Remove most of the fd related FHC code

Stats were not removed, including management UI stats
relating to FDs.

Web-MQTT and Web-STOMP configuration relating to FHC
were not removed.

The file_handle_cache itself must be kept until we
remove CQv1.

deps/amqp_client/src/amqp_network_connection.erl

@@ -118,7 +118,6 @@ do_connect({Addr, Family},
                                              connection_timeout = Timeout,
                                              socket_options     = ExtraOpts},
            SIF, State) ->
-    ok = obtain(),
     case gen_tcp:connect(Addr, Port,
                          [Family | ?RABBIT_TCP_OPTS] ++ ExtraOpts,
                          Timeout) of
@@ -134,7 +133,6 @@ do_connect({Addr, Family},
            SIF, State) ->
     {ok, GlobalSslOpts} = application:get_env(amqp_client, ssl_options),
     app_utils:start_applications([asn1, crypto, public_key, ssl]),
-    ok = obtain(),
     case gen_tcp:connect(Addr, Port,
                          [Family | ?RABBIT_TCP_OPTS] ++ ExtraOpts,
                          Timeout) of
@@ -379,11 +377,5 @@ handshake_recv(Expecting) ->
         end
     end.
 
-obtain() ->
-    case code:is_loaded(file_handle_cache) of
-        false -> ok;
-        _     -> file_handle_cache:obtain()
-    end.
-
 get_reason(#'connection.close'{reply_code = ErrCode}) ->
     ?PROTOCOL:amqp_exception(ErrCode).

deps/rabbit/src/rabbit.erl

@@ -744,9 +744,6 @@ status() ->
                                         get_disk_free_limit, []}},
             {disk_free,                {rabbit_disk_monitor,
                                         get_disk_free, []}}]),
-    S3 = rabbit_misc:with_exit_handler(
-           fun () -> [] end,
-           fun () -> [{file_descriptors, file_handle_cache:info()}] end),
     S4 = [{processes,        [{limit, erlang:system_info(process_limit)},
                               {used, erlang:system_info(process_count)}]},
           {run_queue,        erlang:statistics(run_queue)},
@@ -781,7 +778,7 @@ status() ->
                (_) -> false
            end,
            maps:to_list(product_info())),
-    S1 ++ S2 ++ S3 ++ S4 ++ S5 ++ S6 ++ S7 ++ S8.
+    S1 ++ S2 ++ S4 ++ S5 ++ S6 ++ S7 ++ S8.
 
 alarms() ->
     Alarms = rabbit_misc:with_exit_handler(rabbit_misc:const([]),
@@ -1656,7 +1653,7 @@ config_files() ->
 start_fhc() ->
     ok = rabbit_sup:start_restartable_child(
       file_handle_cache,
-      [fun rabbit_alarm:set_alarm/1, fun rabbit_alarm:clear_alarm/1]),
+      [fun(_) -> ok end, fun(_) -> ok end]),
     ensure_working_fhc().
 
 ensure_working_fhc() ->

deps/rabbit/src/rabbit_amqqueue.erl

@@ -7,7 +7,6 @@
 
 -module(rabbit_amqqueue).
 
--export([warn_file_limit/0]).
 -export([recover/1, stop/1, start/1, declare/6, declare/7,
          delete_immediately/1, delete_exclusive/2, delete/4, purge/1,
          forget_all_durable/1]).
@@ -119,21 +118,6 @@
          active, activity_status, arguments]).
 -define(KILL_QUEUE_DELAY_INTERVAL, 100).
 
-warn_file_limit() ->
-    DurableQueues = find_recoverable_queues(),
-    L = length(DurableQueues),
-
-    %% if there are not enough file handles, the server might hang
-    %% when trying to recover queues, warn the user:
-    case file_handle_cache:get_limit() < L of
-        true ->
-            rabbit_log:warning(
-              "Recovering ~tp queues, available file handles: ~tp. Please increase max open file handles limit to at least ~tp!",
-              [L, file_handle_cache:get_limit(), L]);
-        false ->
-            ok
-    end.
-
 -spec recover(rabbit_types:vhost()) ->
     {Recovered :: [amqqueue:amqqueue()],
      Failed :: [amqqueue:amqqueue()]}.
@@ -183,11 +167,6 @@ find_local_durable_queues(VHostName) ->
                                                    rabbit_queue_type:is_recoverable(Q)
                                        end).
 
-find_recoverable_queues() ->
-    rabbit_db_queue:filter_all_durable(fun(Q) ->
-                                               rabbit_queue_type:is_recoverable(Q)
-                                       end).
-
 -spec declare(name(),
               boolean(),
               boolean(),

deps/rabbit/src/rabbit_amqqueue_process.erl

@@ -210,8 +210,6 @@ init_it2(Recover, From, State = #q{q                   = Q,
                (Res == created orelse Res == existing) ->
             case matches(Recover, Q, Q1) of
                 true ->
-                    ok = file_handle_cache:register_callback(
-                           rabbit_amqqueue, set_maximum_since_use, [self()]),
                     BQ = backing_queue_module(),
                     BQS = bq_init(BQ, Q, TermsOrNew),
                     send_reply(From, {new, Q}),
@@ -1189,7 +1187,6 @@ prioritise_cast(Msg, _Len, State) ->
     case Msg of
         delete_immediately                   -> 8;
         {delete_exclusive, _Pid}             -> 8;
-        {set_maximum_since_use, _Age}        -> 8;
         {run_backing_queue, _Mod, _Fun}      -> 6;
         {ack, _AckTags, _ChPid}              -> 4; %% [1]
         {resume, _ChPid}                     -> 3;
@@ -1499,10 +1496,6 @@ handle_cast({deactivate_limit, ChPid}, State) ->
     noreply(possibly_unblock(rabbit_queue_consumers:deactivate_limit_fun(),
                              ChPid, State));
 
-handle_cast({set_maximum_since_use, Age}, State) ->
-    ok = file_handle_cache:set_maximum_since_use(Age),
-    noreply(State);
-
 handle_cast({credit, SessionPid, CTag, Credit, Drain},
             #q{q = Q,
                backing_queue = BQ,

deps/rabbit/src/rabbit_classic_queue_index_v2.erl

@@ -41,15 +41,6 @@
 -define(HEADER_SIZE, 64). %% bytes
 -define(ENTRY_SIZE,  32). %% bytes
 
-%% The file_handle_cache module tracks reservations at
-%% the level of the process. This means we cannot
-%% handle them independently in the store and index.
-%% Because the index may reserve more FDs than the
-%% store the index becomes responsible for this and
-%% will always reserve at least 2 FDs, and release
-%% everything when terminating.
--define(STORE_FD_RESERVATIONS, 2).
-
 -include_lib("rabbit_common/include/rabbit.hrl").
 %% Set to true to get an awful lot of debug logs.
 -if(false).
@@ -538,7 +529,6 @@ terminate(VHost, Terms, State0 = #qi { dir = Dir,
         ok = file:sync(Fd),
         ok = file:close(Fd)
     end, OpenFds),
-    file_handle_cache:release_reservation(),
     %% Write recovery terms for faster recovery.
     _ = rabbit_recovery_terms:store(VHost,
                                 filename:basename(rabbit_file:binary_to_filename(Dir)),
@@ -555,7 +545,6 @@ delete_and_terminate(State = #qi { dir = Dir,
     _ = maps:map(fun(_, Fd) ->
         ok = file:close(Fd)
     end, OpenFds),
-    file_handle_cache:release_reservation(),
     %% Erase the data on disk.
     ok = erase_index_dir(rabbit_file:binary_to_filename(Dir)),
     State#qi{ segments = #{},
@@ -626,18 +615,9 @@ new_segment_file(Segment, SegmentEntryCount, State = #qi{ segments = Segments })
 %% using too many FDs when the consumer lags a lot. We
 %% limit at 4 because we try to keep up to 2 for reading
 %% and 2 for writing.
-reduce_fd_usage(SegmentToOpen, State = #qi{ fds = OpenFds })
+reduce_fd_usage(_SegmentToOpen, State = #qi{ fds = OpenFds })
         when map_size(OpenFds) < 4 ->
-    %% The only case where we need to update reservations is
-    %% when we are opening a segment that wasn't already open,
-    %% and we are not closing another segment at the same time.
-    case OpenFds of
-        #{SegmentToOpen := _} ->
     State;
-        _ ->
-            file_handle_cache:set_reservation(?STORE_FD_RESERVATIONS + map_size(OpenFds) + 1),
-            State
-    end;
 reduce_fd_usage(SegmentToOpen, State = #qi{ fds = OpenFds0 }) ->
     case OpenFds0 of
         #{SegmentToOpen := _} ->
@@ -868,7 +848,6 @@ delete_segment(Segment, State0 = #qi{ fds = OpenFds0 }) ->
     State = case maps:take(Segment, OpenFds0) of
         {Fd, OpenFds} ->
             ok = file:close(Fd),
-            file_handle_cache:set_reservation(?STORE_FD_RESERVATIONS + map_size(OpenFds)),
             State0#qi{ fds = OpenFds };
         error ->
             State0

deps/rabbit/src/rabbit_classic_queue_store_v2.erl

@@ -41,11 +41,6 @@
 %% need to look into the store to discard them. Messages on disk
 %% will be dropped at the same time as the index deletes the
 %% corresponding segment file.
-%%
-%% The file_handle_cache reservations are done by the v2 index
-%% because they are handled at a pid level. Since we are using
-%% up to 2 FDs in this module we make the index reserve 2 extra
-%% FDs.
 
 -module(rabbit_classic_queue_store_v2).
 

deps/rabbit/src/rabbit_fifo.erl

@@ -894,10 +894,8 @@ state_enter0(leader, #?MODULE{consumers = Cons,
     Mons = [{monitor, process, P} || P <- Pids],
     Nots = [{send_msg, P, leader_change, ra_event} || P <- Pids],
     NodeMons = lists:usort([{monitor, node, node(P)} || P <- Pids]),
-    FHReservation = [{mod_call, rabbit_quorum_queue,
-                      file_handle_leader_reservation, [Resource]}],
     NotifyDecs = notify_decorators_startup(Resource),
-    Effects = TimerEffs ++ Mons ++ Nots ++ NodeMons ++ FHReservation ++ [NotifyDecs],
+    Effects = TimerEffs ++ Mons ++ Nots ++ NodeMons ++ [NotifyDecs],
     case BLH of
         undefined ->
             Effects;
@@ -914,12 +912,7 @@ state_enter0(eol, #?MODULE{enqueuers = Enqs,
     AllConsumers = maps:merge(Custs, WaitingConsumers1),
     [{send_msg, P, eol, ra_event}
      || P <- maps:keys(maps:merge(Enqs, AllConsumers))] ++
-    [{aux, eol},
+    [{aux, eol} | Effects];
-     {mod_call, rabbit_quorum_queue, file_handle_release_reservation, []} | Effects];
-state_enter0(State, #?MODULE{cfg = #cfg{resource = _Resource}}, Effects)
-  when State =/= leader ->
-    FHReservation = {mod_call, rabbit_quorum_queue, file_handle_other_reservation, []},
-    [FHReservation | Effects];
 state_enter0(_, _, Effects) ->
     %% catch all as not handling all states
     Effects.

deps/rabbit/src/rabbit_fifo_v0.erl

@@ -548,7 +548,6 @@ state_enter(leader, #?STATE{consumers = Cons,
                              enqueuers = Enqs,
                              waiting_consumers = WaitingConsumers,
                              cfg = #cfg{name = Name,
-                                        resource = Resource,
                                         become_leader_handler = BLH},
                              prefix_msgs = {0, [], 0, []}
                             }) ->
@@ -559,8 +558,7 @@ state_enter(leader, #?STATE{consumers = Cons,
     Mons = [{monitor, process, P} || P <- Pids],
     Nots = [{send_msg, P, leader_change, ra_event} || P <- Pids],
     NodeMons = lists:usort([{monitor, node, node(P)} || P <- Pids]),
-    FHReservation = [{mod_call, rabbit_quorum_queue, file_handle_leader_reservation, [Resource]}],
+    Effects = Mons ++ Nots ++ NodeMons,
-    Effects = Mons ++ Nots ++ NodeMons ++ FHReservation,
     case BLH of
         undefined ->
             Effects;
@@ -575,11 +573,7 @@ state_enter(eol, #?STATE{enqueuers = Enqs,
                                     #{}, WaitingConsumers0),
     AllConsumers = maps:merge(Custs, WaitingConsumers1),
     [{send_msg, P, eol, ra_event}
-     || P <- maps:keys(maps:merge(Enqs, AllConsumers))] ++
+     || P <- maps:keys(maps:merge(Enqs, AllConsumers))];
-        [{mod_call, rabbit_quorum_queue, file_handle_release_reservation, []}];
-state_enter(State, #?STATE{cfg = #cfg{resource = _Resource}}) when State =/= leader ->
-    FHReservation = {mod_call, rabbit_quorum_queue, file_handle_other_reservation, []},
-    [FHReservation];
  state_enter(_, _) ->
     %% catch all as not handling all states
     [].

deps/rabbit/src/rabbit_fifo_v1.erl

@@ -676,7 +676,6 @@ state_enter(leader, #?STATE{consumers = Cons,
                              enqueuers = Enqs,
                              waiting_consumers = WaitingConsumers,
                              cfg = #cfg{name = Name,
-                                        resource = Resource,
                                         become_leader_handler = BLH},
                              prefix_msgs = {0, [], 0, []}
                             }) ->
@@ -687,8 +686,7 @@ state_enter(leader, #?STATE{consumers = Cons,
     Mons = [{monitor, process, P} || P <- Pids],
     Nots = [{send_msg, P, leader_change, ra_event} || P <- Pids],
     NodeMons = lists:usort([{monitor, node, node(P)} || P <- Pids]),
-    FHReservation = [{mod_call, rabbit_quorum_queue, file_handle_leader_reservation, [Resource]}],
+    Effects = Mons ++ Nots ++ NodeMons,
-    Effects = Mons ++ Nots ++ NodeMons ++ FHReservation,
     case BLH of
         undefined ->
             Effects;
@@ -704,11 +702,7 @@ state_enter(eol, #?STATE{enqueuers = Enqs,
     AllConsumers = maps:merge(Custs, WaitingConsumers1),
     [{send_msg, P, eol, ra_event}
      || P <- maps:keys(maps:merge(Enqs, AllConsumers))] ++
-                   [{aux, eol},
+                   [{aux, eol}];
-                    {mod_call, rabbit_quorum_queue, file_handle_release_reservation, []}];
-state_enter(State, #?STATE{cfg = #cfg{resource = _Resource}}) when State =/= leader ->
-    FHReservation = {mod_call, rabbit_quorum_queue, file_handle_other_reservation, []},
-    [FHReservation];
  state_enter(_, _) ->
     %% catch all as not handling all states
     [].

deps/rabbit/src/rabbit_file.erl

@@ -18,8 +18,6 @@
 -export([filename_as_a_directory/1]).
 -export([filename_to_binary/1, binary_to_filename/1]).
 
--import(file_handle_cache, [with_handle/1, with_handle/2]).
-
 -define(TMP_EXT, ".tmp").
 
 %%----------------------------------------------------------------------------
@@ -56,7 +54,7 @@ file_size(File) ->
 
 -spec ensure_dir((file:filename())) -> ok_or_error().
 
-ensure_dir(File) -> with_handle(fun () -> ensure_dir_internal(File) end).
+ensure_dir(File) -> ensure_dir_internal(File).
 
 ensure_dir_internal("/")  ->
     ok;
@@ -81,16 +79,17 @@ wildcard(Pattern, Dir) ->
 -spec list_dir(file:filename()) ->
           rabbit_types:ok_or_error2([file:filename()], any()).
 
-list_dir(Dir) -> with_handle(fun () -> prim_file:list_dir(Dir) end).
+list_dir(Dir) -> prim_file:list_dir(Dir).
 
 read_file_info(File) ->
-    with_handle(fun () -> file:read_file_info(File, [raw]) end).
+    file:read_file_info(File, [raw]).
 
 -spec read_term_file
         (file:filename()) -> {'ok', [any()]} | rabbit_types:error(any()).
 
 read_term_file(File) ->
     try
+        %% @todo OTP-27+ has file:read_file(File, [raw]).
         F = fun() ->
                     {ok, FInfo} = file:read_file_info(File, [raw]),
                     {ok, Fd} = file:open(File, [read, raw, binary]),
@@ -100,7 +99,7 @@ read_term_file(File) ->
                         file:close(Fd)
                     end
             end,
-        {ok, Data} = with_handle(F),
+        {ok, Data} = F(),
         {ok, Tokens, _} = erl_scan:string(binary_to_list(Data)),
         TokenGroups = group_tokens(Tokens),
         {ok, [begin
@@ -166,8 +165,6 @@ with_synced_copy(Path, Modes, Fun) ->
         true ->
             {error, append_not_supported, Path};
         false ->
-            with_handle(
-              fun () ->
             Bak = Path ++ ?TMP_EXT,
             case prim_file:open(Bak, Modes) of
                 {ok, Hdl} ->
@@ -181,7 +178,6 @@ with_synced_copy(Path, Modes, Fun) ->
                     end;
                 {error, _} = E -> E
             end
-              end)
     end.
 
 %% TODO the semantics of this function are rather odd. But see bug 25021.
@@ -198,16 +194,12 @@ append_file(File, Suffix) ->
 append_file(_, _, "") ->
     ok;
 append_file(File, 0, Suffix) ->
-    with_handle(fun () ->
     case prim_file:open([File, Suffix], [append]) of
         {ok, Fd} -> prim_file:close(Fd);
         Error    -> Error
-                        end
+    end;
-                end);
 append_file(File, _, Suffix) ->
-    case with_handle(2, fun () ->
+    case file:copy(File, {[File, Suffix], [append]}) of
-                                file:copy(File, {[File, Suffix], [append]})
-                        end) of
         {ok, _BytesCopied} -> ok;
         Error              -> Error
     end.
@@ -223,21 +215,19 @@ ensure_parent_dirs_exist(Filename) ->
 
 -spec rename(file:filename(), file:filename()) -> ok_or_error().
 
-rename(Old, New) -> with_handle(fun () -> prim_file:rename(Old, New) end).
+rename(Old, New) -> prim_file:rename(Old, New).
 
 -spec delete([file:filename()]) -> ok_or_error().
 
-delete(File) -> with_handle(fun () -> prim_file:delete(File) end).
+delete(File) -> prim_file:delete(File).
 
 -spec recursive_delete([file:filename()]) ->
           rabbit_types:ok_or_error({file:filename(), any()}).
 
 recursive_delete(Files) ->
-    with_handle(
+    lists:foldl(fun (Path,  ok) -> recursive_delete1(Path);
-      fun () -> lists:foldl(fun (Path,  ok) -> recursive_delete1(Path);
                     (_Path, {error, _Err} = Error) -> Error
-                            end, ok, Files)
+                end, ok, Files).
-      end).
 
 recursive_delete1(Path) ->
     case is_dir_no_handle(Path) and not(is_symlink_no_handle(Path)) of
@@ -315,10 +305,8 @@ recursive_copy(Src, Dest) ->
 lock_file(Path) ->
     case is_file(Path) of
         true  -> {error, eexist};
-        false -> with_handle(
+        false -> {ok, Lock} = prim_file:open(Path, [write]),
-                   fun () -> {ok, Lock} = prim_file:open(Path, [write]),
                  ok = prim_file:close(Lock)
-                   end)
     end.
 
 -spec filename_as_a_directory(file:filename()) -> file:filename().

deps/rabbit/src/rabbit_networking.erl

@@ -576,7 +576,7 @@ handshake(Ref, ProxyProtocolEnabled) ->
                         {'EXIT', normal} ->
                             {error, handshake_failed};
                         {ok, Sock} ->
-                            setup_socket(Sock),
+                            ok = tune_buffer_size(Sock),
                             {ok, {rabbit_proxy_socket, Sock, ProxyInfo}}
                     end
             end;
@@ -585,15 +585,11 @@ handshake(Ref, ProxyProtocolEnabled) ->
                 {'EXIT', normal} ->
                     {error, handshake_failed};
                 {ok, Sock} ->
-                    setup_socket(Sock),
+                    ok = tune_buffer_size(Sock),
                     {ok, Sock}
             end
     end.
 
-setup_socket(Sock) ->
-    ok = tune_buffer_size(Sock),
-    ok = file_handle_cache:obtain().
-
 tune_buffer_size(Sock) ->
     case tune_buffer_size1(Sock) of
         ok         -> ok;

deps/rabbit/src/rabbit_quorum_queue.erl

@@ -51,9 +51,6 @@
          grow/4,
          grow/5]).
 -export([transfer_leadership/2, get_replicas/1, queue_length/1]).
--export([file_handle_leader_reservation/1,
-         file_handle_other_reservation/0]).
--export([file_handle_release_reservation/0]).
 -export([list_with_minimum_quorum/0,
          list_with_local_promotable/0,
          list_with_local_promotable_for_cli/0,
@@ -1415,24 +1412,6 @@ matches_strategy(even, Members) ->
 is_match(Subj, E) ->
    nomatch /= re:run(Subj, E).
 
-file_handle_leader_reservation(QName) ->
-    try
-        {ok, Q} = rabbit_amqqueue:lookup(QName),
-        ClusterSize = length(get_nodes(Q)),
-        file_handle_cache:set_reservation(2 + ClusterSize)
-    catch Class:Err ->
-              rabbit_log:warning("~s:~s/~b failed with ~w ~w",
-                                 [?MODULE, ?FUNCTION_NAME, ?FUNCTION_ARITY,
-                                  Class, Err])
-    end.
-
-
-file_handle_other_reservation() ->
-    file_handle_cache:set_reservation(2).
-
-file_handle_release_reservation() ->
-    file_handle_cache:release_reservation().
-
 -spec reclaim_memory(rabbit_types:vhost(), Name :: rabbit_misc:resource_name()) -> ok | {error, term()}.
 reclaim_memory(Vhost, QueueName) ->
     QName = #resource{virtual_host = Vhost, name = QueueName, kind = queue},

deps/rabbit/src/rabbit_reader.erl

@@ -374,11 +374,7 @@ start_connection(Parent, HelperSups, RanchRef, Deb, Sock) ->
     after
         %% We don't call gen_tcp:close/1 here since it waits for
         %% pending output to be sent, which results in unnecessary
-        %% delays. We could just terminate - the reader is the
+        %% delays.
-        %% controlling process and hence its termination will close
-        %% the socket. However, to keep the file_handle_cache
-        %% accounting as accurate as possible we ought to close the
-        %% socket w/o delay before termination.
         rabbit_net:fast_close(RealSocket),
         rabbit_networking:unregister_connection(self()),
         rabbit_core_metrics:connection_closed(self()),

deps/rabbit/src/rabbit_vhost.erl

@@ -36,8 +36,6 @@ recover() ->
     %% faster than other nodes handled DOWN messages from us.
     rabbit_amqqueue:on_node_down(node()),
 
-    rabbit_amqqueue:warn_file_limit(),
-
     %% Prepare rabbit_semi_durable_route table
     {Time, _} = timer:tc(fun() ->
                                  rabbit_binding:recover()

deps/rabbit/test/backing_queue_SUITE.erl

@@ -97,8 +97,7 @@ init_per_group(Group, Config) ->
             rabbit_ct_helpers:run_steps(Config1,
               rabbit_ct_broker_helpers:setup_steps() ++
               rabbit_ct_client_helpers:setup_steps() ++ [
-                fun(C) -> init_per_group1(Group, C) end,
+                fun(C) -> init_per_group1(Group, C) end
-                fun setup_file_handle_cache/1
               ]);
         false ->
             rabbit_ct_helpers:run_steps(Config, [
@@ -137,17 +136,6 @@ init_per_group1(from_cluster_node2, Config) ->
 init_per_group1(_, Config) ->
     Config.
 
-setup_file_handle_cache(Config) ->
-    ok = rabbit_ct_broker_helpers:rpc(Config, 0,
-      ?MODULE, setup_file_handle_cache1, []),
-    Config.
-
-setup_file_handle_cache1() ->
-    %% FIXME: Why are we doing this?
-    application:set_env(rabbit, file_handles_high_watermark, 100),
-    ok = file_handle_cache:set_limit(100),
-    ok.
-
 end_per_group(Group, Config) ->
     case lists:member({group, Group}, all()) of
         true ->

deps/rabbit/test/quorum_queue_SUITE.erl

@@ -80,8 +80,6 @@ groups() ->
                                             reject_after_leader_transfer,
                                             shrink_all,
                                             rebalance,
-                                            file_handle_reservations,
-                                            file_handle_reservations_above_limit,
                                             node_removal_is_not_quorum_critical,
                                             leader_locator_client_local,
                                             leader_locator_balanced,
@@ -2053,61 +2051,6 @@ node_removal_is_not_quorum_critical(Config) ->
     ?assertEqual([], Qs).
 
 
-file_handle_reservations(Config) ->
-    case rabbit_ct_helpers:is_mixed_versions() of
-        true ->
-            {skip, "file_handle_reservations tests isn't mixed version compatible"};
-        false ->
-            file_handle_reservations0(Config)
-    end.
-
-file_handle_reservations0(Config) ->
-    Servers = [Server1 | _] = rabbit_ct_broker_helpers:get_node_configs(Config, nodename),
-    Ch = rabbit_ct_client_helpers:open_channel(Config, Server1),
-    QQ = ?config(queue_name, Config),
-    ?assertEqual({'queue.declare_ok', QQ, 0, 0},
-                 declare(Ch, QQ, [{<<"x-queue-type">>, longstr, <<"quorum">>}])),
-    RaName = ra_name(QQ),
-    {ok, _, {_, Leader}} = ra:members({RaName, Server1}),
-    [Follower1, Follower2] = Servers -- [Leader],
-    ?assertEqual([{files_reserved, 5}],
-                 rpc:call(Leader, file_handle_cache, info, [[files_reserved]])),
-    ?assertEqual([{files_reserved, 2}],
-                 rpc:call(Follower1, file_handle_cache, info, [[files_reserved]])),
-    ?assertEqual([{files_reserved, 2}],
-                 rpc:call(Follower2, file_handle_cache, info, [[files_reserved]])),
-    force_leader_change(Servers, QQ),
-    {ok, _, {_, Leader0}} = ra:members({RaName, Server1}),
-    [Follower01, Follower02] = Servers -- [Leader0],
-    ?assertEqual([{files_reserved, 5}],
-                 rpc:call(Leader0, file_handle_cache, info, [[files_reserved]])),
-    ?assertEqual([{files_reserved, 2}],
-                 rpc:call(Follower01, file_handle_cache, info, [[files_reserved]])),
-    ?assertEqual([{files_reserved, 2}],
-                 rpc:call(Follower02, file_handle_cache, info, [[files_reserved]])).
-
-file_handle_reservations_above_limit(Config) ->
-    [S1, S2, S3] = rabbit_ct_broker_helpers:get_node_configs(Config, nodename),
-
-    Ch = rabbit_ct_client_helpers:open_channel(Config, S1),
-    QQ = ?config(queue_name, Config),
-    QQ2 = ?config(alt_queue_name, Config),
-
-    Limit = rpc:call(S1, file_handle_cache, get_limit, []),
-
-    ok = rpc:call(S1, file_handle_cache, set_limit, [3]),
-    ok = rpc:call(S2, file_handle_cache, set_limit, [3]),
-    ok = rpc:call(S3, file_handle_cache, set_limit, [3]),
-
-    ?assertEqual({'queue.declare_ok', QQ, 0, 0},
-                 declare(Ch, QQ, [{<<"x-queue-type">>, longstr, <<"quorum">>}])),
-    ?assertEqual({'queue.declare_ok', QQ2, 0, 0},
-                 declare(Ch, QQ2, [{<<"x-queue-type">>, longstr, <<"quorum">>}])),
-
-    ok = rpc:call(S1, file_handle_cache, set_limit, [Limit]),
-    ok = rpc:call(S2, file_handle_cache, set_limit, [Limit]),
-    ok = rpc:call(S3, file_handle_cache, set_limit, [Limit]).
-
 cleanup_data_dir(Config) ->
     %% With Khepri this test needs to run in a 3-node cluster, otherwise the queue can't
     %% be deleted in minority

deps/rabbit/test/rabbit_fifo_SUITE.erl

@@ -725,29 +725,6 @@ duplicate_delivery_test(C) ->
     ?assertEqual(1, lqueue:len(Messages)),
     ok.
 
-state_enter_file_handle_leader_reservation_test(_) ->
-    S0 = init(#{name => the_name,
-                queue_resource => rabbit_misc:r(<<"/">>, queue, <<"test">>),
-                become_leader_handler => {m, f, [a]}}),
-
-    Resource = {resource, <<"/">>, queue, <<"test">>},
-    Effects = rabbit_fifo:state_enter(leader, S0),
-    ?assertMatch([{mod_call, m, f, [a, the_name]},
-                  _Timer,
-                  {mod_call, rabbit_quorum_queue, file_handle_leader_reservation, [Resource]}
-                  | _], Effects),
-    ok.
-
-state_enter_file_handle_other_reservation_test(_) ->
-    S0 = init(#{name => the_name,
-                queue_resource => rabbit_misc:r(<<"/">>, queue, <<"test">>)}),
-    Effects = rabbit_fifo:state_enter(other, S0),
-    ?assertEqual([
-        {mod_call, rabbit_quorum_queue, file_handle_other_reservation, []}
-      ],
-      Effects),
-    ok.
-
 state_enter_monitors_and_notifications_test(C) ->
     Oth = spawn(fun () -> ok end),
     {State0, _} = enq(C, 1, 1, first, test_init(test)),
@@ -1251,8 +1228,7 @@ single_active_consumer_state_enter_leader_include_waiting_consumers_test(C) ->
 
     Effects = rabbit_fifo:state_enter(leader, State1),
     %% 2 effects for each consumer process (channel process), 1 effect for the node,
-    %% 1 effect for file handle reservation
+    ?assertEqual(2 * 3 + 1 + 1 + 1, length(Effects)).
-    ?assertEqual(2 * 3 + 1 + 1 + 1 + 1, length(Effects)).
 
 single_active_consumer_state_enter_eol_include_waiting_consumers_test(C) ->
     Resource = rabbit_misc:r("/", queue, atom_to_binary(?FUNCTION_NAME, utf8)),
@@ -1282,9 +1258,8 @@ single_active_consumer_state_enter_eol_include_waiting_consumers_test(C) ->
 
     Effects = rabbit_fifo:state_enter(eol, State1),
     %% 1 effect for each consumer process (channel process),
-    %% 1 effect for file handle reservation
     %% 1 effect for eol to handle rabbit_fifo_usage entries
-    ?assertEqual(5, length(Effects)).
+    ?assertEqual(4, length(Effects)).
 
 query_consumers_test(C) ->
     State0 = init(#{name => ?FUNCTION_NAME,

deps/rabbit/test/rabbit_fifo_int_SUITE.erl

@@ -63,8 +63,6 @@ end_per_group(_, Config) ->
 init_per_testcase(TestCase, Config) ->
     meck:new(rabbit_quorum_queue, [passthrough]),
     meck:expect(rabbit_quorum_queue, handle_tick, fun (_, _, _) -> ok end),
-    meck:expect(rabbit_quorum_queue, file_handle_leader_reservation, fun (_) -> ok end),
-    meck:expect(rabbit_quorum_queue, file_handle_other_reservation, fun () -> ok end),
     meck:expect(rabbit_quorum_queue, cancel_consumer_handler, fun (_, _) -> ok end),
     ra_server_sup_sup:remove_all(?RA_SYSTEM),
     ServerName2 = list_to_atom(atom_to_list(TestCase) ++ "2"),

deps/rabbit/test/rabbit_fifo_v0_SUITE.erl

@@ -541,29 +541,6 @@ duplicate_delivery_test(_) ->
     ?assertEqual(1, maps:size(Messages)),
     ok.
 
-state_enter_file_handle_leader_reservation_test(_) ->
-    S0 = init(#{name => the_name,
-                queue_resource => rabbit_misc:r(<<"/">>, queue, <<"test">>),
-                become_leader_handler => {m, f, [a]}}),
-
-    Resource = {resource, <<"/">>, queue, <<"test">>},
-    Effects = rabbit_fifo_v0:state_enter(leader, S0),
-    ?assertEqual([
-        {mod_call, m, f, [a, the_name]},
-        {mod_call, rabbit_quorum_queue, file_handle_leader_reservation, [Resource]}
-      ], Effects),
-    ok.
-
-state_enter_file_handle_other_reservation_test(_) ->
-    S0 = init(#{name => the_name,
-                queue_resource => rabbit_misc:r(<<"/">>, queue, <<"test">>)}),
-    Effects = rabbit_fifo_v0:state_enter(other, S0),
-    ?assertEqual([
-        {mod_call, rabbit_quorum_queue, file_handle_other_reservation, []}
-      ],
-      Effects),
-    ok.
-
 state_enter_monitors_and_notifications_test(_) ->
     Oth = spawn(fun () -> ok end),
     {State0, _} = enq(1, 1, first, test_init(test)),
@@ -998,8 +975,7 @@ single_active_consumer_state_enter_leader_include_waiting_consumers_test(_) ->
 
     Effects = rabbit_fifo_v0:state_enter(leader, State1),
     %% 2 effects for each consumer process (channel process), 1 effect for the node,
-    %% 1 effect for file handle reservation
+    ?assertEqual(2 * 3 + 1, length(Effects)).
-    ?assertEqual(2 * 3 + 1 + 1, length(Effects)).
 
 single_active_consumer_state_enter_eol_include_waiting_consumers_test(_) ->
     Resource = rabbit_misc:r("/", queue, atom_to_binary(?FUNCTION_NAME, utf8)),
@@ -1029,8 +1005,7 @@ single_active_consumer_state_enter_eol_include_waiting_consumers_test(_) ->
 
     Effects = rabbit_fifo_v0:state_enter(eol, State1),
     %% 1 effect for each consumer process (channel process),
-    %% 1 effect for file handle reservation
+    ?assertEqual(3, length(Effects)).
-    ?assertEqual(4, length(Effects)).
 
 query_consumers_test(_) ->
     State0 = init(#{name => ?FUNCTION_NAME,

deps/rabbit/test/unit_file_handle_cache_SUITE.erl

@@ -27,7 +27,6 @@ groups() ->
           file_handle_cache, %% Change FHC limit.
           file_handle_cache_reserve,
           file_handle_cache_reserve_release,
-          file_handle_cache_reserve_above_limit,
           file_handle_cache_reserve_monitor,
           file_handle_cache_reserve_open_file_above_limit
         ]}
@@ -189,27 +188,6 @@ file_handle_cache_reserve_release1(_Config) ->
     ?assertEqual([{files_reserved, 0}], file_handle_cache:info([files_reserved])),
     passed.
 
-file_handle_cache_reserve_above_limit(Config) ->
-    passed = rabbit_ct_broker_helpers:rpc(Config, 0,
-      ?MODULE, file_handle_cache_reserve_above_limit1, [Config]).
-
-file_handle_cache_reserve_above_limit1(_Config) ->
-    Limit = file_handle_cache:get_limit(),
-    ok = file_handle_cache:set_limit(5),
-    %% Reserves are always accepted, even if above the limit
-    %% These are for special processes such as quorum queues
-    ok = file_handle_cache:obtain(5),
-    ?assertEqual([{file_descriptor_limit, []}],  rabbit_alarm:get_alarms()),
-
-    ok = file_handle_cache:set_reservation(7),
-
-    Props = file_handle_cache:info([files_reserved, sockets_used]),
-    ?assertEqual(7, proplists:get_value(files_reserved, Props)),
-    ?assertEqual(5, proplists:get_value(sockets_used, Props)),
-
-    ok = file_handle_cache:set_limit(Limit),
-    passed.
-
 file_handle_cache_reserve_open_file_above_limit(Config) ->
     passed = rabbit_ct_broker_helpers:rpc(Config, 0,
       ?MODULE, file_handle_cache_reserve_open_file_above_limit1, [Config]).

deps/rabbit/test/unit_gen_server2_SUITE.erl

@@ -65,7 +65,7 @@ gen_server2_with_state(Config) ->
       ?MODULE, gen_server2_with_state1, [Config]).
 
 gen_server2_with_state1(_Config) ->
-    fhc_state = gen_server2:with_state(file_handle_cache,
+    state = gen_server2:with_state(background_gc,
                                    fun (S) -> element(1, S) end),
     passed.
 

deps/rabbit_common/src/worker_pool_worker.erl

@@ -17,7 +17,6 @@
 -export([start_link/1, next_job_from/2, submit/3, submit_async/2,
          run/1]).
 
--export([set_maximum_since_use/2]).
 -export([set_timeout/2, set_timeout/3, clear_timeout/1]).
 
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
@@ -32,7 +31,6 @@
 -spec submit(pid(), fun (() -> A) | mfargs(), 'reuse' | 'single') -> A.
 -spec submit_async(pid(), fun (() -> any()) | mfargs()) -> 'ok'.
 -spec run(fun (() -> A)) -> A; (mfargs()) -> any().
--spec set_maximum_since_use(pid(), non_neg_integer()) -> 'ok'.
 
 %%----------------------------------------------------------------------------
 
@@ -53,9 +51,6 @@ submit(Pid, Fun, ProcessModel) ->
 submit_async(Pid, Fun) ->
     gen_server2:cast(Pid, {submit_async, Fun, self()}).
 
-set_maximum_since_use(Pid, Age) ->
-    gen_server2:cast(Pid, {set_maximum_since_use, Age}).
-
 run({M, F, A}) -> apply(M, F, A);
 run(Fun)       -> Fun().
 
@@ -76,15 +71,12 @@ run(Fun, single) ->
 %%----------------------------------------------------------------------------
 
 init([PoolName]) ->
-    ok = file_handle_cache:register_callback(?MODULE, set_maximum_since_use,
-                                             [self()]),
     ok = worker_pool:ready(PoolName, self()),
     put(worker_pool_worker, true),
     put(worker_pool_name, PoolName),
     {ok, undefined, hibernate,
      {backoff, ?HIBERNATE_AFTER_MIN, ?HIBERNATE_AFTER_MIN, ?DESIRED_HIBERNATE}}.
 
-prioritise_cast({set_maximum_since_use, _Age}, _Len, _State) -> 8;
 prioritise_cast({next_job_from, _CPid},        _Len, _State) -> 7;
 prioritise_cast(_Msg,                          _Len, _State) -> 0.
 
@@ -120,10 +112,6 @@ handle_cast({submit_async, Fun, CPid}, {from, CPid, MRef}) ->
     ok = worker_pool:idle(get(worker_pool_name), self()),
     {noreply, undefined, hibernate};
 
-handle_cast({set_maximum_since_use, Age}, State) ->
-    ok = file_handle_cache:set_maximum_since_use(Age),
-    {noreply, State, hibernate};
-
 handle_cast(Msg, State) ->
     {stop, {unexpected_cast, Msg}, State}.
 

deps/rabbitmq_cli/lib/rabbitmq/cli/ctl/commands/status_command.ex

@@ -164,12 +164,6 @@ defmodule RabbitMQ.CLI.Ctl.Commands.StatusCommand do
           "#{category}: #{IU.convert(val[:bytes], unit)} #{unit} (#{val[:percentage]} %)"
         end)
 
-    file_descriptors = [
-      "\n#{bright("File Descriptors")}\n",
-      "Total: #{m[:file_descriptors][:total_used]}, limit: #{m[:file_descriptors][:total_limit]}",
-      "Sockets: #{m[:file_descriptors][:sockets_used]}, limit: #{m[:file_descriptors][:sockets_limit]}"
-    ]
-
     disk_space_section = [
       "\n#{bright("Free Disk Space")}\n",
       "Low free disk space watermark: #{IU.convert(m[:disk_free_limit], unit)} #{unit}",
@@ -200,7 +194,7 @@ defmodule RabbitMQ.CLI.Ctl.Commands.StatusCommand do
         log_section ++
         alarms_section ++
         memory_section ++
-        file_descriptors ++ disk_space_section ++ totals_section ++ listeners_section
+        disk_space_section ++ totals_section ++ listeners_section
 
     {:ok, Enum.join(lines, line_separator())}
   end
@@ -264,7 +258,6 @@ defmodule RabbitMQ.CLI.Ctl.Commands.StatusCommand do
       vm_memory_high_watermark_limit: Keyword.get(result, :vm_memory_limit),
       disk_free_limit: Keyword.get(result, :disk_free_limit),
       disk_free: Keyword.get(result, :disk_free),
-      file_descriptors: Enum.into(Keyword.get(result, :file_descriptors), %{}),
       alarms: Keyword.get(result, :alarms),
       listeners: listener_maps(Keyword.get(result, :listeners, [])),
       memory: Keyword.get(result, :memory) |> Enum.into(%{}),

deps/rabbitmq_web_mqtt/src/rabbit_web_mqtt_handler.erl

@@ -41,8 +41,7 @@
           conserve = false :: boolean(),
           stats_timer :: option(rabbit_event:state()),
           keepalive = rabbit_mqtt_keepalive:init() :: rabbit_mqtt_keepalive:state(),
-          conn_name :: option(binary()),
+          conn_name :: option(binary())
-          should_use_fhc :: rabbit_types:option(boolean())
         }).
 
 -type state() :: #state{}.
@@ -82,15 +81,10 @@ init(Req, Opts) ->
                 true ->
                     WsOpts0 = proplists:get_value(ws_opts, Opts, #{}),
                     WsOpts  = maps:merge(#{compress => true}, WsOpts0),
-                    ShouldUseFHC = application:get_env(?APP, use_file_handle_cache, true),
-                    case ShouldUseFHC of
-                      true  -> ?LOG_INFO("Web MQTT: file handle cache use is enabled");
-                      false -> ?LOG_INFO("Web MQTT: file handle cache use is disabled")
-                    end,
 
                     {?MODULE,
                      cowboy_req:set_resp_header(<<"sec-websocket-protocol">>, <<"mqtt">>, Req),
-                     #state{socket = maps:get(proxy_header, Req, undefined), should_use_fhc = ShouldUseFHC},
+                     #state{socket = maps:get(proxy_header, Req, undefined)},
                      WsOpts}
             end
     end.
@@ -111,15 +105,8 @@ info(Pid, Items) ->
 -spec websocket_init(state()) ->
     {cowboy_websocket:commands(), state()} |
     {cowboy_websocket:commands(), state(), hibernate}.
-websocket_init(State0 = #state{socket = Sock, should_use_fhc = ShouldUseFHC}) ->
+websocket_init(State0 = #state{socket = Sock}) ->
     logger:set_process_metadata(#{domain => ?RMQLOG_DOMAIN_CONN ++ [web_mqtt]}),
-    case ShouldUseFHC of
-      true  ->
-        ok = file_handle_cache:obtain();
-      false -> ok;
-      undefined ->
-        ok = file_handle_cache:obtain()
-    end,
     case rabbit_net:connection_string(Sock, inbound) of
         {ok, ConnStr} ->
             ConnName = rabbit_data_coercion:to_binary(ConnStr),
@@ -271,18 +258,10 @@ terminate(Reason, Request, #state{} = State) ->
 terminate(_Reason, _Request,
           {SendWill, #state{conn_name = ConnName,
                             proc_state = PState,
-                            keepalive = KState,
+                            keepalive = KState} = State}) ->
-                            should_use_fhc = ShouldUseFHC} = State}) ->
     ?LOG_INFO("Web MQTT closing connection ~ts", [ConnName]),
     maybe_emit_stats(State),
     _ = rabbit_mqtt_keepalive:cancel_timer(KState),
-    case ShouldUseFHC of
-      true  ->
-        ok = file_handle_cache:release();
-      false -> ok;
-      undefined ->
-        ok = file_handle_cache:release()
-    end,
     case PState of
         connect_packet_unprocessed ->
             ok;
@@ -296,12 +275,9 @@ terminate(_Reason, _Request,
 no_supported_sub_protocol(Protocol, Req) ->
     %% The client MUST include “mqtt” in the list of WebSocket Sub Protocols it offers [MQTT-6.0.0-3].
     ?LOG_ERROR("Web MQTT: 'mqtt' not included in client offered subprotocols: ~tp", [Protocol]),
-    %% Set should_use_fhc to false, because at this early stage of init no fhc
-    %% obtain was called, so terminate/3 should not call fhc release
-    %% (even if use_file_handle_cache is true)
     {ok,
      cowboy_req:reply(400, #{<<"connection">> => <<"close">>}, Req),
-     #state{should_use_fhc = false}}.
+     #state{}}.
 
 handle_data(Data, State0 = #state{}) ->
     case handle_data1(Data, State0) of

deps/rabbitmq_web_stomp/src/rabbit_web_stomp_handler.erl

@@ -42,8 +42,7 @@
     peername,
     auth_hd,
     stats_timer,
-    connection,
+    connection
-    should_use_fhc :: rabbit_types:option(boolean())
 }).
 
 -define(APP, rabbitmq_web_stomp).
@@ -84,11 +83,6 @@ init(Req0, Opts) ->
     end,
     WsOpts0 = proplists:get_value(ws_opts, Opts, #{}),
     WsOpts  = maps:merge(#{compress => true}, WsOpts0),
-    ShouldUseFHC = application:get_env(?APP, use_file_handle_cache, true),
-    case ShouldUseFHC of
-      true  -> ?LOG_INFO("Web STOMP: file handle cache use is enabled");
-      false -> ?LOG_INFO("Web STOMP: file handle cache use is disabled")
-    end,
     {?MODULE, Req, #state{
         frame_type         = proplists:get_value(type, Opts, text),
         heartbeat_sup      = KeepaliveSup,
@@ -98,18 +92,10 @@ init(Req0, Opts) ->
         conserve_resources = false,
         socket             = SockInfo,
         peername           = PeerAddr,
-        auth_hd            = cowboy_req:header(<<"authorization">>, Req),
+        auth_hd            = cowboy_req:header(<<"authorization">>, Req)
-        should_use_fhc     = ShouldUseFHC
     }, WsOpts}.
 
-websocket_init(State = #state{should_use_fhc = ShouldUseFHC}) ->
+websocket_init(State) ->
-    case ShouldUseFHC of
-      true  ->
-        ok = file_handle_cache:obtain();
-      false -> ok;
-      undefined ->
-        ok = file_handle_cache:obtain()
-    end,
     process_flag(trap_exit, true),
     {ok, ProcessorState} = init_processor_state(State),
     {ok, rabbit_event:init_stats_timer(
@@ -330,15 +316,8 @@ maybe_block(State, _) ->
 stop(State) ->
     stop(State, 1000, "STOMP died").
 
-stop(State = #state{proc_state = ProcState, should_use_fhc = ShouldUseFHC}, CloseCode, Error0) ->
+stop(State = #state{proc_state = ProcState}, CloseCode, Error0) ->
     maybe_emit_stats(State),
-    case ShouldUseFHC of
-      true  ->
-        ok = file_handle_cache:release();
-      false -> ok;
-      undefined ->
-        ok = file_handle_cache:release()
-    end,
     _ = rabbit_stomp_processor:flush_and_die(ProcState),
     Error1 = rabbit_data_coercion:to_binary(Error0),
     {[{close, CloseCode, Error1}], State}.