Remove file_handle_cache

The module is no longer used now that CQv1 has been removed.
The only useful function remaining is `ulimit/1` which is
used both in metrics and to provide a warning if too low
on startup. It was moved to rabbit_runtime. The startup
warning logic was moved out into rabbitmq_prelaunch.

We still have some FHC related metrics that are set to 0
and are kept for compatibility reasons.

Also remove unused rabbit env queue_index_max_journal_entries.

Author: lhoguin

deps/rabbit/Makefile

@@ -28,9 +28,6 @@ define PROJECT_ENV
 	    {heartbeat, 60},
 	    {msg_store_file_size_limit, 16777216},
 	    {msg_store_shutdown_timeout, 600000},
-	    {fhc_write_buffering, true},
-	    {fhc_read_buffering, false},
-	    {queue_index_max_journal_entries, 32768},
 	    {queue_index_embed_msgs_below, 4096},
 	    {default_user, <<"guest">>},
 	    {default_pass, <<"guest">>},
@@ -269,7 +266,7 @@ PARALLEL_CT_SET_1_D = amqqueue_backward_compatibility channel_interceptor channe
 
 PARALLEL_CT_SET_2_A = cluster confirms_rejects consumer_timeout rabbit_access_control rabbit_confirms rabbit_core_metrics_gc rabbit_cuttlefish rabbit_db_binding rabbit_db_exchange
 PARALLEL_CT_SET_2_B = crashing_queues deprecated_features direct_exchange_routing_v2 disconnect_detected_during_alarm exchanges unit_gen_server2
-PARALLEL_CT_SET_2_C = disk_monitor dynamic_qq unit_disk_monitor unit_file_handle_cache unit_log_management unit_operator_policy prevent_startup_if_node_was_reset
+PARALLEL_CT_SET_2_C = disk_monitor dynamic_qq unit_disk_monitor unit_log_management unit_operator_policy prevent_startup_if_node_was_reset
 PARALLEL_CT_SET_2_D = queue_length_limits queue_parallel quorum_queue_member_reconciliation rabbit_fifo rabbit_fifo_dlx rabbit_stream_coordinator
 
 PARALLEL_CT_SET_3_A = definition_import per_user_connection_channel_limit_partitions per_vhost_connection_limit_partitions policy priority_queue_recovery rabbit_fifo_v0 rabbit_stream_sac_coordinator_v4 rabbit_stream_sac_coordinator unit_credit_flow unit_queue_consumers unit_queue_location unit_quorum_queue

deps/rabbit/src/file_handle_cache.erl

@@ -17,8 +17,7 @@
          stop_and_halt/0, await_startup/0, await_startup/1, await_startup/3,
          status/0, is_running/0, is_serving/0, alarms/0,
          is_running/1, is_serving/1, environment/0, rotate_logs/0,
-         force_event_refresh/1,
-         start_fhc/0]).
+         force_event_refresh/1]).
 
 -export([start/2, stop/1, prep_stop/1]).
 -export([start_apps/1, start_apps/2, stop_apps/1]).
@@ -82,7 +81,7 @@
 
 -rabbit_boot_step({database,
                    [{mfa,         {rabbit_db, init, []}},
-                    {requires,    file_handle_cache},
+                    {requires,    code_server_cache},
                     {enables,     external_infrastructure}]}).
 
 -rabbit_boot_step({networking_metadata_store,
@@ -101,13 +100,6 @@
                    [{description, "code_server cache server"},
                     {mfa,         {rabbit_sup, start_child, [code_server_cache]}},
                     {requires,    rabbit_alarm},
-                    {enables,     file_handle_cache}]}).
-
--rabbit_boot_step({file_handle_cache,
-                   [{description, "file handle cache server"},
-                    {mfa,         {rabbit, start_fhc, []}},
-                    %% FHC needs memory monitor to be running
-                    {requires,    code_server_cache},
                     {enables,     worker_pool}]}).
 
 -rabbit_boot_step({worker_pool,
@@ -765,9 +757,6 @@ 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)},
@@ -802,7 +791,7 @@ 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([]),
@@ -1642,63 +1631,6 @@ home_dir() ->
 config_files() ->
     rabbit_config:config_files().
 
-%% We don't want this in fhc since it references rabbit stuff. And we can't put
-%% this in the bootstep directly.
-start_fhc() ->
-    ok = rabbit_sup:start_restartable_child(
-      file_handle_cache,
-      [fun(_) -> ok end, fun(_) -> ok end]),
-    ensure_working_fhc(),
-    maybe_warn_low_fd_limit().
-
-ensure_working_fhc() ->
-    %% To test the file handle cache, we simply read a file we know it
-    %% exists (Erlang kernel's .app file).
-    %%
-    %% To avoid any pollution of the application process' dictionary by
-    %% file_handle_cache, we spawn a separate process.
-    Parent = self(),
-    TestFun = fun() ->
-        ReadBuf = case application:get_env(rabbit, fhc_read_buffering) of
-            {ok, true}  -> "ON";
-            {ok, false} -> "OFF"
-        end,
-        WriteBuf = case application:get_env(rabbit, fhc_write_buffering) of
-            {ok, true}  -> "ON";
-            {ok, false} -> "OFF"
-        end,
-        ?LOG_INFO("FHC read buffering: ~ts", [ReadBuf],
-                  #{domain => ?RMQLOG_DOMAIN_GLOBAL}),
-        ?LOG_INFO("FHC write buffering: ~ts", [WriteBuf],
-                  #{domain => ?RMQLOG_DOMAIN_GLOBAL}),
-        Filename = filename:join(code:lib_dir(kernel), "ebin/kernel.app"),
-        {ok, Fd} = file_handle_cache:open(Filename, [raw, binary, read], []),
-        {ok, _} = file_handle_cache:read(Fd, 1),
-        ok = file_handle_cache:close(Fd),
-        Parent ! fhc_ok
-    end,
-    TestPid = spawn_link(TestFun),
-    %% Because we are waiting for the test fun, abuse the
-    %% 'mnesia_table_loading_retry_timeout' parameter to find a sane timeout
-    %% value.
-    Timeout = rabbit_table:retry_timeout(),
-    receive
-        fhc_ok                       -> ok;
-        {'EXIT', TestPid, Exception} -> throw({ensure_working_fhc, Exception})
-    after Timeout ->
-            throw({ensure_working_fhc, {timeout, TestPid}})
-    end.
-
-maybe_warn_low_fd_limit() ->
-    case file_handle_cache:ulimit() of
-        %% unknown is included as atom() > integer().
-        L when L > 1024 ->
-            ok;
-        L ->
-            ?LOG_WARNING("Available file handles: ~tp. "
-                "Please consider increasing system limits", [L])
-    end.
-
 %% Any configuration that
 %% 1. is not allowed to change while RabbitMQ is running, and
 %% 2. is read often

deps/rabbit/src/rabbit.erl

@@ -769,20 +769,13 @@ gen_result([{msg, MsgId, Msg}|Tail], Offset, Acc) ->
 %% -------------------------------------------------------------------
 
 setup_backing_queue_test_group(Config) ->
-    {ok, MaxJournal} =
-        application:get_env(rabbit, queue_index_max_journal_entries),
-    application:set_env(rabbit, queue_index_max_journal_entries, 128),
     {ok, Bytes} =
         application:get_env(rabbit, queue_index_embed_msgs_below),
     rabbit_ct_helpers:set_config(Config, [
-        {rmq_queue_index_max_journal_entries, MaxJournal},
         {rmq_queue_index_embed_msgs_below, Bytes}
       ]).
 
 teardown_backing_queue_test_group(Config) ->
-    %% FIXME: Undo all the setup function did.
-    application:set_env(rabbit, queue_index_max_journal_entries,
-                        ?config(rmq_queue_index_max_journal_entries, Config)),
     %% We will have restarted the message store, and thus changed
     %% the order of the children of rabbit_sup. This will cause
     %% problems if there are subsequent failures - see bug 24262.