[erlang-questions] extended timer module to handle absolute time-of-day timers

Michael McDaniel <>
Tue Jan 13 17:03:39 CET 2009


 Thanks - I like it.  Just as I like timed_supervisor.erl which I use
 everyday (strictly speaking, it's always running!).

 I think the new functions would be useful additions to the
 OTP included timer module.


~Michael


On Mon, Jan 12, 2009 at 11:48:27PM -0500, Serge Aleynikov wrote:
> Sorry - previous email had a wrong attachment.
>
>
> I extended the timer module to handle absolute time specifications.
>
> With this implementation it's possible to have messages sent on given
> days of week at a certain time of day.  Five new functions are added:
>      apply_at_local_time/4, send_at_local_time/3, exit_at_local_time/3,
>      apply_daily_at_local_time/5, send_daily_at_local_time/4.
>
>
> Example1: Send a shutdown message to Pid at 23:00:00 every Friday and
> Sunday.
>      timer:send_daily_at_local_time([fri,sun], {23,0,0}, Pid, shutdown).
>
> Example2: Send a restart message to Pid at "6:00:00":
>      timer:send_at_local_time({6,0,0}, Pid, restart).
>
> Legacy timer_server's functionality is not affected.
>
> The rationale behind this extension is that I frequently needed
> functionality to schedule some "cron-like" recurrent activities, and was
> always relying either on cron+erl_call or coding that activity with help
> of timer:send_after/3 or timer:send_interval/2.  As I finally got sick
> of dealing with shortcomings of the timer module, I put together this
> extension.
>
> Let me know if you also find it useful, and in such case perhaps we can
> get it included in the OTP.
>
> Serge
>

> %% ``The contents of this file are subject to the Erlang Public License,
> %% Version 1.1, (the "License"); you may not use this file except in
> %% compliance with the License. You should have received a copy of the
> %% Erlang Public License along with this software. If not, it can be
> %% retrieved via the world wide web at http://www.erlang.org/.
> %%
> %% Software distributed under the License is distributed on an "AS IS"
> %% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
> %% the License for the specific language governing rights and limitations
> %% under the License.
> %%
> %% The Initial Developer of the Original Code is Ericsson Utvecklings AB.
> %% Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings
> %% AB. All Rights Reserved.''
> %%
> %% Contributor: Serge Aleynikov <>
> %%  12-Jan-2009 Added support for absolute time timers including:
> %%      apply_at_local_time/4, send_at_local_time/3, exit_at_local_time/3,
> %%      apply_daily_at_local_time/5, send_daily_at_local_time/4
> %%
> %%     $Id$
> %%
> -module(timer).
> 
> -export([apply_after/4,
> 	 send_after/3, send_after/2,
> 	 exit_after/3, exit_after/2, kill_after/2, kill_after/1,
> 	 apply_interval/4, send_interval/3, send_interval/2,
>      apply_at_local_time/4, send_at_local_time/3,
>      exit_at_local_time/3, kill_at_local_time/2,
>      apply_daily_at_local_time/5, send_daily_at_local_time/4,
> 	 cancel/1, sleep/1, tc/3, now_diff/2,
> 	 seconds/1, minutes/1, hours/1, hms/3]).
> 
> -export([start_link/0, start/0,
> 	 handle_call/3,  handle_info/2,
> 	 init/1,
> 	 code_change/3, handle_cast/2, terminate/2]).
> 
> %% internal exports for test purposes only
> -export([get_status/0]).
> 
> %% Max
> -define(MAX_TIMEOUT, 16#0800000).
> -define(TIMER_TAB, timer_tab).
> -define(INTERVAL_TAB, timer_interval_tab).
> 
> %%
> %% Interface functions
> %%
> %% Time is in milliseconds.
> %% TimeOfDay is in time() format (e.g. {3,59,15} = "03:59:15")
> %%
> apply_at_local_time(TimeOfDay, M, F, A) ->
>     req(apply_at_local_time, {TimeOfDay, {M, F, A}}).
> 
> apply_after(Time, M, F, A) ->
>     req(apply_after, {Time, {M, F, A}}).
> 
> send_at_local_time(TimeOfDay, Pid, Message) ->
>     req(apply_at_local_time, {TimeOfDay, {?MODULE, send, [Pid, Message]}}).
> 
> send_after(Time, Pid, Message) ->
>     req(apply_after, {Time, {?MODULE, send, [Pid, Message]}}).
> 
> send_after(Time, Message) ->
>     send_after(Time, self(), Message).
> 
> exit_at_local_time(TimeOfDay, Pid, Reason) ->
>     req(apply_at_local_time, {TimeOfDay, {erlang, exit, [Pid, Reason]}}).
> 
> exit_after(Time, Pid, Reason) ->
>     req(apply_after, {Time, {erlang, exit, [Pid, Reason]}}).
> 
> exit_after(Time, Reason) ->
>     exit_after(Time, self(), Reason).
> 
> kill_at_local_time(TimeOfDay, Pid) ->
>     exit_at_local_time(TimeOfDay, Pid, kill).
> 
> kill_after(Time, Pid) ->
>     exit_after(Time, Pid, kill).
> 
> kill_after(Time) ->
>     exit_after(Time, self(), kill).
> 
> %% @spec (DaysOfWeek, TimeOfDay::time(), M, F, A) ->
> %%              {ok, TRef::ref()} | {error, Reason}
> %%          DaysOfWeek = [DayOfWeek]
> %%          DayOfWeek  = integer() | sun | mon | tue | wed | thu | fri | sat
> apply_daily_at_local_time(DaysOfWeek, TimeOfDay, M, F, A) ->
>     req(apply_daily_at_local_time, {DaysOfWeek, TimeOfDay, self(), {M, F, A}}).
> 
> apply_interval(Time, M, F, A) ->
>     req(apply_interval, {Time, self(), {M, F, A}}).
> 
> %% @spec (DaysOfWeek, TimeOfDay::time(), Pid::pid(), M, F, A) ->
> %%              {ok, TRef::ref()} | {error, Reason}
> %%          DaysOfWeek = [DayOfWeek]
> %%          DayOfWeek  = integer() | sun | mon | tue | wed | thu | fri | sat
> send_daily_at_local_time(DaysOfWeek, TimeOfDay, Pid, Message) ->
>     Details = {?MODULE, send, [Pid, Message]},
>     req(apply_daily_at_local_time, {DaysOfWeek, TimeOfDay, Pid, Details}).
> 
> send_interval(Time, Pid, Message) ->
>     req(apply_interval, {Time, Pid, {?MODULE, send, [Pid, Message]}}).
> 
> send_interval(Time, Message) ->
>     send_interval(Time, self(), Message).
> 
> cancel(BRef) ->
>     req(cancel, BRef).
> 
> sleep(T) ->
>     receive
>     after T -> ok
>     end.
> 
> %%
> %% Measure the execution time (in microseconds) for an MFA.
> %%
> tc(M, F, A) ->
>     Before = erlang:now(),
>     Val = (catch apply(M, F, A)),
>     After = erlang:now(),
>     {now_diff(After, Before), Val}.
> 
> %%
> %% Calculate the time difference (in microseconds) of two
> %% erlang:now() timestamps, T2-T1.
> %%
> now_diff({A2, B2, C2}, {A1, B1, C1}) ->
>     ((A2-A1)*1000000 + B2-B1)*1000000 + C2-C1.
> 
> %%
> %% Convert seconds, minutes etc. to milliseconds.
> %%
> seconds(Seconds) ->
>     1000*Seconds.
> minutes(Minutes) ->
>     1000*60*Minutes.
> hours(Hours) ->
>     1000*60*60*Hours.
> hms(H, M, S) ->
>     hours(H) + minutes(M) + seconds(S).
> 
> %%
> %%   Start/init functions
> %%
> 
> %%   Start is only included because of backward compatibility!
> start() ->
>     ensure_started().
> 
> start_link() ->
>     gen_server:start_link({local, timer_server}, ?MODULE, [], []).
> 
> init([]) ->
>     process_flag(trap_exit, true),
>     ets:new(?TIMER_TAB,[named_table,ordered_set,protected]),
>     ets:new(?INTERVAL_TAB,[named_table,protected]),
>     {ok, [], infinity}.
> 
> ensure_started() ->
>     case whereis(timer_server) of
> 	undefined ->
> 	    C = {timer_server, {?MODULE, start_link, []}, permanent, 1000,
> 		 worker, [?MODULE]},
> 	    supervisor:start_child(kernel_safe_sup, C),  % kernel_safe_sup
> 	    ok;
> 	_ -> ok
>     end.
> 
> %% server calls
> 
> req(Req, Arg) ->
>     SysTime = now(),
>     ensure_started(),
>     gen_server:call(timer_server, {Req, Arg, SysTime}, infinity).
> 
> %%
> %% handle_call(Request, From, Timers) ->
> %%  {reply, Response, Timers, Timeout}
> %%
> %% Time and Timeout is in milliseconds. WhenStarted is in now() format.
> %% Started is in microseconds.
> %%
> handle_call({apply_after, {Time, Op}, WhenStarted}, _From, _Ts)
>   when is_integer(Time), Time >= 0 ->
>     Started = system_time(WhenStarted),
>     BRef = {Started + 1000*Time, make_ref()},
>     Timer = {BRef, timeout, Op},
>     ets:insert(?TIMER_TAB, Timer),
>     Timeout = timer_timeout(now()),
>     {reply, {ok, BRef}, [], Timeout};
> 
> handle_call({apply_at_local_time, {{H,M,S} = _Time, Op}, WhenStarted}, From, Ts)
>   when is_integer(H), H >= 0, H < 24
>      , is_integer(M), M >= 0, M < 61
>      , is_integer(S), S >= 0, S < 61
> ->
>     {_, {H1,M1,S1}} = calendar:now_to_local_time(WhenStarted),
>     Interval = hms(H-H1, M-M1, S-S1),
>     if Interval < 0 ->
> 	    {reply, {error, expired}, [], next_timeout()};
>     true ->
>         handle_call({apply_after, {Interval, Op}, WhenStarted}, From, Ts)
>     end;
> 
> handle_call({apply_daily_at_local_time, {DaysOfWeek, {H,M,S} = Time, To, MFA}, WhenStarted}, _From, _Ts)
>   when is_integer(H), H >= 0, H < 24
>      , is_integer(M), M >= 0, M < 61
>      , is_integer(S), S >= 0, S < 61
>      , is_list(DaysOfWeek)
> ->
>     try
>         DaysOfWeek =:= [] andalso throw(badarg),
>         %% Represent days of week
>         %% as a 7-element tuple with 1's being the days of week
>         %% when to fire the timer and 0's when not to fire.
>         DOWs = lists:foldl(fun(I, T) -> setelement(I, T, 1) end,
>                     erlang:make_tuple(7, 0), [to_dow(D) || D <- DaysOfWeek]),
>         {Date, Started} = calendar:now_to_local_time(WhenStarted),
>         DOW = calendar:day_of_the_week(Date),
>         Interval = dow_interval(DOWs, DOW, Time, Started, 0),
>         %% To must be a pid or a registered name
>         Pid = get_pid(To),
>         is_pid(Pid) orelse throw(badarg),
>         catch link(Pid),
>         Ref      = make_ref(),
>         BRef1    = {interval, Ref},
>         BRef2    = {system_time(WhenStarted) + Interval*1000000, Ref},
>         Timer    = {BRef2, {daily_local_time, DOWs, Time, Pid}, MFA},
>         ets:insert(?INTERVAL_TAB,{BRef1,BRef2,Pid}),
>         ets:insert(?TIMER_TAB, Timer),
>         Timeout  = timer_timeout(now()),
>         {reply, {ok, BRef1}, [], Timeout}
>     catch throw:Reason ->
> 	    {reply, {error, Reason}, [], next_timeout()}
>     end;
> 
> handle_call({apply_interval, {Time, To, MFA}, WhenStarted}, _From, _Ts)
>   when is_integer(Time), Time >= 0 ->
>     Started = system_time(WhenStarted),
>     %% To must be a pid or a registered name
>     case get_pid(To) of
> 	Pid when is_pid(Pid) ->
> 	    catch link(Pid),
> 	    NowSysTime = now(),
> 	    Ref = make_ref(),
> 	    BRef1 = {interval, Ref},
> 	    Interval = Time*1000,
> 	    BRef2 = {Started + Interval, Ref},
> 	    Timer = {BRef2, {repeat, Interval, Pid}, MFA},
> 	    ets:insert(?INTERVAL_TAB,{BRef1,BRef2,Pid}),
> 	    ets:insert(?TIMER_TAB, Timer),
> 	    Timeout = timer_timeout(NowSysTime),
> 	    {reply, {ok, BRef1}, [], Timeout};
> 	_ ->
> 	    {reply, {error, badarg}, [], next_timeout()}
>     end;
> 
> handle_call({cancel, BRef = {_Time, Ref}, _}, _From, Ts)
>                                            when is_reference(Ref) ->
>     delete_ref(BRef),
>     {reply, {ok, cancel}, Ts, next_timeout()};
> handle_call({cancel, _BRef, _}, _From, Ts) ->
>     {reply, {error, badarg}, Ts, next_timeout()};
> handle_call({apply_after, _, _}, _From, Ts) ->
>     {reply, {error, badarg}, Ts, next_timeout()};
> handle_call({apply_at_local_time, {_, _Op}, _}, _From, Ts) ->
>     {reply, {error, badarg}, Ts, next_timeout()};
> handle_call({apply_interval, _, _}, _From, Ts) ->
>     {reply, {error, badarg}, Ts, next_timeout()};
> handle_call(_Else, _From, Ts) ->			% Catch anything else
>     {noreply, Ts, next_timeout()}.
> 
> handle_info(timeout, Ts) ->                     % Handle timeouts
>     Timeout = timer_timeout(now()),
>     {noreply, Ts, Timeout};
> handle_info({'EXIT',  Pid, _Reason}, Ts) ->      % Oops, someone died
>     pid_delete(Pid),
>     {noreply, Ts, next_timeout()};
> handle_info(_OtherMsg, Ts) ->                         % Other Msg's
>     {noreply, Ts, next_timeout()}.
> 
> handle_cast(_Req, Ts) ->                         % Not predicted but handled
>     {noreply, Ts, next_timeout()}.
> 
> terminate(_Reason, _State) ->
>     ok.
> 
> code_change(_OldVsn, State, _Extra) ->
>     %% According to the man for gen server no timer can be set here.
>     {ok, State}.
> 
> %%
> %% timer_timeout(NowSysTime)
> %%
> %% Apply and remove already timed-out timers. A timer is a tuple
> %% {Time, BRef, Op, MFA}, where Time is in microseconds.
> %% Returns {Timeout, Timers}, where Timeout is in milliseconds.
> %%
> timer_timeout(NowSysTime) ->
>     SysTime = system_time(NowSysTime),
>     case ets:first(?TIMER_TAB) of
> 	'$end_of_table' ->
> 	    infinity;
> 	{Time, _Ref} when Time > SysTime ->
> 	    Timeout = (Time - SysTime) div 1000,
> 	    %% Returned timeout must fit in a small int
> 	    min(Timeout, ?MAX_TIMEOUT);
> 	Key ->
> 	    case ets:lookup(?TIMER_TAB, Key) of
> 		[{Key, timeout, MFA}] ->
> 		    ets:delete(?TIMER_TAB,Key),
> 		    do_apply(MFA),
> 		    timer_timeout(NowSysTime);
> 		[{{Time, Ref}, Repeat = {repeat, Interv, To}, MFA}] ->
> 		    ets:delete(?TIMER_TAB,Key),
> 		    NewTime = Time + Interv,
> 		    %% Update the interval entry (last in table)
> 		    ets:insert(?INTERVAL_TAB,{{interval,Ref},{NewTime,Ref},To}),
> 		    do_apply(MFA),
> 		    ets:insert(?TIMER_TAB, {{NewTime, Ref}, Repeat, MFA}),
> 		    timer_timeout(NowSysTime);
>         [{{_Time, Ref}, Repeat = {daily_local_time, DOWs, TimeOfDay, Pid}, MFA}] ->
> 		    ets:delete(?TIMER_TAB,Key),
>             {Date, CurTime} = calendar:now_to_local_time(add_second(NowSysTime)),
>             DOW = calendar:day_of_the_week(Date),
>             Interval = dow_interval(DOWs, DOW, TimeOfDay, CurTime, 0),
>             NewTime  = system_time(NowSysTime) + Interval*1000000,
> 		    %% Update the interval entry (last in table)
> 		    ets:insert(?INTERVAL_TAB,{{interval,Ref},{NewTime,Ref},Pid}),
> 		    do_apply(MFA),
> 		    ets:insert(?TIMER_TAB, {{NewTime, Ref}, Repeat, MFA}),
> 		    timer_timeout(NowSysTime)
> 	    end
>     end.
> 
> %%
> %% delete_ref
> %%
> 
> delete_ref(BRef = {interval, _}) ->
>     case ets:lookup(?INTERVAL_TAB, BRef) of
> 	[{_, BRef2, _Pid}] ->
> 	    ets:delete(?INTERVAL_TAB, BRef),
> 	    ets:delete(?TIMER_TAB, BRef2);
> 	_ -> % TimerReference does not exist, do nothing
> 	    ok
>     end;
> delete_ref(BRef) ->
>     ets:delete(?TIMER_TAB,BRef).
> 
> %%
> %% pid_delete
> %%
> 
> pid_delete(Pid) ->
>     IntervalTimerList =
> 	ets:select(?INTERVAL_TAB,
> 		   [{{'_', '_','$1'},
> 		     [{'==','$1',Pid}],
> 		     ['$_']}]),
>     lists:foreach(fun({IntKey, TimerKey, _ }) ->
> 			  ets:delete(?INTERVAL_TAB,IntKey),
> 			  ets:delete(?TIMER_TAB,TimerKey)
> 		  end, IntervalTimerList).
> 
> %% Calculate time to the next timeout. Returned timeout must fit in a
> %% small int.
> 
> next_timeout() ->
>     case ets:first(?TIMER_TAB) of
> 	'$end_of_table' ->
> 	    infinity;
> 	{Time, _ } ->
> 	    min(positive((Time - system_time()) div 1000), ?MAX_TIMEOUT)
>     end.
> 
> %% Help functions
> do_apply({M,F,A}) ->
>     case {M, F, A} of
> 	{?MODULE, send, A} ->
> 	    %% If send op. send directly, (faster than spawn)
> 	    catch send(A);
> 	{erlang, exit, [Name, Reason]} ->
> 	    catch exit(get_pid(Name), Reason);
> 	_ ->
> 	    %% else spawn process with the operation
> 	    catch spawn(M,F,A)
>     end.
> 
> max(X, Y) when X > Y ->
>     X;
> max(_X, Y) ->
>     Y.
> 
> min(X, Y) when X < Y ->
>     X;
> min(_X, Y) ->
>     Y.
> 
> positive(X) ->
>     max(X, 0).
> 
> to_dow(mon) -> 1;
> to_dow(tue) -> 2;
> to_dow(wed) -> 3;
> to_dow(thu) -> 4;
> to_dow(fri) -> 5;
> to_dow(sat) -> 6;
> to_dow(sun) -> 7;
> to_dow(I) when is_integer(I), I >= 1, I =< 7 -> I;
> to_dow(_)   -> throw(badarg).
> 
> seconds_diff({H2,M2,S2}, {H1,M1,S1}) ->
>     (H2-H1)*3600 + (M2-M1)*60 + (S2-S1).
> 
> add_second({M,S,U}) when S < 1000000 ->
>     {M,S+1,U};
> add_second({M,_,U}) ->
>     {M+1,0,U}.
> 
> dow_interval(DOWs, Dow, Time, NowTime, 0) when element(Dow, DOWs) =:= 1 ->
>     case seconds_diff(Time, NowTime) of
>     TodayInterval when TodayInterval >= 0 ->
>         TodayInterval;
>     _ ->
>         % Current time passed target time for today.
>         % Find interval from NowTime to future Time.
>         dow_interval(DOWs, Dow, Time, NowTime, 1)
>     end;
> dow_interval(DOWs, Dow, Time, NowTime, _) ->
>     % Current time is in another DayOfWeek.
>     % Find interval from NowTime to future Time.
>     NextDays = get_days(DOWs, (Dow rem 7) + 1, 0),
>     seconds_diff({24,0,0}, NowTime)     % Seconds from now until end-of-day
>     + NextDays*86400                    % Seconds in days until given day of week
>     + seconds_diff(Time, {0,0,0}).      % Seconds from beginning of day to Time
> 
> get_days(DOWs, Dow, N) when element(Dow, DOWs) =:= 1 ->
>     N;
> get_days(DOWs, Dow, N) when N < 8 ->
>     get_days(DOWs, (Dow rem 7) + 1, N+1);
> get_days(_, _, _) ->
>     throw(badarg).
> 
> %%
> %%  system_time() -> time in microseconds
> %%
> system_time() ->
>     Now = erlang:now(),
>     system_time(Now).
> system_time(Now) ->
>     {M,S,U} = Now,
>     1000000*(M*1000000 + S) + U.
> 
> send([Pid, Msg]) ->
>     Pid ! Msg.
> 
> get_pid(Name) when is_pid(Name) ->
>     Name;
> get_pid(undefined) ->
>     undefined;
> get_pid(Name) when is_atom(Name) ->
>     get_pid(whereis(Name));
> get_pid(_) ->
>     undefined.
> 
> %%
> %% get_status() ->
> %%    {{TimerTabName,TotalNumTimers},{IntervalTabName,NumIntervalTimers}}
> %%
> %% This function is for test purposes only; it is used by the test suite.
> %% There is a small possibility that there is a mismatch of one entry
> %% between the 2 tables if this call is made when the timer server is
> %% in the middle of a transaction
> 
> get_status() ->
>     Info1 = ets:info(?TIMER_TAB),
>     {value,{size,TotalNumTimers}} = lists:keysearch(size, 1, Info1),
>     Info2 = ets:info(?INTERVAL_TAB),
>     {value,{size,NumIntervalTimers}} = lists:keysearch(size, 1, Info2),
>     {{?TIMER_TAB,TotalNumTimers},{?INTERVAL_TAB,NumIntervalTimers}}.

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> 
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-- 
Michael McDaniel
Portland, Oregon, USA
http://trip.autosys.us
http://autosys.us




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