How to perform failure recovery and reconnection in Java database connection?

Database connection failure recovery and reconnection strategy: detection of connection failures: heartbeat query, connection attempt, connection pool monitoring. Reconnection strategy: immediate reconnection, delayed reconnection, exponential fallback. Code example: Delayed reconnection policy is used to manage the number of retries and delays. Practical case: Applications that use connection pools can verify and reconnect connections through methods in the pool.

Java database connection failure recovery and reconnection

When dealing with database connections, you may encounter various types of failures or outages, such as network problems, server failure, or failure of the database itself. To ensure application robustness and reliability, it is critical to implement a failover and reconnection strategy.

Detecting connection failure

There are several ways to detect that the connection to the database has been lost or interrupted:

• Heartbeat Query: Periodically sends a query to the database to verify that the connection is still valid.
• Connection Attempt: Attempt to perform a database operation, such as a query or update, and catch any connection errors.
• Connection pool monitoring: When using a connection pool, the pool can automatically monitor connections and mark failed connections.

Reconnection Policy

Once a connection failure is detected, the application needs to implement a reconnection policy:

• Reconnect immediately: Try to reconnect to the database immediately. This restores connectivity quickly, but may cause application performance degradation if the failure is persistent.
• Delayed reconnection: Retry after a period of time, such as a few seconds or minutes. This reduces excessive load on the database server, but can result in delayed application response in the event of a prolonged outage.
• Exponential backoff: The time interval between initial reconnect attempts increases exponentially. This can gradually reduce the number of requests to the database, but in the case of a severe failure, reconnecting will take more time.

Code Example

The following code snippet shows how to use the delayed reconnect strategy to restore the connection to the database:

// 数据库连接信息
private static final String JDBC_URL = "jdbc:mysql://localhost:3306/database";
private static final String USERNAME = "user";
private static final String PASSWORD = "password";

private static Connection connection = null;

// 重试次数
private static int retryCount = 0;

// 重试时延（毫秒）
private static final int RETRY_DELAY = 3000;

public static void main(String[] args) {
    // 尝试连接到数据库
    try {
        connection = DriverManager.getConnection(JDBC_URL, USERNAME, PASSWORD);
    } catch (SQLException e) {
        e.printStackTrace();
    }

    // 监控连接并重连（如果连接丢失）
    while (true) {
        try {
            // 向数据库发送查询以验证连接
            Statement statement = connection.createStatement();
            statement.executeQuery("SELECT 1");

            // 重置重试计数器
            retryCount = 0;
        } catch (SQLException e) {
            // 检测到连接故障

            // 检查重试次数并等待重试
            if (retryCount < 5) {
                try {
                    // 延迟后重试连接
                    Thread.sleep(RETRY_DELAY);
                    connection = DriverManager.getConnection(JDBC_URL, USERNAME, PASSWORD);
                    retryCount++;
                } catch (InterruptedException | SQLException ex) {
                    // 睡眠或重新连接失败
                    ex.printStackTrace();
                }
            } else {
                // 超出重试次数，等待用户输入
                System.out.println("连接无法恢复。请检查数据库状态或手动重新启动应用程序。");
            }
        }
    }
}

Practical case

In an application that uses a database connection pool, you can use the pool.validate() method to regularly verify whether the connections in the connection pool are valid. If the connection fails, the application can use the pool.reconnect() method to reconnect. This strategy ensures that the application can quickly restore its connection to the database after a brief outage.

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