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>
BlancosWay · Sep 10, 2015 · b78e421 · b78e421
1 parent 9f517fc
commit b78e421
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Showing 10 changed files with 965 additions and 15 deletions.
diff --git a/daemon/graphdriver/driver.go b/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
 }

diff --git a/daemon/graphdriver/plugin.go b/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)
+}
diff --git a/daemon/graphdriver/plugin_unsupported.go b/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
+}
diff --git a/daemon/graphdriver/proxy.go b/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
+}