Cleanup introspection interface

Split service proxy from service plugin.
Make introspection service easier for clients to use.
Update service proxy to support grpc and ttrpc.

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

core/introspection/proxy/remote.go

@@ -0,0 +1,108 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package introspectionproxy
+
+import (
+	"context"
+	"fmt"
+
+	api "github.com/containerd/containerd/v2/api/services/introspection/v1"
+	"github.com/containerd/containerd/v2/core/introspection"
+	"github.com/containerd/containerd/v2/protobuf"
+	"github.com/containerd/errdefs"
+	"github.com/containerd/log"
+	"github.com/containerd/ttrpc"
+	"google.golang.org/grpc"
+	"google.golang.org/protobuf/types/known/anypb"
+	"google.golang.org/protobuf/types/known/emptypb"
+)
+
+var _ = (introspection.Service)(&introspectionRemote{})
+
+// NewIntrospectionServiceFromClient creates a new introspection service from an API client
+func NewIntrospectionProxy(client any) introspection.Service {
+	switch c := client.(type) {
+	case api.IntrospectionClient:
+		return &introspectionRemote{client: convertIntrospection{c}}
+	case api.TTRPCIntrospectionService:
+		return &introspectionRemote{client: c}
+	case grpc.ClientConnInterface:
+		return &introspectionRemote{client: convertIntrospection{api.NewIntrospectionClient(c)}}
+	case *ttrpc.Client:
+		return &introspectionRemote{client: api.NewTTRPCIntrospectionClient(c)}
+	default:
+		panic(fmt.Errorf("unsupported introspection client %T: %w", client, errdefs.ErrNotImplemented))
+	}
+}
+
+type introspectionRemote struct {
+	client api.TTRPCIntrospectionService
+}
+
+func (i *introspectionRemote) Plugins(ctx context.Context, filters ...string) (*api.PluginsResponse, error) {
+	log.G(ctx).WithField("filters", filters).Debug("remote introspection plugin filters")
+	resp, err := i.client.Plugins(ctx, &api.PluginsRequest{
+		Filters: filters,
+	})
+
+	if err != nil {
+		return nil, errdefs.FromGRPC(err)
+	}
+
+	return resp, nil
+}
+
+func (i *introspectionRemote) Server(ctx context.Context) (*api.ServerResponse, error) {
+	resp, err := i.client.Server(ctx, &emptypb.Empty{})
+
+	if err != nil {
+		return nil, errdefs.FromGRPC(err)
+	}
+
+	return resp, nil
+}
+
+func (i *introspectionRemote) PluginInfo(ctx context.Context, pluginType, id string, options any) (resp *api.PluginInfoResponse, err error) {
+	var optionsPB *anypb.Any
+	if options != nil {
+		optionsPB, err = protobuf.MarshalAnyToProto(options)
+		if err != nil {
+			return nil, fmt.Errorf("failed to marshal runtime requst: %w", err)
+		}
+	}
+	resp, err = i.client.PluginInfo(ctx, &api.PluginInfoRequest{
+		Type:    pluginType,
+		ID:      id,
+		Options: optionsPB,
+	})
+
+	return resp, errdefs.FromGRPC(err)
+}
+
+type convertIntrospection struct {
+	client api.IntrospectionClient
+}
+
+func (c convertIntrospection) Plugins(ctx context.Context, req *api.PluginsRequest) (*api.PluginsResponse, error) {
+	return c.client.Plugins(ctx, req)
+}
+func (c convertIntrospection) Server(ctx context.Context, in *emptypb.Empty) (*api.ServerResponse, error) {
+	return c.client.Server(ctx, in)
+}
+func (c convertIntrospection) PluginInfo(ctx context.Context, req *api.PluginInfoRequest) (*api.PluginInfoResponse, error) {
+	return c.client.PluginInfo(ctx, req)
+}