move checkpoint message to variable message

paddle/fluid/operators/detail/grpc_server.cc

@@ -208,10 +208,12 @@ class RequestCheckpointNotify final : public RequestBase {
 
     std::string checkpoint_notify = request_->Varname();
     std::string checkpoint_dir = request_->Varname();
-
     framework::Variable* invar = nullptr;
     framework::Variable* outvar = nullptr;
 
+    VLOG(4) << "RequestCheckpointNotify notify: " << checkpoint_notify
+            << ", dir: " << checkpoint_dir;
+
     request_handler_->Handle(checkpoint_notify, scope, invar, &outvar,
                              checkpoint_dir);
     Finish(reply_, &responder_);