Optimise gen_servers

- introduce hibernation when appropriate,
- remove dead `code_change/3` callbacks,
- remove dead comments,
- improve specs for start_link/ and init/1 callbacks

src/domain/mongoose_domain_sup.erl

@@ -10,6 +10,7 @@
 -export([start_link/2, restart_core/1]).
 -ignore_xref([start_link/2, restart_core/1]).
 
+-spec start_link() -> supervisor:startlink_ret().
 start_link() ->
     supervisor:start_link({local, ?MODULE}, ?MODULE, []).
 
@@ -21,6 +22,7 @@ restart_core(Args) ->
     supervisor:delete_child(?MODULE, mongoose_domain_core),
     supervisor:start_child(?MODULE, worker_spec(mongoose_domain_core, fill_args(Args))).
 
+-spec init(list()) -> {ok, {supervisor:sup_flags(), [supervisor:child_spec()]}}.
 init(Args) ->
     DomainCore = worker_spec(mongoose_domain_core, fill_args(Args)),
     SubdomainCore = worker_spec(mongoose_subdomain_core, []),

src/ejabberd_local.erl

@@ -57,8 +57,7 @@
 -export([disco_local_features/3]).
 
 %% gen_server callbacks
--export([init/1, handle_call/3, handle_cast/2, handle_info/2,
-         terminate/2, code_change/3]).
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2]).
 
 -export([do_route/4]).
 
@@ -89,13 +88,9 @@
 %%====================================================================
 %% API
 %%====================================================================
-%%--------------------------------------------------------------------
-%% Function: start_link() -> {ok, Pid} | ignore | {error, Error}
-%% Description: Starts the server
-%%--------------------------------------------------------------------
--spec start_link() -> 'ignore' | {'error', _} | {'ok', pid()}.
+-spec start_link() -> gen_server:start_ret().
 start_link() ->
-    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+    gen_server:start_link({local, ?MODULE}, ?MODULE, noargs, []).
 
 -spec process_iq(Acc :: mongoose_acc:t(),
                  From :: jid:jid(),
@@ -261,22 +256,13 @@ disco_local_features(Acc, _, _) ->
 %%                         {stop, Reason}
 %% Description: Initiates the server
 %%--------------------------------------------------------------------
-init([]) ->
+init(noargs) ->
     catch ets:new(?IQTABLE, [named_table, protected, {read_concurrency, true}]),
     catch ets:new(?NSTABLE, [named_table, bag, protected, {read_concurrency, true}]),
     catch ets:new(?IQRESPONSE, [named_table, public]),
     gen_hook:add_handlers(hooks()),
     {ok, #state{}}.
 
-%%--------------------------------------------------------------------
-%% Function: %% handle_call(Request, From, State) -> {reply, Reply, State} |
-%%                                      {reply, Reply, State, Timeout} |
-%%                                      {noreply, State} |
-%%                                      {noreply, State, Timeout} |
-%%                                      {stop, Reason, Reply, State} |
-%%                                      {stop, Reason, State}
-%% Description: Handling call messages
-%%--------------------------------------------------------------------
 handle_call({unregister_host, Host}, _From, State) ->
     Node = node(),
     [mongoose_c2s:stop(Pid, host_was_unregistered)
@@ -293,21 +279,9 @@ handle_call(_Request, _From, State) ->
     Reply = ok,
     {reply, Reply, State}.
 
-%%--------------------------------------------------------------------
-%% Function: handle_cast(Msg, State) -> {noreply, State} |
-%%                                      {noreply, State, Timeout} |
-%%                                      {stop, Reason, State}
-%% Description: Handling cast messages
-%%--------------------------------------------------------------------
 handle_cast(_Msg, State) ->
     {noreply, State}.
 
-%%--------------------------------------------------------------------
-%% Function: handle_info(Info, State) -> {noreply, State} |
-%%                                       {noreply, State, Timeout} |
-%%                                       {stop, Reason, State}
-%% Description: Handling all non call/cast messages
-%%--------------------------------------------------------------------
 handle_info({route, Acc, From, To, El}, State) ->
     spawn(fun() -> process_packet(Acc, From, To, El, #{}) end),
     {noreply, State};
@@ -341,13 +315,6 @@ handle_info(_Info, State) ->
 terminate(_Reason, _State) ->
     gen_hook:delete_handlers(hooks()).
 
-%%--------------------------------------------------------------------
-%% Func: code_change(OldVsn, State, Extra) -> {ok, NewState}
-%% Description: Convert process state when code is changed
-%%--------------------------------------------------------------------
-code_change(_OldVsn, State, _Extra) ->
-    {ok, State}.
-
 %%--------------------------------------------------------------------
 %%% Internal functions
 %%--------------------------------------------------------------------

src/ejabberd_router.erl

@@ -36,7 +36,7 @@
 -export([start_link/0]).
 
 %% gen_server callbacks
--export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2]).
 
 -ignore_xref([route_error/4, start_link/0]).
 
@@ -49,9 +49,9 @@
 %% API
 %%====================================================================
 
--spec start_link() -> 'ignore' | {'error', _} | {'ok', pid()}.
+-spec start_link() -> gen_server:start_ret().
 start_link() ->
-    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+    gen_server:start_link({local, ?MODULE}, ?MODULE, noargs, [{hibernate_after, 0}]).
 
 %% @doc The main routing function. It puts the message through a chain
 %% of filtering/routing modules, as defined in config 'routing_modules'
@@ -133,13 +133,12 @@ route_error_reply(From, To, Acc, Error) ->
 %% gen_server callbacks
 %%====================================================================
 
-init([]) ->
+init(noargs) ->
     mongoose_component:start(),
     {ok, #state{}}.
 
 handle_call(_Request, _From, State) ->
-    Reply = ok,
-    {reply, Reply, State}.
+    {reply, ok, State}.
 
 handle_cast(_Msg, State) ->
     {noreply, State}.
@@ -151,9 +150,6 @@ terminate(_Reason, _State) ->
     mongoose_component:stop(),
     ok.
 
-code_change(_OldVsn, State, _Extra) ->
-    {ok, State}.
-
 %%--------------------------------------------------------------------
 %%% Internal functions
 %%--------------------------------------------------------------------

src/ejabberd_sm.erl

@@ -140,7 +140,7 @@ start() ->
     Spec = {?MODULE, {?MODULE, start_link, []}, permanent, brutal_kill, worker, [?MODULE]},
     {ok, _} = ejabberd_sup:start_child(Spec).
 
--spec start_link() -> 'ignore' | {'error', _} | {'ok', pid()}.
+-spec start_link() -> gen_server:start_ret().
 start_link() ->
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
 

src/ejabberd_sm_backend_sup.erl

@@ -1,9 +1,6 @@
 %%%-------------------------------------------------------------------
 %%% @author Konrad Kaplita
 %%% @copyright (C) 2011, Konrad Kaplita
-%%% @doc
-%%%
-%%% @end
 %%% Created : 18 Nov 2011 by Konrad Kaplita
 %%%-------------------------------------------------------------------
 -module(ejabberd_sm_backend_sup).
@@ -20,32 +17,11 @@
 
 -define(SERVER, ?MODULE).
 
-%%%===================================================================
-%%% API functions
-%%%===================================================================
-
-%%--------------------------------------------------------------------
-%% @doc
-%% Starts the supervisor
-%% @end
-%%--------------------------------------------------------------------
--spec start_link() -> {ok, Pid :: pid()} | ignore | {error, Reason :: term()}.
+-spec start_link() -> supervisor:startlink_ret().
 start_link() ->
-    supervisor:start_link({local, ?SERVER}, ?MODULE, []).
-
-%%%===================================================================
-%%% Supervisor callbacks
-%%%===================================================================
+    supervisor:start_link({local, ?SERVER}, ?MODULE, noargs).
 
-%%--------------------------------------------------------------------
 %% @private
-%% @doc
-%% Whenever a supervisor is started using supervisor:start_link/[2, 3],
-%% this function is called by the new process to find out about
-%% restart strategy, maximum restart frequency and child
-%% specifications.
-%% @end
-%%--------------------------------------------------------------------
--spec init([]) -> {ok, {{one_for_one, 1000, 3600}, []}}.
-init([]) ->
+-spec init(noargs) -> {ok, {supervisor:sup_flags(), [supervisor:child_spec()]}}.
+init(noargs) ->
     {ok, {{one_for_one, 1000, 3600}, []}}.

src/ejabberd_sup.erl

@@ -37,10 +37,12 @@
 
 -include("mongoose_logger.hrl").
 
+-spec start_link() -> supervisor:startlink_err().
 start_link() ->
-    supervisor:start_link({local, ?MODULE}, ?MODULE, []).
+    supervisor:start_link({local, ?MODULE}, ?MODULE, noargs).
 
-init([]) ->
+-spec init(noargs) -> {ok, {supervisor:sup_flags(), [supervisor:child_spec()]}}.
+init(noargs) ->
     Hooks = worker_spec(gen_hook),
     Instrument = worker_spec(mongoose_instrument),
     Cleaner = worker_spec(mongoose_cleaner),

src/gen_hook.erl

@@ -15,7 +15,6 @@
 -export([init/1,
          handle_call/3,
          handle_cast/2,
-         code_change/3,
          handle_info/2,
          terminate/2]).
 
@@ -76,6 +75,7 @@
 %%%----------------------------------------------------------------------
 %%% API
 %%%----------------------------------------------------------------------
+-spec start_link() -> gen_server:start_ret().
 start_link() ->
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
 
@@ -200,7 +200,7 @@ handle_call({delete_handler, Key = {Name, Tag}, #hook_handler{} = HookHandler},
     {reply, ok, NewState};
 handle_call(reload_hooks, _From, State) ->
     persistent_term:put(?MODULE, State),
-    {reply, ok, State};
+    {reply, ok, State, hibernate};
 handle_call(Request, From, State) ->
     ?UNEXPECTED_CALL(Request, From),
     {reply, bad_request, State}.
@@ -217,9 +217,6 @@ terminate(_Reason, _State) ->
     persistent_term:erase(?MODULE),
     ok.
 
-code_change(_OldVsn, State, _Extra) ->
-    {ok, State}.
-
 %%%----------------------------------------------------------------------
 %%% Internal functions
 %%%----------------------------------------------------------------------

src/instrument/mongoose_instrument.erl

@@ -14,7 +14,7 @@
 -export([add_handler/2, remove_handler/1]).
 
 %% gen_server callbacks
--export([init/1, handle_call/3, handle_cast/2, code_change/3, handle_info/2, terminate/2]).
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2]).
 
 -ignore_xref([start_link/0, set_up/3, tear_down/2, span/4, add_handler/2, remove_handler/1]).
 
@@ -180,7 +180,8 @@ init([]) ->
     {ok, #{events => #{}, probe_timers => #{}}}.
 
 -spec handle_call(any(), gen_server:from(), state()) ->
-          {reply, ok | {ok, handlers()} | {error, map()}, state()}.
+          {reply, ok | {ok, handlers()} | {error, map()}, state()} |
+          {reply, ok | {ok, handlers()} | {error, map()}, state(), hibernate}.
 handle_call({set_up, EventName, Labels, Config}, _From,
             #{events := Events, probe_timers := ProbeTimers} = State) ->
     case set_up_and_register_event(EventName, Labels, Config, Events) of
@@ -226,7 +227,7 @@ handle_call({remove_handler, Key}, _From, State = #{events := Events}) ->
     end;
 handle_call(persist, _From, State = #{events := Events}) ->
     persistent_term:put(?MODULE, Events),
-    {reply, ok, State};
+    {reply, ok, State, hibernate};
 handle_call({lookup, EventName, Labels}, _From, State = #{events := Events}) ->
     {reply, lookup(EventName, Labels, Events), State};
 handle_call(Request, From, State) ->
@@ -250,10 +251,6 @@ terminate(_Reason, _State) ->
      || {Key, Opts = #{}} <- maps:to_list(mongoose_config:get_opt(instrumentation))],
     ok.
 
--spec code_change(any(), state(), any()) -> {ok, state()}.
-code_change(_OldVsn, State, _Extra) ->
-    {ok, State}.
-
 %% Internal functions
 
 -spec update_if_persisted(event_map(), event_map()) -> ok.

src/listeners/mongoose_listener_sup.erl

@@ -1,5 +1,4 @@
 %% @doc Supervisor for the socket listeners
-
 -module(mongoose_listener_sup).
 
 -behaviour(supervisor).
@@ -8,13 +7,11 @@
 
 -ignore_xref([start_link/0, init/1]).
 
--include("mongoose_logger.hrl").
-
 %% API
 
--spec start_link() -> {ok, pid()}.
+-spec start_link() -> supervisor:startlink_ret().
 start_link() ->
-    supervisor:start_link({local, ?MODULE}, ?MODULE, []).
+    supervisor:start_link({local, ?MODULE}, ?MODULE, noargs).
 
 -spec start_child(supervisor:child_spec()) -> ok.
 start_child(ChildSpec) ->
@@ -24,8 +21,8 @@ start_child(ChildSpec) ->
 
 %% Supervisor callbacks
 
--spec init([]) -> {ok, {supervisor:sup_flags(), []}}.
-init([]) ->
+-spec init(noargs) -> {ok, {supervisor:sup_flags(), [supervisor:child_spec()]}}.
+init(noargs) ->
     {ok, {#{strategy => one_for_one,
             intensity => 10,
             period => 1}, []}}.

src/mod_caps.erl

@@ -88,8 +88,7 @@
 start_link(HostType, Opts) ->
     mod_caps_backend:init(HostType, Opts),
     Proc = gen_mod:get_module_proc(HostType, ?PROCNAME),
-    gen_server:start_link({local, Proc}, ?MODULE,
-                          [HostType, Opts], []).
+    gen_server:start_link({local, Proc}, ?MODULE, [HostType, Opts], [{hibernate_after, 0}]).
 
 -spec start(mongooseim:host_type(), gen_mod:module_opts()) -> any().
 start(HostType, Opts) ->

src/mongoose_cleaner.erl

@@ -10,8 +10,7 @@
          handle_call/3,
          handle_cast/2,
          handle_info/2,
-         terminate/2,
-         code_change/3]).
+         terminate/2]).
 
 -ignore_xref([start_link/0]).
 
@@ -26,14 +25,15 @@
 %%% API
 %%%===================================================================
 
+-spec start_link() -> gen_server:start_ret().
 start_link() ->
-    gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
+    gen_server:start_link({local, ?SERVER}, ?MODULE, noargs, []).
 
 %%%===================================================================
 %%% gen_server callbacks
 %%%===================================================================
 
-init([]) ->
+init(noargs) ->
     case net_kernel:monitor_nodes(true) of
         ok ->
             {ok, #state{}};
@@ -45,8 +45,7 @@ init([]) ->
     end.
 
 handle_call(_Request, _From, State) ->
-    Reply = ok,
-    {reply, Reply, State}.
+    {reply, ok, State}.
 
 handle_cast(_Msg, State) ->
     {noreply, State}.
@@ -63,9 +62,6 @@ handle_info(_Info, State) ->
 terminate(_Reason, _State) ->
     ok.
 
-code_change(_OldVsn, State, _Extra) ->
-    {ok, State}.
-
 %%%===================================================================
 %%% Internal functions
 %%%===================================================================