merge default into bug23559

1 files changed, 90 insertions, 153 deletions

diff --git a/src/delegate.erl b/src/delegate.erl
index 11abe73b0d..17046201ad 100644
--- a/src/delegate.erl
+++ b/src/delegate.erl
@@ -1,41 +1,24 @@
-%%   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/
+%% 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.
+%% 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 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): ______________________________________.
+%% The Initial Developer of the Original Code is VMware, Inc.
+%% Copyright (c) 2007-2011 VMware, Inc.  All rights reserved.
 %%
 
 -module(delegate).
 
--define(DELEGATE_PROCESS_COUNT_MULTIPLIER, 2).
-
 -behaviour(gen_server2).
 
--export([start_link/2, invoke_no_result/2, invoke/2, process_count/0]).
+-export([start_link/1, invoke_no_result/2, invoke/2]).
 
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
          terminate/2, code_change/3]).
@@ -44,13 +27,14 @@
 
 -ifdef(use_specs).
 
--spec(start_link/2 ::
-        (atom(), non_neg_integer()) -> {'ok', pid()} | {'error', any()}).
+-spec(start_link/1 ::
+        (non_neg_integer()) -> {'ok', pid()} | {'error', any()}).
 -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()).
+-spec(invoke/2 ::
+        ( pid(),  fun ((pid()) -> A)) -> A;
+        ([pid()], fun ((pid()) -> A)) -> {[{pid(), A}],
+                                          [{pid(), term()}]}).
 
 -endif.
 
@@ -61,157 +45,110 @@
 
 %%----------------------------------------------------------------------------
 
-start_link(Prefix, Hash) ->
-    gen_server2:start_link({local, server(Prefix, Hash)}, ?MODULE, [], []).
+start_link(Num) ->
+    gen_server2:start_link({local, delegate_name(Num)}, ?MODULE, [], []).
 
+invoke(Pid, Fun) when is_pid(Pid) andalso node(Pid) =:= node() ->
+    Fun(Pid);
 invoke(Pid, Fun) when is_pid(Pid) ->
-    [Res] = invoke_per_node(split_delegate_per_node([Pid]), Fun),
-    case Res of
-        {ok, Result, _} ->
+    case invoke([Pid], Fun) of
+        {[{Pid, Result}], []} ->
             Result;
-        {error, {Class, Reason, StackTrace}, _} ->
+        {[], [{Pid, {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
+    {LocalPids, Grouped} = group_pids_by_node(Pids),
+    %% The use of multi_call is only safe because the timeout is
+    %% infinity, and thus there is no process spawned in order to do
+    %% the sending. Thus calls can't overtake preceding calls/casts.
+    {Replies, BadNodes} =
+        case orddict:fetch_keys(Grouped) of
+            []          -> {[], []};
+            RemoteNodes -> gen_server2:multi_call(
+                             RemoteNodes, delegate(RemoteNodes),
+                             {invoke, Fun, Grouped}, infinity)
         end,
-        {[], []},
-        invoke_per_node(split_delegate_per_node(Pids), Fun)).
+    BadPids = [{Pid, {exit, {nodedown, BadNode}, []}} ||
+                  BadNode <- BadNodes,
+                  Pid     <- orddict:fetch(BadNode, Grouped)],
+    ResultsNoNode = lists:append([safe_invoke(LocalPids, Fun) |
+                                  [Results || {_Node, Results} <- Replies]]),
+    lists:foldl(
+      fun ({ok,    Pid, Result}, {Good, Bad}) -> {[{Pid, Result} | Good], Bad};
+          ({error, Pid, Error},  {Good, Bad}) -> {Good, [{Pid, Error} | Bad]}
+      end, {[], BadPids}, ResultsNoNode).
 
-invoke_no_result(Pid, Fun) when is_pid(Pid) ->
-    invoke_no_result_per_node(split_delegate_per_node([Pid]), Fun),
+invoke_no_result(Pid, Fun) when is_pid(Pid) andalso node(Pid) =:= node() ->
+    safe_invoke(Pid, Fun), %% we don't care about any error
     ok;
+invoke_no_result(Pid, Fun) when is_pid(Pid) ->
+    invoke_no_result([Pid], Fun);
 
 invoke_no_result(Pids, Fun) when is_list(Pids) ->
-    invoke_no_result_per_node(split_delegate_per_node(Pids),  Fun),
+    {LocalPids, Grouped} = group_pids_by_node(Pids),
+    case orddict:fetch_keys(Grouped) of
+        []          -> ok;
+        RemoteNodes -> gen_server2:abcast(RemoteNodes, delegate(RemoteNodes),
+                                          {invoke, Fun, Grouped})
+    end,
+    safe_invoke(LocalPids, Fun), %% must not die
     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) ->
+group_pids_by_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(outgoing,
-                          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(incoming, 1);
-                Count ->
-                    Name = server(incoming,
-                                  erlang:phash2({self(), Node}, Count)),
-                    put({delegate_remote_server_name, Node}, Name),
-                    Name
-            end;
-        Name -> Name
+    lists:foldl(
+      fun (Pid, {Local, Remote}) when node(Pid) =:= LocalNode ->
+              {[Pid | Local], Remote};
+          (Pid, {Local, Remote}) ->
+              {Local,
+               orddict:update(
+                 node(Pid), fun (List) -> [Pid | List] end, [Pid], Remote)}
+      end, {[], orddict:new()}, Pids).
+
+delegate_name(Hash) ->
+    list_to_atom("delegate_" ++ integer_to_list(Hash)).
+
+delegate(RemoteNodes) ->
+    case get(delegate) of
+        undefined -> Name = delegate_name(
+                              erlang:phash2(self(),
+                                            delegate_sup:count(RemoteNodes))),
+                     put(delegate, Name),
+                     Name;
+        Name      -> Name
     end.
 
-server(Prefix, Hash) ->
-    list_to_atom("delegate_" ++
-                     atom_to_list(Prefix) ++ "_" ++
-                     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}
+        {ok, Pid, Fun(Pid)}
+    catch Class:Reason ->
+            {error, Pid, {Class, Reason, erlang:get_stacktrace()}}
     end.
 
-process_count() ->
-    ?DELEGATE_PROCESS_COUNT_MULTIPLIER * erlang:system_info(schedulers).
-
-%%--------------------------------------------------------------------
+%%----------------------------------------------------------------------------
 
 init([]) ->
-    {ok, no_state, hibernate,
+    {ok, node(), 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_call({invoke, Fun, Grouped}, _From, Node) ->
+    {reply, safe_invoke(orddict:fetch(Node, Grouped), Fun), Node, hibernate}.
 
-handle_cast({thunk, Thunk}, State) ->
-    Thunk(),
-    {noreply, State, hibernate}.
+handle_cast({invoke, Fun, Grouped}, Node) ->
+    safe_invoke(orddict:fetch(Node, Grouped), Fun),
+    {noreply, Node, hibernate}.
 
-handle_info(_Info, State) ->
-    {noreply, State, hibernate}.
+handle_info(_Info, Node) ->
+    {noreply, Node, hibernate}.
 
 terminate(_Reason, _State) ->
     ok.
 
-code_change(_OldVsn, State, _Extra) ->
-    {ok, State}.
-
-%%--------------------------------------------------------------------
+code_change(_OldVsn, Node, _Extra) ->
+    {ok, Node}.