#How To Access MySQL-MGR Instances

There are multiple ways to connect to a MySQL-MGR instance when accessing it from a business application. This section describes how to choose a connection address to access the MySQL-MGR instance and provides examples for demonstration.

#Applicable scenarios

Access Method	Applicable Scenarios
Access within the Cluster	In single-master or multi-master mode, applications within the cluster access the MGR instance through the port exposed by the SVC.
Access from outside the Cluster	In single-master or multi-master mode, applications outside the cluster access the MGR instance through the NodePort port.

#Common client programs

The example demonstrates programs using JDBC and GORM clients. Please refer to the corresponding framework documentation for other clients.

When using the code, please modify the relevant variables to your actual values. The variable descriptions are as follows:

Variable	Description
host	The IP or SVC name of the host for the corresponding access method
port	The port number for the corresponding access method
user	The username for MySQL-MGR
password	The actual password for the MySQL-MGR user
database	The name of the database to be accessed

#JDBC

1. Cluster Internal Access

   import java.sql.*;
   public class Main {
       static final String DB_URL = "jdbc:mysql://mgr-0:3306,mgr-1:3306,mgr-2:3306/mysql";
       static final String USER = "root";
       static final String PASS = "123456";
       public static void main(String[] args) {
           try {
               Connection conn = DriverManager.getConnection(DB_URL,USER,PASS);
               Statement statement = conn.createStatement();
           }catch(SQLException se){
               se.printStackTrace();
           }
       }
   }

2. External Access to the Cluster - via NodePort

   import java.sql.*;
   public class Main {
       static final String DB_URL = "jdbc:mysql://192.168.1.100:32630,192.168.1.101:32630,192.168.1.102:32630/mysql";
       static final String USER = "root";
       static final String PASS = "123456";
       public static void main(String[] args) {
           try {
               Connection conn = DriverManager.getConnection(DB_URL,USER,PASS);
               Statement statement = conn.createStatement();
           }catch(SQLException e){
               e.printStackTrace();
           }
       }
   }

#GORM

1. Cluster Internal Access

   import (
       "gorm.io/driver/mysql"
       "gorm.io/gorm"
       "gorm.io/plugin/dbresolver"
   )
   
   func main() {
       writeDSN:="root:123456@tcp(mgr-read-write:32631)/mysql"
       readDSN := "root:123456@tcp(mgr-read-only:32630)/mysql"
       db, err := gorm.Open(mysql.Open(writeDSN), &gorm.Config{})
       if err != nil {
           panic(err)
       }
       err = db.Use(dbresolver.Register(dbresolver.Config{
           Replicas:          []gorm.Dialector{mysql.Open(readDSN)},
           Policy:            dbresolver.RandomPolicy{},
           TraceResolverMode: true,
       }))
       if err != nil {
           panic(err)
       }
   }

2. External Access to the Cluster - via NodePort

   package main
   
   import (
       "gorm.io/driver/mysql"
       "gorm.io/gorm"
       "gorm.io/plugin/dbresolver"
   )
   
   func main() {
       writeDSNs := []string{
           "root:123456@tcp(192.168.18.130:32631)/mysql",
           "root:123456@tcp(192.168.18.131:32631)/mysql",
           "root:123456@tcp(192.168.18.132:32631)/mysql",
       }
       readDSNs := []string{
           "root:123456@tcp(192.168.18.131:32630)/mysql",
           "root:123456@tcp(192.168.18.132:32630)/mysql",
           "root:123456@tcp(192.168.18.133:32630)/mysql",
       }
       db, err := gorm.Open(mysql.Open(writeDSNs[0]), &gorm.Config{})
       if err != nil {
           panic(err)
       }
       sources := make([]gorm.Dialector, 0)
       replicas := make([]gorm.Dialector, 0)
       for _, dsn := range writeDSNs {
           sources = append(sources, mysql.Open(dsn))
       }
       for _, dsn := range readDSNs {
           replicas = append(replicas, mysql.Open(dsn))
       }
       err = db.Use(dbresolver.Register(dbresolver.Config{
           Sources:           sources,
           Replicas:          replicas,
           Policy:            dbresolver.RandomPolicy{},
           TraceResolverMode: true,
       }))
       if err != nil {
           panic(err)
       }
   }