
    }
    
    public String getSink() {
        return sink;
    }
}

/**
 * 監(jiān)聽Nacos配置改變，創(chuàng)建消費者，更新消費
 */
@Component
public class ConsumerManager {

    @Value("${spring.kafka.bootstrap-servers}")
    private String servers;

    @Value("${spring.kafka.consumer.enable-auto-commit}")
    private boolean enableAutoCommit;
    
    @Value("${spring.kafka.consumer.group-id}")
    private boolean groupId;
    
    @Autowired
    private NacosConfig nacosConfig;
    
    @Autowired
    private KafkaTemplate kafkaTemplate;
    
    // 用于存放當前消費者使用的topic
    private String topic;
    
    // 用于執(zhí)行消費者線程
    private ExecutorService executorService;
    
    /**
     * 監(jiān)聽input
     */
    @NacosConfigListener(dataId = "node1-server", groupId = "input")
    public void inputListener(String input) {
        // 這個監(jiān)聽觸發(fā)的時候 實際NacosConfig中input的值已經(jīng)是最新的值了 我們只是需要這個監(jiān)聽觸發(fā)我們更新消費者的業(yè)務
        String inputTopic = nacosConfig.getInput();
        // 我使用nacosConfig中讀取的原因是因為監(jiān)聽到內(nèi)容是input=xxxx而不是xxxx,如果使用需要自己截取一下,nacosConfig中的內(nèi)容框架會處理好，大家看一下第一張圖的配置內(nèi)容就明白了
        // 先檢查當前局部變量topic是否有值,有值代表是更新消費者，沒有值只需要創(chuàng)建即可
        if(topic != null) {
            // 停止舊的消費者線程
            executorService.shutdownNow();
            executorService == null;
        }
        // 根據(jù)為新的topic創(chuàng)建消費者
        topic = inputTopic;
        ThreadFactory threadFactory = new ThreadFactoryBuilder().setNameFormat(topic + "-pool-%d").build();
        executorService = new ThreadPoolExecutor(1, 1, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>(2), threadFactory);
        // 執(zhí)行消費業(yè)務
        executorService.execute(() -> consumer(topic));
    }
    
    /**
     * 創(chuàng)建消費者
     */
    public void consumer(String topic) {
        Properties properties = new Properties();
        properties.put("bootstrap.servers", servers);
        properties.put("enable.auto.commit", enableAutoCommit);
        properties.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        properties.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        properties.put("group.id", groupId);
        KafkaConsumer<String, String> consumer = new KafkaConsumer<>(properties);
        consumer.subscribe(Arrays.asList(topic));
        try {
            while (!Thread.currentThread().isInterrupted()) {
                Duration duration = Duration.ofSeconds(1L);
                ConsumerRecords<String, String> records = consumer.poll(duration);
                for (ConsumerRecord<String, String> record : records) {
                    String message = record.value();
                    // 執(zhí)行數(shù)據(jù)處理業(yè)務 省略業(yè)務實現(xiàn)
                    String handleMessage =  handle(message);
                    // 處理完成后發(fā)送到下一個節(jié)點
                    kafkaTemplate.send(nacosConfig.getSink(), handleMessage);
                }
            }
            consumer.commitAsync();
        }
        } catch (Exception e) {
            LOGGER.error(e.getMessage(), e);
        } finally {
            try {
                consumer.commitSync();
            } finally {
                consumer.close();
            }
        }
    }
}