Zero sockets_used/sockets_limit stats

They are no longer used.

This removes a couple file_handle_cache:info/1 calls.

We are not removing them from the HTTP API to avoid
breaking things unintentionally.

Author: lhoguin

deps/rabbit/test/unit_file_handle_cache_SUITE.erl

@@ -25,7 +25,6 @@ groups() ->
     [
       {non_parallel_tests, [], [
           file_handle_cache, %% Change FHC limit.
-          file_handle_cache_reserve,
           file_handle_cache_reserve_release,
           file_handle_cache_reserve_monitor,
           file_handle_cache_reserve_open_file_above_limit
@@ -134,47 +133,6 @@ file_handle_cache1(_Config) ->
     ok = file_handle_cache:set_limit(Limit),
     passed.
 
-file_handle_cache_reserve(Config) ->
-    passed = rabbit_ct_broker_helpers:rpc(Config, 0,
-      ?MODULE, file_handle_cache_reserve1, [Config]).
-
-file_handle_cache_reserve1(_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:set_reservation(7),
-
-    Self = self(),
-    spawn(fun () -> ok = file_handle_cache:obtain(),
-                    Self ! obtained
-          end),
-
-    Props = file_handle_cache:info([files_reserved, sockets_used]),
-    ?assertEqual(7, proplists:get_value(files_reserved, Props)),
-    ?assertEqual(0, proplists:get_value(sockets_used, Props)),
-
-    %% The obtain should still be blocked, as there are no file handles
-    %% available
-    receive
-        obtained ->
-            throw(error_file_obtained)
-    after 1000 ->
-            %% Let's release 5 file handles, that should leave
-            %% enough free for the `obtain` to go through
-            file_handle_cache:set_reservation(2),
-            Props0 = file_handle_cache:info([files_reserved, sockets_used]),
-            ?assertEqual(2, proplists:get_value(files_reserved, Props0)),
-            ?assertEqual(1, proplists:get_value(sockets_used, Props0)),
-            receive
-                obtained ->
-                    ok = file_handle_cache:set_limit(Limit),
-                    passed
-            after 5000 ->
-                    throw(error_file_not_released)
-            end
-    end.
-
 file_handle_cache_reserve_release(Config) ->
     passed = rabbit_ct_broker_helpers:rpc(Config, 0,
       ?MODULE, file_handle_cache_reserve_release1, [Config]).

deps/rabbit_common/src/file_handle_cache.erl

@@ -1087,9 +1087,8 @@ infos(Items, State) -> [{Item, i(Item, State)} || Item <- Items].
 
 i(total_limit,   #fhc_state{limit               = Limit}) -> Limit;
 i(total_used,    State)                                   -> used(State);
-i(sockets_limit, #fhc_state{obtain_limit        = Limit}) -> Limit;
-i(sockets_used,  #fhc_state{obtain_count_socket = Count,
-                            reserve_count_socket = RCount}) -> Count + RCount;
+i(sockets_limit, _) -> 0;
+i(sockets_used,  _) -> 0;
 i(files_reserved,  #fhc_state{reserve_count_file   = RCount}) -> RCount;
 i(Item, _) -> throw({bad_argument, Item}).
 

deps/rabbitmq_management_agent/src/rabbit_mgmt_external_stats.erl

@@ -195,10 +195,11 @@ i(fd_used, State) ->
     get_used_fd(State);
 i(fd_total, #state{fd_total = FdTotal}=State) ->
     {State, FdTotal};
+%% sockets_used and sockets_total are unused since RabbitMQ 4.0.
 i(sockets_used, State) ->
-    {State, proplists:get_value(sockets_used, file_handle_cache:info([sockets_used]))};
+    {State, 0};
 i(sockets_total, State) ->
-    {State, proplists:get_value(sockets_limit, file_handle_cache:info([sockets_limit]))};
+    {State, 0};
 i(os_pid, State) ->
     {State, rabbit_data_coercion:to_utf8_binary(os:getpid())};
 i(mem_used, State) ->