Merge pull request #909 from vburenin/diff-plugin

Make Diff/Apply plugable

cmd/containerd/builtins.go

@@ -2,6 +2,7 @@ package main
 
 // register containerd builtins here
 import (
+	_ "github.com/containerd/containerd/differ"
 	_ "github.com/containerd/containerd/services/containers"
 	_ "github.com/containerd/containerd/services/content"
 	_ "github.com/containerd/containerd/services/diff"

cmd/containerd/config.go

@@ -49,6 +49,9 @@ type config struct {
 	Metrics metricsConfig `toml:"metrics"`
 	// Snapshotter specifies which snapshot driver to use
 	Snapshotter string `toml:"snapshotter"`
+	// Differ specifies which differ to use. Differ is tightly coupled with the snapshotter
+	// so not all combinations may work.
+	Differ string `toml:"differ"`
 	// Plugins provides plugin specific configuration for the initialization of a plugin
 	Plugins map[string]toml.Primitive `toml:"plugins"`
 	// Enable containerd as a subreaper

cmd/containerd/config_linux.go

@@ -12,5 +12,6 @@ func defaultConfig() *config {
 			Address: "/run/containerd/debug.sock",
 		},
 		Snapshotter: "overlay",
+		Differ:      "base",
 	}
 }

cmd/containerd/config_unix.go

@@ -14,5 +14,6 @@ func defaultConfig() *config {
 			Address: "/run/containerd/debug.sock",
 		},
 		Snapshotter: "naive",
+		Differ:      "base",
 	}
 }

cmd/containerd/config_windows.go

@@ -17,5 +17,6 @@ func defaultConfig() *config {
 			Address: `\\.\pipe\containerd-debug`,
 		},
 		Snapshotter: "windows",
+		Differ:      "base",
 	}
 }

cmd/containerd/main.go

@@ -130,7 +130,13 @@ func main() {
 		if err != nil {
 			return err
 		}
-		services, err := loadServices(runtimes, store, snapshotter, meta)
+
+		differ, err := loadDiffer(snapshotter, store)
+		if err != nil {
+			return err
+		}
+
+		services, err := loadServices(runtimes, store, snapshotter, meta, differ)
 		if err != nil {
 			return err
 		}
@@ -351,6 +357,40 @@ func loadSnapshotter(store content.Store) (snapshot.Snapshotter, error) {
 	return nil, fmt.Errorf("snapshotter not loaded: %v", conf.Snapshotter)
 }
 
+func loadDiffer(snapshotter snapshot.Snapshotter, store content.Store) (plugin.Differ, error) {
+	for name, sr := range plugin.Registrations() {
+		if sr.Type != plugin.DiffPlugin {
+			continue
+		}
+		moduleName := fmt.Sprintf("diff-%s", conf.Differ)
+		if name != moduleName {
+			continue
+		}
+
+		log.G(global).Infof("loading differ plugin %q...", name)
+		ic := &plugin.InitContext{
+			Root:        conf.Root,
+			State:       conf.State,
+			Content:     store,
+			Snapshotter: snapshotter,
+			Context:     log.WithModule(global, moduleName),
+		}
+		if sr.Config != nil {
+			if err := conf.decodePlugin(name, sr.Config); err != nil {
+				return nil, err
+			}
+			ic.Config = sr.Config
+		}
+		sn, err := sr.Init(ic)
+		if err != nil {
+			return nil, err
+		}
+
+		return sn.(plugin.Differ), nil
+	}
+	return nil, fmt.Errorf("differ not loaded: %v", conf.Differ)
+}
+
 func newGRPCServer() *grpc.Server {
 	s := grpc.NewServer(
 		grpc.UnaryInterceptor(interceptor),
@@ -359,7 +399,9 @@ func newGRPCServer() *grpc.Server {
 	return s
 }
 
-func loadServices(runtimes map[string]plugin.Runtime, store content.Store, sn snapshot.Snapshotter, meta *bolt.DB) ([]plugin.Service, error) {
+func loadServices(runtimes map[string]plugin.Runtime,
+	store content.Store, sn snapshot.Snapshotter,
+	meta *bolt.DB, differ plugin.Differ) ([]plugin.Service, error) {
 	var o []plugin.Service
 	for name, sr := range plugin.Registrations() {
 		if sr.Type != plugin.GRPCPlugin {
@@ -374,6 +416,7 @@ func loadServices(runtimes map[string]plugin.Runtime, store content.Store, sn sn
 			Content:     store,
 			Meta:        meta,
 			Snapshotter: sn,
+			Differ:      differ,
 		}
 		if sr.Config != nil {
 			if err := conf.decodePlugin(name, sr.Config); err != nil {