1
0
Fork 0
mirror of https://github.com/moby/moby.git synced 2022-11-09 12:21:53 -05:00
moby--moby/daemon/graphdriver/driver.go
John Howard 52f4d09ffb Windows: Graph driver implementation
Signed-off-by: John Howard <jhoward@microsoft.com>
2015-07-10 14:33:11 -07:00

197 lines
6.4 KiB
Go

package graphdriver
import (
"errors"
"fmt"
"os"
"path/filepath"
"strings"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/pkg/archive"
)
type FsMagic uint32
const (
FsMagicUnsupported = FsMagic(0x00000000)
)
var (
DefaultDriver string
// All registred drivers
drivers map[string]InitFunc
ErrNotSupported = errors.New("driver not supported")
ErrPrerequisites = errors.New("prerequisites for driver not satisfied (wrong filesystem?)")
ErrIncompatibleFS = fmt.Errorf("backing file system is unsupported for this graph driver")
)
type InitFunc func(root string, options []string) (Driver, error)
// ProtoDriver defines the basic capabilities of a driver.
// This interface exists solely to be a minimum set of methods
// for client code which choose not to implement the entire Driver
// interface and use the NaiveDiffDriver wrapper constructor.
//
// Use of ProtoDriver directly by client code is not recommended.
type ProtoDriver interface {
// String returns a string representation of this driver.
String() string
// Create creates a new, empty, filesystem layer with the
// specified id and parent. Parent may be "".
Create(id, parent string) error
// Remove attempts to remove the filesystem layer with this id.
Remove(id string) error
// Get returns the mountpoint for the layered filesystem referred
// to by this id. You can optionally specify a mountLabel or "".
// Returns the absolute path to the mounted layered filesystem.
Get(id, mountLabel string) (dir string, err error)
// Put releases the system resources for the specified id,
// e.g, unmounting layered filesystem.
Put(id string) error
// Exists returns whether a filesystem layer with the specified
// ID exists on this driver.
Exists(id string) bool
// Status returns a set of key-value pairs which give low
// level diagnostic status about this driver.
Status() [][2]string
// Returns a set of key-value pairs which give low level information
// about the image/container driver is managing.
GetMetadata(id string) (map[string]string, error)
// Cleanup performs necessary tasks to release resources
// held by the driver, e.g., unmounting all layered filesystems
// known to this driver.
Cleanup() error
}
// Driver is the interface for layered/snapshot file system drivers.
type Driver interface {
ProtoDriver
// Diff produces an archive of the changes between the specified
// layer and its parent layer which may be "".
Diff(id, parent string) (archive.Archive, error)
// Changes produces a list of changes between the specified layer
// and its parent layer. If parent is "", then all changes will be ADD changes.
Changes(id, parent string) ([]archive.Change, error)
// ApplyDiff extracts the changeset from the given diff into the
// layer with the specified id and parent, returning the size of the
// new layer in bytes.
ApplyDiff(id, parent string, diff archive.ArchiveReader) (size int64, err error)
// DiffSize calculates the changes between the specified id
// and its parent and returns the size in bytes of the changes
// relative to its base filesystem directory.
DiffSize(id, parent string) (size int64, err error)
}
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, options []string) (Driver, error) {
if initFunc, exists := drivers[name]; exists {
return initFunc(filepath.Join(home, name), options)
}
logrus.Errorf("Failed to GetDriver graph %s %s", name, home)
return nil, ErrNotSupported
}
func New(root string, options []string) (driver Driver, err error) {
for _, name := range []string{os.Getenv("DOCKER_DRIVER"), DefaultDriver} {
if name != "" {
logrus.Debugf("[graphdriver] trying provided driver %q", name) // so the logs show specified driver
return GetDriver(name, root, options)
}
}
// Guess for prior driver
priorDrivers := scanPriorDrivers(root)
for _, name := range priority {
if name == "vfs" {
// don't use vfs even if there is state present.
continue
}
for _, prior := range priorDrivers {
// of the state found from prior drivers, check in order of our priority
// which we would prefer
if prior == name {
driver, err = GetDriver(name, root, options)
if err != nil {
// unlike below, we will return error here, because there is prior
// state, and now it is no longer supported/prereq/compatible, so
// something changed and needs attention. Otherwise the daemon's
// images would just "disappear".
logrus.Errorf("[graphdriver] prior storage driver %q failed: %s", name, err)
return nil, err
}
if err := checkPriorDriver(name, root); err != nil {
return nil, err
}
logrus.Infof("[graphdriver] using prior storage driver %q", name)
return driver, nil
}
}
}
// Check for priority drivers first
for _, name := range priority {
driver, err = GetDriver(name, root, options)
if err != nil {
if err == ErrNotSupported || err == ErrPrerequisites || err == ErrIncompatibleFS {
continue
}
return nil, err
}
return driver, nil
}
// Check all registered drivers if no priority driver is found
for _, initFunc := range drivers {
if driver, err = initFunc(root, options); err != nil {
if err == ErrNotSupported || err == ErrPrerequisites || err == ErrIncompatibleFS {
continue
}
return nil, err
}
return driver, nil
}
return nil, fmt.Errorf("No supported storage backend found")
}
// scanPriorDrivers returns an un-ordered scan of directories of prior storage drivers
func scanPriorDrivers(root string) []string {
priorDrivers := []string{}
for driver := range drivers {
p := filepath.Join(root, driver)
if _, err := os.Stat(p); err == nil && driver != "vfs" {
priorDrivers = append(priorDrivers, driver)
}
}
return priorDrivers
}
func checkPriorDriver(name, root string) error {
priorDrivers := []string{}
for _, prior := range scanPriorDrivers(root) {
if prior != name && prior != "vfs" {
if _, err := os.Stat(filepath.Join(root, prior)); err == nil {
priorDrivers = append(priorDrivers, prior)
}
}
}
if len(priorDrivers) > 0 {
return errors.New(fmt.Sprintf("%q contains other graphdrivers: %s; Please cleanup or explicitly choose storage driver (-s <DRIVER>)", root, strings.Join(priorDrivers, ",")))
}
return nil
}