Crude but working implementation

4 files changed, 533 insertions, 51 deletions

diff --git a/src/mirrored_supervisor.erl b/src/mirrored_supervisor.erl
index 91b4bd74d9..b7e11464c0 100644
--- a/src/mirrored_supervisor.erl
+++ b/src/mirrored_supervisor.erl
@@ -16,15 +16,24 @@
 
 -module(mirrored_supervisor).
 
--define(SUPERVISOR, supervisor2).
--define(GEN_SERVER, gen_server2).
--define(TABLE, ?MODULE).
 
 %% TODO documentation
 %% We need a thing like a supervisor, except that it joins something
 %% like a process group, and if a child process dies it can be
 %% restarted under another supervisor (probably on another node).
 
+-define(SUPERVISOR, supervisor2).
+-define(GEN_SERVER, gen_server2).
+-define(ETS_TABLE, ?MODULE).
+-define(ID, ?MODULE).
+
+-define(MNESIA_TABLE_NAME, mirrored_sup_childspec).
+-define(MNESIA_TABLE,
+        {?MNESIA_TABLE_NAME,
+         [{record_name, mirrored_sup_childspec},
+          {attributes, record_info(fields, mirrored_sup_childspec)}]}).
+-define(MNESIA_TABLE_MATCH, {match, #mirrored_sup_childspec{ _ = '_' }}).
+
 -export([start_link/2,start_link/3,
 	 start_child/2, restart_child/2,
 	 delete_child/2, terminate_child/2,
@@ -39,13 +48,15 @@
          handle_cast/2]).
 
 -export([start_internal/2]).
+-export([create_tables/0, table_definitions/0]).
 
--record(state, {}).
+-record(mirrored_sup_childspec, {id, sup_pid, childspec}).
 
-%%----------------------------------------------------------------------------
+-record(state, {name}).
 
--define(ID, ?MODULE).
+%%----------------------------------------------------------------------------
 
+%% TODO this is going to make testing awkward. Maybe we need a local name and a group name?
 start_link(_Mod, _Args) ->
     exit(mirrored_supervisors_must_be_locally_named).
 
@@ -59,49 +70,97 @@ start_link({local, SupName}, Mod, Args) ->
 start_link({_, _SupName}, _Mod, _Args) ->
     exit(mirrored_supervisors_must_be_locally_named).
 
-start_child(Sup, ChildSpec)  -> call(Sup, {start_child,     [Sup, ChildSpec]}).
-restart_child(Sup, Name)     -> call(Sup, {restart_child,   [Sup, Name]}).
-delete_child(Sup, Name)      -> call(Sup, {delete_child,    [Sup, Name]}).
-terminate_child(Sup, Name)   -> call(Sup, {terminate_child, [Sup, Name]}).
-which_children(Sup)          -> call(Sup, {which_children,  [Sup]}).
-find_child(Sup, Name)        -> call(Sup, {find_child,      [Sup, Name]}).
+start_child(Sup, ChildSpec)  -> call(Sup, {start_child,  ChildSpec}).
+delete_child(Sup, Name)      -> call(Sup, {delete_child, Name}).
+restart_child(Sup, Name)     -> call(Sup, {msg, restart_child,   [Sup, Name]}).
+terminate_child(Sup, Name)   -> call(Sup, {msg, terminate_child, [Sup, Name]}).
+which_children(Sup)          -> call(Sup, {msg, which_children,  [Sup]}).
+find_child(Sup, Name)        -> call(Sup, {msg, find_child,      [Sup, Name]}).
 check_childspecs(ChildSpecs) -> ?SUPERVISOR:check_childspecs(ChildSpecs).
 
 behaviour_info(callbacks) -> [{init,1}];
 behaviour_info(_Other)    -> undefined.
 
 call(SupName, Msg) ->
-    [{SupName, Pid}] = ets:lookup(?TABLE, SupName),
-    ?GEN_SERVER:call(Pid, {sup_msg, Msg}, infinity).
+    [{SupName, Pid}] = ets:lookup(?ETS_TABLE, SupName),
+    ?GEN_SERVER:call(Pid, Msg, infinity).
 
 %%----------------------------------------------------------------------------
 
 start_internal(SupName, Args) ->
-    {ok, Pid} = ?GEN_SERVER:start_link(?MODULE, Args, [{timeout, infinity}]),
-    Ins = fun() -> true = ets:insert(?TABLE, {SupName, Pid}) end,
+    {ok, Pid} = ?GEN_SERVER:start_link(?MODULE, {SupName, Args},
+                                       [{timeout, infinity}]),
+    Ins = fun() -> true = ets:insert(?ETS_TABLE, {SupName, Pid}) end,
     try
         Ins()
-    catch error:badarg -> ets:new(?TABLE, [named_table]),
+    catch error:badarg -> ets:new(?ETS_TABLE, [named_table]),
                           Ins()
     end,
     {ok, Pid}.
 
 %%----------------------------------------------------------------------------
 
-init(_Args) ->
-    {ok, #state{}}.
-
-handle_call({sup_msg, {F, A}}, _From, State) ->
+init({SupName, _Args}) ->
+    pg2_fixed:create(SupName),
+    [begin
+         io:format("Announce to ~p~n", [Pid]),
+         gen_server2:call(Pid, {hello, self()}, infinity),
+         erlang:monitor(process, Pid)
+     end
+     || Pid <- pg2_fixed:get_members(SupName)],
+    ok = pg2_fixed:join(SupName, self()),
+    {ok, #state{name = SupName}}.
+
+handle_call({start_child, ChildSpec}, _From, State = #state{name = SupName}) ->
+    {reply, case mnesia:transaction(fun() -> check_start(ChildSpec) end) of
+                {atomic, start}   -> io:format("Start ~p~n", [id(ChildSpec)]),
+                                     apply(?SUPERVISOR,
+                                           start_child, [SupName, ChildSpec]);
+                {atomic, already} -> io:format("Already ~p~n", [id(ChildSpec)]),
+                                           {ok, already}
+            end, State};
+
+handle_call({delete_child, ChildSpec}, _From,
+            State = #state{name = SupName}) ->
+    {atomic, ok} = mnesia:transaction(fun() -> delete(ChildSpec) end),
+    {reply, apply(?SUPERVISOR, delete_child, [SupName, id(ChildSpec)]), State};
+
+handle_call({msg, F, A}, _From, State) ->
     {reply, apply(?SUPERVISOR, F, A), State};
 
-handle_call(Msg, _From, State) ->
-    {reply, {unexpected_call, Msg}, State}.
+handle_call({hello, Pid}, _From, State) ->
+    io:format("Hello from ~p~n", [Pid]),
+    erlang:monitor(process, Pid),
+    {reply, ok, State};
 
-handle_cast(_Msg, State) ->
-    {noreply, State}.
+handle_call(alive, _From, State) ->
+    {reply, true, State};
 
-handle_info(_Info, State) ->
-    {noreply, State}.
+handle_call(Msg, _From, State) ->
+    {stop, {unexpected_call, Msg}, State}.
+
+handle_cast(Msg, State) ->
+    {stop, {unexpected_cast, Msg}, State}.
+
+handle_info({'DOWN', _Ref, process, Pid, _Reason},
+            State = #state{name = SupName}) ->
+    io:format("Pid ~p down!~n", [Pid]),
+    %% TODO load balance this
+    Self = self(),
+    case lists:sort(pg2_fixed:get_members(SupName)) of
+        [Self | _] -> {atomic, ChildSpecs} =
+                          mnesia:transaction(fun() -> restart_all(Pid) end),
+                      [begin
+                           apply(?SUPERVISOR, start_child,
+                                 [SupName, ChildSpec]),
+                           io:format("Restarted ~p~n", [id(ChildSpec)])
+                       end || ChildSpec <- ChildSpecs];
+        _          -> ok
+    end,
+    {noreply, State};
+
+handle_info(Info, State) ->
+    {stop, {unexpected_info, Info}, State}.
 
 terminate(_Reason, _State) ->
     ok.
@@ -109,32 +168,61 @@ terminate(_Reason, _State) ->
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
 
+%%----------------------------------------------------------------------------
 
+check_start(ChildSpec) ->
+    case mnesia:wread({?MNESIA_TABLE_NAME, id(ChildSpec)}) of
+        []  -> write(ChildSpec),
+               start;
+        [S] -> #mirrored_sup_childspec{sup_pid = Pid} = S,
+               case alive(Pid) of
+                   true  -> already; %% TODO return real pid?
+                   false -> delete(ChildSpec),
+                            write(ChildSpec),
+                            start
+               end
+    end.
+
+alive(Pid) ->
+    gen_server:call(Pid, alive, infinity).
+
+write(ChildSpec) ->
+    ok = mnesia:write(#mirrored_sup_childspec{id        = id(ChildSpec),
+                                              sup_pid   = self(),
+                                              childspec = ChildSpec}).
+
+delete(ChildSpec) ->
+    ok = mnesia:delete({?MNESIA_TABLE_NAME, id(ChildSpec)}).
+
+id({Id, _, _, _, _, _}) -> Id.
+
+restart_all(OldPid) ->
+    MatchHead = #mirrored_sup_childspec{sup_pid   = OldPid,
+                                        childspec = '$1',
+                                        _         = '_'},
+    [begin
+         delete(ChildSpec),
+         write(ChildSpec),
+         ChildSpec
+     end || ChildSpec <-
+                mnesia:select(?MNESIA_TABLE_NAME, [{MatchHead, [], ['$1']}])].
 
+%%----------------------------------------------------------------------------
 
-%%-export([create_tables/0, table_definitions/0]).
-
-%% -define(TABLE, {?GROUP_TABLE, [{record_name, gm_group},
-%%                                {attributes, record_info(fields, gm_group)}]}).
-%% -define(TABLE_MATCH, {match, #gm_group { _ = '_' }}).
-
-%% -define(GROUP_TABLE, gm_group).
-
-
-%% create_tables() ->
-%%     create_tables([?TABLE]).
-
-%% create_tables([]) ->
-%%     ok;
-%% create_tables([{Table, Attributes} | Tables]) ->
-%%     case mnesia:create_table(Table, Attributes) of
-%%         {atomic, ok}                          -> create_tables(Tables);
-%%         {aborted, {already_exists, gm_group}} -> create_tables(Tables);
-%%         Err                                   -> Err
-%%     end.
+create_tables() ->
+    create_tables([?MNESIA_TABLE]).
 
-%% table_definitions() ->
-%%     {Name, Attributes} = ?TABLE,
-%%     [{Name, [?TABLE_MATCH | Attributes]}].
+create_tables([]) ->
+    ok;
+create_tables([{Table, Attributes} | Ts]) ->
+    case mnesia:create_table(Table, Attributes) of
+        {atomic, ok}                                    -> create_tables(Ts);
+        {aborted, {already_exists, ?MNESIA_TABLE_NAME}} -> create_tables(Ts);
+        Err                                             -> Err
+    end.
 
+table_definitions() ->
+    {Name, Attributes} = ?MNESIA_TABLE,
+    [{Name, [?MNESIA_TABLE_MATCH | Attributes]}].
 
+%%----------------------------------------------------------------------------
diff --git a/src/pg2_fixed.erl b/src/pg2_fixed.erl
new file mode 100644
index 0000000000..224715eb70
--- /dev/null
+++ b/src/pg2_fixed.erl
@@ -0,0 +1,388 @@
+%% This is the version of pg2 from R14B02, which contains the fix
+%% described at
+%% http://erlang.2086793.n4.nabble.com/pg2-still-busted-in-R13B04-td2230601.html.
+%% The only changes are a search-and-replace to rename the module and
+%% avoid clashes with other versions of pg2.
+
+
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1997-2010. All Rights Reserved.
+%%
+%% 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 online 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.
+%%
+%% %CopyrightEnd%
+%%
+-module(pg2_fixed).
+
+-export([create/1, delete/1, join/2, leave/2]).
+-export([get_members/1, get_local_members/1]).
+-export([get_closest_pid/1, which_groups/0]).
+-export([start/0,start_link/0,init/1,handle_call/3,handle_cast/2,handle_info/2,
+         terminate/2]).
+
+%%% As of R13B03 monitors are used instead of links.
+
+%%%
+%%% Exported functions
+%%%
+
+-spec start_link() -> {'ok', pid()} | {'error', term()}.
+
+start_link() ->
+    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
+-spec start() -> {'ok', pid()} | {'error', term()}.
+
+start() ->
+    ensure_started().
+
+-spec create(term()) -> 'ok'.
+
+create(Name) ->
+    ensure_started(),
+    case ets:member(pg2_fixed_table, {group, Name}) of
+        false ->
+            global:trans({{?MODULE, Name}, self()},
+                         fun() ->
+                                 gen_server:multi_call(?MODULE, {create, Name})
+                         end),
+            ok;
+        true ->
+            ok
+    end.
+
+-type name() :: term().
+
+-spec delete(name()) -> 'ok'.
+
+delete(Name) ->
+    ensure_started(),
+    global:trans({{?MODULE, Name}, self()},
+                 fun() ->
+                         gen_server:multi_call(?MODULE, {delete, Name})
+                 end),
+    ok.
+
+-spec join(name(), pid()) -> 'ok' | {'error', {'no_such_group', term()}}.
+
+join(Name, Pid) when is_pid(Pid) ->
+    ensure_started(),
+    case ets:member(pg2_fixed_table, {group, Name}) of
+        false ->
+            {error, {no_such_group, Name}};
+        true ->
+            global:trans({{?MODULE, Name}, self()},
+                         fun() ->
+                                 gen_server:multi_call(?MODULE,
+                                                       {join, Name, Pid})
+                         end),
+            ok
+    end.
+
+-spec leave(name(), pid()) -> 'ok' | {'error', {'no_such_group', name()}}.
+
+leave(Name, Pid) when is_pid(Pid) ->
+    ensure_started(),
+    case ets:member(pg2_fixed_table, {group, Name}) of
+        false ->
+            {error, {no_such_group, Name}};
+        true ->
+            global:trans({{?MODULE, Name}, self()},
+                         fun() ->
+                                 gen_server:multi_call(?MODULE,
+                                                       {leave, Name, Pid})
+                         end),
+            ok
+    end.
+
+-type get_members_ret() :: [pid()] | {'error', {'no_such_group', name()}}.
+
+-spec get_members(name()) -> get_members_ret().
+   
+get_members(Name) ->
+    ensure_started(),
+    case ets:member(pg2_fixed_table, {group, Name}) of
+        true ->
+            group_members(Name);
+        false ->
+            {error, {no_such_group, Name}}
+    end.
+
+-spec get_local_members(name()) -> get_members_ret().
+
+get_local_members(Name) ->
+    ensure_started(),
+    case ets:member(pg2_fixed_table, {group, Name}) of
+        true ->
+            local_group_members(Name);
+        false ->
+            {error, {no_such_group, Name}}
+    end.
+
+-spec which_groups() -> [name()].
+
+which_groups() ->
+    ensure_started(),
+    all_groups().
+
+-type gcp_error_reason() :: {'no_process', term()} | {'no_such_group', term()}.
+
+-spec get_closest_pid(term()) -> pid() | {'error', gcp_error_reason()}.
+
+get_closest_pid(Name) ->
+    case get_local_members(Name) of
+        [Pid] ->
+            Pid;
+        [] ->
+            {_,_,X} = erlang:now(),
+            case get_members(Name) of
+                [] -> {error, {no_process, Name}};
+                Members ->
+                    lists:nth((X rem length(Members))+1, Members)
+            end;
+        Members when is_list(Members) ->
+            {_,_,X} = erlang:now(),
+            lists:nth((X rem length(Members))+1, Members);
+        Else ->
+            Else
+    end.
+
+%%%
+%%% Callback functions from gen_server
+%%%
+
+-record(state, {}).
+
+-spec init([]) -> {'ok', #state{}}.
+
+init([]) ->
+    Ns = nodes(),
+    net_kernel:monitor_nodes(true),
+    lists:foreach(fun(N) ->
+                          {?MODULE, N} ! {new_pg2_fixed, node()},
+                          self() ! {nodeup, N}
+                  end, Ns),
+    pg2_fixed_table = ets:new(pg2_fixed_table, [ordered_set, protected, named_table]),
+    {ok, #state{}}.
+
+-type call() :: {'create', name()}
+              | {'delete', name()}
+              | {'join', name(), pid()}
+              | {'leave', name(), pid()}.
+
+-spec handle_call(call(), _, #state{}) -> 
+        {'reply', 'ok', #state{}}.
+
+handle_call({create, Name}, _From, S) ->
+    assure_group(Name),
+    {reply, ok, S};
+handle_call({join, Name, Pid}, _From, S) ->
+    ets:member(pg2_fixed_table, {group, Name}) andalso join_group(Name, Pid),
+    {reply, ok, S};
+handle_call({leave, Name, Pid}, _From, S) ->
+    ets:member(pg2_fixed_table, {group, Name}) andalso leave_group(Name, Pid),
+    {reply, ok, S};
+handle_call({delete, Name}, _From, S) ->
+    delete_group(Name),
+    {reply, ok, S};
+handle_call(Request, From, S) ->
+    error_logger:warning_msg("The pg2_fixed server received an unexpected message:\n"
+                             "handle_call(~p, ~p, _)\n", 
+                             [Request, From]),
+    {noreply, S}.
+
+-type all_members() :: [[name(),...]].
+-type cast() :: {'exchange', node(), all_members()}
+              | {'del_member', name(), pid()}.
+
+-spec handle_cast(cast(), #state{}) -> {'noreply', #state{}}.
+
+handle_cast({exchange, _Node, List}, S) ->
+    store(List),
+    {noreply, S};
+handle_cast(_, S) ->
+    %% Ignore {del_member, Name, Pid}.
+    {noreply, S}.
+
+-spec handle_info(tuple(), #state{}) -> {'noreply', #state{}}.
+
+handle_info({'DOWN', MonitorRef, process, _Pid, _Info}, S) ->
+    member_died(MonitorRef),
+    {noreply, S};
+handle_info({nodeup, Node}, S) ->
+    gen_server:cast({?MODULE, Node}, {exchange, node(), all_members()}),
+    {noreply, S};
+handle_info({new_pg2_fixed, Node}, S) ->
+    gen_server:cast({?MODULE, Node}, {exchange, node(), all_members()}),
+    {noreply, S};
+handle_info(_, S) ->
+    {noreply, S}.
+
+-spec terminate(term(), #state{}) -> 'ok'.
+
+terminate(_Reason, _S) ->
+    true = ets:delete(pg2_fixed_table),
+    ok.
+
+%%%
+%%% Local functions
+%%%
+
+%%% One ETS table, pg2_fixed_table, is used for bookkeeping. The type of the
+%%% table is ordered_set, and the fast matching of partially
+%%% instantiated keys is used extensively.
+%%%
+%%% {{group, Name}}
+%%%    Process group Name.
+%%% {{ref, Pid}, RPid, MonitorRef, Counter}
+%%% {{ref, MonitorRef}, Pid}
+%%%    Each process has one monitor. Sometimes a process is spawned to
+%%%    monitor the pid (RPid). Counter is incremented when the Pid joins
+%%%    some group.
+%%% {{member, Name, Pid}, GroupCounter}
+%%% {{local_member, Name, Pid}}
+%%%    Pid is a member of group Name, GroupCounter is incremented when the
+%%%    Pid joins the group Name.
+%%% {{pid, Pid, Name}}
+%%%    Pid is a member of group Name.
+
+store(List) ->
+    _ = [(assure_group(Name)
+          andalso
+          [join_group(Name, P) || P <- Members -- group_members(Name)]) ||
+            [Name, Members] <- List],
+    ok.
+
+assure_group(Name) ->
+    Key = {group, Name},
+    ets:member(pg2_fixed_table, Key) orelse true =:= ets:insert(pg2_fixed_table, {Key}).
+
+delete_group(Name) ->
+    _ = [leave_group(Name, Pid) || Pid <- group_members(Name)],
+    true = ets:delete(pg2_fixed_table, {group, Name}),
+    ok.
+
+member_died(Ref) ->
+    [{{ref, Ref}, Pid}] = ets:lookup(pg2_fixed_table, {ref, Ref}),
+    Names = member_groups(Pid),
+    _ = [leave_group(Name, P) || 
+            Name <- Names,
+            P <- member_in_group(Pid, Name)],
+    %% Kept for backward compatibility with links. Can be removed, eventually.
+    _ = [gen_server:abcast(nodes(), ?MODULE, {del_member, Name, Pid}) ||
+            Name <- Names],
+    ok.
+
+join_group(Name, Pid) ->
+    Ref_Pid = {ref, Pid}, 
+    try _ = ets:update_counter(pg2_fixed_table, Ref_Pid, {4, +1})
+    catch _:_ ->
+            {RPid, Ref} = do_monitor(Pid),
+            true = ets:insert(pg2_fixed_table, {Ref_Pid, RPid, Ref, 1}),
+            true = ets:insert(pg2_fixed_table, {{ref, Ref}, Pid})
+    end,
+    Member_Name_Pid = {member, Name, Pid},
+    try _ = ets:update_counter(pg2_fixed_table, Member_Name_Pid, {2, +1, 1, 1})
+    catch _:_ ->
+            true = ets:insert(pg2_fixed_table, {Member_Name_Pid, 1}),
+            _ = [ets:insert(pg2_fixed_table, {{local_member, Name, Pid}}) ||
+                    node(Pid) =:= node()],
+            true = ets:insert(pg2_fixed_table, {{pid, Pid, Name}})
+    end.
+
+leave_group(Name, Pid) ->
+    Member_Name_Pid = {member, Name, Pid},
+    try ets:update_counter(pg2_fixed_table, Member_Name_Pid, {2, -1, 0, 0}) of
+        N ->
+            if 
+                N =:= 0 ->
+                    true = ets:delete(pg2_fixed_table, {pid, Pid, Name}),
+                    _ = [ets:delete(pg2_fixed_table, {local_member, Name, Pid}) ||
+                            node(Pid) =:= node()],
+                    true = ets:delete(pg2_fixed_table, Member_Name_Pid);
+                true ->
+                    ok
+            end,
+            Ref_Pid = {ref, Pid}, 
+            case ets:update_counter(pg2_fixed_table, Ref_Pid, {4, -1}) of
+                0 ->
+                    [{Ref_Pid,RPid,Ref,0}] = ets:lookup(pg2_fixed_table, Ref_Pid),
+                    true = ets:delete(pg2_fixed_table, {ref, Ref}),
+                    true = ets:delete(pg2_fixed_table, Ref_Pid),
+                    true = erlang:demonitor(Ref, [flush]),
+                    kill_monitor_proc(RPid, Pid);
+                _ ->
+                    ok
+            end
+    catch _:_ ->
+            ok
+    end.
+
+all_members() ->
+    [[G, group_members(G)] || G <- all_groups()].
+
+group_members(Name) ->
+    [P || 
+        [P, N] <- ets:match(pg2_fixed_table, {{member, Name, '$1'},'$2'}),
+        _ <- lists:seq(1, N)].
+
+local_group_members(Name) ->
+    [P || 
+        [Pid] <- ets:match(pg2_fixed_table, {{local_member, Name, '$1'}}),
+        P <- member_in_group(Pid, Name)].
+
+member_in_group(Pid, Name) ->
+    case ets:lookup(pg2_fixed_table, {member, Name, Pid}) of
+        [] -> [];
+        [{{member, Name, Pid}, N}] ->
+            lists:duplicate(N, Pid)
+    end.
+
+member_groups(Pid) ->
+    [Name || [Name] <- ets:match(pg2_fixed_table, {{pid, Pid, '$1'}})].
+
+all_groups() ->
+    [N || [N] <- ets:match(pg2_fixed_table, {{group,'$1'}})].
+
+ensure_started() ->
+    case whereis(?MODULE) of
+        undefined ->
+            C = {pg2_fixed, {?MODULE, start_link, []}, permanent,
+                 1000, worker, [?MODULE]},
+            supervisor:start_child(kernel_safe_sup, C);
+        Pg2_FixedPid ->
+            {ok, Pg2_FixedPid}
+    end.
+
+
+kill_monitor_proc(RPid, Pid) ->
+    RPid =:= Pid orelse exit(RPid, kill).
+
+%% When/if erlang:monitor() returns before trying to connect to the
+%% other node this function can be removed.
+do_monitor(Pid) ->
+    case (node(Pid) =:= node()) orelse lists:member(node(Pid), nodes()) of
+        true ->
+            %% Assume the node is still up
+            {Pid, erlang:monitor(process, Pid)};
+        false ->
+            F = fun() -> 
+                        Ref = erlang:monitor(process, Pid),
+                        receive 
+                            {'DOWN', Ref, process, Pid, _Info} ->
+                                exit(normal)
+                        end
+                end,
+            erlang:spawn_monitor(F)
+    end.
diff --git a/src/rabbit_mnesia.erl b/src/rabbit_mnesia.erl
index 8d5c86464c..463da98c60 100644
--- a/src/rabbit_mnesia.erl
+++ b/src/rabbit_mnesia.erl
@@ -242,7 +242,8 @@ table_definitions() ->
       [{record_name, amqqueue},
        {attributes, record_info(fields, amqqueue)},
        {match, #amqqueue{name = queue_name_match(), _='_'}}]}]
-        ++ gm:table_definitions().
+        ++ gm:table_definitions()
+        ++ mirrored_supervisor:table_definitions().
 
 binding_match() ->
     #binding{source = exchange_name_match(),
diff --git a/src/rabbit_upgrade_functions.erl b/src/rabbit_upgrade_functions.erl
index 0f7a781043..15887af1d7 100644
--- a/src/rabbit_upgrade_functions.erl
+++ b/src/rabbit_upgrade_functions.erl
@@ -32,6 +32,7 @@
 -rabbit_upgrade({user_admin_to_tags,    mnesia, [user_to_internal_user]}).
 -rabbit_upgrade({ha_mirrors,            mnesia, []}).
 -rabbit_upgrade({gm,                    mnesia, []}).
+-rabbit_upgrade({mirrored_supervisor,   mnesia, []}).
 
 %% -------------------------------------------------------------------
 
@@ -155,6 +156,10 @@ gm() ->
     create(gm_group, [{record_name, gm_group},
                       {attributes, [name, version, members]}]).
 
+mirrored_supervisor() ->
+    create(mirrored_sup_childspec, [{record_name, mirrored_sup_childspec},
+                                    {attributes, [id, sup_pid, childspec]}]).
+
 %%--------------------------------------------------------------------
 
 transform(TableName, Fun, FieldList) ->