diff options
| -rw-r--r-- | lib/stdlib/doc/src/gen_statem.xml | 79 | ||||
| -rw-r--r-- | lib/stdlib/src/gen_statem.erl | 668 | ||||
| -rw-r--r-- | lib/stdlib/test/gen_statem_SUITE.erl | 30 | ||||
| -rw-r--r-- | system/doc/design_principles/statem.xml | 29 |
4 files changed, 442 insertions, 364 deletions
diff --git a/lib/stdlib/doc/src/gen_statem.xml b/lib/stdlib/doc/src/gen_statem.xml index 64267c2af5..fd498ee82e 100644 --- a/lib/stdlib/doc/src/gen_statem.xml +++ b/lib/stdlib/doc/src/gen_statem.xml @@ -533,7 +533,7 @@ handle_event(_, _, State, Data) -> Type <c>info</c> originates from regular process messages sent to the <c>gen_statem</c>. Also, the state machine implementation can generate events of types - <c>timeout</c>, <c>state_timeout</c>, <c>enter</c>, + <c>timeout</c>, <c>state_timeout</c>, and <c>internal</c> to itself. </p> </desc> @@ -639,6 +639,20 @@ handle_event(_, _, State, Data) -> </p> <list type="ordered"> <item> + <p> + If the state changes or is the initial state, and + <seealso marker="#type-state_enter"><em>state enter calls</em></seealso> + are used, the <c>gen_statem</c> calls + the new state callback with arguments + <seealso marker="#type-state_enter">(enter, OldState, Data)</seealso>. + Any + <seealso marker="#type-enter_action"><c>actions</c></seealso> + returned from this call are handled as if they were + appended to the actions + returned by the state callback that changed states. + </p> + </item> + <item> <p> All <seealso marker="#type-action">actions</seealso> @@ -668,36 +682,36 @@ handle_event(_, _, State, Data) -> </p> </item> <item> - <p> - If the state changes or is the initial state, and - <seealso marker="#type-state_enter"><em>state enter calls</em></seealso> - are used, the <c>gen_statem</c> calls - the new state callback with arguments - <seealso marker="#type-state_enter">(enter, OldState, Data)</seealso>. - Any - <seealso marker="#type-enter_action"><c>actions</c></seealso> - returned from this call are handled as if they were - appended to the actions - returned by the state callback that changed states. - </p> - </item> - <item> - <p> - If there are enqueued events the (possibly new) - <seealso marker="#state callback">state callback</seealso> - is called with the oldest enqueued event, - and we start again from the top of this list. - </p> - </item> - <item> <p> Timeout timers <seealso marker="#type-state_timeout"><c>state_timeout()</c></seealso> and <seealso marker="#type-event_timeout"><c>event_timeout()</c></seealso> - are handled. This may lead to a time-out zero event - being generated to the + are handled. Time-outs with zero time are guaranteed to be + delivered to the state machine before any external + not yet received event so if there is such a timeout requested, + the corresponding time-out zero event is enqueued as + the newest event. + </p> + <p> + Any event cancels an + <seealso marker="#type-event_timeout"><c>event_timeout()</c></seealso> + so a zero time event time-out is only generated + if the event queue is empty. + </p> + <p> + A state change cancels a + <seealso marker="#type-state_timeout"><c>state_timeout()</c></seealso> + and any new transition option of this type + belongs to the new state. + </p> + </item> + <item> + <p> + If there are enqueued events the <seealso marker="#state callback">state callback</seealso> + for the possibly new state + is called with the oldest enqueued event, and we start again from the top of this list. </p> </item> @@ -759,8 +773,9 @@ handle_event(_, _, State, Data) -> after this time (in milliseconds) unless another event arrives or has arrived in which case this time-out is cancelled. - Note that a retried, inserted or state time-out zero - events counts as arrived. + Note that a retried or inserted event counts as arrived. + So does a state time-out zero event, if it was generated + before this timer is requested. </p> <p> If the value is <c>infinity</c>, no timer is started, as @@ -802,7 +817,7 @@ handle_event(_, _, State, Data) -> <p> Setting this timer while it is running will restart it with the new time-out value. Therefore it is possible to cancel - this timeout by setting it to <c>infinity</c>. + this time-out by setting it to <c>infinity</c>. </p> </desc> </datatype> @@ -1130,7 +1145,7 @@ handle_event(_, _, State, Data) -> <c><anno>Timeout</anno></c> can also be a tuple <c>{clean_timeout,<anno>T</anno>}</c> or <c>{dirty_timeout,<anno>T</anno>}</c>, where - <c><anno>T</anno></c> is the timeout time. + <c><anno>T</anno></c> is the time-out time. <c>{clean_timeout,<anno>T</anno>}</c> works like just <c>T</c> described in the note above and uses a proxy process for <c>T < infinity</c>, @@ -1773,7 +1788,7 @@ handle_event(_, _, State, Data) -> StateFunctionResult </name> <name>Module:handle_event(enter, OldState, State, Data) -> - StateEnterResult + StateEnterResult(State) </name> <name>Module:handle_event(EventType, EventContent, State, Data) -> HandleEventResult @@ -1802,8 +1817,8 @@ handle_event(_, _, State, Data) -> <seealso marker="#type-event_handler_result">event_handler_result</seealso>(<seealso marker="#type-state_name">state_name()</seealso>) </v> <v> - StateEnterResult = - <seealso marker="#type-state_enter_result">state_enter_result</seealso>(<seealso marker="#type-state">state()</seealso>) + StateEnterResult(State) = + <seealso marker="#type-state_enter_result">state_enter_result(State)</seealso> </v> <v> HandleEventResult = diff --git a/lib/stdlib/src/gen_statem.erl b/lib/stdlib/src/gen_statem.erl index 17d1ebecec..018aca90e6 100644 --- a/lib/stdlib/src/gen_statem.erl +++ b/lib/stdlib/src/gen_statem.erl @@ -85,7 +85,8 @@ -type state_enter() :: 'state_enter'. -type transition_option() :: - postpone() | hibernate() | event_timeout(). + postpone() | hibernate() | + event_timeout() | state_timeout(). -type postpone() :: %% If 'true' postpone the current event %% and retry it when the state changes (=/=) @@ -108,7 +109,7 @@ %% * All action()s are executed in order of apperance. %% * Postponing the current event is performed %% iff 'postpone' is 'true'. - %% * A state timer is started iff 'timeout' is set. + %% * A state timeout is started iff 'timeout' is set. %% * Pending events are handled or if there are %% no pending events the server goes into receive %% or hibernate (iff 'hibernate' is 'true') @@ -154,12 +155,12 @@ -type handle_event_result() :: event_handler_result(state()). %% --type state_enter_result(StateType) :: +-type state_enter_result(State) :: {'next_state', % {next_state,NextState,NewData,[]} - State :: StateType, + State, NewData :: data()} | {'next_state', % State transition, maybe to the same state - State :: StateType, + State, NewData :: data(), Actions :: [enter_action()] | enter_action()} | state_callback_result(enter_action()). @@ -231,9 +232,9 @@ -callback handle_event( 'enter', OldState :: state(), - State :: state(), % Current state + State, % Current state Data :: data()) -> - state_enter_result(state()); + state_enter_result(State); (event_type(), EventContent :: term(), State :: state(), % Current state @@ -596,8 +597,8 @@ enter(Module, Opts, State, Data, Server, Actions, Parent) -> data => Data, postponed => P, %% The rest of the fields are set from to the arguments to - %% loop_event_actions/9 when it finally loops back to loop/3 - %% in loop_events_done/9 + %% loop_event_actions/10 when it finally loops back to loop/3 + %% in loop_events/10 %% %% Marker for initial state, cleared immediately when used init_state => true @@ -605,9 +606,10 @@ enter(Module, Opts, State, Data, Server, Actions, Parent) -> NewDebug = sys_debug(Debug, S, State, {enter,Event,State}), case call_callback_mode(S) of {ok,NewS} -> - StateTimer = undefined, + TimerRefs = #{}, + TimerTypes = #{}, loop_event_actions( - Parent, NewDebug, NewS, StateTimer, + Parent, NewDebug, NewS, TimerRefs, TimerTypes, Events, Event, State, Data, NewActions); {Class,Reason,Stacktrace} -> terminate( @@ -747,6 +749,10 @@ print_event(Dev, {out,Reply,{To,_Tag}}, {Name,State}) -> io:format( Dev, "*DBG* ~p send ~p to ~p from state ~p~n", [Name,Reply,To,State]); +print_event(Dev, {terminate,Reason}, {Name,State}) -> + io:format( + Dev, "*DBG* ~p terminate ~p in state ~p~n", + [Name,Reason,State]); print_event(Dev, {Tag,Event,NextState}, {Name,State}) -> StateString = case NextState of @@ -806,7 +812,7 @@ loop(Parent, Debug, #{hibernate := Hibernate} = S) -> %% Entry point for wakeup_from_hibernate/3 loop_receive( - Parent, Debug, #{timer := Timer, state_timer := StateTimer} = S) -> + Parent, Debug, #{timer_refs := TimerRefs, timer_types := TimerTypes} = S) -> receive Msg -> case Msg of @@ -822,18 +828,23 @@ loop_receive( %% but this will stand out in the crash report... terminate( exit, Reason, ?STACKTRACE(), Debug, S, [EXIT]); - {timeout,Timer,Content} - when Timer =/= undefined -> - loop_receive_result( - Parent, Debug, S, StateTimer, - {timeout,Content}); - {timeout,StateTimer,Content} - when StateTimer =/= undefined -> - loop_receive_result( - Parent, Debug, S, undefined, - {state_timeout,Content}); + {timeout,TimerRef,TimerMsg} -> + case TimerRefs of + #{TimerRef := TimerType} -> + Event = {TimerType,TimerMsg}, + %% Unregister the triggered timeout + loop_receive_result( + Parent, Debug, S, + maps:remove(TimerRef, TimerRefs), + maps:remove(TimerType, TimerTypes), + Event); + _ -> + Event = {info,Msg}, + loop_receive_result( + Parent, Debug, S, + TimerRefs, TimerTypes, Event) + end; _ -> - cancel_timer(Timer), Event = case Msg of {'$gen_call',From,Request} -> @@ -844,12 +855,15 @@ loop_receive( {info,Msg} end, loop_receive_result( - Parent, Debug, S, StateTimer, Event) + Parent, Debug, S, + TimerRefs, TimerTypes, Event) end end. -loop_receive_result(Parent, Debug, #{state := State} = S, StateTimer, Event) -> - %% The fields 'timer', 'state_timer' and 'hibernate' +loop_receive_result( + Parent, Debug, #{state := State} = S, + TimerRefs, TimerTypes, Event) -> + %% The fields 'timer_refs', 'timer_types' and 'hibernate' %% are now invalid in state map S - they will be recalculated %% and restored when we return to loop/3 %% @@ -857,82 +871,196 @@ loop_receive_result(Parent, Debug, #{state := State} = S, StateTimer, Event) -> %% Here the queue of not yet handled events is created Events = [], Hibernate = false, - loop_event(Parent, NewDebug, S, StateTimer, Events, Event, Hibernate). + loop_event( + Parent, NewDebug, S, TimerRefs, TimerTypes, Events, Event, Hibernate). -%% Process the event queue, or if it is empty -%% loop back to loop/3 to receive a new event -loop_events( - Parent, Debug, S, StateTimeout, - [Event|Events], _Timeout, State, Data, P, Hibernate) -> +%% Entry point for handling an event, received or enqueued +loop_event( + Parent, Debug, #{state := State, data := Data} = S, TimerRefs, TimerTypes, + Events, {Type,Content} = Event, Hibernate) -> %% - %% If there was an event timer requested we just ignore that - %% since we have events to handle which cancels the timer - loop_event( - Parent, Debug, S, StateTimeout, - Events, Event, State, Data, P, Hibernate); -loop_events( - Parent, Debug, S, {state_timeout,Time,EventContent}, - [] = Events, Timeout, State, Data, P, Hibernate) -> - if - Time =:= 0 -> - %% Simulate an immediate timeout - %% so we do not get the timeout message - %% after any received event - %% - %% This faked event will cancel - %& any not yet started event timer - Event = {state_timeout,EventContent}, - StateTimer = undefined, - loop_event( - Parent, Debug, S, StateTimer, - Events, Event, State, Data, P, Hibernate); - true -> - StateTimer = erlang:start_timer(Time, self(), EventContent), - loop_events( - Parent, Debug, S, StateTimer, - Events, Timeout, State, Data, P, Hibernate) - end; -loop_events( - Parent, Debug, S, StateTimer, - [] = Events, Timeout, State, Data, P, Hibernate) -> - case Timeout of - {timeout,0,EventContent} -> - %% Simulate an immediate timeout - %% so we do not get the timeout message - %% after any received event - %% - Event = {timeout,EventContent}, - loop_event( - Parent, Debug, S, StateTimer, - Events, Event, State, Data, P, Hibernate); - {timeout,Time,EventContent} -> - Timer = erlang:start_timer(Time, self(), EventContent), - loop_events_done( - Parent, Debug, S, StateTimer, - State, Data, P, Hibernate, Timer); - undefined -> - %% No event timeout has been requested - Timer = undefined, - loop_events_done( - Parent, Debug, S, StateTimer, - State, Data, P, Hibernate, Timer) + %% If Hibernate is true here it can only be + %% because it was set from an event action + %% and we did not go into hibernation since there + %% were events in queue, so we do what the user + %% might rely on i.e collect garbage which + %% would have happened if we actually hibernated + %% and immediately was awakened + Hibernate andalso garbage_collect(), + case call_state_function(S, Type, Content, State, Data) of + {ok,Result,NewS} -> + %% Cancel event timeout + {NewTimerRefs,NewTimerTypes} = + cancel_timer_by_type( + timeout, TimerRefs, TimerTypes), + {NewData,NextState,Actions} = + parse_event_result( + true, Debug, NewS, Result, + Events, Event, State, Data), + loop_event_actions( + Parent, Debug, S, NewTimerRefs, NewTimerTypes, + Events, Event, NextState, NewData, Actions); + {Class,Reason,Stacktrace} -> + terminate( + Class, Reason, Stacktrace, Debug, S, [Event|Events]) end. -%% Back to the top -loop_events_done( - Parent, Debug, S, StateTimer, - State, Data, P, Hibernate, Timer) -> +loop_event_actions( + Parent, Debug, + #{state := State, state_enter := StateEnter} = S, TimerRefs, TimerTypes, + Events, Event, NextState, NewData, Actions) -> + case parse_actions(Debug, S, State, Actions) of + {ok,NewDebug,Hibernate,TimeoutsR,Postpone,NextEventsR} -> + if + StateEnter, NextState =/= State -> + loop_event_enter( + Parent, NewDebug, S, TimerRefs, TimerTypes, + Events, Event, NextState, NewData, + Hibernate, TimeoutsR, Postpone, NextEventsR); + StateEnter -> + case maps:is_key(init_state, S) of + true -> + %% Avoid infinite loop in initial state + %% with state entry events + NewS = maps:remove(init_state, S), + loop_event_enter( + Parent, NewDebug, NewS, TimerRefs, TimerTypes, + Events, Event, NextState, NewData, + Hibernate, TimeoutsR, Postpone, NextEventsR); + false -> + loop_event_result( + Parent, NewDebug, S, TimerRefs, TimerTypes, + Events, Event, NextState, NewData, + Hibernate, TimeoutsR, Postpone, NextEventsR) + end; + true -> + loop_event_result( + Parent, NewDebug, S, TimerRefs, TimerTypes, + Events, Event, NextState, NewData, + Hibernate, TimeoutsR, Postpone, NextEventsR) + end; + {Class,Reason,Stacktrace} -> + terminate( + Class, Reason, Stacktrace, + Debug, S#{data := NewData}, [Event|Events]) + end. + +loop_event_enter( + Parent, Debug, #{state := State} = S, TimerRefs, TimerTypes, + Events, Event, NextState, NewData, + Hibernate, TimeoutsR, Postpone, NextEventsR) -> + case call_state_function(S, enter, State, NextState, NewData) of + {ok,Result,NewS} -> + {NewerData,_,Actions} = + parse_event_result( + false, Debug, NewS, Result, + Events, Event, NextState, NewData), + loop_event_enter_actions( + Parent, Debug, NewS, TimerRefs, TimerTypes, + Events, Event, NextState, NewerData, + Hibernate, TimeoutsR, Postpone, NextEventsR, Actions); + {Class,Reason,Stacktrace} -> + terminate( + Class, Reason, Stacktrace, + Debug, S#{state := NextState, data := NewData}, + [Event|Events]) + end. + +loop_event_enter_actions( + Parent, Debug, S, TimerRefs, TimerTypes, + Events, Event, NextState, NewData, + Hibernate, TimeoutsR, Postpone, NextEventsR, Actions) -> + case + parse_enter_actions( + Debug, S, NextState, Actions, + Hibernate, TimeoutsR) + of + {ok,NewDebug,NewHibernate,NewTimeoutsR,_,_} -> + loop_event_result( + Parent, NewDebug, S, TimerRefs, TimerTypes, + Events, Event, NextState, NewData, + NewHibernate, NewTimeoutsR, Postpone, NextEventsR); + {Class,Reason,Stacktrace} -> + terminate( + Class, Reason, Stacktrace, + Debug, S#{state := NextState, data := NewData}, + [Event|Events]) + end. + +loop_event_result( + Parent, Debug, + #{state := State, postponed := P_0} = S, TimerRefs_0, TimerTypes_0, + Events, Event, NextState, NewData, + Hibernate, TimeoutsR, Postpone, NextEventsR) -> + %% + %% All options have been collected and next_events are buffered. + %% Do the actual state transition. + %% + {NewDebug,P_1} = % Move current event to postponed if Postpone + case Postpone of + true -> + {sys_debug(Debug, S, State, {postpone,Event,State}), + [Event|P_0]}; + false -> + {sys_debug(Debug, S, State, {consume,Event,State}), + P_0} + end, + {Events_1,NewP,{TimerRefs_1,TimerTypes_1}} = + %% Move all postponed events to queue and cancel the + %% state timeout if the state changes + if + NextState =:= State -> + {Events,P_1,{TimerRefs_0,TimerTypes_0}}; + true -> + {lists:reverse(P_1, Events),[], + cancel_timer_by_type( + state_timeout, TimerRefs_0, TimerTypes_0)} + end, + {TimerRefs_2,TimerTypes_2,TimeoutEvents} = + %% Stop and start timers non-event timers + parse_timers(TimerRefs_1, TimerTypes_1, TimeoutsR), + %% Place next events last in reversed queue + Events_2R = lists:reverse(Events_1, NextEventsR), + %% Enqueue immediate timeout events and start event timer + {NewTimerRefs,NewTimerTypes,Events_3R} = + process_timeout_events( + TimerRefs_2, TimerTypes_2, TimeoutEvents, Events_2R), + NewEvents = lists:reverse(Events_3R), + loop_events( + Parent, NewDebug, S, NewTimerRefs, NewTimerTypes, + NewEvents, Hibernate, NextState, NewData, NewP). + +%% Loop until out of enqueued events +%% +loop_events( + Parent, Debug, S, TimerRefs, TimerTypes, + [] = _Events, Hibernate, State, Data, P) -> + %% Update S and loop back to loop/3 to receive a new event NewS = S#{ state := State, data := Data, postponed := P, hibernate => Hibernate, - timer => Timer, - state_timer => StateTimer}, - loop(Parent, Debug, NewS). + timer_refs => TimerRefs, + timer_types => TimerTypes}, + loop(Parent, Debug, NewS); +loop_events( + Parent, Debug, S, TimerRefs, TimerTypes, + [Event|Events], Hibernate, State, Data, P) -> + %% Update S and continue with enqueued events + NewS = + S#{ + state := State, + data := Data, + postponed := P}, + loop_event( + Parent, Debug, NewS, TimerRefs, TimerTypes, Events, Event, Hibernate). + +%%--------------------------------------------------------------------------- +%% Server loop helpers call_callback_mode(#{module := Module} = S) -> try Module:callback_mode() of @@ -996,6 +1124,7 @@ parse_callback_mode([H|T], CBMode, StateEnter) -> parse_callback_mode(_, _CBMode, StateEnter) -> {undefined,StateEnter}. + call_state_function( #{callback_mode := undefined} = S, Type, Content, State, Data) -> @@ -1061,42 +1190,6 @@ call_state_function( {Class,Reason,erlang:get_stacktrace()} end. -%% Update S and continue -loop_event( - Parent, Debug, S, StateTimer, - Events, Event, State, Data, P, Hibernate) -> - NewS = - S#{ - state := State, - data := Data, - postponed := P}, - loop_event(Parent, Debug, NewS, StateTimer, Events, Event, Hibernate). - -loop_event( - Parent, Debug, #{state := State, data := Data} = S, StateTimer, - Events, {Type,Content} = Event, Hibernate) -> - %% - %% If Hibernate is true here it can only be - %% because it was set from an event action - %% and we did not go into hibernation since there - %% were events in queue, so we do what the user - %% might rely on i.e collect garbage which - %% would have happened if we actually hibernated - %% and immediately was awakened - Hibernate andalso garbage_collect(), - case call_state_function(S, Type, Content, State, Data) of - {ok,Result,NewS} -> - {NewData,NextState,Actions} = - parse_event_result( - true, Debug, NewS, Result, - Events, Event, State, Data), - loop_event_actions( - Parent, Debug, S, StateTimer, - Events, Event, NextState, NewData, Actions); - {Class,Reason,Stacktrace} -> - terminate( - Class, Reason, Stacktrace, Debug, S, [Event|Events]) - end. %% Interpret all callback return variants parse_event_result( @@ -1146,32 +1239,32 @@ parse_event_result( Debug, S, [Event|Events]) end. + parse_enter_actions( Debug, S, State, Actions, - Hibernate, Timeout, StateTimeout) -> + Hibernate, TimeoutsR) -> Postpone = forbidden, - NextEvents = forbidden, + NextEventsR = forbidden, parse_actions( Debug, S, State, listify(Actions), - Hibernate, Timeout, StateTimeout, Postpone, NextEvents). + Hibernate, TimeoutsR, Postpone, NextEventsR). parse_actions(Debug, S, State, Actions) -> Hibernate = false, - Timeout = undefined, - StateTimeout = undefined, + TimeoutsR = [], Postpone = false, - NextEvents = [], + NextEventsR = [], parse_actions( Debug, S, State, listify(Actions), - Hibernate, Timeout, StateTimeout, Postpone, NextEvents). + Hibernate, TimeoutsR, Postpone, NextEventsR). %% parse_actions( Debug, _S, _State, [], - Hibernate, Timeout, StateTimeout, Postpone, NextEvents) -> - {ok,Debug,Hibernate,Timeout,StateTimeout,Postpone,NextEvents}; + Hibernate, TimeoutsR, Postpone, NextEventsR) -> + {ok,Debug,Hibernate,TimeoutsR,Postpone,NextEventsR}; parse_actions( Debug, S, State, [Action|Actions], - Hibernate, Timeout, StateTimeout, Postpone, NextEvents) -> + Hibernate, TimeoutsR, Postpone, NextEventsR) -> case Action of %% Actual actions {reply,From,Reply} -> @@ -1180,8 +1273,7 @@ parse_actions( NewDebug = do_reply(Debug, S, State, From, Reply), parse_actions( NewDebug, S, State, Actions, - Hibernate, Timeout, StateTimeout, - Postpone, NextEvents); + Hibernate, TimeoutsR, Postpone, NextEventsR); false -> {error, {bad_action_from_state_function,Action}, @@ -1191,7 +1283,7 @@ parse_actions( {hibernate,NewHibernate} when is_boolean(NewHibernate) -> parse_actions( Debug, S, State, Actions, - NewHibernate, Timeout, StateTimeout, Postpone, NextEvents); + NewHibernate, TimeoutsR, Postpone, NextEventsR); {hibernate,_} -> {error, {bad_action_from_state_function,Action}, @@ -1199,43 +1291,44 @@ parse_actions( hibernate -> parse_actions( Debug, S, State, Actions, - true, Timeout, StateTimeout, Postpone, NextEvents); - {state_timeout,Time,_} = NewStateTimeout + true, TimeoutsR, Postpone, NextEventsR); + {state_timeout,Time,_} = StateTimeout when is_integer(Time), Time >= 0; Time =:= infinity -> parse_actions( Debug, S, State, Actions, - Hibernate, Timeout, NewStateTimeout, Postpone, NextEvents); + Hibernate, [StateTimeout|TimeoutsR], Postpone, NextEventsR); {state_timeout,_,_} -> {error, {bad_action_from_state_function,Action}, ?STACKTRACE()}; - {timeout,infinity,_} -> % Clear timer - it will never trigger + {timeout,infinity,_} -> + %% Ignore - timeout will never happen and already cancelled parse_actions( Debug, S, State, Actions, - Hibernate, undefined, StateTimeout, Postpone, NextEvents); - {timeout,Time,_} = NewTimeout when is_integer(Time), Time >= 0 -> + Hibernate, TimeoutsR, Postpone, NextEventsR); + {timeout,Time,_} = Timeout when is_integer(Time), Time >= 0 -> parse_actions( Debug, S, State, Actions, - Hibernate, NewTimeout, StateTimeout, Postpone, NextEvents); + Hibernate, [Timeout|TimeoutsR], Postpone, NextEventsR); {timeout,_,_} -> {error, {bad_action_from_state_function,Action}, ?STACKTRACE()}; - infinity -> % Clear timer - it will never trigger + infinity -> % Ignore - timeout will never happen parse_actions( Debug, S, State, Actions, - Hibernate, undefined, StateTimeout, Postpone, NextEvents); + Hibernate, TimeoutsR, Postpone, NextEventsR); Time when is_integer(Time), Time >= 0 -> - NewTimeout = {timeout,Time,Time}, + Timeout = {timeout,Time,Time}, parse_actions( Debug, S, State, Actions, - Hibernate, NewTimeout, StateTimeout, Postpone, NextEvents); + Hibernate, [Timeout|TimeoutsR], Postpone, NextEventsR); {postpone,NewPostpone} when is_boolean(NewPostpone), Postpone =/= forbidden -> parse_actions( Debug, S, State, Actions, - Hibernate, Timeout, StateTimeout, NewPostpone, NextEvents); + Hibernate, TimeoutsR, NewPostpone, NextEventsR); {postpone,_} -> {error, {bad_action_from_state_function,Action}, @@ -1243,16 +1336,16 @@ parse_actions( postpone when Postpone =/= forbidden -> parse_actions( Debug, S, State, Actions, - Hibernate, Timeout, StateTimeout, true, NextEvents); + Hibernate, TimeoutsR, true, NextEventsR); {next_event,Type,Content} -> case event_type(Type) of - true when NextEvents =/= forbidden -> + true when NextEventsR =/= forbidden -> NewDebug = sys_debug(Debug, S, State, {in,{Type,Content}}), parse_actions( NewDebug, S, State, Actions, - Hibernate, Timeout, StateTimeout, - Postpone, [{Type,Content}|NextEvents]); + Hibernate, TimeoutsR, Postpone, + [{Type,Content}|NextEventsR]); _ -> {error, {bad_action_from_state_function,Action}, @@ -1264,158 +1357,92 @@ parse_actions( ?STACKTRACE()} end. -loop_event_actions( - Parent, Debug, - #{state := State, state_enter := StateEnter} = S, StateTimer, - Events, Event, NextState, NewData, Actions) -> - case parse_actions(Debug, S, State, Actions) of - {ok,NewDebug,Hibernate,Timeout,StateTimeout,Postpone,NextEvents} -> + +%% Stop and start timers as well as create timeout zero events +%% and pending event timer +%% +%% Stop and start timers non-event timers +parse_timers(TimerRefs, TimerTypes, TimeoutsR) -> + parse_timers(TimerRefs, TimerTypes, TimeoutsR, #{}, []). +%% +parse_timers(TimerRefs, TimerTypes, [], _Seen, TimeoutEvents) -> + {TimerRefs,TimerTypes,TimeoutEvents}; +parse_timers( + TimerRefs, TimerTypes, [Timeout|TimeoutsR], Seen, TimeoutEvents) -> + {TimerType,Time,TimerMsg} = Timeout, + case Seen of + #{TimerType := _} -> + %% Type seen before - ignore + parse_timers( + TimerRefs, TimerTypes, TimeoutsR, Seen, TimeoutEvents); + #{} -> + %% Unseen type - handle + NewSeen = Seen#{TimerType => true}, + %% Cancel any running timer + {NewTimerRefs,NewTimerTypes} = + cancel_timer_by_type(TimerType, TimerRefs, TimerTypes), if - StateEnter, NextState =/= State -> - loop_event_enter( - Parent, NewDebug, S, StateTimer, - Events, Event, NextState, NewData, - Hibernate, Timeout, StateTimeout, Postpone, NextEvents); - StateEnter -> - case maps:is_key(init_state, S) of - true -> - %% Avoid infinite loop in initial state - %% with state entry events - NewS = maps:remove(init_state, S), - loop_event_enter( - Parent, NewDebug, NewS, StateTimer, - Events, Event, NextState, NewData, - Hibernate, Timeout, StateTimeout, - Postpone, NextEvents); - false -> - loop_event_result( - Parent, NewDebug, S, StateTimer, - Events, Event, NextState, NewData, - Hibernate, Timeout, StateTimeout, - Postpone, NextEvents) - end; + Time =:= infinity -> + %% Ignore - timer will never fire + parse_timers( + NewTimerRefs, NewTimerTypes, TimeoutsR, + NewSeen, TimeoutEvents); + TimerType =:= timeout -> + %% Handle event timer later + parse_timers( + NewTimerRefs, NewTimerTypes, TimeoutsR, + NewSeen, [Timeout|TimeoutEvents]); + Time =:= 0 -> + %% Handle zero time timeouts later + TimeoutEvent = {TimerType,TimerMsg}, + parse_timers( + NewTimerRefs, NewTimerTypes, TimeoutsR, + NewSeen, [TimeoutEvent|TimeoutEvents]); true -> - loop_event_result( - Parent, NewDebug, S, StateTimer, - Events, Event, NextState, NewData, - Hibernate, Timeout, StateTimeout, Postpone, NextEvents) - end; - {Class,Reason,Stacktrace} -> - terminate( - Class, Reason, Stacktrace, - Debug, S#{data := NewData}, [Event|Events]) + %% Start a new timer + TimerRef = erlang:start_timer(Time, self(), TimerMsg), + parse_timers( + NewTimerRefs#{TimerRef => TimerType}, + NewTimerTypes#{TimerType => TimerRef}, + TimeoutsR, NewSeen, TimeoutEvents) + end end. -loop_event_enter( - Parent, Debug, #{state := State} = S, StateTimer, - Events, Event, NextState, NewData, - Hibernate, Timeout, StateTimeout, Postpone, NextEvents) -> - case call_state_function(S, enter, State, NextState, NewData) of - {ok,Result,NewS} -> - {NewerData,_,Actions} = - parse_event_result( - false, Debug, NewS, Result, - Events, Event, NextState, NewData), - loop_event_enter_actions( - Parent, Debug, NewS, StateTimer, - Events, Event, NextState, NewerData, - Hibernate, Timeout, StateTimeout, Postpone, NextEvents, Actions); - {Class,Reason,Stacktrace} -> - terminate( - Class, Reason, Stacktrace, - Debug, S#{state := NextState, data := NewData}, - [Event|Events]) - end. +%% Enqueue immediate timeout events and start event timer +process_timeout_events(TimerRefs, TimerTypes, [], EventsR) -> + {TimerRefs, TimerTypes, EventsR}; +process_timeout_events( + TimerRefs, TimerTypes, + [{timeout,0,TimerMsg}|TimeoutEvents], []) -> + %% No enqueued events - insert a timeout zero event + TimeoutEvent = {timeout,TimerMsg}, + process_timeout_events( + TimerRefs, TimerTypes, + TimeoutEvents, [TimeoutEvent]); +process_timeout_events( + TimerRefs, TimerTypes, + [{timeout,Time,TimerMsg}], []) -> + %% No enqueued events - start event timer + TimerRef = erlang:start_timer(Time, self(), TimerMsg), + process_timeout_events( + TimerRefs#{TimerRef => timeout}, TimerTypes#{timeout => TimerRef}, + [], []); +process_timeout_events( + TimerRefs, TimerTypes, + [{timeout,_Time,_TimerMsg}|TimeoutEvents], EventsR) -> + %% There will be some other event so optimize by not starting + %% an event timer to just have to cancel it again + process_timeout_events( + TimerRefs, TimerTypes, + TimeoutEvents, EventsR); +process_timeout_events( + TimerRefs, TimerTypes, + [{_TimeoutType,_TimeoutMsg} = TimeoutEvent|TimeoutEvents], EventsR) -> + process_timeout_events( + TimerRefs, TimerTypes, + TimeoutEvents, [TimeoutEvent|EventsR]). -loop_event_enter_actions( - Parent, Debug, S, StateTimer, - Events, Event, NextState, NewData, - Hibernate, Timeout, StateTimeout, Postpone, NextEvents, Actions) -> - case - parse_enter_actions( - Debug, S, NextState, Actions, - Hibernate, Timeout, StateTimeout) - of - {ok,NewDebug,NewHibernate,NewTimeout,NewStateTimeout,_,_} -> - loop_event_result( - Parent, NewDebug, S, StateTimer, - Events, Event, NextState, NewData, - NewHibernate, NewTimeout, NewStateTimeout, Postpone, NextEvents); - {Class,Reason,Stacktrace} -> - terminate( - Class, Reason, Stacktrace, - Debug, S#{state := NextState, data := NewData}, - [Event|Events]) - end. -loop_event_result( - Parent, Debug, - #{state := State, postponed := P_0} = S, StateTimer, - Events, Event, NextState, NewData, - Hibernate, Timeout, StateTimeout, Postpone, NextEvents) -> - %% - %% All options have been collected and next_events are buffered. - %% Do the actual state transition. - %% - NewStateTimeout = - case StateTimeout of - {state_timeout,Time,_} -> - %% New timeout -> cancel timer - case StateTimer of - {state_timeout,_,_} -> - ok; - _ -> - cancel_timer(StateTimer) - end, - case Time of - infinity -> - undefined; - _ -> - StateTimeout - end; - undefined when NextState =/= State -> - %% State change -> cancel timer - case StateTimer of - {state_timeout,_,_} -> - ok; - _ -> - cancel_timer(StateTimer) - end, - undefined; - undefined -> - StateTimer - end, - %% - P_1 = % Move current event to postponed if Postpone - case Postpone of - true -> - [Event|P_0]; - false -> - P_0 - end, - {Events_1,NewP} = % Move all postponed events to queue if state change - if - NextState =:= State -> - {Events,P_1}; - true -> - {lists:reverse(P_1, Events),[]} - end, - %% Place next events first in queue - NewEvents = lists:reverse(NextEvents, Events_1), - %% - NewDebug = - sys_debug( - Debug, S, State, - case Postpone of - true -> - {postpone,Event,State}; - false -> - {consume,Event,State} - end), - %% - loop_events( - Parent, NewDebug, S, NewStateTimeout, - NewEvents, Timeout, NextState, NewData, NewP, Hibernate). %%--------------------------------------------------------------------------- %% Server helpers @@ -1474,16 +1501,20 @@ terminate( sys:print_log(Debug), erlang:raise(C, R, ST) end, - case Reason of - normal -> ok; - shutdown -> ok; - {shutdown,_} -> ok; - _ -> - error_info( - Class, Reason, Stacktrace, S, Q, P, - format_status(terminate, get(), S)), - sys:print_log(Debug) - end, + _ = + case Reason of + normal -> + sys_debug(Debug, S, State, {terminate,Reason}); + shutdown -> + sys_debug(Debug, S, State, {terminate,Reason}); + {shutdown,_} -> + sys_debug(Debug, S, State, {terminate,Reason}); + _ -> + error_info( + Class, Reason, Stacktrace, S, Q, P, + format_status(terminate, get(), S)), + sys:print_log(Debug) + end, case Stacktrace of [] -> erlang:Class(Reason); @@ -1605,8 +1636,19 @@ listify(Item) when is_list(Item) -> listify(Item) -> [Item]. -cancel_timer(undefined) -> - ok; +%% Cancel timer if running, otherwise no op +cancel_timer_by_type(TimerType, TimerRefs, TimerTypes) -> + case TimerTypes of + #{TimerType := TimerRef} -> + cancel_timer(TimerRef), + {maps:remove(TimerRef, TimerRefs), + maps:remove(TimerType, TimerTypes)}; + #{} -> + {TimerRefs,TimerTypes} + end. + +%%cancel_timer(undefined) -> +%% ok; cancel_timer(TRef) -> case erlang:cancel_timer(TRef) of false -> diff --git a/lib/stdlib/test/gen_statem_SUITE.erl b/lib/stdlib/test/gen_statem_SUITE.erl index 300baaf1c6..8f2ba0cab2 100644 --- a/lib/stdlib/test/gen_statem_SUITE.erl +++ b/lib/stdlib/test/gen_statem_SUITE.erl @@ -742,26 +742,40 @@ state_timeout(_Config) -> %% Verify that {state_timeout,0,_} %% comes after next_event and that %% {timeout,0,_} is cancelled by - %% {state_timeout,0,_} + %% pending {state_timeout,0,_} {keep_state, {ok,2,Data}, [{timeout,0,3}]}; - (state_timeout, 2, {ok,2,{Time,From}}) -> - {next_state, state3, 3, + (state_timeout, 2, {ok,2,Data}) -> + %% Verify that timeout 0's are processed + %% in order + {keep_state, {ok,3,Data}, + [{timeout,0,4},{state_timeout,0,5}]}; + (timeout, 4, {ok,3,Data}) -> + %% Verify that timeout 0 is cancelled by + %% enqueued state_timeout 0 and that + %% multiple state_timeout 0 can be enqueued + {keep_state, {ok,4,Data}, + [{state_timeout,0,6},{timeout,0,7}]}; + (state_timeout, 5, {ok,4,Data}) -> + {keep_state, {ok,5,Data}}; + (state_timeout, 6, {ok,5,{Time,From}}) -> + {next_state, state3, 6, [{reply,From,ok}, - {state_timeout,Time,3}]} + {state_timeout,Time,8}]} end, state3 => fun - (info, message_to_self, 3) -> - {keep_state, '3'}; - ({call,From}, check, '3') -> + (info, message_to_self, 6) -> + {keep_state, 7}; + ({call,From}, check, 7) -> {keep_state, From}; - (state_timeout, 3, From) -> + (state_timeout, 8, From) -> {stop_and_reply, normal, {reply,From,ok}} end}, {ok,STM} = gen_statem:start_link(?MODULE, {map_statem,Machine,[]}, []), + sys:trace(STM, true), TRef = erlang:start_timer(1000, self(), kull), ok = gen_statem:call(STM, {go,500}), ok = gen_statem:call(STM, check), diff --git a/system/doc/design_principles/statem.xml b/system/doc/design_principles/statem.xml index bece95e6b8..f627145f9f 100644 --- a/system/doc/design_principles/statem.xml +++ b/system/doc/design_principles/statem.xml @@ -1015,17 +1015,24 @@ open(cast, {button,_}, Data) -> ... ]]></code> <p> - The fact that a postponed event is only retried after a state change - translates into a requirement on the event and state space. - If you have a choice between storing a state data item - in the <c>State</c> or in the <c>Data</c>: - if a change in the item value affects which events that - are handled, then this item is to be part of the state. - </p> - <p> - You want to avoid that you maybe much later decide - to postpone an event in one state and by misfortune it is never retried, - as the code only changes the <c>Data</c> but not the <c>State</c>. + Since a postponed event is only retried after a state change, + you have to think about where to keep a state data item. + You can keep it in the server <c>Data</c> + or in the <c>State</c> itself, + for example by having two more or less identical states + to keep a boolean value, or by using a complex state with + <seealso marker="#Callback Modes">callback mode</seealso> + <seealso marker="stdlib:gen_statem#type-callback_mode"><c>handle_event_function</c></seealso>. + If a change in the value changes the set of events that is handled, + then the value should be kept in the State. + Otherwise no postponed events will be retried + since only the server Data changes. + </p> + <p> + This is not important if you do not postpone events. + But if you later decide to start postponing some events, + then the design flaw of not having separate states + when they should be, might become a hard to find bug. </p> <section> |