最近在生产中发现vertica有个别节点老是宕机（又碰到的童鞋交流下），实际业务中有Python通过odbc连接vertica，还有Java通过jdbc连接vertica。假如你连接的那个节点正好是down的节点或者是standby节点，那么就会连接失败，程序就会报错，影响正常业务。其实vertica官方文档已经给出了解决方法，下面我们来看一下如何实现。

官方给出的代码如下：

[VMartBadNode]Description=VMart Vertica DatabaseDriver=/opt/vertica/lib64/libverticaodbc.soDatabase=VMartServername=badnode.example.comBackupServerNode=node02.example.com,node03.example.com

其中上面的BackupServerNode就是备用的IP

代码：

import java.sql.*;import java.util.Properties;public class ConnectionFailoverExample {    public static void main(String[] args) {        // Assume using JDBC 4.0 driver on JVM 6+. No driver loading needed.        Properties myProp = new Properties();        myProp.put("user", "dbadmin");        myProp.put("password", "vertica");        // Set two backup hosts to be used if connecting to the first host        // fails. All of these hosts will be tried in order until the connection        // succeeds or all of the connections fail.        myProp.put("BackupServerNode", "VerticaHost02,VerticaHost03");        Connection conn;        try {            // The connection string is set to try to connect to a known            // bnad host (in this case, a host that never existed).             conn = DriverManager.getConnection(                    "jdbc:vertica://BadVerticaHost:5433/vmart", myProp);            System.out.println("Connected!");            // Query system to table to see what node we are connected to.             // Assume a single row in response set.                        Statement stmt = conn.createStatement();            ResultSet rs = stmt.executeQuery(                    "SELECT node_name FROM v_monitor.current_session;");                  rs.next();            System.out.println("Connected to node " + rs.getString(1).trim());            // Done with connection.            conn.close();        } catch (SQLException e) {            // Catch-all for other exceptions            e.printStackTrace();        }    }}

另外也可以通过jdbc连接串来实现：

jdbc:vertica://192.168.111.25:5433/DBname?ConnectionLoadBalance=1&BackupServerNode=192.168.111.12:5433,192.168.111.13:5433

其中ConnectionLoadBalance是vertica的负载均衡，如果在库中没有开启该功能的话，此时是没有作用的，不影响。

SELECT SET_LOAD_BALANCE_POLICY('ROUNDROBIN');

取消该功能：

SELECT SET_LOAD_BALANCE_POLICY('NONE');

查询是否开启：

SELECT GET_LOAD_BALANCE_POLICY();

通过这次设置，加了几个备用连接节点，确保业务正常。