This is a go package for managing access to multiple MySQL/MariaDB servers. This
package takes a list of DB handlers (as slice of *sql.DB) and provides methods
for getting currently active master slave DB instance.
Server role (master or slave) is selected by periodically checking value of
read_only variable in the server configuration. When read_only flag is set
to true server is considered to have a slave role otherwise server role is
master. This is important to take into consideration when performing server
failover. If server is actually running in slave mode but have read_only flag
set to false it will receive DML queries from the services using this package
and this will most likely cause data replication failure.
package main
import (
"database/sql"
"log"
"github.com/advbet/dbfailover"
_ "github.com/go-sql-driver/mysql"
)
type Service struct {
dbs *dbfailover.DBs
}
func main() {
dsns := []string{
"user:pass@tcp(127.0.0.1:3306)/db",
"user:pass@tcp(127.0.0.2:3306)/db",
"user:pass@tcp(127.0.0.3:3306)/db",
}
var dbhs []*sql.DB
for _, dsn := range dsns {
db, err := sql.Open("mysql", dsn)
if err != nil {
log.Print("failed to create db pool instance", err)
continue
}
dbhs = append(dbhs, db)
}
dbs, err := dbfailover.New(dbhs)
if err != nil {
log.Fatal("failed to create DBs", err)
}
defer dbs.Stop()
svc := Service{
dbs: dbs,
}
svc.Insert()
svc.Query()
}
func (s *Service) Insert() {
// Access master server
_, err := s.dbs.Master().Query(`INSERT INTO user(id, name) VALUES(NULL, "John")`)
if err != nil {
log.Fatal("insert query on master failed", err)
}
}
func (s *Service) Query() {
// Access slave server
_, err := s.dbs.Slave().Query(`SELECT id, name FROM user`)
if err != nil {
log.Fatal("select query on slave failed", err)
}
}