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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 Developers of the Original Code are LShift Ltd,
%% Cohesive Financial Technologies LLC, and Rabbit Technologies Ltd.
%%
%% Portions created before 22-Nov-2008 00:00:00 GMT by LShift Ltd,
%% Cohesive Financial Technologies LLC, or Rabbit Technologies Ltd
%% are Copyright (C) 2007-2008 LShift Ltd, Cohesive Financial
%% Technologies LLC, and Rabbit Technologies Ltd.
%%
%% Portions created by LShift Ltd are Copyright (C) 2007-2010 LShift
%% Ltd. Portions created by Cohesive Financial Technologies LLC are
%% Copyright (C) 2007-2010 Cohesive Financial Technologies
%% LLC. Portions created by Rabbit Technologies Ltd are Copyright
%% (C) 2007-2010 Rabbit Technologies Ltd.
%%
%% All Rights Reserved.
%%
%% Contributor(s): ______________________________________.
%%
-module(delegate).
-define(DELEGATE_PROCESS_COUNT_MULTIPLIER, 2).
-behaviour(gen_server2).
-export([start_link/1, invoke_no_result/2, invoke/2, process_count/0]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
terminate/2, code_change/3]).
%%----------------------------------------------------------------------------
-ifdef(use_specs).
-spec(start_link/1 :: (non_neg_integer()) -> {'ok', pid()}).
-spec(invoke_no_result/2 :: (pid() | [pid()], fun ((pid()) -> any())) -> 'ok').
-spec(invoke/2 :: (pid() | [pid()], fun ((pid()) -> A)) -> A).
-spec(process_count/0 :: () -> non_neg_integer()).
-endif.
%%----------------------------------------------------------------------------
-define(HIBERNATE_AFTER_MIN, 1000).
-define(DESIRED_HIBERNATE, 10000).
%%----------------------------------------------------------------------------
start_link(Hash) ->
gen_server2:start_link({local, server(Hash)}, ?MODULE, [], []).
invoke(Pid, Fun) when is_pid(Pid) ->
[Res] = invoke_per_node(split_delegate_per_node([Pid]), Fun),
case Res of
{ok, Result, _} ->
Result;
{error, {Class, Reason, StackTrace}, _} ->
erlang:raise(Class, Reason, StackTrace)
end;
invoke(Pids, Fun) when is_list(Pids) ->
lists:foldl(
fun ({Status, Result, Pid}, {Good, Bad}) ->
case Status of
ok -> {[{Pid, Result}|Good], Bad};
error -> {Good, [{Pid, Result}|Bad]}
end
end,
{[], []},
invoke_per_node(split_delegate_per_node(Pids), Fun)).
invoke_no_result(Pid, Fun) when is_pid(Pid) ->
invoke_no_result_per_node(split_delegate_per_node([Pid]), Fun),
ok;
invoke_no_result(Pids, Fun) when is_list(Pids) ->
invoke_no_result_per_node(split_delegate_per_node(Pids), Fun),
ok.
%%----------------------------------------------------------------------------
internal_call(Node, Thunk) when is_atom(Node) ->
gen_server2:call({remote_server(Node), Node}, {thunk, Thunk}, infinity).
internal_cast(Node, Thunk) when is_atom(Node) ->
gen_server2:cast({remote_server(Node), Node}, {thunk, Thunk}).
split_delegate_per_node(Pids) ->
LocalNode = node(),
{Local, Remote} =
lists:foldl(
fun (Pid, {L, D}) ->
Node = node(Pid),
case Node of
LocalNode -> {[Pid|L], D};
_ -> {L, orddict:append(Node, Pid, D)}
end
end,
{[], orddict:new()}, Pids),
{Local, orddict:to_list(Remote)}.
invoke_per_node(NodePids, Fun) ->
lists:append(delegate_per_node(NodePids, Fun, fun internal_call/2)).
invoke_no_result_per_node(NodePids, Fun) ->
delegate_per_node(NodePids, Fun, fun internal_cast/2),
ok.
delegate_per_node({LocalPids, NodePids}, Fun, DelegateFun) ->
%% In the case where DelegateFun is internal_cast, the safe_invoke
%% is not actually async! However, in practice Fun will always be
%% something that does a gen_server:cast or similar, so I don't
%% think it's a problem unless someone misuses this
%% function. Making this *actually* async would be painful as we
%% can't spawn at this point or we break effect ordering.
[safe_invoke(LocalPids, Fun)|
delegate_per_remote_node(NodePids, Fun, DelegateFun)].
delegate_per_remote_node(NodePids, Fun, DelegateFun) ->
Self = self(),
%% Note that this is unsafe if the Fun requires reentrancy to the
%% local_server. I.e. if self() == local_server(Node) then we'll
%% block forever.
[gen_server2:cast(
local_server(Node),
{thunk, fun () ->
Self ! {result,
DelegateFun(
Node, fun () -> safe_invoke(Pids, Fun) end)}
end}) || {Node, Pids} <- NodePids],
[receive {result, Result} -> Result end || _ <- NodePids].
local_server(Node) ->
case get({delegate_local_server_name, Node}) of
undefined ->
Name = server(erlang:phash2({self(), Node}, process_count())),
put({delegate_local_server_name, Node}, Name),
Name;
Name -> Name
end.
remote_server(Node) ->
case get({delegate_remote_server_name, Node}) of
undefined ->
case rpc:call(Node, delegate, process_count, []) of
{badrpc, _} ->
%% Have to return something, if we're just casting
%% then we don't want to blow up
server(1);
Count ->
Name = server(erlang:phash2({self(), Node}, Count)),
put({delegate_remote_server_name, Node}, Name),
Name
end;
Name -> Name
end.
server(Hash) ->
list_to_atom("delegate_process_" ++ integer_to_list(Hash)).
safe_invoke(Pids, Fun) when is_list(Pids) ->
[safe_invoke(Pid, Fun) || Pid <- Pids];
safe_invoke(Pid, Fun) when is_pid(Pid) ->
try
{ok, Fun(Pid), Pid}
catch
Class:Reason ->
{error, {Class, Reason, erlang:get_stacktrace()}, Pid}
end.
process_count() ->
?DELEGATE_PROCESS_COUNT_MULTIPLIER * erlang:system_info(schedulers).
%%--------------------------------------------------------------------
init([]) ->
{ok, no_state, hibernate,
{backoff, ?HIBERNATE_AFTER_MIN, ?HIBERNATE_AFTER_MIN, ?DESIRED_HIBERNATE}}.
%% We don't need a catch here; we always go via safe_invoke. A catch here would
%% be the wrong thing anyway since the Thunk can throw multiple errors.
handle_call({thunk, Thunk}, _From, State) ->
{reply, Thunk(), State, hibernate}.
handle_cast({thunk, Thunk}, State) ->
Thunk(),
{noreply, State, hibernate}.
handle_info(_Info, State) ->
{noreply, State}.
terminate(_Reason, _State) ->
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
%%--------------------------------------------------------------------
|
