Set process flags when Erlang/OTP 27 to help debugging

https://www.erlang.org/blog/highlights-otp-27/#process-labels

src/ejabberd_c2s.erl

@@ -290,6 +290,7 @@ reject_unauthenticated_packet(State, _Pkt) ->
 process_auth_result(#{sasl_mech := Mech, auth_module := AuthModule,
 		      socket := Socket, ip := IP, lserver := LServer} = State,
 		    true, User) ->
+    misc:set_proc_label({?MODULE, User, LServer}),
     ?INFO_MSG("(~ts) Accepted c2s ~ts authentication for ~ts@~ts by ~ts backend from ~ts",
               [xmpp_socket:pp(Socket), Mech, User, LServer,
                ejabberd_auth:backend_type(AuthModule),
@@ -617,6 +618,7 @@ init([State, Opts]) ->
 		    access => Access,
 		    shaper => Shaper},
     State2 = xmpp_stream_in:set_timeout(State1, Timeout),
+    misc:set_proc_label({?MODULE, init_state}),
     ejabberd_hooks:run_fold(c2s_init, {ok, State2}, [Opts]).
 
 handle_call(get_presence, From, #{jid := JID} = State) ->

src/ejabberd_listener.erl

@@ -121,6 +121,7 @@ init({Port, _, udp} = EndPoint, Module, Opts, SockOpts) ->
 			     ExtraOpts2]) of
 	{ok, Socket} ->
             set_definitive_udsocket(Port, Opts),
+            misc:set_proc_label({?MODULE, udp, Port}),
 	    case inet:sockname(Socket) of
 		{ok, {Addr, Port1}} ->
 		    proc_lib:init_ack({ok, self()}),
@@ -155,6 +156,7 @@ init({Port, _, tcp} = EndPoint, Module, Opts, SockOpts) ->
 	    case inet:sockname(ListenSocket) of
 		{ok, {Addr, Port1}} ->
 		    proc_lib:init_ack({ok, self()}),
+                    misc:set_proc_label({?MODULE, tcp, Port}),
 		    case application:ensure_started(ejabberd) of
 			ok ->
 			    Sup = start_module_sup(Module, Opts),

src/misc.erl

@@ -43,6 +43,7 @@
 	 get_my_ipv4_address/0, get_my_ipv6_address/0, parse_ip_mask/1,
 	 crypto_hmac/3, crypto_hmac/4, uri_parse/1, uri_parse/2, uri_quote/1,
          json_encode/1, json_decode/1,
+	 set_proc_label/1,
 	 match_ip_mask/3, format_hosts_list/1, format_cycle/1, delete_dir/1,
 	 semver_to_xxyy/1, logical_processors/0, get_mucsub_event_type/1]).
 
@@ -780,3 +781,11 @@ to_string(B) when is_binary(B) ->
     binary_to_list(B);
 to_string(S) ->
     S.
+
+-ifdef(OTP_BELOW_27).
+set_proc_label(_Label) ->
+    ok.
+-else.
+set_proc_label(Label) ->
+    proc_lib:set_label(Label).
+-endif.

src/mod_muc_room.erl

@@ -292,6 +292,7 @@ get_disco_item(Pid, Filter, JID, Lang) ->
 init([Host, ServerHost, Access, Room, HistorySize,
       RoomShaper, Creator, _Nick, DefRoomOpts, QueueType]) ->
     process_flag(trap_exit, true),
+    misc:set_proc_label({?MODULE, Room, Host}),
     Shaper = ejabberd_shaper:new(RoomShaper),
     RoomQueue = room_queue_new(ServerHost, Shaper, QueueType),
     State = set_opts(DefRoomOpts,
@@ -314,6 +315,7 @@ init([Host, ServerHost, Access, Room, HistorySize,
     {ok, normal_state, reset_hibernate_timer(State1)};
 init([Host, ServerHost, Access, Room, HistorySize, RoomShaper, Opts, QueueType]) ->
     process_flag(trap_exit, true),
+    misc:set_proc_label({?MODULE, Room, Host}),
     Shaper = ejabberd_shaper:new(RoomShaper),
     RoomQueue = room_queue_new(ServerHost, Shaper, QueueType),
     Jid = jid:make(Room, Host),