生产者
说明
KafkaTemplate封装了一个生成器，并提供了方便的方法来发送数据到kafka主题。 提供了异步和同步方法，异步方法返回一个Future。
其构造方法有：
ListenableFuture> sendDefault(V data);
ListenableFuture> sendDefault(K key, V data);
ListenableFuture> sendDefault(int partition, K key, V data);
ListenableFuture> send(String topic, V data);
ListenableFuture> send(String topic, K key, V data);
ListenableFuture> send(String topic, int partition, V data);
ListenableFuture> send(String topic, int partition, K key, V data);
ListenableFuture> send(Message message);
前3个方法需要向Temple提供默认主题
配置
使用Producer配置类
@Configuration
@EnableKafka
public class ProducerConfig {
@Value("${kafka.producer.servers}")
private String servers;
@Value("${kafka.producer.retries}")
private int retries;
@Value("${kafka.producer.batch.size}")
private int batchSize;
@Value("${kafka.producer.linger}")
private int linger;
@Value("${kafka.producer.buffer.memory}")
private int bufferMemory;
public Map producerConfigs() {
Map props = new HashMap<>();
props.put(Config.BOOTSTRAP_SERVERS_CONFIG, servers);
props.put(Config.RETRIES_CONFIG, retries);
props.put(Config.BATCH_SIZE_CONFIG, batchSize);
props.put(Config.LINGER_MS_CONFIG, linger);
props.put(Config.BUFFER_MEMORY_CONFIG, bufferMemory);
props.put(Config.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
props.put(Config.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
props.put(Config.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
return props;
}
public ProducerFactory producerFactory() {
return new DefaultKafkaProducerFactory<>(producerConfigs());
}
@Bean
public KafkaTemplate kafkaTemplate() {
return new KafkaTemplate(producerFactory());
}
}
示例
@RestController
@RequestMapping("/kafka/producer")
public class ProducerController {
private static Logger logger = LoggerFactory.getLogger(ProducerController.class);
@Value("${topic.name}")
private String topicName;
@Autowired
private KafkaTemplate kafkaTemplate;
@RequestMapping("/send")
public Object sendKafka(String message) {
try {
logger.info("send kafka message: {}", message);
kafkaTemplate.send(topicName, UUID.randomUUID().toString(), message);
return "success";
} catch (Exception e) {
logger.error("发送kafka失败", e);
return "fail";
}
}
}
消费者
说明
可以通过配置MessageListenerContainer并提供MessageListener或通过使用@KafkaListener注释来接收消息。
MessageListenerContainer有两个实现：
- KafkaMessageListenerContainer：从单个线程上的所有主题/分区接收所有消息
- ConcurrentMessageListenerContainer：委托给1个或多个KafkaMessageListenerContainer以提供多线程消费。通过container.setConcurrency(3)，来设置多个线程
配置
使用Consumer配置类
@Configuration
@EnableKafka
public class ConsumerConfig {
@Value("${kafka.consumer.servers}")
private String servers;
@Value("${kafka.consumer.enable.auto.commit}")
private boolean enableAutoCommit;
@Value("${kafka.consumer.session.timeout}")
private String sessionTimeout;
@Value("${kafka.consumer.auto.commit.interval}")
private String autoCommitInterval;
@Value("${kafka.consumer.group.id}")
private String groupId;
@Value("${kafka.consumer.topic}")
private String topic;
@Value("${kafka.consumer.auto.offset.reset}")
private String autoOffsetReset;
@Value("${kafka.consumer.concurrency}")
private int concurrency;
/**
* KafkaMessageListenerContainer： 从单个线程上的所有主题/分区接收所有消息
@Bean(initMethod = "doStart")
public KafkaMessageListenerContainer kafkaMessageListenerContainer() {
KafkaMessageListenerContainer container = new KafkaMessageListenerContainer<>(consumerFactory(), containerProperties());
return container;
}
*/
/**
* ConcurrentMessageListenerContainer：
* 委托给1个或多个KafkaMessageListenerContainer以提供多线程消费。
* 通过container.setConcurrency(3)，来设置多个线程
*/
@Bean(initMethod = "doStart")
public ConcurrentMessageListenerContainer concurrentMessageListenerContainer() {
ConcurrentMessageListenerContainer container = new ConcurrentMessageListenerContainer<>(consumerFactory(), containerProperties());
container.setConcurrency(concurrency);
return container;
}
public ConsumerFactory consumerFactory() {
return new DefaultKafkaConsumerFactory<>(consumerConfigs());
}
public ContainerProperties containerProperties() {
ContainerProperties containerProperties = new ContainerProperties(topic);
containerProperties.setMessageListener(messageListener());
return containerProperties;
}
public Map consumerConfigs() {
Map propsMap = new HashMap<>();
propsMap.put(Config.BOOTSTRAP_SERVERS_CONFIG, servers);
propsMap.put(Config.ENABLE_AUTO_COMMIT_CONFIG, enableAutoCommit);
propsMap.put(Config.AUTO_COMMIT_INTERVAL_MS_CONFIG, autoCommitInterval);
propsMap.put(Config.SESSION_TIMEOUT_MS_CONFIG, sessionTimeout);
propsMap.put(Config.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
propsMap.put(Config.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
propsMap.put(Config.GROUP_ID_CONFIG, groupId);
propsMap.put(Config.AUTO_OFFSET_RESET_CONFIG, autoOffsetReset);
return propsMap;
}
public MessageListener messageListener() {
return new CustomMessageListener();
}
}
消息接收
Java实现
直接使用kafka0.10 client去收发消息
@Test
public void receive(){
Properties props = new Properties();
props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, broker);
props.put(ConsumerConfig.GROUP_ID_CONFIG, groupId);
props.put(ConsumerConfig.CLIENT_ID_CONFIG, clientId);
props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, "true");
props.put(ConsumerConfig.AUTO_COMMIT_INTERVAL_MS_CONFIG, "1000");
props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
KafkaConsumer consumer = new KafkaConsumer<>(props);
try{
consumer.subscribe(Arrays.asList(topic));
while (true) {
ConsumerRecords records = consumer.poll(10000);
records.forEach(record -> {
System.out.printf("client : %s , topic: %s , partition: %d , offset = %d, key = %s, value = %s%n", clientId, record.topic(),
record.partition(), record.offset(), record.key(), record.value());
});
}
}catch (Exception e){
e.printStackTrace();
}finally {
consumer.close();
}
}
使用MessageListener接口
继承MessageListener接口
public class CustomMessageListener implements MessageListener {
private static Logger logger = LoggerFactory.getLogger(CustomMessageListener.class);
@Override
public void onMessage(ConsumerRecord data) {
logger.info("received key: {}, value: {}", data.key(), data.value());
}
//或包含消费者的onMessage方法，以手动提交ofset
}
使用@KafkaListener注解
@KafkaListener(id = "foo", topics = "myTopic")
public void listen(String data) {
...
}
@KafkaListener(id = "bar", topicPartitions =
{ @TopicPartition(topic = "topic1", partitions = { "0", "1" }),
@TopicPartition(topic = "topic2", partitions = "0",
partitionOffsets = @PartitionOffset(partition = "1", initialOffset = "100"))
})
public void listen(ConsumerRecord record) {
...
}
总结
- 对于生产者来说，封装KafkaProducer到KafkaTemplate相对简单
- 对于消费者来说，由于spring是采用注解的形式去标注消息处理方法
- 先在KafkaListenerAnnotationBeanPostProcessor中扫描bean，然后注册到KafkaListenerEndpointRegistrar
- 而KafkaListenerEndpointRegistrar在afterPropertiesSet的时候去创建MessageListenerContainer
- messageListener包含了原始endpoint携带的bean以及method转换成的InvocableHandlerMethod
- ConcurrentMessageListenerContainer这个衔接上，根据配置的spring.kafka.listener.concurrency来生成多个并发的KafkaMessageListenerContainer实例
- 每个KafkaMessageListenerContainer都自己创建一个ListenerConsumer，然后自己创建一个独立的kafka consumer，每个ListenerConsumer在线程池里头运行，这样来实现并发
- 每个ListenerConsumer里头都有一个recordsToProcess队列，从原始的kafka consumer poll出来的记录会放到这个队列里头，
- 然后有一个ListenerInvoker线程循环超时等待从recordsToProcess取出记录，然后调用messageListener的onMessage方法(即KafkaListener注解标准的方法)
项目源码
https://github.com/scjqwe/spring-kafka-examples
参考
- https://docs.spring.io/spring-kafka/docs/1.0.4.RELEASE/reference/html/_reference.html
- https://segmentfault.com/a/1190000011471181
- http://www.2bowl.info/apache-kafka%E7%BC%96%E7%A8%8B%E5%85%A5%E9%97%A8%E4%BA%8C-spring%E6%95%B4%E5%90%88kafka/