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moby--moby/daemon/graphdriver/driver.go
Brian Goff 362369b4bb Adds ability to squash image after build
Allow built images to be squash to scratch.
Squashing does not destroy any images or layers, and preserves the
build cache.

Introduce a new CLI argument --squash to docker build
Introduce a new param to the build API endpoint `squash`

Once the build is complete, docker creates a new image loading the diffs
from each layer into a single new layer and references all the parent's
layers.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
2016-11-01 13:41:59 -04:00

250 lines
8.9 KiB
Go

package graphdriver
import (
"errors"
"fmt"
"io"
"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"
"github.com/docker/docker/pkg/plugingetter"
)
// 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)
// 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
}
// DiffDriver is the interface to use to implement graph diffs
type DiffDriver interface {
// Diff produces an archive of the changes between the specified
// layer and its parent layer which may be "".
Diff(id, parent string) (io.ReadCloser, 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 io.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)
}
// Driver is the interface for layered/snapshot file system drivers.
type Driver interface {
ProtoDriver
DiffDriver
}
// 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
}
func init() {
drivers = make(map[string]InitFunc)
}
// Register registers an InitFunc for the driver.
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, pg plugingetter.PluginGetter) (Driver, error) {
if initFunc, exists := drivers[name]; exists {
return initFunc(filepath.Join(home, name), options, uidMaps, gidMaps)
}
if pluginDriver, err := lookupPlugin(name, home, options, pg); 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, name string, options []string, uidMaps, gidMaps []idtools.IDMap, pg plugingetter.PluginGetter) (Driver, error) {
if name != "" {
logrus.Debugf("[graphdriver] trying provided driver: %s", name) // so the logs show specified driver
return GetDriver(name, root, options, uidMaps, gidMaps, pg)
}
// 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 %s 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("%s 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: %s", name)
return driver, nil
}
}
// 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
}
return driver, nil
}
// 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
}
return driver, nil
}
return nil, fmt.Errorf("No supported storage backend found")
}
// 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
}