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moby--moby/graphdriver/driver.go
2013-11-08 11:36:58 -08:00

83 lines
1.8 KiB
Go

package graphdriver
import (
"fmt"
"github.com/dotcloud/docker/archive"
"github.com/dotcloud/docker/utils"
"os"
"path"
)
type InitFunc func(root string) (Driver, error)
type Driver interface {
Create(id, parent string) error
Remove(id string) error
Get(id string) (dir string, err error)
Diff(id string) (archive.Archive, error)
DiffSize(id string) (bytes int64, err error)
Changes(id string) ([]archive.Change, error)
Cleanup() error
}
var (
// All registred drivers
drivers map[string]InitFunc
// Slice of drivers that should be used in an order
priority = []string{
"aufs",
"devicemapper",
"dummy",
}
)
func init() {
drivers = make(map[string]InitFunc)
}
func Register(name string, initFunc InitFunc) error {
if _, exists := drivers[name]; exists {
return fmt.Errorf("Name already registered %s", name)
}
drivers[name] = initFunc
return nil
}
func getDriver(name, home string) (Driver, error) {
if initFunc, exists := drivers[name]; exists {
return initFunc(path.Join(home, name))
}
return nil, fmt.Errorf("No such driver: %s", name)
}
func New(root string) (Driver, error) {
var driver Driver
var lastError error
// Use environment variable DOCKER_DRIVER to force a choice of driver
if name := os.Getenv("DOCKER_DRIVER"); name != "" {
return getDriver(name, root)
}
// Check for priority drivers first
for _, name := range priority {
driver, lastError = getDriver(name, root)
if lastError != nil {
utils.Debugf("Error loading driver %s: %s", name, lastError)
continue
}
return driver, nil
}
// Check all registered drivers if no priority driver is found
for _, initFunc := range drivers {
driver, lastError = initFunc(root)
if lastError != nil {
continue
}
return driver, nil
}
return nil, lastError
}