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If a graphdriver fails initialization due to ErrNotSupported we ignore that and keep trying the next. But if some driver has a different error (for instance if you specified an unknown option for it) we fail the daemon startup, printing the error, rather than falling back to an unexected driver (typically vfs) which may not match what you have run earlier. Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
100 lines
2 KiB
Go
100 lines
2 KiB
Go
package graphdriver
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import (
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"errors"
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"fmt"
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"github.com/dotcloud/docker/archive"
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"os"
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"path"
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)
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type InitFunc func(root string) (Driver, error)
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type Driver interface {
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String() string
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Create(id, parent string) error
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Remove(id string) error
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Get(id, mountLabel string) (dir string, err error)
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Put(id string)
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Exists(id string) bool
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Status() [][2]string
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Cleanup() error
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}
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type Differ interface {
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Diff(id string) (archive.Archive, error)
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Changes(id string) ([]archive.Change, error)
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ApplyDiff(id string, diff archive.ArchiveReader) error
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DiffSize(id string) (bytes int64, err error)
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}
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var (
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DefaultDriver string
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// All registred drivers
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drivers map[string]InitFunc
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// Slice of drivers that should be used in an order
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priority = []string{
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"aufs",
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"btrfs",
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"devicemapper",
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"vfs",
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}
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ErrNotSupported = errors.New("driver not supported")
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)
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func init() {
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drivers = make(map[string]InitFunc)
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}
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func Register(name string, initFunc InitFunc) error {
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if _, exists := drivers[name]; exists {
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return fmt.Errorf("Name already registered %s", name)
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}
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drivers[name] = initFunc
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return nil
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}
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func GetDriver(name, home string) (Driver, error) {
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if initFunc, exists := drivers[name]; exists {
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return initFunc(path.Join(home, name))
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}
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return nil, ErrNotSupported
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}
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func New(root string) (driver Driver, err error) {
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for _, name := range []string{os.Getenv("DOCKER_DRIVER"), DefaultDriver} {
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if name != "" {
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return GetDriver(name, root)
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}
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}
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// Check for priority drivers first
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for _, name := range priority {
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driver, err = GetDriver(name, root)
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if err != nil {
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if err == ErrNotSupported {
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continue
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}
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return nil, err
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}
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return driver, nil
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}
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// Check all registered drivers if no priority driver is found
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for _, initFunc := range drivers {
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if driver, err = initFunc(root); err != nil {
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if err == ErrNotSupported {
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continue
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}
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return nil, err
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}
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return driver, nil
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}
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return nil, fmt.Errorf("No supported storage backend found")
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}
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