handling deferred events

[Dmitry Banschikov <me@…>]

My FSM has two states(connected, disconnected). One of the states is submachine with number of other substates. One of this substates has deferred events specified.

When my root machine goes from state with submachine(connected) to disconnected, should any deferred events be cleared? If no, then why when we enter back in st_connected, deferred events are not handled immediately? MSM process them only after processing normal event(I think that after processing events MSM check if there are any deferred events).

In test case I expect either no output after string 'On cmd with reply: 5' (when right behaviour is to clear deferred events), or 'On cmd with reply: 1' (when right behaviour is to process all deferred events on entry into st_connected state).

Tested on 1.51, 1.53, trunk.

[Dmitry Banschikov <me@…>]

Processing of deferred events for submachine

[Christophe Henry]

Correct, this is a bug, precisely, entering the submachine does not check for waiting deferred events. This would be solved by adding inside do_entry inside state_machine.hpp:

handle_defer_helper<library_sm> defer_helper(m_deferred_events_queue); defer_helper.do_post_handle_deferred(HANDLED_TRUE);

before : process_message_queue(this);

This will have for effect that MSM will process ev_async_send_cmd_with_reply(1) when entering, and ev_async_send_cmd_with_reply(2) will be the last displayed text.

But frankly, after seeing this, I'm unsure whether it's a great idea to keep deferred events while leaving the submachine, I need to think about it.

To check if it solves your problem, I committed this fix in trunk rev. 86759.

[Dmitry Banschikov <me@…>]

Yes, with rev. 86759 output of test case is more expected. Actually, I need all deferred events be cleared on exit from state. For such behaviour I use this workaround:

        template <class Event, class Fsm>
        void on_exit(Event const&, Fsm& fsm)
        {   
            std::cout << "On exit" << std::endl;
            op_.reset();
            fsm.template get_state<test_machine_front_t::st_connected&>().get_deferred_queue().clear();
        }

[Christophe Henry]

Ok, next possible solution, should make most happy: the decision of throwing away the deferred events upon exit is made by the history policy:

• NoHistory: logically, we throw deferred events
• AlwaysHistory: keep them all
• ShallowHistory: like AlwayHistory, but depending on the event.

I committed to trunk, rev. 86799 (let's see if I get the last commit to svn ever ;-) ). Hope it solves your problem.