Add grpc health check service

Fixes: #615

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

services/healthcheck/service.go

@@ -0,0 +1,31 @@
+package healthcheck
+
+import (
+	"github.com/docker/containerd/plugin"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/health"
+	"google.golang.org/grpc/health/grpc_health_v1"
+)
+
+type Service struct {
+	serve *health.Server
+}
+
+func init() {
+	plugin.Register("healthcheck-grpc", &plugin.Registration{
+		Type: plugin.GRPCPlugin,
+		Init: NewService,
+	})
+}
+
+func NewService(ic *plugin.InitContext) (interface{}, error) {
+	return &Service{
+		health.NewServer(),
+	}, nil
+}
+
+func (s *Service) Register(server *grpc.Server) error {
+	grpc_health_v1.RegisterHealthServer(server, s.serve)
+	return nil
+}