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

244 lines
8.7 KiB
Go
Raw Normal View History

package graphdriver
2013-11-04 18:22:34 -05:00
import (
"errors"
2013-11-04 18:22:34 -05:00
"fmt"
"os"
"path/filepath"
"strings"
"github.com/Sirupsen/logrus"
"github.com/vbatts/tar-split/tar/storage"
"github.com/docker/docker/pkg/archive"
"github.com/docker/docker/pkg/idtools"
2013-11-04 18:22:34 -05:00
)
// FsMagic unsigned id of the filesystem in use.
type FsMagic uint32
const (
// FsMagicUnsupported is a predefined constant value other than a valid filesystem id.
FsMagicUnsupported = FsMagic(0x00000000)
)
var (
// All registered drivers
drivers map[string]InitFunc
// ErrNotSupported returned when driver is not supported.
ErrNotSupported = errors.New("driver not supported")
// ErrPrerequisites retuned when driver does not meet prerequisites.
ErrPrerequisites = errors.New("prerequisites for driver not satisfied (wrong filesystem?)")
// ErrIncompatibleFS returned when file system is not supported.
ErrIncompatibleFS = fmt.Errorf("backing file system is unsupported for this graph driver")
)
// InitFunc initializes the storage driver.
type InitFunc func(root string, options []string, uidMaps, gidMaps []idtools.IDMap) (Driver, error)
2013-11-04 23:51:12 -05:00
// 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
// CreateReadWrite creates a new, empty filesystem layer that is ready
// to be used as the storage for a container.
CreateReadWrite(id, parent, mountLabel string, storageOpt map[string]string) error
// Create creates a new, empty, filesystem layer with the
// specified id and parent and mountLabel. Parent and mountLabel may be "".
Create(id, parent, mountLabel string, storageOpt map[string]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.
// The archive.Reader must be an uncompressed stream.
ApplyDiff(id, parent string, diff archive.Reader) (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)
}
// DiffGetterDriver is the interface for layered file system drivers that
// provide a specialized function for getting file contents for tar-split.
type DiffGetterDriver interface {
Driver
// DiffGetter returns an interface to efficiently retrieve the contents
// of files in a layer.
DiffGetter(id string) (FileGetCloser, error)
}
// FileGetCloser extends the storage.FileGetter interface with a Close method
// for cleaning up.
type FileGetCloser interface {
storage.FileGetter
// Close cleans up any resources associated with the FileGetCloser.
Close() error
}
// Checker makes checks on specified filesystems.
type Checker interface {
// IsMounted returns true if the provided path is mounted for the specific checker
IsMounted(path string) bool
}
2013-11-07 15:31:50 -05:00
func init() {
drivers = make(map[string]InitFunc)
}
// Register registers an InitFunc for the driver.
2013-11-04 18:22:34 -05:00
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
}
// GetDriver initializes and returns the registered driver
func GetDriver(name, home string, options []string, uidMaps, gidMaps []idtools.IDMap) (Driver, error) {
if initFunc, exists := drivers[name]; exists {
return initFunc(filepath.Join(home, name), options, uidMaps, gidMaps)
}
if pluginDriver, err := lookupPlugin(name, home, options); err == nil {
return pluginDriver, nil
}
logrus.Errorf("Failed to GetDriver graph %s %s", name, home)
return nil, ErrNotSupported
}
// getBuiltinDriver initializes and returns the registered driver, but does not try to load from plugins
func getBuiltinDriver(name, home string, options []string, uidMaps, gidMaps []idtools.IDMap) (Driver, error) {
if initFunc, exists := drivers[name]; exists {
return initFunc(filepath.Join(home, name), options, uidMaps, gidMaps)
}
logrus.Errorf("Failed to built-in GetDriver graph %s %s", name, home)
return nil, ErrNotSupported
}
// New creates the driver and initializes it at the specified root.
func New(root string, name string, options []string, uidMaps, gidMaps []idtools.IDMap) (Driver, error) {
if name != "" {
logrus.Debugf("[graphdriver] trying provided driver %q", name) // so the logs show specified driver
return GetDriver(name, root, options, uidMaps, gidMaps)
}
// Guess for prior driver
driversMap := scanPriorDrivers(root)
for _, name := range priority {
if name == "vfs" {
// don't use vfs even if there is state present.
continue
}
if _, prior := driversMap[name]; prior {
// of the state found from prior drivers, check in order of our priority
// which we would prefer
driver, err := getBuiltinDriver(name, root, options, uidMaps, gidMaps)
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
}
// abort starting when there are other prior configured drivers
// to ensure the user explicitly selects the driver to load
if len(driversMap)-1 > 0 {
var driversSlice []string
for name := range driversMap {
driversSlice = append(driversSlice, name)
}
return nil, fmt.Errorf("%q contains several valid graphdrivers: %s; Please cleanup or explicitly choose storage driver (-s <DRIVER>)", root, strings.Join(driversSlice, ", "))
}
logrus.Infof("[graphdriver] using prior storage driver %q", name)
return driver, nil
}
}
2013-11-04 18:22:34 -05:00
// Check for priority drivers first
for _, name := range priority {
driver, err := getBuiltinDriver(name, root, options, uidMaps, gidMaps)
if err != nil {
if isDriverNotSupported(err) {
continue
}
return nil, err
2013-11-04 18:22:34 -05:00
}
return driver, nil
2013-11-04 18:22:34 -05:00
}
// Check all registered drivers if no priority driver is found
for name, initFunc := range drivers {
driver, err := initFunc(filepath.Join(root, name), options, uidMaps, gidMaps)
if err != nil {
if isDriverNotSupported(err) {
continue
}
return nil, err
2013-11-04 18:22:34 -05:00
}
return driver, nil
}
return nil, fmt.Errorf("No supported storage backend found")
2013-11-04 18:22:34 -05:00
}
// isDriverNotSupported returns true if the error initializing
// the graph driver is a non-supported error.
func isDriverNotSupported(err error) bool {
return err == ErrNotSupported || err == ErrPrerequisites || err == ErrIncompatibleFS
}
// scanPriorDrivers returns an un-ordered scan of directories of prior storage drivers
func scanPriorDrivers(root string) map[string]bool {
driversMap := make(map[string]bool)
for driver := range drivers {
p := filepath.Join(root, driver)
if _, err := os.Stat(p); err == nil && driver != "vfs" {
driversMap[driver] = true
}
}
return driversMap
}