Create extpoint for graphdrivers

Allows people to create out-of-process graphdrivers that can be used
with Docker.

Extensions must be started before Docker otherwise Docker will fail to
start.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

daemon/graphdriver/driver.go

@@ -111,6 +111,9 @@ func GetDriver(name, home string, options []string) (Driver, error) {
 	if initFunc, exists := drivers[name]; exists {
 		return initFunc(filepath.Join(home, name), options)
 	}
+	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
 }

daemon/graphdriver/plugin.go

@@ -0,0 +1,33 @@
+// +build experimental
+// +build daemon
+
+package graphdriver
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/docker/docker/pkg/plugins"
+)
+
+type pluginClient interface {
+	// Call calls the specified method with the specified arguments for the plugin.
+	Call(string, interface{}, interface{}) error
+	// Stream calls the specified method with the specified arguments for the plugin and returns the response IO stream
+	Stream(string, interface{}) (io.ReadCloser, error)
+	// SendFile calls the specified method, and passes through the IO stream
+	SendFile(string, io.Reader, interface{}) error
+}
+
+func lookupPlugin(name, home string, opts []string) (Driver, error) {
+	pl, err := plugins.Get(name, "GraphDriver")
+	if err != nil {
+		return nil, fmt.Errorf("Error looking up graphdriver plugin %s: %v", name, err)
+	}
+	return newPluginDriver(name, home, opts, pl.Client)
+}
+
+func newPluginDriver(name, home string, opts []string, c pluginClient) (Driver, error) {
+	proxy := &graphDriverProxy{name, c}
+	return proxy, proxy.Init(home, opts)
+}

daemon/graphdriver/plugin_unsupported.go

@@ -0,0 +1,7 @@
+// +build !experimental
+
+package graphdriver
+
+func lookupPlugin(name, home string, opts []string) (Driver, error) {
+	return nil, ErrNotSupported
+}

daemon/graphdriver/proxy.go

@@ -0,0 +1,210 @@
+// +build experimental
+// +build daemon
+
+package graphdriver
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/docker/docker/pkg/archive"
+)
+
+type graphDriverProxy struct {
+	name   string
+	client pluginClient
+}
+
+type graphDriverRequest struct {
+	ID         string `json:",omitempty"`
+	Parent     string `json:",omitempty"`
+	MountLabel string `json:",omitempty"`
+}
+
+type graphDriverResponse struct {
+	Err      string            `json:",omitempty"`
+	Dir      string            `json:",omitempty"`
+	Exists   bool              `json:",omitempty"`
+	Status   [][2]string       `json:",omitempty"`
+	Changes  []archive.Change  `json:",omitempty"`
+	Size     int64             `json:",omitempty"`
+	Metadata map[string]string `json:",omitempty"`
+}
+
+type graphDriverInitRequest struct {
+	Home string
+	Opts []string
+}
+
+func (d *graphDriverProxy) Init(home string, opts []string) error {
+	args := &graphDriverInitRequest{
+		Home: home,
+		Opts: opts,
+	}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.Init", args, &ret); err != nil {
+		return err
+	}
+	if ret.Err != "" {
+		return errors.New(ret.Err)
+	}
+	return nil
+}
+
+func (d *graphDriverProxy) String() string {
+	return d.name
+}
+
+func (d *graphDriverProxy) Create(id, parent string) error {
+	args := &graphDriverRequest{
+		ID:     id,
+		Parent: parent,
+	}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.Create", args, &ret); err != nil {
+		return err
+	}
+	if ret.Err != "" {
+		return errors.New(ret.Err)
+	}
+	return nil
+}
+
+func (d *graphDriverProxy) Remove(id string) error {
+	args := &graphDriverRequest{ID: id}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.Remove", args, &ret); err != nil {
+		return err
+	}
+	if ret.Err != "" {
+		return errors.New(ret.Err)
+	}
+	return nil
+}
+
+func (d *graphDriverProxy) Get(id, mountLabel string) (string, error) {
+	args := &graphDriverRequest{
+		ID:         id,
+		MountLabel: mountLabel,
+	}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.Get", args, &ret); err != nil {
+		return "", err
+	}
+	var err error
+	if ret.Err != "" {
+		err = errors.New(ret.Err)
+	}
+	return ret.Dir, err
+}
+
+func (d *graphDriverProxy) Put(id string) error {
+	args := &graphDriverRequest{ID: id}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.Put", args, &ret); err != nil {
+		return err
+	}
+	if ret.Err != "" {
+		return errors.New(ret.Err)
+	}
+	return nil
+}
+
+func (d *graphDriverProxy) Exists(id string) bool {
+	args := &graphDriverRequest{ID: id}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.Exists", args, &ret); err != nil {
+		return false
+	}
+	return ret.Exists
+}
+
+func (d *graphDriverProxy) Status() [][2]string {
+	args := &graphDriverRequest{}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.Status", args, &ret); err != nil {
+		return nil
+	}
+	return ret.Status
+}
+
+func (d *graphDriverProxy) GetMetadata(id string) (map[string]string, error) {
+	args := &graphDriverRequest{
+		ID: id,
+	}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.GetMetadata", args, &ret); err != nil {
+		return nil, err
+	}
+	if ret.Err != "" {
+		return nil, errors.New(ret.Err)
+	}
+	return ret.Metadata, nil
+}
+
+func (d *graphDriverProxy) Cleanup() error {
+	args := &graphDriverRequest{}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.Cleanup", args, &ret); err != nil {
+		return nil
+	}
+	if ret.Err != "" {
+		return errors.New(ret.Err)
+	}
+	return nil
+}
+
+func (d *graphDriverProxy) Diff(id, parent string) (archive.Archive, error) {
+	args := &graphDriverRequest{
+		ID:     id,
+		Parent: parent,
+	}
+	body, err := d.client.Stream("GraphDriver.Diff", args)
+	if err != nil {
+		body.Close()
+		return nil, err
+	}
+	return archive.Archive(body), nil
+}
+
+func (d *graphDriverProxy) Changes(id, parent string) ([]archive.Change, error) {
+	args := &graphDriverRequest{
+		ID:     id,
+		Parent: parent,
+	}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.Changes", args, &ret); err != nil {
+		return nil, err
+	}
+	if ret.Err != "" {
+		return nil, errors.New(ret.Err)
+	}
+
+	return ret.Changes, nil
+}
+
+func (d *graphDriverProxy) ApplyDiff(id, parent string, diff archive.Reader) (int64, error) {
+	var ret graphDriverResponse
+	if err := d.client.SendFile(fmt.Sprintf("GraphDriver.ApplyDiff?id=%s&parent=%s", id, parent), diff, &ret); err != nil {
+		return -1, err
+	}
+	if ret.Err != "" {
+		return -1, errors.New(ret.Err)
+	}
+	return ret.Size, nil
+}
+
+func (d *graphDriverProxy) DiffSize(id, parent string) (int64, error) {
+	args := &graphDriverRequest{
+		ID:     id,
+		Parent: parent,
+	}
+	var ret graphDriverResponse
+	if err := d.client.Call("GraphDriver.DiffSize", args, &ret); err != nil {
+		return -1, err
+	}
+	if ret.Err != "" {
+		return -1, errors.New(ret.Err)
+	}
+	return ret.Size, nil
+}

experimental/plugins_graphdriver.md

@@ -0,0 +1,321 @@
+# Experimental: Docker graph driver plugins
+
+Docker graph driver plugins enable admins to use an external/out-of-process
+graph driver for use with Docker engine. This is an alternative to using the
+built-in storage drivers, such as aufs/overlay/devicemapper/btrfs.
+
+A graph driver plugin is used for image and container fs storage, as such
+the plugin must be started and available for connections prior to Docker Engine
+being started.
+
+# Write a graph driver plugin
+
+See the [plugin documentation](/docs/extend/plugins.md) for detailed information
+on the underlying plugin protocol.
+
+
+## Graph Driver plugin protocol
+
+If a plugin registers itself as a `GraphDriver` when activated, then it is
+expected to provide the rootfs for containers as well as image layer storage.
+
+### /GraphDriver.Init
+
+**Request**:
+```
+{
+  "Home": "/graph/home/path",
+  "Opts": []
+}
+```
+
+Initialize the graph driver plugin with a home directory and array of options.
+Plugins are not required to accept these options as the Docker Engine does not
+require that the plugin use this path or options, they are only being passed
+through from the user.
+
+**Response**:
+```
+{
+  "Err": null
+}
+```
+
+Respond with a string error if an error occurred.
+
+
+### /GraphDriver.Create
+
+**Request**:
+```
+{
+  "ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
+  "Parent": "2cd9c322cb78a55e8212aa3ea8425a4180236d7106938ec921d0935a4b8ca142"
+}
+```
+
+Create a new, empty, filesystem layer with the specified `ID` and `Parent`.
+`Parent` may be an empty string, which would indicate that there is no parent
+layer.
+
+**Response**:
+```
+{
+  "Err: null
+}
+```
+
+Respond with a string error if an error occurred.
+
+
+### /GraphDriver.Remove
+
+**Request**:
+```
+{
+  "ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187"
+}
+```
+
+Remove the filesystem layer with this given `ID`.
+
+**Response**:
+```
+{
+  "Err: null
+}
+```
+
+Respond with a string error if an error occurred.
+
+### /GraphDriver.Get
+
+**Request**:
+```
+{
+  "ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187"
+  "MountLabel": ""
+}
+```
+
+Get the mountpoint for the layered filesystem referred to by the given `ID`.
+
+**Response**:
+```
+{
+  "Dir": "/var/mygraph/46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
+  "Err": ""
+}
+```
+
+Respond with the absolute path to the mounted layered filesystem.
+Respond with a string error if an error occurred.
+
+### /GraphDriver.Put
+
+**Request**:
+```
+{
+  "ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187"
+}
+```
+
+Release the system resources for the specified `ID`, such as unmounting the
+filesystem layer.
+
+**Response**:
+```
+{
+  "Err: null
+}
+```
+
+Respond with a string error if an error occurred.
+
+### /GraphDriver.Exists
+
+**Request**:
+```
+{
+  "ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187"
+}
+```
+
+Determine if a filesystem layer with the specified `ID` exists.
+
+**Response**:
+```
+{
+  "Exists": true
+}
+```
+
+Respond with a boolean for whether or not the filesystem layer with the specified
+`ID` exists.
+
+### /GraphDriver.Status
+
+**Request**:
+```
+{}
+```
+
+Get low-level diagnostic information about the graph driver.
+
+**Response**:
+```
+{
+  "Status": [[]]
+}
+```
+
+Respond with a 2-D array with key/value pairs for the underlying status
+information.
+
+
+### /GraphDriver.GetMetadata
+
+**Request**:
+```
+{
+  "ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187"
+}
+```
+
+Get low-level diagnostic information about the layered filesystem with the
+with the specified `ID`
+
+**Response**:
+```
+{
+  "Metadata": {},
+  "Err": null
+}
+```
+
+Respond with a set of key/value pairs containing the low-level diagnostic
+information about the layered filesystem.
+Respond with a string error if an error occurred.
+
+### /GraphDriver.Cleanup
+
+**Request**:
+```
+{}
+```
+
+Perform neccessary tasks to release resources help by the plugin, for example
+unmounting all the layered file systems.
+
+**Response**:
+```
+{
+  "Err: null
+}
+```
+
+Respond with a string error if an error occurred.
+
+
+### /GraphDriver.Diff
+
+**Request**:
+```
+{
+  "ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
+  "Parent": "2cd9c322cb78a55e8212aa3ea8425a4180236d7106938ec921d0935a4b8ca142"
+}
+```
+
+Get an archive of the changes between the filesystem layers specified by the `ID`
+and `Parent`. `Parent` may be an empty string, in which case there is no parent.
+
+**Response**:
+```
+{{ TAR STREAM }}
+```
+
+### /GraphDriver.Changes
+
+**Request**:
+```
+{
+  "ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
+  "Parent": "2cd9c322cb78a55e8212aa3ea8425a4180236d7106938ec921d0935a4b8ca142"
+}
+```
+
+Get a list of changes between the filesystem layers specified by the `ID` and
+`Parent`. `Parent` may be an empty string, in which case there is no parent.
+
+**Response**:
+```
+{
+  "Changes": [{}],
+  "Err": null
+}
+```
+
+Responds with a list of changes. The structure of a change is:
+```
+  "Path": "/some/path",
+  "Kind": 0,
+```
+
+Where teh `Path` is the filesystem path within the layered filesystem that is
+changed and `Kind` is an integer specifying the type of change that occurred:
+
+- 0 - Modified
+- 1 - Added
+- 2 - Deleted
+
+Respond with a string error if an error occurred.
+
+### /GraphDriver.ApplyDiff
+
+**Request**:
+```
+{{ TAR STREAM }}
+```
+
+Extract the changeset from the given diff into the layer with the specified `ID`
+and `Parent`
+
+**Query Parameters**:
+
+- id (required)- the `ID` of the new filesystem layer to extract the diff to
+- parent (required)- the `Parent` of the given `ID`
+
+**Response**:
+```
+{
+  "Size": 512366,
+  "Err": null
+}
+```
+
+Respond with the size of the new layer in bytes.
+Respond with a string error if an error occurred.
+
+### /GraphDriver.DiffSize
+
+**Request**:
+```
+{
+  "ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
+  "Parent": "2cd9c322cb78a55e8212aa3ea8425a4180236d7106938ec921d0935a4b8ca142"
+}
+```
+
+Calculate the changes between the specified `ID`
+
+**Response**:
+```
+{
+  "Size": 512366,
+  "Err": null
+}
+```
+
+Respond with the size changes between the specified `ID` and `Parent`
+Respond with a string error if an error occurred.

integration-cli/check_test.go

@@ -1,12 +1,22 @@
 package main
 
 import (
+	"fmt"
 	"testing"
 
+	"github.com/docker/docker/pkg/reexec"
 	"github.com/go-check/check"
 )
 
 func Test(t *testing.T) {
+	reexec.Init() // This is required for external graphdriver tests
+
+	if !isLocalDaemon {
+		fmt.Println("INFO: Testing against a remote daemon")
+	} else {
+		fmt.Println("INFO: Testing against a local daemon")
+	}
+
 	check.TestingT(t)
 }
 

integration-cli/docker_cli_external_graphdriver_unix_test.go

@@ -0,0 +1,348 @@
+// +build experimental
+// +build !windows
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+
+	"github.com/docker/docker/daemon/graphdriver"
+	"github.com/docker/docker/daemon/graphdriver/vfs"
+	"github.com/docker/docker/pkg/archive"
+	"github.com/go-check/check"
+)
+
+func init() {
+	check.Suite(&DockerExternalGraphdriverSuite{
+		ds: &DockerSuite{},
+	})
+}
+
+type DockerExternalGraphdriverSuite struct {
+	server *httptest.Server
+	ds     *DockerSuite
+	d      *Daemon
+	ec     *graphEventsCounter
+}
+
+type graphEventsCounter struct {
+	activations int
+	creations   int
+	removals    int
+	gets        int
+	puts        int
+	stats       int
+	cleanups    int
+	exists      int
+	init        int
+	metadata    int
+	diff        int
+	applydiff   int
+	changes     int
+	diffsize    int
+}
+
+func (s *DockerExternalGraphdriverSuite) SetUpTest(c *check.C) {
+	s.d = NewDaemon(c)
+	s.ec = &graphEventsCounter{}
+}
+
+func (s *DockerExternalGraphdriverSuite) TearDownTest(c *check.C) {
+	s.d.Stop()
+	s.ds.TearDownTest(c)
+}
+
+func (s *DockerExternalGraphdriverSuite) SetUpSuite(c *check.C) {
+	mux := http.NewServeMux()
+	s.server = httptest.NewServer(mux)
+
+	type graphDriverRequest struct {
+		ID         string `json:",omitempty"`
+		Parent     string `json:",omitempty"`
+		MountLabel string `json:",omitempty"`
+	}
+
+	type graphDriverResponse struct {
+		Err      error             `json:",omitempty"`
+		Dir      string            `json:",omitempty"`
+		Exists   bool              `json:",omitempty"`
+		Status   [][2]string       `json:",omitempty"`
+		Metadata map[string]string `json:",omitempty"`
+		Changes  []archive.Change  `json:",omitempty"`
+		Size     int64             `json:",omitempty"`
+	}
+
+	respond := func(w http.ResponseWriter, data interface{}) {
+		w.Header().Set("Content-Type", "appplication/vnd.docker.plugins.v1+json")
+		switch t := data.(type) {
+		case error:
+			fmt.Fprintln(w, fmt.Sprintf(`{"Err": %s}`, t.Error()))
+		case string:
+			fmt.Fprintln(w, t)
+		default:
+			json.NewEncoder(w).Encode(&data)
+		}
+	}
+
+	base, err := ioutil.TempDir("", "external-graph-test")
+	c.Assert(err, check.IsNil)
+	vfsProto, err := vfs.Init(base, []string{})
+	if err != nil {
+		c.Fatalf("error initializing graph driver: %v", err)
+	}
+	driver := graphdriver.NaiveDiffDriver(vfsProto)
+
+	mux.HandleFunc("/Plugin.Activate", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.activations++
+		respond(w, `{"Implements": ["GraphDriver"]}`)
+	})
+
+	mux.HandleFunc("/GraphDriver.Init", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.init++
+		respond(w, "{}")
+	})
+
+	mux.HandleFunc("/GraphDriver.Create", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.creations++
+
+		var req graphDriverRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+		if err := driver.Create(req.ID, req.Parent); err != nil {
+			respond(w, err)
+			return
+		}
+		respond(w, "{}")
+	})
+
+	mux.HandleFunc("/GraphDriver.Remove", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.removals++
+
+		var req graphDriverRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+
+		if err := driver.Remove(req.ID); err != nil {
+			respond(w, err)
+			return
+		}
+		respond(w, "{}")
+	})
+
+	mux.HandleFunc("/GraphDriver.Get", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.gets++
+
+		var req graphDriverRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			http.Error(w, err.Error(), 500)
+		}
+
+		dir, err := driver.Get(req.ID, req.MountLabel)
+		if err != nil {
+			respond(w, err)
+			return
+		}
+		respond(w, &graphDriverResponse{Dir: dir})
+	})
+
+	mux.HandleFunc("/GraphDriver.Put", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.puts++
+
+		var req graphDriverRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+
+		if err := driver.Put(req.ID); err != nil {
+			respond(w, err)
+			return
+		}
+		respond(w, "{}")
+	})
+
+	mux.HandleFunc("/GraphDriver.Exists", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.exists++
+
+		var req graphDriverRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+		respond(w, &graphDriverResponse{Exists: driver.Exists(req.ID)})
+	})
+
+	mux.HandleFunc("/GraphDriver.Status", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.stats++
+		respond(w, `{"Status":{}}`)
+	})
+
+	mux.HandleFunc("/GraphDriver.Cleanup", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.cleanups++
+		err := driver.Cleanup()
+		if err != nil {
+			respond(w, err)
+			return
+		}
+		respond(w, `{}`)
+	})
+
+	mux.HandleFunc("/GraphDriver.GetMetadata", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.metadata++
+
+		var req graphDriverRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+
+		data, err := driver.GetMetadata(req.ID)
+		if err != nil {
+			respond(w, err)
+			return
+		}
+		respond(w, &graphDriverResponse{Metadata: data})
+	})
+
+	mux.HandleFunc("/GraphDriver.Diff", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.diff++
+
+		var req graphDriverRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+
+		diff, err := driver.Diff(req.ID, req.Parent)
+		if err != nil {
+			respond(w, err)
+			return
+		}
+		io.Copy(w, diff)
+	})
+
+	mux.HandleFunc("/GraphDriver.Changes", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.changes++
+		var req graphDriverRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+
+		changes, err := driver.Changes(req.ID, req.Parent)
+		if err != nil {
+			respond(w, err)
+			return
+		}
+		respond(w, &graphDriverResponse{Changes: changes})
+	})
+
+	mux.HandleFunc("/GraphDriver.ApplyDiff", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.applydiff++
+		id := r.URL.Query().Get("id")
+		parent := r.URL.Query().Get("parent")
+
+		size, err := driver.ApplyDiff(id, parent, r.Body)
+		if err != nil {
+			respond(w, err)
+			return
+		}
+		respond(w, &graphDriverResponse{Size: size})
+	})
+
+	mux.HandleFunc("/GraphDriver.DiffSize", func(w http.ResponseWriter, r *http.Request) {
+		s.ec.diffsize++
+
+		var req graphDriverRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+
+		size, err := driver.DiffSize(req.ID, req.Parent)
+		if err != nil {
+			respond(w, err)
+			return
+		}
+		respond(w, &graphDriverResponse{Size: size})
+	})
+
+	if err := os.MkdirAll("/etc/docker/plugins", 0755); err != nil {
+		c.Fatal(err)
+	}
+
+	if err := ioutil.WriteFile("/etc/docker/plugins/test-external-graph-driver.spec", []byte(s.server.URL), 0644); err != nil {
+		c.Fatal(err)
+	}
+}
+
+func (s *DockerExternalGraphdriverSuite) TearDownSuite(c *check.C) {
+	s.server.Close()
+
+	if err := os.RemoveAll("/etc/docker/plugins"); err != nil {
+		c.Fatal(err)
+	}
+}
+
+func (s *DockerExternalGraphdriverSuite) TestExternalGraphDriver(c *check.C) {
+	c.Assert(s.d.StartWithBusybox("-s", "test-external-graph-driver"), check.IsNil)
+
+	out, err := s.d.Cmd("run", "-d", "--name=graphtest", "busybox", "sh", "-c", "echo hello > /hello")
+	c.Assert(err, check.IsNil, check.Commentf(out))
+
+	err = s.d.Restart("-s", "test-external-graph-driver")
+
+	out, err = s.d.Cmd("inspect", "--format='{{.GraphDriver.Name}}'", "graphtest")
+	c.Assert(err, check.IsNil, check.Commentf(out))
+	c.Assert(strings.TrimSpace(out), check.Equals, "test-external-graph-driver")
+
+	out, err = s.d.Cmd("diff", "graphtest")
+	c.Assert(err, check.IsNil, check.Commentf(out))
+	c.Assert(strings.Contains(out, "A /hello"), check.Equals, true)
+
+	out, err = s.d.Cmd("rm", "-f", "graphtest")
+	c.Assert(err, check.IsNil, check.Commentf(out))
+
+	out, err = s.d.Cmd("info")
+	c.Assert(err, check.IsNil, check.Commentf(out))
+
+	err = s.d.Stop()
+	c.Assert(err, check.IsNil)
+
+	c.Assert(s.ec.activations, check.Equals, 2)
+	c.Assert(s.ec.init, check.Equals, 2)
+	c.Assert(s.ec.creations >= 1, check.Equals, true)
+	c.Assert(s.ec.removals >= 1, check.Equals, true)
+	c.Assert(s.ec.gets >= 1, check.Equals, true)
+	c.Assert(s.ec.puts >= 1, check.Equals, true)
+	c.Assert(s.ec.stats, check.Equals, 1)
+	c.Assert(s.ec.cleanups, check.Equals, 2)
+	c.Assert(s.ec.exists >= 1, check.Equals, true)
+	c.Assert(s.ec.applydiff >= 1, check.Equals, true)
+	c.Assert(s.ec.changes, check.Equals, 1)
+	c.Assert(s.ec.diffsize, check.Equals, 0)
+	c.Assert(s.ec.diff, check.Equals, 0)
+	c.Assert(s.ec.metadata, check.Equals, 1)
+}
+
+func (s *DockerExternalGraphdriverSuite) TestExternalGraphDriverPull(c *check.C) {
+	testRequires(c, Network)
+	c.Assert(s.d.Start(), check.IsNil)
+
+	out, err := s.d.Cmd("pull", "busybox:latest")
+	c.Assert(err, check.IsNil, check.Commentf(out))
+
+	out, err = s.d.Cmd("run", "-d", "busybox", "top")
+	c.Assert(err, check.IsNil, check.Commentf(out))
+}

integration-cli/docker_test_vars.go

@@ -68,11 +68,8 @@ func init() {
 	// Similarly, it will be perfectly valid to also run CLI tests from
 	// a Linux CLI (built with the daemon tag) against a Windows daemon.
 	if len(os.Getenv("DOCKER_REMOTE_DAEMON")) > 0 {
-		fmt.Println("INFO: Testing against a remote daemon")
 		isLocalDaemon = false
 	} else {
-		fmt.Println("INFO: Testing against a local daemon")
 		isLocalDaemon = true
 	}
-
 }

pkg/plugins/client.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"net/http"
 	"strings"
@@ -52,19 +53,41 @@ type Client struct {
 // Call calls the specified method with the specified arguments for the plugin.
 // It will retry for 30 seconds if a failure occurs when calling.
 func (c *Client) Call(serviceMethod string, args interface{}, ret interface{}) error {
-	return c.callWithRetry(serviceMethod, args, ret, true)
-}
-
-func (c *Client) callWithRetry(serviceMethod string, args interface{}, ret interface{}, retry bool) error {
 	var buf bytes.Buffer
 	if err := json.NewEncoder(&buf).Encode(args); err != nil {
 		return err
 	}
-
-	req, err := http.NewRequest("POST", "/"+serviceMethod, &buf)
+	body, err := c.callWithRetry(serviceMethod, &buf, true)
 	if err != nil {
 		return err
 	}
+	defer body.Close()
+	return json.NewDecoder(body).Decode(&ret)
+}
+
+// Stream calls the specified method with the specified arguments for the plugin and returns the response body
+func (c *Client) Stream(serviceMethod string, args interface{}) (io.ReadCloser, error) {
+	var buf bytes.Buffer
+	if err := json.NewEncoder(&buf).Encode(args); err != nil {
+		return nil, err
+	}
+	return c.callWithRetry(serviceMethod, &buf, true)
+}
+
+// SendFile calls the specified method, and passes through the IO stream
+func (c *Client) SendFile(serviceMethod string, data io.Reader, ret interface{}) error {
+	body, err := c.callWithRetry(serviceMethod, data, true)
+	if err != nil {
+		return err
+	}
+	return json.NewDecoder(body).Decode(&ret)
+}
+
+func (c *Client) callWithRetry(serviceMethod string, data io.Reader, retry bool) (io.ReadCloser, error) {
+	req, err := http.NewRequest("POST", "/"+serviceMethod, data)
+	if err != nil {
+		return nil, err
+	}
 	req.Header.Add("Accept", versionMimetype)
 	req.URL.Scheme = "http"
 	req.URL.Host = c.addr
@@ -76,12 +99,12 @@ func (c *Client) callWithRetry(serviceMethod string, args interface{}, ret inter
 		resp, err := c.http.Do(req)
 		if err != nil {
 			if !retry {
-				return err
+				return nil, err
 			}
 
 			timeOff := backoff(retries)
 			if abort(start, timeOff) {
-				return err
+				return nil, err
 			}
 			retries++
 			logrus.Warnf("Unable to connect to plugin: %s, retrying in %v", c.addr, timeOff)
@@ -89,16 +112,14 @@ func (c *Client) callWithRetry(serviceMethod string, args interface{}, ret inter
 			continue
 		}
 
-		defer resp.Body.Close()
 		if resp.StatusCode != http.StatusOK {
 			remoteErr, err := ioutil.ReadAll(resp.Body)
 			if err != nil {
-				return &remoteError{err.Error(), serviceMethod}
+				return nil, &remoteError{err.Error(), serviceMethod}
 			}
-			return &remoteError{string(remoteErr), serviceMethod}
+			return nil, &remoteError{string(remoteErr), serviceMethod}
 		}
-
-		return json.NewDecoder(resp.Body).Decode(&ret)
+		return resp.Body, nil
 	}
 }
 

pkg/plugins/client_test.go

@@ -30,7 +30,7 @@ func teardownRemotePluginServer() {
 
 func TestFailedConnection(t *testing.T) {
 	c, _ := NewClient("tcp://127.0.0.1:1", tlsconfig.Options{InsecureSkipVerify: true})
-	err := c.callWithRetry("Service.Method", nil, nil, false)
+	_, err := c.callWithRetry("Service.Method", nil, false)
 	if err == nil {
 		t.Fatal("Unexpected successful connection")
 	}