生产者
- 做消息的持久化
- 消息持久化不能保证完全不丢失消息,可以存在存储磁盘的时候还没有存储完成,但是服务宕机了也会导致消息丢失,通过发布确定保证消息不丢失
- 消息确定机制
import com.rabbitmq.client.*;
public class PersistentProducer {
private final static String QUEUE_NAME = "persistent_queue";
public static void main(String[] argv) throws Exception {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
try (Connection connection = factory.newConnection();
Channel channel = connection.createChannel()) {
channel.queueDeclare(QUEUE_NAME, true, false, false, null);
channel.confirmSelect();
String message = "Persistent message with producer confirm!";
channel.basicPublish("", QUEUE_NAME,
MessageProperties.PERSISTENT_TEXT_PLAIN,
message.getBytes());
if (channel.waitForConfirms()) {
System.out.println("Message sent successfully!");
} else {
System.out.println("Message failed to send!");
}
}
}
}
- channel.queueDeclare(QUEUE_NAME, true, false, false, null):队列是持久化的,确保 RabbitMQ 重启后队列不会丢失。
- MessageProperties.PERSISTENT_TEXT_PLAIN:确保消息持久化存储。
- channel.confirmSelect():启用生产者确认,确保消息成功送达 RabbitMQ。
- channel.waitForConfirms():等待确认,如果生产者发送消息时发生失败,会捕获错误。
交换机
- 选择合适的交换机类型:常见的交换机类型包括 direct、fanout、topic 和 headers,选择正确的类型来确保消息路由正确。
- 使用死信队列(Dead Letter Exchange, DLX):如果消息因某些原因无法被消费,可以将消息转发到死信队列进行进一步处理。
import com.rabbitmq.client.*;
public class DirectExchangeProducer {
private final static String EXCHANGE_NAME = "direct_logs";
private final static String QUEUE_NAME = "persistent_queue";
public static void main(String[] argv) throws Exception {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
try (Connection connection = factory.newConnection();
Channel channel = connection.createChannel()) {
channel.exchangeDeclare(EXCHANGE_NAME, "direct");
channel.queueDeclare(QUEUE_NAME, true, false, false, null);
channel.queueBind(QUEUE_NAME, EXCHANGE_NAME, "info");
String message = "Hello, Direct Exchange!";
channel.basicPublish(EXCHANGE_NAME, "info",
MessageProperties.PERSISTENT_TEXT_PLAIN,
message.getBytes());
System.out.println("Sent: " + message);
}
}
}
public class DeadLetterConsumer {
private final static String DLX_QUEUE = "dlx_queue";
public static void main(String[] argv) throws Exception {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
try (Connection connection = factory.newConnection();
Channel channel = connection.createChannel()) {
channel.queueDeclare(DLX_QUEUE, true, false, false, null);
DeliverCallback deliverCallback = (consumerTag, delivery) -> {
String message = new String(delivery.getBody(), "UTF-8");
System.out.println("Dead Letter Queue Received: " + message);
};
channel.basicConsume(DLX_QUEUE, true, deliverCallback, consumerTag -> {});
}
}
}
消费者
import com.rabbitmq.client.*;
public class AckConsumer {
private final static String QUEUE_NAME = "persistent_queue";
public static void main(String[] argv) throws Exception {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
try (Connection connection = factory.newConnection();
Channel channel = connection.createChannel()) {
channel.queueDeclare(QUEUE_NAME, true, false, false, null);
DeliverCallback deliverCallback = (consumerTag, delivery) -> {
String message = new String(delivery.getBody(), "UTF-8");
System.out.println("Received: " + message);
try {
if (message.contains("error")) {
throw new Exception("Error while processing message");
}
channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
System.out.println("Message processed and acknowledged");
} catch (Exception e) {
System.out.println("Error processing message, requeueing: " + e.getMessage());
channel.basicNack(delivery.getEnvelope().getDeliveryTag(), false, true);
}
};
channel.basicConsume(QUEUE_NAME, false, deliverCallback, consumerTag -> {});
}
}
}
- channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false):消息处理成功后确认消息。
- channel.basicNack(delivery.getEnvelope().getDeliveryTag(), false, true):如果消费失败,重新将消息投递到队列中,供其他消费者处理。
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