Add some helpers for wrapping scoping core plugins

internal/core/core.go

@@ -0,0 +1,40 @@
+package core
+
+import (
+	"github.com/hashicorp/go-plugin"
+	"google.golang.org/grpc"
+)
+
+type closer interface {
+	Closer(func() error)
+}
+
+type closes interface {
+	Close() error
+}
+
+func wrapInstance(p plugin.GRPCPlugin, b *plugin.GRPCBroker, c closer) (uint32, error) {
+	id := b.NextId()
+	errChan := make(chan error, 1)
+
+	go b.AcceptAndServe(id, func(opts []grpc.ServerOption) *grpc.Server {
+		server := plugin.DefaultGRPCServer(opts)
+		if err := p.GRPCServer(b, server); err != nil {
+			errChan <- err
+			return nil
+		}
+		c.Closer(func() error {
+			server.GracefulStop()
+			return nil
+		})
+		close(errChan)
+		return server
+	})
+
+	err := <-errChan
+	if err != nil {
+		return 0, err
+	}
+
+	return id, nil
+}