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%% Copyright (c) 2017, Loïc Hoguin <[email protected]>
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-module(cowboy_children).
-export([init/0]).
-export([up/4]).
-export([down/2]).
-export([shutdown/2]).
-export([shutdown_timeout/3]).
-export([terminate/1]).
-export([which_children/2]).
-export([count_children/1]).
-record(child, {
pid :: pid(),
streamid :: cowboy_stream:streamid() | undefined,
shutdown :: timeout(),
timer = undefined :: undefined | reference()
}).
-type children() :: [#child{}].
-export_type([children/0]).
-spec init() -> [].
init() ->
[].
-spec up(Children, pid(), cowboy_stream:streamid(), timeout())
-> Children when Children::children().
up(Children, Pid, StreamID, Shutdown) ->
[#child{
pid=Pid,
streamid=StreamID,
shutdown=Shutdown
}|Children].
-spec down(Children, pid())
-> {ok, cowboy_stream:streamid() | undefined, Children} | error
when Children::children().
down(Children0, Pid) ->
case lists:keytake(Pid, #child.pid, Children0) of
{value, #child{streamid=StreamID, timer=Ref}, Children} ->
_ = case Ref of
undefined -> ok;
_ -> erlang:cancel_timer(Ref, [{async, true}, {info, false}])
end,
{ok, StreamID, Children};
false ->
error
end.
%% We ask the processes to shutdown first. This gives
%% a chance to processes that are trapping exits to
%% shut down gracefully. Others will exit immediately.
%%
%% @todo We currently fire one timer per process being
%% shut down. This is probably not the most efficient.
%% A more efficient solution could be to maintain a
%% single timer and decrease the shutdown time of all
%% processes when it fires. This is however much more
%% complex, and there aren't that many processes that
%% will need to be shutdown through this function, so
%% this is left for later.
-spec shutdown(Children, cowboy_stream:streamid())
-> Children when Children::children().
shutdown(Children0, StreamID) ->
[
case Child of
#child{pid=Pid, streamid=StreamID, shutdown=Shutdown} ->
exit(Pid, shutdown),
Ref = erlang:start_timer(Shutdown, self(), {shutdown, Pid}),
Child#child{streamid=undefined, timer=Ref};
_ ->
Child
end
|| Child <- Children0].
-spec shutdown_timeout(children(), reference(), pid()) -> ok.
shutdown_timeout(Children, Ref, Pid) ->
case lists:keyfind(Pid, #child.pid, Children) of
#child{timer=Ref} ->
exit(Pid, kill),
ok;
_ ->
ok
end.
-spec terminate(children()) -> ok.
terminate(Children) ->
%% For each child, either ask for it to shut down,
%% or cancel its shutdown timer if it already is.
%%
%% We do not need to flush stray timeout messages out because
%% we are either terminating or switching protocols,
%% and in the latter case we flush all messages.
_ = [case TRef of
undefined -> exit(Pid, shutdown);
_ -> erlang:cancel_timer(TRef, [{async, true}, {info, false}])
end || #child{pid=Pid, timer=TRef} <- Children],
before_terminate_loop(Children).
before_terminate_loop([]) ->
ok;
before_terminate_loop(Children) ->
%% Find the longest shutdown time.
Time = longest_shutdown_time(Children, 0),
%% We delay the creation of the timer if one of the
%% processes has an infinity shutdown value.
TRef = case Time of
infinity -> undefined;
_ -> erlang:start_timer(Time, self(), terminate)
end,
%% Loop until that time or until all children are dead.
terminate_loop(Children, TRef).
terminate_loop([], TRef) ->
%% Don't forget to cancel the timer, if any!
case TRef of
undefined ->
ok;
_ ->
_ = erlang:cancel_timer(TRef, [{async, true}, {info, false}]),
ok
end;
terminate_loop(Children, TRef) ->
receive
{'EXIT', Pid, _} when TRef =:= undefined ->
{value, #child{shutdown=Shutdown}, Children1}
= lists:keytake(Pid, #child.pid, Children),
%% We delayed the creation of the timer. If a process with
%% infinity shutdown just ended, we might have to start that timer.
case Shutdown of
infinity -> before_terminate_loop(Children1);
_ -> terminate_loop(Children1, TRef)
end;
{'EXIT', Pid, _} ->
terminate_loop(lists:keydelete(Pid, #child.pid, Children), TRef);
{timeout, TRef, terminate} ->
%% Brutally kill any remaining children.
_ = [exit(Pid, kill) || #child{pid=Pid} <- Children],
ok
end.
longest_shutdown_time([], Time) ->
Time;
longest_shutdown_time([#child{shutdown=ChildTime}|Tail], Time) when ChildTime > Time ->
longest_shutdown_time(Tail, ChildTime);
longest_shutdown_time([_|Tail], Time) ->
longest_shutdown_time(Tail, Time).
-spec which_children(children(), module()) -> [{module(), pid(), worker, [module()]}].
which_children(Children, Module) ->
[{Module, Pid, worker, [Module]} || #child{pid=Pid} <- Children].
-spec count_children(children()) -> [{atom(), non_neg_integer()}].
count_children(Children) ->
Count = length(Children),
[
{specs, 1},
{active, Count},
{supervisors, 0},
{workers, Count}
].
|
