spring boot连接clickhouse集群，实现故障节点自动切换

程序去连接clickhouse集群，要求当连接到故障节点时，可以自动去连接后面的可用节点，实现高可用。

1. 新建ClickhouseDatasource，使用自定义的datasource

   @Bean(name="clickHouseDataSource")
    public DataSource clickHouseDataSource() throws Exception {
        ClickHouseDataSourceWithFailover datasource = new ClickHouseDataSourceWithFailover(ConnectInfo.ckIPs, userName, password, 5000);
        return datasource;
    }

2. 自定义ClickHouseDataSourceWithFailover，连接失败时自动连接下一个节点

   public class ClickHouseDataSourceWithFailover extends ClickHouseDataSource {
   private final List<String> nodes;
   private final String username;
   private final String password;
   private final int timeout;

    public ClickHouseDataSourceWithFailover(List<String> nodes, String username, String password, int timeout) throws SQLException {
        super(String.format("jdbc:clickhouse://%s:8123/audit?connect_timeout=%d&socket_timeout=500000", nodes.get(0), timeout));
        this.nodes = nodes;
        this.username = username;
        this.password = password;
        this.timeout = timeout;
    }
   
    @Override
    public ClickHouseConnection getConnection() throws SQLException {
        for (String node : nodes) {
            try {
                String url = String.format("jdbc:clickhouse://%s:8123/db?connect_timeout=%d&socket_timeout=500000", node, timeout);
                Properties properties = new Properties();
                properties.put("username", username);
                properties.put("password", password);
   
                ClickHouseDataSource dataSource = new ClickHouseDataSource(url, properties);
                return dataSource.getConnection();
            } catch (SQLException e) {
                log.error("Failed to connect to node: {}, ex:{}", node, e);
            }
        }
        throw new SQLException("Unable to connect to any ClickHouse node.");
    }

   }