gen_fsm:send_after | start_timer

[Sean Hinde]

Hi,

Anyone else think it would be useful to extend gen_fsm to have it's own
state aware timer functionality?

At the moment all timers sent with erlang:send_after or erlang:start_timer
arrive in handle_info rather than in the callback for the current state. I
find that handle_info becomes very large and unwieldy with more than a
couple of timers running and 4 or more states..

Usage would be something like:

%%----------------------------------------------------------------------
%% Func: init/1
%% Returns: {ok, StateName, StateData}          |
%%          {ok, StateName, StateData, Timeout} |
%%          ignore                              |
%%          {stop, StopReason}                   
%%----------------------------------------------------------------------
init([]) ->
    gen_fsm:start_timer(2000, "Hello from init"),
    {ok, state1, #state{}}.

%%----------------------------------------------------------------------
%% Func: StateName/2
%% Returns: {next_state, NextStateName, NextStateData}          |
%%          {next_state, NextStateName, NextStateData, Timeout} |
%%          {stop, Reason, NewStateData}                         
%%----------------------------------------------------------------------
state1(Event, StateData) ->
    gen_fsm:start_timer(2000, "Hello from state 1"),
    io:format("SH:~p~n",[Event]),
    {next_state, state2, StateData}.

state2(Event, StateData) ->
    io:format("SH:~p~n",[Event]),
    gen_fsm:send_after(2000, "Hello from state 2"),
    {next_state, state1, StateData}.

Possible implementation follows as a diff -c:

*** /opt/rcs/5.0.2.5/lib/stdlib-1.9.4/src/gen_fsm.erl   Thu Jun  7 15:04:40
2001
--- gen_fsm.erl Mon Jul  9 13:14:09 2001

***************

*** 110,115 ****

--- 110,117 ----

         sync_send_all_state_event/2, sync_send_all_state_event/3,

         reply/2]).

 

+ -export([start_timer/2, send_after/2]).

+

  %% Internal exports

  -export([init_it/6, print_event/3,

         system_continue/3,

***************

*** 199,204 ****

--- 201,217 ----

                           [Name, Event, Timeout]}})

      end.

 

+ %% Designed to be only callable within one of the callbacks

+ %% hence using the self() of this instance of the process.

+ %% This is to ensure that timers don't go astray in global

+ %% e.g. when straddling a failover, or turn up in a restarted

+ %% instance of the process.

+ start_timer(Time, Msg) ->

+     erlang:start_timer(Time, self(), {'$gen_fsm_timer', Msg}).

+

+ send_after(Time, Msg) ->

+     erlang:send_after(Time, self(), {'$gen_fsm_timer', Msg}).

+

  %%% ---------------------------------------------------

  %%% Initiate the new process.

  %%% Register the name using the Rfunc function

***************

*** 288,293 ****

--- 301,314 ----

            io:format(Dev,

                      "*DBG* ~p got all_state_event ~p in state ~w~n",

                      [Name, Event, StateName]);

+       {'$gen_fsm_timer', Msg} ->

+           io:format(Dev,

+                     "*DBG* ~p got timer ~p in state ~w~n",

+                     [Name, Msg, StateName]);

+       {timeout, Ref, {'$gen_fsm_timer', Msg}} ->

+           io:format(Dev,

+                     "*DBG* ~p got timer ~p in state ~w~n",

+                     [Name, {timeout, Ref, Msg}, StateName]);

        _ ->

            io:format(Dev, "*DBG* ~p got ~p in state ~w~n",

                      [Name, Msg, StateName])

***************

*** 367,372 ****

--- 388,397 ----

  dispatch({'$gen_sync_all_state_event', From, Event},

         Mod, StateName, StateData) ->

      apply(Mod, handle_sync_event, [Event, From, StateName, StateData]);

+ dispatch({'$gen_fsm_timer', Msg}, Mod, StateName, StateData) ->

+     apply(Mod, StateName, [Msg, StateData]);

+ dispatch({timeout, Ref, {'$gen_fsm_timer', Msg}}, Mod, StateName,
StateData) -
>

+     apply(Mod, StateName, [{timeout, Ref, Msg}, StateData]);

  dispatch(Info, Mod, StateName, StateData) ->

      apply(Mod, handle_info, [Info, StateName, StateData]).

 

***************

*** 423,428 ****

--- 448,457 ----

      "** Last event in was ~p (for all states)~n";

  get_msg_str({'$gen_sync_all_state_event', Event}) ->

      "** Last sync event in was ~p (for all states)~n";

+ get_msg_str({'$gen_fsm_timer', Msg}) ->

+     "** Last timer event in was ~p~n";

+ get_msg_str({timeout, Ref, {'$gen_fsm_timer', Msg}}) ->

+     "** Last timer event in was ~p~n";

  get_msg_str(Msg) ->

      "** Last message in was ~p~n".

 

***************

*** 430,435 ****

--- 459,466 ----

  get_msg({'$gen_sync_event', Event}) -> Event;

  get_msg({'$gen_all_state_event', Event}) -> Event;

  get_msg({'$gen_sync_all_state_event', Event}) -> Event;

+ get_msg({'$gen_fsm_timer', Msg}) -> Msg;

+ get_msg({timeout, Ref, {'$gen_fsm_timer', Msg}}) -> {timeout, Ref, Msg};

  get_msg(Msg) -> Msg.

 

  %%-----------------------------------------------------------------



                  


- Sean



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