@@ -189,6 +189,21 @@ func (container *Container) ToDiskLocking() error {

 	return err

 }

+// CheckpointTo makes the Container's current state visible to queries.

+// Callers must hold a Container lock.

+func (container *Container) CheckpointTo(store ViewDB) error {

+	return store.Save(container.snapshot())

+}

+

+// CheckpointAndSaveToDisk is equivalent to calling CheckpointTo and ToDisk.

+// Callers must hold a Container lock.

+func (container *Container) CheckpointAndSaveToDisk(store ViewDB) error {

+	if err := container.CheckpointTo(store); err != nil {

+		return err

+	}

+	return container.ToDisk()

+}

+

 // readHostConfig reads the host configuration from disk for the container.

 func (container *Container) readHostConfig() error {

 	container.HostConfig = &containertypes.HostConfig{}

@@ -41,7 +41,7 @@ type Snapshot struct {

 }

 // Snapshot provides a read only view of a Container. Callers must hold a Lock on the container object.

-func (container *Container) Snapshot() *Snapshot {

+func (container *Container) snapshot() *Snapshot {

 	snapshot := &Snapshot{

 		ID:           container.ID,

 		Name:         container.Name,

@@ -8,6 +8,19 @@ const (

 	memdbIDIndex = "id"

 )

+// ViewDB provides an in-memory transactional (ACID) container Store

+type ViewDB interface {

+	Snapshot() View

+	Save(snapshot *Snapshot) error

+	Delete(id string) error

+}

+

+// View can be used by readers to avoid locking

+type View interface {

+	All() ([]Snapshot, error)

+	Get(id string) (*Snapshot, error)

+}

+

 var schema = &memdb.DBSchema{

 	Tables: map[string]*memdb.TableSchema{

 		memdbTable: {

@@ -23,46 +36,44 @@ var schema = &memdb.DBSchema{

 	},

 }

-// MemDB provides an in-memory transactional (ACID) container Store

-type MemDB struct {

+type memDB struct {

 	store *memdb.MemDB

 }

-// NewMemDB provides the default implementation, with the default schema

-func NewMemDB() (*MemDB, error) {

+// NewViewDB provides the default implementation, with the default schema

+func NewViewDB() (ViewDB, error) {

 	store, err := memdb.NewMemDB(schema)

 	if err != nil {

 		return nil, err

 	}

-	return &MemDB{store: store}, nil

+	return &memDB{store: store}, nil

 }

 // Snapshot provides a consistent read-only View of the database

-func (db *MemDB) Snapshot() *View {

-	return &View{db.store.Txn(false)}

+func (db *memDB) Snapshot() View {

+	return &memdbView{db.store.Txn(false)}

 }

 // Save atomically updates the in-memory store

-func (db *MemDB) Save(snapshot *Snapshot) error {

+func (db *memDB) Save(snapshot *Snapshot) error {

 	txn := db.store.Txn(true)

 	defer txn.Commit()

 	return txn.Insert(memdbTable, snapshot)

 }

 // Delete removes an item by ID

-func (db *MemDB) Delete(id string) error {

+func (db *memDB) Delete(id string) error {

 	txn := db.store.Txn(true)

 	defer txn.Commit()

 	return txn.Delete(memdbTable, &Snapshot{ID: id})

 }

-// View can be used by readers to avoid locking

-type View struct {

+type memdbView struct {

 	txn *memdb.Txn

 }

 // All returns a all items in this snapshot

-func (v *View) All() ([]Snapshot, error) {

+func (v *memdbView) All() ([]Snapshot, error) {

 	var all []Snapshot

 	iter, err := v.txn.Get(memdbTable, memdbIDIndex)

 	if err != nil {

@@ -80,7 +91,7 @@ func (v *View) All() ([]Snapshot, error) {

 }

 //Get returns an item by id

-func (v *View) Get(id string) (*Snapshot, error) {

+func (v *memdbView) Get(id string) (*Snapshot, error) {

 	s, err := v.txn.First(memdbTable, memdbIDIndex, id)

 	if err != nil {

 		return nil, err

@@ -3,27 +3,26 @@ package container

 import "testing"

 func TestViewSave(t *testing.T) {

-	db, err := NewMemDB()

+	db, err := NewViewDB()

 	if err != nil {

 		t.Fatal(err)

 	}

-	snapshot := NewBaseContainer("id", "root").Snapshot()

-	if err := db.Save(snapshot); err != nil {

+	c := NewBaseContainer("id", "root")

+	if err := c.CheckpointTo(db); err != nil {

 		t.Fatal(err)

-

 	}

 }

 func TestViewAll(t *testing.T) {

 	var (

-		db, _ = NewMemDB()

-		one   = NewBaseContainer("id1", "root1").Snapshot()

-		two   = NewBaseContainer("id2", "root2").Snapshot()

+		db, _ = NewViewDB()

+		one   = NewBaseContainer("id1", "root1")

+		two   = NewBaseContainer("id2", "root2")

 	)

 	one.Pid = 10

 	two.Pid = 20

-	db.Save(one)

-	db.Save(two)

+	one.CheckpointTo(db)

+	two.CheckpointTo(db)

 	all, err := db.Snapshot().All()

 	if err != nil {

 		t.Fatal(err)

@@ -44,10 +43,10 @@ func TestViewAll(t *testing.T) {

 }

 func TestViewGet(t *testing.T) {

-	db, _ := NewMemDB()

+	db, _ := NewViewDB()

 	one := NewBaseContainer("id", "root")

 	one.ImageID = "some-image-123"

-	db.Save(one.Snapshot())

+	one.CheckpointTo(db)

 	s, err := db.Snapshot().Get("id")

 	if err != nil {

 		t.Fatal(err)

@@ -108,13 +108,13 @@ func (daemon *Daemon) Register(c *container.Container) error {

 	}

 	// once in the memory store it is visible to other goroutines

-	// grab a Lock until it has been replicated to avoid races

+	// grab a Lock until it has been checkpointed to avoid races

 	c.Lock()

 	defer c.Unlock()

 	daemon.containers.Add(c.ID, c)

 	daemon.idIndex.Add(c.ID)

-	return daemon.containersReplica.Save(c.Snapshot())

+	return c.CheckpointTo(daemon.containersReplica)

 }

 func (daemon *Daemon) newContainer(name string, platform string, config *containertypes.Config, hostConfig *containertypes.HostConfig, imgID image.ID, managed bool) (*container.Container, error) {

@@ -218,10 +218,7 @@ func (daemon *Daemon) setHostConfig(container *container.Container, hostConfig *

 	runconfig.SetDefaultNetModeIfBlank(hostConfig)

 	container.HostConfig = hostConfig

-	if err := daemon.containersReplica.Save(container.Snapshot()); err != nil {

-		return err

-	}

-	return container.ToDisk()

+	return container.CheckpointAndSaveToDisk(daemon.containersReplica)

 }

 // verifyContainerSettings performs validation of the hostconfig and config

@@ -45,14 +45,11 @@ func (daemon *Daemon) getDNSSearchSettings(container *container.Container) []str

 	return nil

 }

-func (daemon *Daemon) saveAndReplicate(container *container.Container) error {

+func (daemon *Daemon) checkpointAndSave(container *container.Container) error {

 	container.Lock()

 	defer container.Unlock()

-	if err := daemon.containersReplica.Save(container.Snapshot()); err != nil {

-		return fmt.Errorf("Error replicating container state: %v", err)

-	}

-	if err := container.ToDisk(); err != nil {

-		return fmt.Errorf("Error saving container to disk: %v", err)

+	if err := container.CheckpointAndSaveToDisk(daemon.containersReplica); err != nil {

+		return fmt.Errorf("Error saving container state: %v", err)

 	}

 	return nil

 }

@@ -1018,10 +1015,8 @@ func (daemon *Daemon) ConnectToNetwork(container *container.Container, idOrName

 			return err

 		}

 	}

-	if err := daemon.saveAndReplicate(container); err != nil {

-		return fmt.Errorf("Error saving container to disk: %v", err)

-	}

-	return nil

+

+	return daemon.checkpointAndSave(container)

 }

 // DisconnectFromNetwork disconnects container from network n.

@@ -1057,8 +1052,8 @@ func (daemon *Daemon) DisconnectFromNetwork(container *container.Container, netw

 		return err

 	}

-	if err := daemon.saveAndReplicate(container); err != nil {

-		return fmt.Errorf("Error saving container to disk: %v", err)

+	if err := daemon.checkpointAndSave(container); err != nil {

+		return err

 	}

 	if n != nil {

@@ -83,7 +83,7 @@ type Daemon struct {

 	ID                    string

 	repository            string

 	containers            container.Store

-	containersReplica     *container.MemDB

+	containersReplica     container.ViewDB

 	execCommands          *exec.Store

 	downloadManager       *xfer.LayerDownloadManager

 	uploadManager         *xfer.LayerUploadManager

@@ -762,7 +762,7 @@ func NewDaemon(config *config.Config, registryService registry.Service, containe

 	d.ID = trustKey.PublicKey().KeyID()

 	d.repository = daemonRepo

 	d.containers = container.NewMemoryStore()

-	if d.containersReplica, err = container.NewMemDB(); err != nil {

+	if d.containersReplica, err = container.NewViewDB(); err != nil {

 		return nil, err

 	}

 	d.execCommands = exec.NewStore()

@@ -105,7 +105,7 @@ func (daemon *Daemon) cleanupContainer(container *container.Container, forceRemo

 	// Mark container dead. We don't want anybody to be restarting it.

 	container.Lock()

 	container.Dead = true

-	if err = daemon.containersReplica.Save(container.Snapshot()); err != nil {

+	if err = container.CheckpointTo(daemon.containersReplica); err != nil {

 		container.Unlock()

 		return err

 	}

@@ -168,9 +168,9 @@ func handleProbeResult(d *Daemon, c *container.Container, result *types.Healthch

 	}

 	// replicate Health status changes

-	if err := d.containersReplica.Save(c.Snapshot()); err != nil {

+	if err := c.CheckpointTo(d.containersReplica); err != nil {

 		// queries will be inconsistent until the next probe runs or other state mutations

-		// trigger a replication

+		// checkpoint the container

 		logrus.Errorf("Error replicating health state for container %s: %v", c.ID, err)

 	}

@@ -29,7 +29,7 @@ func TestNoneHealthcheck(t *testing.T) {

 		},

 		State: &container.State{},

 	}

-	store, err := container.NewMemDB()

+	store, err := container.NewViewDB()

 	if err != nil {

 		t.Fatal(err)

 	}

@@ -69,7 +69,7 @@ func TestHealthStates(t *testing.T) {

 		},

 	}

-	store, err := container.NewMemDB()

+	store, err := container.NewViewDB()

 	if err != nil {

 		t.Fatal(err)

 	}

@@ -114,7 +114,7 @@ func (daemon *Daemon) Containers(config *types.ContainerListOptions) ([]*types.C

 	return daemon.reduceContainers(config, daemon.transformContainer)

 }

-func (daemon *Daemon) filterByNameIDMatches(view *container.View, ctx *listContext) ([]container.Snapshot, error) {

+func (daemon *Daemon) filterByNameIDMatches(view container.View, ctx *listContext) ([]container.Snapshot, error) {

 	idSearch := false

 	names := ctx.filters.Get("name")

 	ids := ctx.filters.Get("id")

@@ -240,7 +240,7 @@ func (daemon *Daemon) reducePsContainer(container *container.Snapshot, ctx *list

 }

 // foldFilter generates the container filter based on the user's filtering options.

-func (daemon *Daemon) foldFilter(view *container.View, config *types.ContainerListOptions) (*listContext, error) {

+func (daemon *Daemon) foldFilter(view container.View, config *types.ContainerListOptions) (*listContext, error) {

 	psFilters := config.Filters

 	if err := psFilters.Validate(acceptedPsFilterTags); err != nil {

@@ -90,10 +90,7 @@ func (daemon *Daemon) StateChanged(id string, e libcontainerd.StateInfo) error {

 		daemon.setStateCounter(c)

 		defer c.Unlock()

-		if err := daemon.containersReplica.Save(c.Snapshot()); err != nil {

-			return err

-		}

-		if err := c.ToDisk(); err != nil {

+		if err := c.CheckpointAndSaveToDisk(daemon.containersReplica); err != nil {

 			return err

 		}

 		return daemon.postRunProcessing(c, e)

@@ -122,11 +119,7 @@ func (daemon *Daemon) StateChanged(id string, e libcontainerd.StateInfo) error {

 		c.HasBeenStartedBefore = true

 		daemon.setStateCounter(c)

-		if err := daemon.containersReplica.Save(c.Snapshot()); err != nil {

-			c.Reset(false)

-			return err

-		}

-		if err := c.ToDisk(); err != nil {

+		if err := c.CheckpointAndSaveToDisk(daemon.containersReplica); err != nil {

 			c.Reset(false)

 			return err

 		}

@@ -137,10 +130,7 @@ func (daemon *Daemon) StateChanged(id string, e libcontainerd.StateInfo) error {

 		// Container is already locked in this case

 		c.Paused = true

 		daemon.setStateCounter(c)

-		if err := daemon.containersReplica.Save(c.Snapshot()); err != nil {

-			return err

-		}

-		if err := c.ToDisk(); err != nil {

+		if err := c.CheckpointAndSaveToDisk(daemon.containersReplica); err != nil {

 			return err

 		}

 		daemon.updateHealthMonitor(c)

@@ -149,10 +139,7 @@ func (daemon *Daemon) StateChanged(id string, e libcontainerd.StateInfo) error {

 		// Container is already locked in this case

 		c.Paused = false

 		daemon.setStateCounter(c)

-		if err := daemon.containersReplica.Save(c.Snapshot()); err != nil {

-			return err

-		}

-		if err := c.ToDisk(); err != nil {

+		if err := c.CheckpointAndSaveToDisk(daemon.containersReplica); err != nil {

 			return err

 		}

 		daemon.updateHealthMonitor(c)

@@ -82,10 +82,7 @@ func (daemon *Daemon) ContainerRename(oldName, newName string) error {

 		daemon.nameIndex.Release(oldName + k)

 	}

 	daemon.releaseName(oldName)

-	if err = daemon.containersReplica.Save(container.Snapshot()); err != nil {

-		return err

-	}

-	if err = container.ToDisk(); err != nil {

+	if err = container.CheckpointAndSaveToDisk(daemon.containersReplica); err != nil {

 		return err

 	}

@@ -102,10 +99,7 @@ func (daemon *Daemon) ContainerRename(oldName, newName string) error {

 		if err != nil {

 			container.Name = oldName

 			container.NetworkSettings.IsAnonymousEndpoint = oldIsAnonymousEndpoint

-			if e := daemon.containersReplica.Save(container.Snapshot()); err != nil {

-				logrus.Errorf("%s: Failed in replicating state on rename failure: %v", container.ID, e)

-			}

-			if e := container.ToDisk(); e != nil {

+			if e := container.CheckpointAndSaveToDisk(daemon.containersReplica); e != nil {

 				logrus.Errorf("%s: Failed in writing to Disk on rename failure: %v", container.ID, e)

 			}

 		}

@@ -117,11 +117,8 @@ func (daemon *Daemon) containerStart(container *container.Container, checkpoint

 			if container.ExitCode() == 0 {

 				container.SetExitCode(128)

 			}

-			if err := daemon.containersReplica.Save(container.Snapshot()); err != nil {

-				logrus.Errorf("%s: failed replicating state on start failure: %v", container.ID, err)

-			}

-			if err := container.ToDisk(); err != nil {

-				logrus.Errorf("%s: failed writing to disk on start failure: %v", container.ID, err)

+			if err := container.CheckpointAndSaveToDisk(daemon.containersReplica); err != nil {

+				logrus.Errorf("%s: failed saving state on start failure: %v", container.ID, err)

 			}

 			container.Reset(false)

@@ -38,8 +38,7 @@ func (daemon *Daemon) update(name string, hostConfig *container.HostConfig) erro

 		if restoreConfig {

 			container.Lock()

 			container.HostConfig = &backupHostConfig

-			daemon.containersReplica.Save(container.Snapshot())

-			container.ToDisk()

+			container.CheckpointAndSaveToDisk(daemon.containersReplica)

 			container.Unlock()

 		}

 	}()

@@ -54,7 +53,7 @@ func (daemon *Daemon) update(name string, hostConfig *container.HostConfig) erro

 		container.Unlock()

 		return errCannotUpdate(container.ID, err)

 	}

-	if err := daemon.containersReplica.Save(container.Snapshot()); err != nil {

+	if err := container.CheckpointTo(daemon.containersReplica); err != nil {

 		restoreConfig = true

 		container.Unlock()

 		return errCannotUpdate(container.ID, err)