Use ets insead of asking supervisor in ejabberd_odbc_sup:get_pids/1 (Thanks to Alexey Shchepin)

src/odbc/ejabberd_odbc.erl

@@ -178,6 +178,7 @@ init([Host, StartInterval]) ->
     end,
     [DBType | _] = db_opts(Host),
     ?GEN_FSM:send_event(self(), connect),
+    ejabberd_odbc_sup:add_pid(Host, self()),
     {ok, connecting, #state{db_type = DBType,
 			    host = Host,
 			    max_pending_requests_len = max_fsm_queue(),
@@ -274,6 +275,7 @@ handle_info(Info, StateName, State) ->
     {next_state, StateName, State}.
 
 terminate(_Reason, _StateName, State) ->
+    ejabberd_odbc_sup:remove_pid(State#state.host, self()),
     case State#state.db_type of
 	mysql ->
 	    %% old versions of mysql driver don't have the stop function

src/odbc/ejabberd_odbc_sup.erl

@@ -30,6 +30,8 @@
 %% API
 -export([start_link/1,
 	 init/1,
+	 add_pid/2,
+	 remove_pid/2,
 	 get_pids/1,
 	 get_random_pid/1
 	]).
@@ -44,7 +46,19 @@
 -define(CONNECT_TIMEOUT, 500). % milliseconds
 
 
+-record(sql_pool, {host, pid}).
+
 start_link(Host) ->
+    mnesia:create_table(sql_pool,
+			[{ram_copies, [node()]},
+			 {type, bag},
+			 {local_content, true},
+			 {attributes, record_info(fields, sql_pool)}]),
+    mnesia:add_table_copy(local_config, node(), ram_copies),
+    F = fun() ->
+		mnesia:delete({sql_pool, Host})
+	end,
+    mnesia:ets(F),
     supervisor:start_link({local, gen_mod:get_module_proc(Host, ?MODULE)},
 			  ?MODULE, [Host]).
 
@@ -86,16 +100,25 @@ init([Host]) ->
 	    end, lists:seq(1, PoolSize))}}.
 
 get_pids(Host) ->
-    Proc = gen_mod:get_module_proc(Host, ?MODULE),
-
-    % throw an exception if supervisor is not ready (i.e. if it cannot
-    % start its children, if the database is down for example)
-    sys:get_status(Proc, ?CONNECT_TIMEOUT),
-
-    [Child ||
-	{_Id, Child, _Type, _Modules} <- supervisor:which_children(Proc),
-	Child /= undefined].
+    Rs = mnesia:dirty_read(sql_pool, Host),
+    [R#sql_pool.pid || R <- Rs].
 
 get_random_pid(Host) ->
     Pids = get_pids(Host),
     lists:nth(erlang:phash(now(), length(Pids)), Pids).
+
+add_pid(Host, Pid) ->
+    F = fun() ->
+		mnesia:write(
+		  #sql_pool{host = Host,
+			    pid = Pid})
+	end,
+    mnesia:ets(F).
+
+remove_pid(Host, Pid) ->
+    F = fun() ->
+		mnesia:delete_object(
+		  #sql_pool{host = Host,
+			    pid = Pid})
+	end,
+    mnesia:ets(F).

src/p1_fsm.erl

@@ -517,6 +517,25 @@ print_event(Dev, return, {Name, StateName}) ->
     io:format(Dev, "*DBG* ~p switched to state ~w~n",
 	      [Name, StateName]).
 
+relay_messages(MRef, TRef, Clone, Queue) ->
+    lists:foreach(
+      fun(Msg) -> Clone ! Msg end,
+      queue:to_list(Queue)),
+    relay_messages(MRef, TRef, Clone).
+
+relay_messages(MRef, TRef, Clone) ->
+    receive
+	{'DOWN', MRef, process, Clone, Reason} ->
+	    Reason;
+	{'EXIT', _Parent, _Reason} ->
+	    {migrated, Clone};
+	{timeout, TRef, timeout} ->
+	    {migrated, Clone};
+	Msg ->
+	    Clone ! Msg,
+	    relay_messages(MRef, TRef, Clone)
+    end.
+
 handle_msg(Msg, Parent, Name, StateName, StateData, Mod, _Time,
 	   Limits, Queue, QueueLen) -> %No debug here
     From = from(Msg),
@@ -535,6 +554,23 @@ handle_msg(Msg, Parent, Name, StateName, StateData, Mod, _Time,
 	    reply(From, Reply),
 	    loop(Parent, Name, NStateName, NStateData, Mod, Time1, [],
 		 Limits, Queue, QueueLen);
+	{migrate, NStateData, {Node, M, F, A}, Time1} ->
+	    Reason = case catch rpc:call(Node, M, F, A, 5000) of
+			 {badrpc, _} = Err ->
+			     {migration_error, Err};
+			 {'EXIT', _} = Err ->
+			     {migration_error, Err};
+			 {error, _} = Err ->
+			     {migration_error, Err};
+			 {ok, Clone} ->
+			     process_flag(trap_exit, true),
+			     MRef = erlang:monitor(process, Clone),
+			     TRef = erlang:start_timer(Time1, self(), timeout),
+			     relay_messages(MRef, TRef, Clone, Queue);
+			 Reply ->
+			     {migration_error, {bad_reply, Reply}}
+		     end,
+	    terminate(Reason, Name, Msg, Mod, StateName, NStateData, []);
 	{stop, Reason, NStateData} ->
 	    terminate(Reason, Name, Msg, Mod, StateName, NStateData, []);
 	{stop, Reason, Reply, NStateData} when From =/= undefined ->
@@ -571,6 +607,23 @@ handle_msg(Msg, Parent, Name, StateName, StateData,
 	    Debug1 = reply(Name, From, Reply, Debug, NStateName),
 	    loop(Parent, Name, NStateName, NStateData,
 		 Mod, Time1, Debug1, Limits, Queue, QueueLen);
+	{migrate, NStateData, {Node, M, F, A}, Time1} ->
+	    Reason = case catch rpc:call(Node, M, F, A, Time1) of
+			 {badrpc, R} ->
+			     {migration_error, R};
+			 {'EXIT', R} ->
+			     {migration_error, R};
+			 {error, R} ->
+			     {migration_error, R};
+			 {ok, Clone} ->
+			     process_flag(trap_exit, true),
+			     MRef = erlang:monitor(process, Clone),
+			     TRef = erlang:start_timer(Time1, self(), timeout),
+			     relay_messages(MRef, TRef, Clone, Queue);
+			 Reply ->
+			     {migration_error, {bad_reply, Reply}}
+		     end,
+	    terminate(Reason, Name, Msg, Mod, StateName, NStateData, Debug);
 	{stop, Reason, NStateData} ->
 	    terminate(Reason, Name, Msg, Mod, StateName, NStateData, Debug);
 	{stop, Reason, Reply, NStateData} when From =/= undefined ->
@@ -633,12 +686,10 @@ terminate(Reason, Name, Msg, Mod, StateName, StateData, Debug) ->
 		    %% Priority shutdown should be considered as
 		    %% shutdown by SASL
 		    exit(shutdown);
-		{process_limit, Limit} ->
-		    %% Priority shutdown should be considered as
-		    %% shutdown by SASL
-		    error_logger:error_msg("FSM limit reached (~p): ~p~n",
-					   [self(), Limit]),
-		    exit(shutdown);
+		{process_limit, _Limit} ->
+		    exit(Reason);
+		{migrated, _Clone} ->
+		    exit(normal);
 		_ ->
 		    error_info(Mod, Reason, Name, Msg, StateName, StateData, Debug),
 		    exit(Reason)
@@ -705,7 +756,12 @@ get_msg(Msg) -> Msg.
 format_status(Opt, StatusData) ->
     [PDict, SysState, Parent, Debug, [Name, StateName, StateData, Mod, _Time]] =
 	StatusData,
-    Header = lists:concat(["Status for state machine ", Name]),
+    NameTag = if is_pid(Name) ->
+		      pid_to_list(Name);
+		 is_atom(Name) ->
+		      Name
+	      end,
+    Header = lists:concat(["Status for state machine ", NameTag]),
     Log = sys:get_debug(log, Debug, []),
     Specfic = 
 	case erlang:function_exported(Mod, format_status, 2) of