Generalize the plugin package

Remove containerd specific parts of the plugin package to prepare its
move out of the main repository. Separate the plugin registration
singleton into a separate package.

Separating out the plugin package and registration makes it easier to
implement external plugins without creating a dependency loop.

Signed-off-by: Derek McGowan <derek@mcg.dev>

runtime/restart/monitor/monitor.go

@@ -26,6 +26,7 @@ import (
 	"github.com/containerd/containerd"
 	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/plugin/registry"
 	"github.com/containerd/containerd/plugins"
 	"github.com/containerd/containerd/runtime/restart"
 	"github.com/containerd/log"
@@ -52,7 +53,7 @@ type Config struct {
 }
 
 func init() {
-	plugin.Register(&plugin.Registration{
+	registry.Register(&plugin.Registration{
 		Type: plugins.InternalPlugin,
 		Requires: []plugin.Type{
 			plugins.EventPlugin,

runtime/v2/example/example.go

@@ -24,6 +24,7 @@ import (
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/pkg/shutdown"
 	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/plugin/registry"
 	"github.com/containerd/containerd/plugins"
 	ptypes "github.com/containerd/containerd/protobuf/types"
 	"github.com/containerd/containerd/runtime/v2/shim"
@@ -31,7 +32,7 @@ import (
 )
 
 func init() {
-	plugin.Register(&plugin.Registration{
+	registry.Register(&plugin.Registration{
 		Type: plugins.TTRPCPlugin,
 		ID:   "task",
 		Requires: []plugin.Type{

runtime/v2/manager.go

@@ -34,6 +34,7 @@ import (
 	"github.com/containerd/containerd/pkg/timeout"
 	"github.com/containerd/containerd/platforms"
 	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/plugin/registry"
 	"github.com/containerd/containerd/plugins"
 	"github.com/containerd/containerd/protobuf"
 	"github.com/containerd/containerd/runtime"
@@ -51,7 +52,7 @@ type Config struct {
 }
 
 func init() {
-	plugin.Register(&plugin.Registration{
+	registry.Register(&plugin.Registration{
 		Type: plugins.RuntimePluginV2,
 		ID:   "task",
 		Requires: []plugin.Type{
@@ -83,10 +84,10 @@ func init() {
 			events := ep.(*exchange.Exchange)
 
 			shimManager, err := NewShimManager(ic.Context, &ManagerConfig{
-				Root:         ic.Root,
-				State:        ic.State,
-				Address:      ic.Address,
-				TTRPCAddress: ic.TTRPCAddress,
+				Root:         ic.Properties[plugins.PropertyRootDir],
+				State:        ic.Properties[plugins.PropertyStateDir],
+				Address:      ic.Properties[plugins.PropertyGRPCAddress],
+				TTRPCAddress: ic.Properties[plugins.PropertyTTRPCAddress],
 				Events:       events,
 				Store:        cs,
 				SchedCore:    config.SchedCore,
@@ -104,7 +105,7 @@ func init() {
 	// However, due to time limits and to avoid migration steps in 1.6 release,
 	// use the following workaround.
 	// This expected to be removed in 1.7.
-	plugin.Register(&plugin.Registration{
+	registry.Register(&plugin.Registration{
 		Type: plugins.RuntimePluginV2,
 		ID:   "shim",
 		InitFn: func(ic *plugin.InitContext) (interface{}, error) {

runtime/v2/runc/pause/sandbox.go

@@ -24,6 +24,7 @@ import (
 
 	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/containerd/pkg/shutdown"
+	"github.com/containerd/containerd/plugin/registry"
 	"github.com/containerd/containerd/plugins"
 	"github.com/containerd/containerd/runtime/v2/shim"
 	"github.com/containerd/log"
@@ -34,7 +35,7 @@ import (
 )
 
 func init() {
-	plugin.Register(&plugin.Registration{
+	registry.Register(&plugin.Registration{
 		Type: plugins.TTRPCPlugin,
 		ID:   "pause",
 		Requires: []plugin.Type{

runtime/v2/runc/task/plugin/plugin_linux.go

@@ -19,13 +19,14 @@ package plugin
 import (
 	"github.com/containerd/containerd/pkg/shutdown"
 	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/plugin/registry"
 	"github.com/containerd/containerd/plugins"
 	"github.com/containerd/containerd/runtime/v2/runc/task"
 	"github.com/containerd/containerd/runtime/v2/shim"
 )
 
 func init() {
-	plugin.Register(&plugin.Registration{
+	registry.Register(&plugin.Registration{
 		Type: plugins.TTRPCPlugin,
 		ID:   "task",
 		Requires: []plugin.Type{

runtime/v2/shim/shim.go

@@ -34,6 +34,7 @@ import (
 	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/pkg/shutdown"
 	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/plugin/registry"
 	"github.com/containerd/containerd/plugins"
 	"github.com/containerd/containerd/protobuf"
 	"github.com/containerd/containerd/protobuf/proto"
@@ -284,7 +285,7 @@ func run(ctx context.Context, manager Manager, name string, config Config) error
 		}
 	}
 
-	plugin.Register(&plugin.Registration{
+	registry.Register(&plugin.Registration{
 		Type: plugins.InternalPlugin,
 		ID:   "shutdown",
 		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
@@ -293,7 +294,7 @@ func run(ctx context.Context, manager Manager, name string, config Config) error
 	})
 
 	// Register event plugin
-	plugin.Register(&plugin.Registration{
+	registry.Register(&plugin.Registration{
 		Type: plugins.EventPlugin,
 		ID:   "publisher",
 		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
@@ -307,24 +308,24 @@ func run(ctx context.Context, manager Manager, name string, config Config) error
 
 		ttrpcUnaryInterceptors = []ttrpc.UnaryServerInterceptor{}
 	)
-	plugins := plugin.Graph(func(*plugin.Registration) bool { return false })
-	for _, p := range plugins {
+
+	for _, p := range registry.Graph(func(*plugin.Registration) bool { return false }) {
 		id := p.URI()
 		log.G(ctx).WithField("type", p.Type).Infof("loading plugin %q...", id)
 
 		initContext := plugin.NewContext(
 			ctx,
-			p,
 			initialized,
-			// NOTE: Root is empty since the shim does not support persistent storage,
-			// shim plugins should make use state directory for writing files to disk.
-			// The state directory will be destroyed when the shim if cleaned up or
-			// on reboot
-			"",
-			bundlePath,
+			map[string]string{
+				// NOTE: Root is empty since the shim does not support persistent storage,
+				// shim plugins should make use state directory for writing files to disk.
+				// The state directory will be destroyed when the shim if cleaned up or
+				// on reboot
+				plugins.PropertyStateDir:     filepath.Join(bundlePath, p.URI()),
+				plugins.PropertyGRPCAddress:  addressFlag,
+				plugins.PropertyTTRPCAddress: ttrpcAddress,
+			},
 		)
-		initContext.Address = addressFlag
-		initContext.TTRPCAddress = ttrpcAddress
 
 		// load the plugin specific configuration if it is provided
 		// TODO: Read configuration passed into shim, or from state directory?