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%% The contents of this file are subject to the Mozilla Public License
%% Version 1.1 (the "License"); you may not use this file except in
%% compliance with the License. You may obtain a copy of the License
%% at http://www.mozilla.org/MPL/
%%
%% 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 Original Code is RabbitMQ.
%%
%% The Initial Developer of the Original Code is GoPivotal, Inc.
%% Copyright (c) 2007-2014 GoPivotal, Inc. All rights reserved.
%%
-module(worker_pool).
%% Generic worker pool manager.
%%
%% Supports nested submission of jobs (nested jobs always run
%% immediately in current worker process).
%%
%% Possible future enhancements:
%%
%% 1. Allow priorities (basically, change the pending queue to a
%% priority_queue).
-behaviour(gen_server2).
-export([start_link/0, submit/1, submit_async/1, idle/1]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
terminate/2, code_change/3]).
%%----------------------------------------------------------------------------
-ifdef(use_specs).
-type(mfargs() :: {atom(), atom(), [any()]}).
-spec(start_link/0 :: () -> {'ok', pid()} | {'error', any()}).
-spec(submit/1 :: (fun (() -> A) | mfargs()) -> A).
-spec(submit_async/1 :: (fun (() -> any()) | mfargs()) -> 'ok').
-spec(idle/1 :: (pid()) -> 'ok').
-endif.
%%----------------------------------------------------------------------------
-define(SERVER, ?MODULE).
-define(HIBERNATE_AFTER_MIN, 1000).
-define(DESIRED_HIBERNATE, 10000).
-record(state, { available, pending }).
%%----------------------------------------------------------------------------
start_link() -> gen_server2:start_link({local, ?SERVER}, ?MODULE, [],
[{timeout, infinity}]).
submit(Fun) ->
case get(worker_pool_worker) of
true -> worker_pool_worker:run(Fun);
_ -> Pid = gen_server2:call(?SERVER, {next_free, self()}, infinity),
worker_pool_worker:submit(Pid, Fun)
end.
submit_async(Fun) -> gen_server2:cast(?SERVER, {run_async, Fun}).
idle(WPid) -> gen_server2:cast(?SERVER, {idle, WPid}).
%%----------------------------------------------------------------------------
init([]) ->
{ok, #state { pending = queue:new(), available = ordsets:new() }, hibernate,
{backoff, ?HIBERNATE_AFTER_MIN, ?HIBERNATE_AFTER_MIN, ?DESIRED_HIBERNATE}}.
handle_call({next_free, CPid}, From, State = #state { available = [],
pending = Pending }) ->
{noreply, State#state{pending = queue:in({next_free, From, CPid}, Pending)},
hibernate};
handle_call({next_free, CPid}, _From, State = #state { available =
[WPid | Avail1] }) ->
worker_pool_worker:next_job_from(WPid, CPid),
{reply, WPid, State #state { available = Avail1 }, hibernate};
handle_call(Msg, _From, State) ->
{stop, {unexpected_call, Msg}, State}.
handle_cast({idle, WPid}, State = #state { available = Avail,
pending = Pending }) ->
{noreply,
case queue:out(Pending) of
{empty, _Pending} ->
State #state { available = ordsets:add_element(WPid, Avail) };
{{value, {next_free, From, CPid}}, Pending1} ->
worker_pool_worker:next_job_from(WPid, CPid),
gen_server2:reply(From, WPid),
State #state { pending = Pending1 };
{{value, {run_async, Fun}}, Pending1} ->
worker_pool_worker:submit_async(WPid, Fun),
State #state { pending = Pending1 }
end, hibernate};
handle_cast({run_async, Fun}, State = #state { available = [],
pending = Pending }) ->
{noreply, State #state { pending = queue:in({run_async, Fun}, Pending)},
hibernate};
handle_cast({run_async, Fun}, State = #state { available = [WPid | Avail1] }) ->
worker_pool_worker:submit_async(WPid, Fun),
{noreply, State #state { available = Avail1 }, hibernate};
handle_cast(Msg, State) ->
{stop, {unexpected_cast, Msg}, State}.
handle_info(Msg, State) ->
{stop, {unexpected_info, Msg}, State}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
terminate(_Reason, State) ->
State.
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