func (c *Cluster) Open(driver string) (err error) {
Loop:
	for _, g := range c.Groups {
		for _, n := range g.Nodes {
			err = n.open(driver)
			if err != nil {
				break Loop
			}
		}
	}
	return
}
Open all db nodes
package shorm
import (
	"bytes"
	"database/sql"
	"fmt"
)
type Shardinger interface {
	GetShardValue() int64
}
type Cluster struct {
	TotalGroups   int        `json:"total_groups"`
	RealGroups    int        `json:"-"`
	Groups        []*DbGroup `json:"groups" xml:"Groups>Group"`
	_defaultGroup *DbGroup
}