package layer // import "github.com/docker/docker/layer" import ( "errors" "fmt" "io" "io/ioutil" "sync" "github.com/docker/distribution" "github.com/docker/docker/daemon/graphdriver" "github.com/docker/docker/pkg/idtools" "github.com/docker/docker/pkg/plugingetter" "github.com/docker/docker/pkg/stringid" "github.com/docker/docker/pkg/system" "github.com/opencontainers/go-digest" "github.com/sirupsen/logrus" "github.com/vbatts/tar-split/tar/asm" "github.com/vbatts/tar-split/tar/storage" ) // maxLayerDepth represents the maximum number of // layers which can be chained together. 125 was // chosen to account for the 127 max in some // graphdrivers plus the 2 additional layers // used to create a rwlayer. const maxLayerDepth = 125 type layerStore struct { store *fileMetadataStore driver graphdriver.Driver useTarSplit bool layerMap map[ChainID]*roLayer layerL sync.Mutex mounts map[string]*mountedLayer mountL sync.Mutex os string } // StoreOptions are the options used to create a new Store instance type StoreOptions struct { Root string MetadataStorePathTemplate string GraphDriver string GraphDriverOptions []string IDMappings *idtools.IDMappings PluginGetter plugingetter.PluginGetter ExperimentalEnabled bool OS string } // NewStoreFromOptions creates a new Store instance func NewStoreFromOptions(options StoreOptions) (Store, error) { driver, err := graphdriver.New(options.GraphDriver, options.PluginGetter, graphdriver.Options{ Root: options.Root, DriverOptions: options.GraphDriverOptions, UIDMaps: options.IDMappings.UIDs(), GIDMaps: options.IDMappings.GIDs(), ExperimentalEnabled: options.ExperimentalEnabled, }) if err != nil { return nil, fmt.Errorf("error initializing graphdriver: %v", err) } logrus.Debugf("Initialized graph driver %s", driver) root := fmt.Sprintf(options.MetadataStorePathTemplate, driver) return newStoreFromGraphDriver(root, driver, options.OS) } // newStoreFromGraphDriver creates a new Store instance using the provided // metadata store and graph driver. The metadata store will be used to restore // the Store. func newStoreFromGraphDriver(root string, driver graphdriver.Driver, os string) (Store, error) { if !system.IsOSSupported(os) { return nil, fmt.Errorf("failed to initialize layer store as operating system '%s' is not supported", os) } caps := graphdriver.Capabilities{} if capDriver, ok := driver.(graphdriver.CapabilityDriver); ok { caps = capDriver.Capabilities() } ms, err := newFSMetadataStore(root) if err != nil { return nil, err } ls := &layerStore{ store: ms, driver: driver, layerMap: map[ChainID]*roLayer{}, mounts: map[string]*mountedLayer{}, useTarSplit: !caps.ReproducesExactDiffs, os: os, } ids, mounts, err := ms.List() if err != nil { return nil, err } for _, id := range ids { l, err := ls.loadLayer(id) if err != nil { logrus.Debugf("Failed to load layer %s: %s", id, err) continue } if l.parent != nil { l.parent.referenceCount++ } } for _, mount := range mounts { if err := ls.loadMount(mount); err != nil { logrus.Debugf("Failed to load mount %s: %s", mount, err) } } return ls, nil } func (ls *layerStore) loadLayer(layer ChainID) (*roLayer, error) { cl, ok := ls.layerMap[layer] if ok { return cl, nil } diff, err := ls.store.GetDiffID(layer) if err != nil { return nil, fmt.Errorf("failed to get diff id for %s: %s", layer, err) } size, err := ls.store.GetSize(layer) if err != nil { return nil, fmt.Errorf("failed to get size for %s: %s", layer, err) } cacheID, err := ls.store.GetCacheID(layer) if err != nil { return nil, fmt.Errorf("failed to get cache id for %s: %s", layer, err) } parent, err := ls.store.GetParent(layer) if err != nil { return nil, fmt.Errorf("failed to get parent for %s: %s", layer, err) } descriptor, err := ls.store.GetDescriptor(layer) if err != nil { return nil, fmt.Errorf("failed to get descriptor for %s: %s", layer, err) } os, err := ls.store.getOS(layer) if err != nil { return nil, fmt.Errorf("failed to get operating system for %s: %s", layer, err) } if os != ls.os { return nil, fmt.Errorf("failed to load layer with os %s into layerstore for %s", os, ls.os) } cl = &roLayer{ chainID: layer, diffID: diff, size: size, cacheID: cacheID, layerStore: ls, references: map[Layer]struct{}{}, descriptor: descriptor, } if parent != "" { p, err := ls.loadLayer(parent) if err != nil { return nil, err } cl.parent = p } ls.layerMap[cl.chainID] = cl return cl, nil } func (ls *layerStore) loadMount(mount string) error { if _, ok := ls.mounts[mount]; ok { return nil } mountID, err := ls.store.GetMountID(mount) if err != nil { return err } initID, err := ls.store.GetInitID(mount) if err != nil { return err } parent, err := ls.store.GetMountParent(mount) if err != nil { return err } ml := &mountedLayer{ name: mount, mountID: mountID, initID: initID, layerStore: ls, references: map[RWLayer]*referencedRWLayer{}, } if parent != "" { p, err := ls.loadLayer(parent) if err != nil { return err } ml.parent = p p.referenceCount++ } ls.mounts[ml.name] = ml return nil } func (ls *layerStore) applyTar(tx *fileMetadataTransaction, ts io.Reader, parent string, layer *roLayer) error { digester := digest.Canonical.Digester() tr := io.TeeReader(ts, digester.Hash()) rdr := tr if ls.useTarSplit { tsw, err := tx.TarSplitWriter(true) if err != nil { return err } metaPacker := storage.NewJSONPacker(tsw) defer tsw.Close() // we're passing nil here for the file putter, because the ApplyDiff will // handle the extraction of the archive rdr, err = asm.NewInputTarStream(tr, metaPacker, nil) if err != nil { return err } } applySize, err := ls.driver.ApplyDiff(layer.cacheID, parent, rdr) if err != nil { return err } // Discard trailing data but ensure metadata is picked up to reconstruct stream io.Copy(ioutil.Discard, rdr) // ignore error as reader may be closed layer.size = applySize layer.diffID = DiffID(digester.Digest()) logrus.Debugf("Applied tar %s to %s, size: %d", layer.diffID, layer.cacheID, applySize) return nil } func (ls *layerStore) Register(ts io.Reader, parent ChainID) (Layer, error) { return ls.registerWithDescriptor(ts, parent, distribution.Descriptor{}) } func (ls *layerStore) registerWithDescriptor(ts io.Reader, parent ChainID, descriptor distribution.Descriptor) (Layer, error) { // err is used to hold the error which will always trigger // cleanup of creates sources but may not be an error returned // to the caller (already exists). var err error var pid string var p *roLayer if string(parent) != "" { p = ls.get(parent) if p == nil { return nil, ErrLayerDoesNotExist } pid = p.cacheID // Release parent chain if error defer func() { if err != nil { ls.layerL.Lock() ls.releaseLayer(p) ls.layerL.Unlock() } }() if p.depth() >= maxLayerDepth { err = ErrMaxDepthExceeded return nil, err } } // Create new roLayer layer := &roLayer{ parent: p, cacheID: stringid.GenerateRandomID(), referenceCount: 1, layerStore: ls, references: map[Layer]struct{}{}, descriptor: descriptor, } if err = ls.driver.Create(layer.cacheID, pid, nil); err != nil { return nil, err } tx, err := ls.store.StartTransaction() if err != nil { return nil, err } defer func() { if err != nil { logrus.Debugf("Cleaning up layer %s: %v", layer.cacheID, err) if err := ls.driver.Remove(layer.cacheID); err != nil { logrus.Errorf("Error cleaning up cache layer %s: %v", layer.cacheID, err) } if err := tx.Cancel(); err != nil { logrus.Errorf("Error canceling metadata transaction %q: %s", tx.String(), err) } } }() if err = ls.applyTar(tx, ts, pid, layer); err != nil { return nil, err } if layer.parent == nil { layer.chainID = ChainID(layer.diffID) } else { layer.chainID = createChainIDFromParent(layer.parent.chainID, layer.diffID) } if err = storeLayer(tx, layer); err != nil { return nil, err } ls.layerL.Lock() defer ls.layerL.Unlock() if existingLayer := ls.getWithoutLock(layer.chainID); existingLayer != nil { // Set error for cleanup, but do not return the error err = errors.New("layer already exists") return existingLayer.getReference(), nil } if err = tx.Commit(layer.chainID); err != nil { return nil, err } ls.layerMap[layer.chainID] = layer return layer.getReference(), nil } func (ls *layerStore) getWithoutLock(layer ChainID) *roLayer { l, ok := ls.layerMap[layer] if !ok { return nil } l.referenceCount++ return l } func (ls *layerStore) get(l ChainID) *roLayer { ls.layerL.Lock() defer ls.layerL.Unlock() return ls.getWithoutLock(l) } func (ls *layerStore) Get(l ChainID) (Layer, error) { ls.layerL.Lock() defer ls.layerL.Unlock() layer := ls.getWithoutLock(l) if layer == nil { return nil, ErrLayerDoesNotExist } return layer.getReference(), nil } func (ls *layerStore) Map() map[ChainID]Layer { ls.layerL.Lock() defer ls.layerL.Unlock() layers := map[ChainID]Layer{} for k, v := range ls.layerMap { layers[k] = v } return layers } func (ls *layerStore) deleteLayer(layer *roLayer, metadata *Metadata) error { err := ls.driver.Remove(layer.cacheID) if err != nil { return err } err = ls.store.Remove(layer.chainID) if err != nil { return err } metadata.DiffID = layer.diffID metadata.ChainID = layer.chainID metadata.Size, err = layer.Size() if err != nil { return err } metadata.DiffSize = layer.size return nil } func (ls *layerStore) releaseLayer(l *roLayer) ([]Metadata, error) { depth := 0 removed := []Metadata{} for { if l.referenceCount == 0 { panic("layer not retained") } l.referenceCount-- if l.referenceCount != 0 { return removed, nil } if len(removed) == 0 && depth > 0 { panic("cannot remove layer with child") } if l.hasReferences() { panic("cannot delete referenced layer") } var metadata Metadata if err := ls.deleteLayer(l, &metadata); err != nil { return nil, err } delete(ls.layerMap, l.chainID) removed = append(removed, metadata) if l.parent == nil { return removed, nil } depth++ l = l.parent } } func (ls *layerStore) Release(l Layer) ([]Metadata, error) { ls.layerL.Lock() defer ls.layerL.Unlock() layer, ok := ls.layerMap[l.ChainID()] if !ok { return []Metadata{}, nil } if !layer.hasReference(l) { return nil, ErrLayerNotRetained } layer.deleteReference(l) return ls.releaseLayer(layer) } func (ls *layerStore) CreateRWLayer(name string, parent ChainID, opts *CreateRWLayerOpts) (RWLayer, error) { var ( storageOpt map[string]string initFunc MountInit mountLabel string ) if opts != nil { mountLabel = opts.MountLabel storageOpt = opts.StorageOpt initFunc = opts.InitFunc } ls.mountL.Lock() defer ls.mountL.Unlock() m, ok := ls.mounts[name] if ok { return nil, ErrMountNameConflict } var err error var pid string var p *roLayer if string(parent) != "" { p = ls.get(parent) if p == nil { return nil, ErrLayerDoesNotExist } pid = p.cacheID // Release parent chain if error defer func() { if err != nil { ls.layerL.Lock() ls.releaseLayer(p) ls.layerL.Unlock() } }() } m = &mountedLayer{ name: name, parent: p, mountID: ls.mountID(name), layerStore: ls, references: map[RWLayer]*referencedRWLayer{}, } if initFunc != nil { pid, err = ls.initMount(m.mountID, pid, mountLabel, initFunc, storageOpt) if err != nil { return nil, err } m.initID = pid } createOpts := &graphdriver.CreateOpts{ StorageOpt: storageOpt, } if err = ls.driver.CreateReadWrite(m.mountID, pid, createOpts); err != nil { return nil, err } if err = ls.saveMount(m); err != nil { return nil, err } return m.getReference(), nil } func (ls *layerStore) GetRWLayer(id string) (RWLayer, error) { ls.mountL.Lock() defer ls.mountL.Unlock() mount, ok := ls.mounts[id] if !ok { return nil, ErrMountDoesNotExist } return mount.getReference(), nil } func (ls *layerStore) GetMountID(id string) (string, error) { ls.mountL.Lock() defer ls.mountL.Unlock() mount, ok := ls.mounts[id] if !ok { return "", ErrMountDoesNotExist } logrus.Debugf("GetMountID id: %s -> mountID: %s", id, mount.mountID) return mount.mountID, nil } func (ls *layerStore) ReleaseRWLayer(l RWLayer) ([]Metadata, error) { ls.mountL.Lock() defer ls.mountL.Unlock() m, ok := ls.mounts[l.Name()] if !ok { return []Metadata{}, nil } if err := m.deleteReference(l); err != nil { return nil, err } if m.hasReferences() { return []Metadata{}, nil } if err := ls.driver.Remove(m.mountID); err != nil { logrus.Errorf("Error removing mounted layer %s: %s", m.name, err) m.retakeReference(l) return nil, err } if m.initID != "" { if err := ls.driver.Remove(m.initID); err != nil { logrus.Errorf("Error removing init layer %s: %s", m.name, err) m.retakeReference(l) return nil, err } } if err := ls.store.RemoveMount(m.name); err != nil { logrus.Errorf("Error removing mount metadata: %s: %s", m.name, err) m.retakeReference(l) return nil, err } delete(ls.mounts, m.Name()) ls.layerL.Lock() defer ls.layerL.Unlock() if m.parent != nil { return ls.releaseLayer(m.parent) } return []Metadata{}, nil } func (ls *layerStore) saveMount(mount *mountedLayer) error { if err := ls.store.SetMountID(mount.name, mount.mountID); err != nil { return err } if mount.initID != "" { if err := ls.store.SetInitID(mount.name, mount.initID); err != nil { return err } } if mount.parent != nil { if err := ls.store.SetMountParent(mount.name, mount.parent.chainID); err != nil { return err } } ls.mounts[mount.name] = mount return nil } func (ls *layerStore) initMount(graphID, parent, mountLabel string, initFunc MountInit, storageOpt map[string]string) (string, error) { // Use "-init" to maintain compatibility with graph drivers // which are expecting this layer with this special name. If all // graph drivers can be updated to not rely on knowing about this layer // then the initID should be randomly generated. initID := fmt.Sprintf("%s-init", graphID) createOpts := &graphdriver.CreateOpts{ MountLabel: mountLabel, StorageOpt: storageOpt, } if err := ls.driver.CreateReadWrite(initID, parent, createOpts); err != nil { return "", err } p, err := ls.driver.Get(initID, "") if err != nil { return "", err } if err := initFunc(p); err != nil { ls.driver.Put(initID) return "", err } if err := ls.driver.Put(initID); err != nil { return "", err } return initID, nil } func (ls *layerStore) getTarStream(rl *roLayer) (io.ReadCloser, error) { if !ls.useTarSplit { var parentCacheID string if rl.parent != nil { parentCacheID = rl.parent.cacheID } return ls.driver.Diff(rl.cacheID, parentCacheID) } r, err := ls.store.TarSplitReader(rl.chainID) if err != nil { return nil, err } pr, pw := io.Pipe() go func() { err := ls.assembleTarTo(rl.cacheID, r, nil, pw) if err != nil { pw.CloseWithError(err) } else { pw.Close() } }() return pr, nil } func (ls *layerStore) assembleTarTo(graphID string, metadata io.ReadCloser, size *int64, w io.Writer) error { diffDriver, ok := ls.driver.(graphdriver.DiffGetterDriver) if !ok { diffDriver = &naiveDiffPathDriver{ls.driver} } defer metadata.Close() // get our relative path to the container fileGetCloser, err := diffDriver.DiffGetter(graphID) if err != nil { return err } defer fileGetCloser.Close() metaUnpacker := storage.NewJSONUnpacker(metadata) upackerCounter := &unpackSizeCounter{metaUnpacker, size} logrus.Debugf("Assembling tar data for %s", graphID) return asm.WriteOutputTarStream(fileGetCloser, upackerCounter, w) } func (ls *layerStore) Cleanup() error { return ls.driver.Cleanup() } func (ls *layerStore) DriverStatus() [][2]string { return ls.driver.Status() } func (ls *layerStore) DriverName() string { return ls.driver.String() } type naiveDiffPathDriver struct { graphdriver.Driver } type fileGetPutter struct { storage.FileGetter driver graphdriver.Driver id string } func (w *fileGetPutter) Close() error { return w.driver.Put(w.id) } func (n *naiveDiffPathDriver) DiffGetter(id string) (graphdriver.FileGetCloser, error) { p, err := n.Driver.Get(id, "") if err != nil { return nil, err } return &fileGetPutter{storage.NewPathFileGetter(p.Path()), n.Driver, id}, nil }