使用Kafka实现Java异步更新通知解决Redis与MySQL数据不一致
背景
在高并发的应用场景中，秒杀系统等业务可能导致Redis与MySQL中的数据不一致。通过异步更新通知，我们可以及时发现不一致并采取相应措施，确保系统的稳定性和一致性。
设计思路
我们将设计一个Java程序，定期巡检Redis和MySQL中的库存数据。当发现不一致时，通过Kafka发送异步通知，以便其他系统及时进行处理。
1. Maven依赖
首先，确保在项目的pom.xml文件中添加以下Maven依赖：
<dependencies> <!-- MySQL连接驱动 --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.23</version> </dependency> <!-- Jedis：Java连接Redis的客户端库 --> <dependency> <groupId>redis.clients</groupId> <artifactId>jedis</artifactId> <version>3.7.0</version> </dependency> <!-- Kafka客户端 --> <dependency> <groupId>org.apache.kafka</groupId> <artifactId>kafka-clients</artifactId> <version>2.8.1</version> </dependency> </dependencies>
2. Java代码实现
import org.apache.kafka.clients.producer.KafkaProducer; import org.apache.kafka.clients.producer.ProducerRecord; import redis.clients.jedis.Jedis; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.Properties; import java.util.Timer; import java.util.TimerTask; public class AsyncInventoryNotifier { // Redis连接信息 private static final String REDIS_HOST = "localhost"; private static final int REDIS_PORT = 6379; private static final int REDIS_DB = 0; // MySQL连接信息 private static final String MYSQL_URL = "jdbc:mysql://localhost:3306/ecommerce"; private static final String MYSQL_USER = "user"; private static final String MYSQL_PASSWORD = "password"; // Kafka连接信息 private static final String KAFKA_BROKER = "localhost:9092"; private static final String KAFKA_TOPIC = "inventory_updates"; public static void main(String[] args) { // 创建定时任务 Timer timer = new Timer(); timer.schedule(new InventoryNotifierTask(), 0, 30 * 60 * 1000); // 每30分钟执行一次 } static class InventoryNotifierTask extends TimerTask { @Override public void run() { System.out.println("Starting async inventory notification..."); try { // 连接Redis Jedis jedis = new Jedis(REDIS_HOST, REDIS_PORT); jedis.select(REDIS_DB); // 连接MySQL Connection mysqlConnection = DriverManager.getConnection(MYSQL_URL, MYSQL_USER, MYSQL_PASSWORD); // 连接Kafka Properties kafkaProps = new Properties(); kafkaProps.put("bootstrap.servers", KAFKA_BROKER); kafkaProps.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer"); kafkaProps.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer"); KafkaProducer<String, String> producer = new KafkaProducer<>(kafkaProps); // 查询所有商品ID PreparedStatement preparedStatement = mysqlConnection.prepareStatement("SELECT id FROM products"); ResultSet resultSet = preparedStatement.executeQuery(); while (resultSet.next()) { int productId = resultSet.getInt("id"); // 从Redis获取缓存库存 int redisStock = Integer.parseInt(jedis.get("product:" + productId + ":stock")); // 从MySQL获取实际库存 PreparedStatement stockStatement = mysqlConnection.prepareStatement("SELECT stock FROM products WHERE id = ?"); stockStatement.setInt(1, productId); ResultSet stockResultSet = stockStatement.executeQuery(); int mysqlStock = 0; if (stockResultSet.next()) { mysqlStock = stockResultSet.getInt("stock"); } // 检测库存一致性 if (redisStock != mysqlStock) { System.out.println("Inventory inconsistency detected for product " + productId + ". Redis: " + redisStock + ", MySQL: " + mysqlStock); // 发送异步通知到Kafka ProducerRecord<String, String> record = new ProducerRecord<>(KAFKA_TOPIC, String.valueOf(productId), "inventory_inconsistency"); producer.send(record); System.out.println("Async notification sent to Kafka."); } } // 关闭连接 jedis.close(); mysqlConnection.close(); producer.close(); } catch (SQLException e) { System.err.println("Error during async inventory notification: " + e.getMessage()); } } } }
代码设计思路解释
- 连接到Redis、MySQL和Kafka：
Jedis jedis = new Jedis(REDIS_HOST, REDIS_PORT); jedis.select(REDIS_DB); Connection mysqlConnection = DriverManager.getConnection(MYSQL_URL, MYSQL_USER, MYSQL_PASSWORD); Properties kafkaProps = new Properties(); kafkaProps.put("bootstrap.servers", KAFKA_BROKER); kafkaProps.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer"); kafkaProps.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer"); KafkaProducer<String, String> producer = new KafkaProducer<>(kafkaProps);
- 查询商品ID并检测库存一致性：
PreparedStatement preparedStatement = mysqlConnection.prepareStatement("SELECT id FROM products"); ResultSet resultSet = preparedStatement.executeQuery(); while (resultSet.next()) { int productId = resultSet.getInt("id"); int redisStock = Integer.parseInt(jedis.get("product:" + productId + ":stock")); PreparedStatement stockStatement = mysqlConnection.prepareStatement("SELECT stock FROM products WHERE id = ?"); stockStatement.setInt(1, productId); ResultSet stockResultSet = stockStatement.executeQuery(); int mysqlStock = 0; if (stockResultSet.next()) { mysqlStock = stockResultSet.getInt("stock"); } if (redisStock != mysqlStock) { // 发送异步通知到Kafka ProducerRecord<String, String> record = new ProducerRecord<>(KAFKA_TOPIC, String.valueOf(productId), "inventory_inconsistency"); producer.send(record
);
System.out.println(“Async notification sent to Kafka.”);
}
}
3. **异步通知：** ```java ProducerRecord<String, String> record = new ProducerRecord<>(KAFKA_TOPIC, String.valueOf(productId), "inventory_inconsistency"); producer.send(record); System.out.println("Async notification sent to Kafka.");
- 关闭连接：
jedis.close(); mysqlConnection.close(); producer.close();
通过这个异步更新通知的设计，我们能够在检测到Redis与MySQL数据不一致的情况时，及时发送异步通知到Kafka，以便其他系统能够实时处理这些不一致性。这种设计适用于高并发应用场景，可以在实际生产环境中部署并根据业务需求调整执行频率。
