Start/stop virtual hosts when reloading configuration file

14 files changed, 248 insertions, 107 deletions

diff --git a/src/acl.erl b/src/acl.erl
index 0feabfb32..99c8e17eb 100644
--- a/src/acl.erl
+++ b/src/acl.erl
@@ -86,6 +86,7 @@ start() ->
 			 {attributes, record_info(fields, access)}]),
     mnesia:add_table_copy(acl, node(), ram_copies),
     mnesia:add_table_copy(access, node(), ram_copies),
+    ejabberd_hooks:add(config_reloaded, ?MODULE, load_from_config, 20),
     load_from_config(),
     ok.
 
diff --git a/src/ejabberd_app.erl b/src/ejabberd_app.erl
index 493600afc..1340607cd 100644
--- a/src/ejabberd_app.erl
+++ b/src/ejabberd_app.erl
@@ -57,10 +57,10 @@ start(normal, _Args) ->
     setup_if_elixir_conf_used(),
     ejabberd_config:start(),
     set_settings_from_config(),
-    acl:start(),
-    shaper:start(),
     connect_nodes(),
     Sup = ejabberd_sup:start_link(),
+    acl:start(),
+    shaper:start(),
     ejabberd_rdbms:start(),
     ejabberd_riak_sup:start(),
     ejabberd_redis:start(),
@@ -88,7 +88,7 @@ start(_, _) ->
 prep_stop(State) ->
     ejabberd_listener:stop_listeners(),
     ejabberd_admin:stop(),
-    broadcast_c2s_shutdown(),
+    ejabberd_sm:stop(),
     gen_mod:stop_modules(),
     timer:sleep(5000),
     State.
@@ -164,16 +164,6 @@ add_windows_nameservers() ->
     ?INFO_MSG("Adding machine's DNS IPs to Erlang system:~n~p", [IPTs]),
     lists:foreach(fun(IPT) -> inet_db:add_ns(IPT) end, IPTs).
 
-
-broadcast_c2s_shutdown() ->
-    Children = ejabberd_sm:get_all_pids(),
-    lists:foreach(
-      fun(C2SPid) when node(C2SPid) == node() ->
-	      ejabberd_c2s:send(C2SPid, xmpp:serr_system_shutdown());
-	 (_) ->
-	      ok
-      end, Children).
-
 %%%
 %%% PID file
 %%%
diff --git a/src/ejabberd_c2s.erl b/src/ejabberd_c2s.erl
index 59b5c32a9..daf9c85a1 100644
--- a/src/ejabberd_c2s.erl
+++ b/src/ejabberd_c2s.erl
@@ -48,7 +48,8 @@
 %% API
 -export([get_presence/1, get_subscription/2, get_subscribed/1,
 	 open_session/1, call/3, send/2, close/1, close/2, stop/1,
-	 reply/2, copy_state/2, set_timeout/2, route/2, add_hooks/1]).
+	 reply/2, copy_state/2, set_timeout/2, route/2,
+	 host_up/1, host_down/1]).
 
 -include("ejabberd.hrl").
 -include("xmpp.hrl").
@@ -145,8 +146,8 @@ route(Pid, Term) ->
 set_timeout(State, Timeout) ->
     xmpp_stream_in:set_timeout(State, Timeout).
 
--spec add_hooks(binary()) -> ok.
-add_hooks(Host) ->
+-spec host_up(binary()) -> ok.
+host_up(Host) ->
     ejabberd_hooks:add(c2s_closed, Host, ?MODULE, process_closed, 100),
     ejabberd_hooks:add(c2s_terminated, Host, ?MODULE,
 		       process_terminated, 100),
@@ -157,6 +158,18 @@ add_hooks(Host) ->
     ejabberd_hooks:add(c2s_handle_cast, Host, ?MODULE,
 		       handle_unexpected_cast, 100).
 
+-spec host_down(binary()) -> ok.
+host_down(Host) ->
+    ejabberd_hooks:delete(c2s_closed, Host, ?MODULE, process_closed, 100),
+    ejabberd_hooks:delete(c2s_terminated, Host, ?MODULE,
+			  process_terminated, 100),
+    ejabberd_hooks:delete(c2s_unauthenticated_packet, Host, ?MODULE,
+			  reject_unauthenticated_packet, 100),
+    ejabberd_hooks:delete(c2s_handle_info, Host, ?MODULE,
+			  process_info, 100),
+    ejabberd_hooks:delete(c2s_handle_cast, Host, ?MODULE,
+			  handle_unexpected_cast, 100).
+
 %% Copies content of one c2s state to another.
 %% This is needed for session migration from one pid to another.
 -spec copy_state(state(), state()) -> state().
diff --git a/src/ejabberd_config.erl b/src/ejabberd_config.erl
index ff0f7b3e8..c79c0cd27 100644
--- a/src/ejabberd_config.erl
+++ b/src/ejabberd_config.erl
@@ -194,7 +194,17 @@ load_file(File) ->
 
 reload_file() ->
     Config = get_ejabberd_config_path(),
+    OldHosts = get_myhosts(),
     load_file(Config),
+    NewHosts = get_myhosts(),
+    lists:foreach(
+      fun(Host) ->
+	      ejabberd_hooks:run(host_up, [Host])
+      end, NewHosts -- OldHosts),
+    lists:foreach(
+      fun(Host) ->
+	      ejabberd_hooks:run(host_down, [Host])
+      end, OldHosts -- NewHosts),
     ejabberd_hooks:run(config_reloaded, []).
 
 -spec convert_to_yaml(file:filename()) -> ok | {error, any()}.
diff --git a/src/ejabberd_local.erl b/src/ejabberd_local.erl
index 2095dfc78..7a9034563 100644
--- a/src/ejabberd_local.erl
+++ b/src/ejabberd_local.erl
@@ -36,7 +36,8 @@
 	 process_iq_reply/1, get_features/1,
 	 register_iq_handler/5, register_iq_response_handler/4,
 	 register_iq_response_handler/5, unregister_iq_handler/2,
-	 unregister_iq_response_handler/2, bounce_resource_packet/1]).
+	 unregister_iq_response_handler/2, bounce_resource_packet/1,
+	 host_up/1, host_down/1]).
 
 %% gen_server callbacks
 -export([init/1, handle_call/3, handle_cast/2,
@@ -196,16 +197,9 @@ get_features(_, _, XMLNSs) ->
 %%====================================================================
 
 init([]) ->
-    lists:foreach(fun (Host) ->
-			  ejabberd_router:register_route(Host,
-							 Host,
-							 {apply, ?MODULE,
-							  route}),
-			  ejabberd_hooks:add(local_send_to_resource_hook, Host,
-					     ?MODULE, bounce_resource_packet,
-					     100)
-		  end,
-		  ?MYHOSTS),
+    lists:foreach(fun host_up/1, ?MYHOSTS),
+    ejabberd_hooks:add(host_up, ?MODULE, host_up, 10),
+    ejabberd_hooks:add(host_down, ?MODULE, host_down, 100),
     catch ets:new(?IQTABLE, [named_table, public, ordered_set]),
     update_table(),
     ejabberd_mnesia:create(?MODULE, iq_response,
@@ -245,6 +239,9 @@ handle_info(Info, State) ->
     {noreply, State}.
 
 terminate(_Reason, _State) ->
+    lists:foreach(fun host_down/1, ?MYHOSTS),
+    ejabberd_hooks:delete(host_up, ?MODULE, host_up, 10),
+    ejabberd_hooks:delete(host_down, ?MODULE, host_down, 100),
     ok.
 
 code_change(_OldVsn, State, _Extra) ->
@@ -281,6 +278,16 @@ update_table() ->
 	    ok
     end.
 
+host_up(Host) ->
+    ejabberd_router:register_route(Host, Host, {apply, ?MODULE, route}),
+    ejabberd_hooks:add(local_send_to_resource_hook, Host,
+		       ?MODULE, bounce_resource_packet, 100).
+
+host_down(Host) ->
+    ejabberd_router:unregister_route(Host),
+    ejabberd_hooks:delete(local_send_to_resource_hook, Host,
+			  ?MODULE, bounce_resource_packet, 100).
+
 -spec get_iq_callback(binary()) -> {ok, module(), atom() | function()} | error.
 get_iq_callback(ID) ->
     case mnesia:dirty_read(iq_response, ID) of
diff --git a/src/ejabberd_rdbms.erl b/src/ejabberd_rdbms.erl
index e3a211f8e..5fc73c624 100644
--- a/src/ejabberd_rdbms.erl
+++ b/src/ejabberd_rdbms.erl
@@ -29,7 +29,7 @@
 
 -author('alexey@process-one.net').
 
--export([start/0, opt_type/1]).
+-export([start/0, opt_type/1, start_hosts/0, start_host/1, stop_host/1]).
 
 -include("ejabberd.hrl").
 -include("logger.hrl").
@@ -38,6 +38,9 @@ start() ->
     file:delete(ejabberd_sql:freetds_config()),
     file:delete(ejabberd_sql:odbc_config()),
     file:delete(ejabberd_sql:odbcinst_config()),
+    ejabberd_hooks:add(host_up, ?MODULE, start_host, 20),
+    ejabberd_hooks:add(host_down, ?MODULE, stop_host, 90),
+    ejabberd_hooks:add(config_reloaded, ?MODULE, start_hosts, 20),
     case lists:any(fun(H) -> needs_sql(H) /= false end,
                    ?MYHOSTS) of
         true ->
@@ -48,13 +51,21 @@ start() ->
 
 %% Start relationnal DB module on the nodes where it is needed
 start_hosts() ->
-    lists:foreach(fun (Host) ->
-			  case needs_sql(Host) of
-			    {true, App} -> start_sql(Host, App);
-			    false -> ok
-			  end
-		  end,
-		  ?MYHOSTS).
+    lists:foreach(fun start_host/1, ?MYHOSTS).
+
+-spec start_host(binary()) -> ok.
+start_host(Host) ->
+    case needs_sql(Host) of
+	{true, App} -> start_sql(Host, App);
+	false -> ok
+    end.
+
+-spec stop_host(binary()) -> ok.
+stop_host(Host) ->
+    SupName = gen_mod:get_module_proc(Host, ejabberd_sql_sup),
+    supervisor:terminate_child(ejabberd_sup, SupName),
+    supervisor:delete_child(ejabberd_sup, SupName),
+    ok.
 
 %% Start the SQL module on the given host
 start_sql(Host, App) ->
@@ -66,10 +77,12 @@ start_sql(Host, App) ->
 		 infinity, supervisor, [ejabberd_sql_sup]},
     case supervisor:start_child(ejabberd_sup, ChildSpec) of
       {ok, _PID} -> ok;
+      {error, {already_started, _}} -> ok;
       _Error ->
 	  ?ERROR_MSG("Start of supervisor ~p failed:~n~p~nRetrying."
 		     "..~n",
 		     [Supervisor_name, _Error]),
+	  timer:sleep(5000),
 	  start_sql(Host, App)
     end.
 
diff --git a/src/ejabberd_redis.erl b/src/ejabberd_redis.erl
index 9d4264df3..6a853737d 100644
--- a/src/ejabberd_redis.erl
+++ b/src/ejabberd_redis.erl
@@ -28,7 +28,7 @@
 -behaviour(ejabberd_config).
 
 %% API
--export([start/0, start_link/0, q/1, qp/1, opt_type/1]).
+-export([start/0, stop/0, start_link/0, q/1, qp/1, host_up/1, opt_type/1]).
 
 %% gen_server callbacks
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
@@ -49,16 +49,16 @@ start_link() ->
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
 
 start() ->
+    ejabberd_hooks:add(config_reloaded, ?MODULE, start, 20),
+    ejabberd_hooks:add(host_up, ?MODULE, host_up, 20),
     case lists:any(
 	   fun(Host) ->
 		   is_redis_configured(Host)
 	   end, ?MYHOSTS) of
 	true ->
-	    Spec = {?MODULE, {?MODULE, start_link, []},
-		    permanent, 2000, worker, [?MODULE]},
-	    supervisor:start_child(ejabberd_sup, Spec);
+	    do_start();
 	false ->
-	    ok
+	    stop()
     end.
 
 q(Command) ->
@@ -71,6 +71,16 @@ qp(Pipeline) ->
     catch _:Reason -> {error, Reason}
     end.
 
+stop() ->
+    supervisor:terminate_child(ejabberd_sup, ?MODULE),
+    supervisor:delete_child(ejabberd_sup, ?MODULE).
+
+host_up(Host) ->
+    case is_redis_configured(Host) of
+	true -> do_start();
+	false -> ok
+    end.
+
 %%%===================================================================
 %%% gen_server callbacks
 %%%===================================================================
@@ -108,6 +118,11 @@ code_change(_OldVsn, State, _Extra) ->
 %%%===================================================================
 %%% Internal functions
 %%%===================================================================
+do_start() ->
+    Spec = {?MODULE, {?MODULE, start_link, []},
+	    permanent, 5000, worker, [?MODULE]},
+    supervisor:start_child(ejabberd_sup, Spec).
+
 is_redis_configured(Host) ->
     ServerConfigured = ejabberd_config:has_option({redis_server, Host}),
     PortConfigured = ejabberd_config:has_option({redis_port, Host}),
diff --git a/src/ejabberd_riak_sup.erl b/src/ejabberd_riak_sup.erl
index 840de29b5..d1ab126f8 100644
--- a/src/ejabberd_riak_sup.erl
+++ b/src/ejabberd_riak_sup.erl
@@ -28,9 +28,9 @@
 -behaviour(ejabberd_config).
 -author('alexey@process-one.net').
 
--export([start/0, start_link/0, init/1, get_pids/0,
+-export([start/0, stop/0, start_link/0, init/1, get_pids/0,
 	 transform_options/1, get_random_pid/0, get_random_pid/1,
-	 opt_type/1]).
+	 host_up/1, opt_type/1]).
 
 -include("ejabberd.hrl").
 -include("logger.hrl").
@@ -45,6 +45,8 @@
 -define(CONNECT_TIMEOUT, 500). % milliseconds
 
 start() ->
+    ejabberd_hooks:add(config_reloaded, ?MODULE, start, 20),
+    ejabberd_hooks:add(host_up, ?MODULE, host_up, 20),
     case lists:any(
 	   fun(Host) ->
 		   is_riak_configured(Host)
@@ -53,6 +55,20 @@ start() ->
 	    ejabberd:start_app(riakc),
             do_start();
 	false ->
+	    stop()
+    end.
+
+stop() ->
+    supervisor:terminate_child(ejabberd_sup, ?MODULE),
+    supervisor:delete_child(ejabberd_sup, ?MODULE),
+    ok.
+
+host_up(Host) ->
+    case is_riak_configured(Host) of
+	true ->
+	    ejabberd:start_app(riakc),
+            do_start();
+	false ->
 	    ok
     end.
 
@@ -77,9 +93,8 @@ is_riak_configured(Host) ->
 	or AuthConfigured or ModuleWithRiakDBConfigured.
 
 do_start() ->
-    SupervisorName = ?MODULE,
     ChildSpec =
-	{SupervisorName,
+	{?MODULE,
 	 {?MODULE, start_link, []},
 	 transient,
 	 infinity,
@@ -88,9 +103,11 @@ do_start() ->
     case supervisor:start_child(ejabberd_sup, ChildSpec) of
 	{ok, _PID} ->
 	    ok;
+	{error, {already_started, _}} ->
+	    ok;
 	_Error ->
 	    ?ERROR_MSG("Start of supervisor ~p failed:~n~p~nRetrying...~n",
-                       [SupervisorName, _Error]),
+                       [?MODULE, _Error]),
             timer:sleep(5000),
 	    start()
     end.
diff --git a/src/ejabberd_s2s.erl b/src/ejabberd_s2s.erl
index 73004a06b..76fb522f0 100644
--- a/src/ejabberd_s2s.erl
+++ b/src/ejabberd_s2s.erl
@@ -44,7 +44,8 @@
 	 list_temporarily_blocked_hosts/0,
 	 external_host_overloaded/1, is_temporarly_blocked/1,
 	 get_commands_spec/0, zlib_enabled/1, get_idle_timeout/1,
-	 tls_required/1, tls_verify/1, tls_enabled/1, tls_options/2]).
+	 tls_required/1, tls_verify/1, tls_enabled/1, tls_options/2,
+	 host_up/1, host_down/1]).
 
 %% gen_server callbacks
 -export([init/1, handle_call/3, handle_cast/2,
@@ -300,8 +301,9 @@ init([]) ->
     ejabberd_mnesia:create(?MODULE, temporarily_blocked,
 			[{ram_copies, [node()]},
 			 {attributes, record_info(fields, temporarily_blocked)}]),
-    ejabberd_s2s_in:add_hooks(),
-    ejabberd_s2s_out:add_hooks(),
+    ejabberd_hooks:add(host_up, ?MODULE, host_up, 50),
+    ejabberd_hooks:add(host_down, ?MODULE, host_down, 60),
+    lists:foreach(fun host_up/1, ?MYHOSTS),
     {ok, #state{}}.
 
 handle_call(_Request, _From, State) ->
@@ -320,6 +322,9 @@ handle_info(_Info, State) -> {noreply, State}.
 
 terminate(_Reason, _State) ->
     ejabberd_commands:unregister_commands(get_commands_spec()),
+    lists:foreach(fun host_down/1, ?MYHOSTS),
+    ejabberd_hooks:delete(host_up, ?MODULE, host_up, 50),
+    ejabberd_hooks:delete(host_down, ?MODULE, host_down, 60),
     ok.
 
 code_change(_OldVsn, State, _Extra) ->
@@ -328,6 +333,26 @@ code_change(_OldVsn, State, _Extra) ->
 %%--------------------------------------------------------------------
 %%% Internal functions
 %%--------------------------------------------------------------------
+host_up(Host) ->
+    ejabberd_s2s_in:host_up(Host),
+    ejabberd_s2s_out:host_up(Host).
+
+host_down(Host) ->
+    lists:foreach(
+      fun(#s2s{fromto = {From, _}, pid = Pid}) when node(Pid) == node() ->
+	      case ejabberd_router:host_of_route(From) of
+		  Host ->
+		      ejabberd_s2s_out:send(Pid, xmpp:serr_system_shutdown()),
+		      ejabberd_s2s_out:stop(Pid);
+		  _ ->
+		      ok
+	      end;
+	 (_) ->
+	      ok
+      end, ets:tab2list(s2s)),
+    ejabberd_s2s_in:host_down(Host),
+    ejabberd_s2s_out:host_down(Host).
+
 -spec clean_table_from_bad_node(node()) -> any().
 clean_table_from_bad_node(Node) ->
     F = fun() ->
diff --git a/src/ejabberd_s2s_in.erl b/src/ejabberd_s2s_in.erl
index f9d9e6f85..4289a8b34 100644
--- a/src/ejabberd_s2s_in.erl
+++ b/src/ejabberd_s2s_in.erl
@@ -42,7 +42,8 @@
 -export([handle_unexpected_info/2, handle_unexpected_cast/2,
 	 reject_unauthenticated_packet/2, process_closed/2]).
 %% API
--export([stop/1, close/1, send/2, update_state/2, establish/1, add_hooks/0]).
+-export([stop/1, close/1, send/2, update_state/2, establish/1,
+	 host_up/1, host_down/1]).
 
 -include("ejabberd.hrl").
 -include("xmpp.hrl").
@@ -90,19 +91,27 @@ establish(State) ->
 update_state(Ref, Callback) ->
     xmpp_stream_in:cast(Ref, {update_state, Callback}).
 
--spec add_hooks() -> ok.
-add_hooks() ->
-    lists:foreach(
-      fun(Host) ->
-	      ejabberd_hooks:add(s2s_in_closed, Host, ?MODULE,
-				 process_closed, 100),
-	      ejabberd_hooks:add(s2s_in_unauthenticated_packet, Host, ?MODULE,
-				 reject_unauthenticated_packet, 100),
-	      ejabberd_hooks:add(s2s_in_handle_info, Host, ?MODULE,
-				 handle_unexpected_info, 100),
-	      ejabberd_hooks:add(s2s_in_handle_cast, Host, ?MODULE,
-				 handle_unexpected_cast, 100)
-      end, ?MYHOSTS).
+-spec host_up(binary()) -> ok.
+host_up(Host) ->
+    ejabberd_hooks:add(s2s_in_closed, Host, ?MODULE,
+		       process_closed, 100),
+    ejabberd_hooks:add(s2s_in_unauthenticated_packet, Host, ?MODULE,
+		       reject_unauthenticated_packet, 100),
+    ejabberd_hooks:add(s2s_in_handle_info, Host, ?MODULE,
+		       handle_unexpected_info, 100),
+    ejabberd_hooks:add(s2s_in_handle_cast, Host, ?MODULE,
+		       handle_unexpected_cast, 100).
+
+-spec host_down(binary()) -> ok.
+host_down(Host) ->
+    ejabberd_hooks:delete(s2s_in_closed, Host, ?MODULE,
+			  process_closed, 100),
+    ejabberd_hooks:delete(s2s_in_unauthenticated_packet, Host, ?MODULE,
+			  reject_unauthenticated_packet, 100),
+    ejabberd_hooks:delete(s2s_in_handle_info, Host, ?MODULE,
+			  handle_unexpected_info, 100),
+    ejabberd_hooks:delete(s2s_in_handle_cast, Host, ?MODULE,
+			  handle_unexpected_cast, 100).
 
 %%%===================================================================
 %%% Hooks
diff --git a/src/ejabberd_s2s_out.erl b/src/ejabberd_s2s_out.erl
index 32dda56ad..77f555475 100644
--- a/src/ejabberd_s2s_out.erl
+++ b/src/ejabberd_s2s_out.erl
@@ -40,7 +40,7 @@
 	 handle_unexpected_cast/2, process_downgraded/2]).
 %% API
 -export([start/3, start_link/3, connect/1, close/1, stop/1, send/2,
-	 route/2, establish/1, update_state/2, add_hooks/0]).
+	 route/2, establish/1, update_state/2, host_up/1, host_down/1]).
 
 -include("ejabberd.hrl").
 -include("xmpp.hrl").
@@ -99,21 +99,31 @@ establish(State) ->
 update_state(Ref, Callback) ->
     xmpp_stream_out:cast(Ref, {update_state, Callback}).
 
--spec add_hooks() -> ok.
-add_hooks() ->
-    lists:foreach(
-      fun(Host) ->
-	      ejabberd_hooks:add(s2s_out_auth_result, Host, ?MODULE,
-				 process_auth_result, 100),
-	      ejabberd_hooks:add(s2s_out_closed, Host, ?MODULE,
-				 process_closed, 100),
-	      ejabberd_hooks:add(s2s_out_handle_info, Host, ?MODULE,
-				 handle_unexpected_info, 100),
-	      ejabberd_hooks:add(s2s_out_handle_cast, Host, ?MODULE,
-				 handle_unexpected_cast, 100),
-	      ejabberd_hooks:add(s2s_out_downgraded, Host, ?MODULE,
-				 process_downgraded, 100)
-      end, ?MYHOSTS).
+-spec host_up(binary()) -> ok.
+host_up(Host) ->
+    ejabberd_hooks:add(s2s_out_auth_result, Host, ?MODULE,
+		       process_auth_result, 100),
+    ejabberd_hooks:add(s2s_out_closed, Host, ?MODULE,
+		       process_closed, 100),
+    ejabberd_hooks:add(s2s_out_handle_info, Host, ?MODULE,
+		       handle_unexpected_info, 100),
+    ejabberd_hooks:add(s2s_out_handle_cast, Host, ?MODULE,
+		       handle_unexpected_cast, 100),
+    ejabberd_hooks:add(s2s_out_downgraded, Host, ?MODULE,
+		       process_downgraded, 100).
+
+-spec host_down(binary()) -> ok.
+host_down(Host) ->
+    ejabberd_hooks:delete(s2s_out_auth_result, Host, ?MODULE,
+			  process_auth_result, 100),
+    ejabberd_hooks:delete(s2s_out_closed, Host, ?MODULE,
+			  process_closed, 100),
+    ejabberd_hooks:delete(s2s_out_handle_info, Host, ?MODULE,
+			  handle_unexpected_info, 100),
+    ejabberd_hooks:delete(s2s_out_handle_cast, Host, ?MODULE,
+			  handle_unexpected_cast, 100),
+    ejabberd_hooks:delete(s2s_out_downgraded, Host, ?MODULE,
+			  process_downgraded, 100).
 
 %%%===================================================================
 %%% Hooks
diff --git a/src/ejabberd_sm.erl b/src/ejabberd_sm.erl
index eaa1ab4ae..ab6f59639 100644
--- a/src/ejabberd_sm.erl
+++ b/src/ejabberd_sm.erl
@@ -36,6 +36,7 @@
 
 %% API
 -export([start/0,
+	 stop/0,
 	 start_link/0,
 	 route/1,
 	 route/2,
@@ -74,6 +75,8 @@
 	 is_existing_resource/3,
 	 get_commands_spec/0,
 	 c2s_handle_info/2,
+	 host_up/1,
+	 host_down/1,
 	 make_sid/0
 	]).
 
@@ -109,9 +112,15 @@
 
 start() ->
     ChildSpec = {?MODULE, {?MODULE, start_link, []},
-		 transient, 1000, worker, [?MODULE]},
+		 transient, 5000, worker, [?MODULE]},
     supervisor:start_child(ejabberd_sup, ChildSpec).
 
+-spec stop() -> ok.
+stop() ->
+    supervisor:terminate_child(ejabberd_sup, ?MODULE),
+    supervisor:delete_child(ejabberd_sup, ?MODULE),
+    ok.
+
 start_link() ->
     ?GEN_SERVER:start_link({local, ?MODULE}, ?MODULE, [], []).
 
@@ -388,20 +397,12 @@ c2s_handle_info(State, _) ->
 %%====================================================================
 
 init([]) ->
+    process_flag(trap_exit, true),
     lists:foreach(fun(Mod) -> Mod:init() end, get_sm_backends()),
     ets:new(sm_iqtable, [named_table, public]),
-    lists:foreach(
-      fun(Host) ->
-	      ejabberd_hooks:add(c2s_handle_info, Host,
-				 ejabberd_sm, c2s_handle_info, 50),
-	      ejabberd_hooks:add(roster_in_subscription, Host,
-				 ejabberd_sm, check_in_subscription, 20),
-	      ejabberd_hooks:add(offline_message_hook, Host,
-				 ejabberd_sm, bounce_offline_message, 100),
-	      ejabberd_hooks:add(remove_user, Host,
-				 ejabberd_sm, disconnect_removed_user, 100),
-	      ejabberd_c2s:add_hooks(Host)
-      end, ?MYHOSTS),
+    ejabberd_hooks:add(host_up, ?MODULE, host_up, 50),
+    ejabberd_hooks:add(host_down, ?MODULE, host_down, 60),
+    lists:foreach(fun host_up/1, ?MYHOSTS),
     ejabberd_commands:register_commands(get_commands_spec()),
     {ok, #state{}}.
 
@@ -433,17 +434,9 @@ handle_info(Info, State) ->
     {noreply, State}.
 
 terminate(_Reason, _State) ->
-    lists:foreach(
-      fun(Host) ->
-	      ejabberd_hooks:delete(c2s_handle_info, Host,
-				    ejabberd_sm, c2s_handle_info, 50),
-	      ejabberd_hooks:delete(roster_in_subscription, Host,
-				    ejabberd_sm, check_in_subscription, 20),
-	      ejabberd_hooks:delete(offline_message_hook, Host,
-				    ejabberd_sm, bounce_offline_message, 100),
-	      ejabberd_hooks:delete(remove_user, Host,
-				    ejabberd_sm, disconnect_removed_user, 100)
-      end, ?MYHOSTS),
+    lists:foreach(fun host_down/1, ?MYHOSTS),
+    ejabberd_hooks:delete(host_up, ?MODULE, host_up, 50),
+    ejabberd_hooks:delete(host_down, ?MODULE, host_down, 60),
     ejabberd_commands:unregister_commands(get_commands_spec()),
     ok.
 
@@ -452,6 +445,36 @@ code_change(_OldVsn, State, _Extra) -> {ok, State}.
 %%--------------------------------------------------------------------
 %%% Internal functions
 %%--------------------------------------------------------------------
+-spec host_up(binary()) -> ok.
+host_up(Host) ->
+    ejabberd_hooks:add(c2s_handle_info, Host,
+		       ejabberd_sm, c2s_handle_info, 50),
+    ejabberd_hooks:add(roster_in_subscription, Host,
+		       ejabberd_sm, check_in_subscription, 20),
+    ejabberd_hooks:add(offline_message_hook, Host,
+		       ejabberd_sm, bounce_offline_message, 100),
+    ejabberd_hooks:add(remove_user, Host,
+		       ejabberd_sm, disconnect_removed_user, 100),
+    ejabberd_c2s:host_up(Host).
+
+-spec host_down(binary()) -> ok.
+host_down(Host) ->
+    Mod = get_sm_backend(Host),
+    lists:foreach(
+      fun(#session{sid = {_, Pid}}) when node(Pid) == node() ->
+	      ejabberd_c2s:send(Pid, xmpp:serr_system_shutdown());
+	 (_) ->
+	      ok
+      end, Mod:get_sessions(Host)),
+    ejabberd_hooks:delete(c2s_handle_info, Host,
+			  ejabberd_sm, c2s_handle_info, 50),
+    ejabberd_hooks:delete(roster_in_subscription, Host,
+			  ejabberd_sm, check_in_subscription, 20),
+    ejabberd_hooks:delete(offline_message_hook, Host,
+			  ejabberd_sm, bounce_offline_message, 100),
+    ejabberd_hooks:delete(remove_user, Host,
+			  ejabberd_sm, disconnect_removed_user, 100),
+    ejabberd_c2s:host_down(Host).
 
 -spec set_session(sid(), binary(), binary(), binary(),
                   prio(), info()) -> ok.
diff --git a/src/ejabberd_system_monitor.erl b/src/ejabberd_system_monitor.erl
index d160afd72..e4c8f4ef7 100644
--- a/src/ejabberd_system_monitor.erl
+++ b/src/ejabberd_system_monitor.erl
@@ -33,7 +33,7 @@
 
 %% API
 -export([start_link/0, process_command/1, register_hook/1,
-	 process_remote_command/1]).
+	 unregister_hook/1, process_remote_command/1]).
 
 -export([init/1, handle_call/3, handle_cast/2,
 	 handle_info/2, terminate/2, code_change/3, opt_type/1]).
@@ -86,6 +86,10 @@ register_hook(Host) ->
     ejabberd_hooks:add(local_send_to_resource_hook, Host,
 		       ?MODULE, process_command, 50).
 
+unregister_hook(Host) ->
+    ejabberd_hooks:delete(local_send_to_resource_hook, Host,
+			  ?MODULE, process_command, 50).
+
 %%====================================================================
 %% gen_server callbacks
 %%====================================================================
@@ -101,6 +105,8 @@ init(Opts) ->
     LH = proplists:get_value(large_heap, Opts),
     process_flag(priority, high),
     erlang:system_monitor(self(), [{large_heap, LH}]),
+    ejabberd_hooks:add(host_up, ?MODULE, register_hook, 50),
+    ejabberd_hooks:add(host_down, ?MODULE, unregister_hook, 60),
     lists:foreach(fun register_hook/1, ?MYHOSTS),
     {ok, #state{}}.
 
diff --git a/src/gen_mod.erl b/src/gen_mod.erl
index b74d1555d..178fccb1f 100644
--- a/src/gen_mod.erl
+++ b/src/gen_mod.erl
@@ -80,6 +80,8 @@ start_link() ->
 
 init([]) ->
     ejabberd_hooks:add(config_reloaded, ?MODULE, config_reloaded, 50),
+    ejabberd_hooks:add(host_up, ?MODULE, start_modules, 40),
+    ejabberd_hooks:add(host_down, ?MODULE, stop_modules, 80),
     ets:new(ejabberd_modules,
 	    [named_table, public,
 	     {keypos, #ejabberd_module.module_host}]),
@@ -162,7 +164,7 @@ sort_modules(Host, ModOpts) ->
       end, ModOpts),
     [digraph:vertex(G, V) || V <- digraph_utils:topsort(G)].
 
--spec start_modules(binary()) -> any().
+-spec start_modules(binary()) -> ok.
 
 start_modules(Host) ->
     Modules = sort_modules(Host, get_modules_options(Host)),
@@ -171,7 +173,7 @@ start_modules(Host) ->
 	    start_module(Host, Module, Opts)
 	end, Modules).
 
--spec start_module(binary(), atom()) -> any().
+-spec start_module(binary(), atom()) -> ok | {ok, pid()} | {error, not_found_in_config}.
 
 start_module(Host, Module) ->
     Modules = get_modules_options(Host),
@@ -293,7 +295,7 @@ is_app_running(AppName) ->
     lists:keymember(AppName, 1,
 		    application:which_applications(Timeout)).
 
--spec stop_modules() -> any().
+-spec stop_modules() -> ok.
 
 stop_modules() ->
     lists:foreach(
@@ -301,7 +303,7 @@ stop_modules() ->
 	    stop_modules(Host)
 	end, ?MYHOSTS).
 
--spec stop_modules(binary()) -> any().
+-spec stop_modules(binary()) -> ok.
 
 stop_modules(Host) ->
     Modules = get_modules_options(Host),