Introduce a way to disable FHC use in web_mqtt

Via `web_mqtt.enable_file_handle_cache`

(cherry picked from commit 1402183)

# Conflicts:
#	deps/rabbitmq_web_mqtt/src/rabbit_web_mqtt_handler.erl

Author: michaelklishin

deps/rabbit_common/src/rabbit_types.erl

@@ -9,7 +9,11 @@
 
 -include("rabbit.hrl").
 
--export_type([maybe/1, info/0, infos/0, info_key/0, info_keys/0,
+-export_type([
+              %% deprecated
+              maybe/1,
+              option/1,
+              info/0, infos/0, info_key/0, info_keys/0,
               message/0, msg_id/0, basic_message/0,
               delivery/0, content/0, decoded_content/0, undecoded_content/0,
               unencoded_content/0, encoded_content/0, message_properties/0,
@@ -28,6 +32,8 @@
               permission_atom/0, rabbit_amqqueue_name/0, binding_key/0, channel_number/0,
               exchange_name/0, exchange_type/0, guid/0, routing_key/0]).
 
+-type(option(T) :: T | 'none' | 'undefined').
+%% Deprecated, 'maybe' is a keyword in modern Erlang
 -type(maybe(T) :: T | 'none').
 -type(timestamp() :: {non_neg_integer(), non_neg_integer(), non_neg_integer()}).
 
@@ -49,11 +55,11 @@
 -type(decoded_content() ::
         #content{class_id              :: rabbit_framing:amqp_class_id(),
                  properties            :: rabbit_framing:amqp_property_record(),
-                 properties_bin        :: maybe(binary()),
+                 properties_bin        :: option(binary()),
                  payload_fragments_rev :: [binary()]}).
 -type(encoded_content() ::
         #content{class_id       :: rabbit_framing:amqp_class_id(),
-                 properties     :: maybe(rabbit_framing:amqp_property_record()),
+                 properties     :: option(rabbit_framing:amqp_property_record()),
                  properties_bin        :: binary(),
                  payload_fragments_rev :: [binary()]}).
 -type(content() :: undecoded_content() | decoded_content()).

deps/rabbitmq_web_mqtt/priv/schema/rabbitmq_web_mqtt.schema

@@ -181,3 +181,12 @@ end}.
 
 {mapping, "web_mqtt.proxy_protocol", "rabbitmq_web_mqtt.proxy_protocol",
     [{datatype, {enum, [true, false]}}]}.
+
+%%
+%% File Handle Cache
+%%
+
+{mapping, "web_mqtt.enable_file_handle_cache", "rabbitmq_web_mqtt.enable_file_handle_cache",
+    [
+        {datatype, {enum, [true, false]}}
+    ]}.

deps/rabbitmq_web_mqtt/src/rabbit_web_mqtt_handler.erl

@@ -28,7 +28,11 @@
          upgrade/5,
          takeover/7]).
 
+<<<<<<< HEAD
 -type option(T) :: undefined | T.
+=======
+-define(APP, rabbitmq_web_mqtt).
+>>>>>>> 1402183bc2 (Introduce a way to disable FHC use in web_mqtt)
 
 -record(state, {
           socket :: {rabbit_proxy_socket, any(), any()} | rabbit_net:socket(),
@@ -39,7 +43,8 @@
           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{}.
@@ -78,19 +83,31 @@ init(Req, Opts) ->
                 false ->
                     no_supported_sub_protocol(Protocol, Req);
                 true ->
+                    ShouldUseFHC = application:get_env(?APP, enable_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)},
+                     #state{socket = maps:get(proxy_header, Req, undefined), should_use_fhc = ShouldUseFHC},
                      WsOpts}
             end
     end.
 
 -spec websocket_init(state()) ->
     {cowboy_websocket:commands(), state()} |
     {cowboy_websocket:commands(), state(), hibernate}.
-websocket_init(State0 = #state{socket = Sock}) ->
+websocket_init(State0 = #state{socket = Sock, should_use_fhc = ShouldUseFHC}) ->
     logger:set_process_metadata(#{domain => ?RMQLOG_DOMAIN_CONN ++ [web_mqtt]}),
-    ok = file_handle_cache:obtain(),
+    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),

deps/rabbitmq_web_mqtt/test/config_schema_SUITE_data/rabbitmq_web_mqtt.snippets

@@ -48,6 +48,18 @@
      [{max_connections, 5000}]}],
    [rabbitmq_web_mqtt]},
 
+  {enable_file_handle_cache_is_disabled,
+   "web_mqtt.enable_file_handle_cache = false",
+   [{rabbitmq_web_mqtt,
+     [{enable_file_handle_cache, false}]}],
+   [rabbitmq_web_mqtt]},
+
+  {enable_file_handle_cache_is_enabled,
+   "web_mqtt.enable_file_handle_cache = true",
+   [{rabbitmq_web_mqtt,
+     [{enable_file_handle_cache, true}]}],
+   [rabbitmq_web_mqtt]},
+
  {ssl_listener,
   "web_mqtt.ssl.listener = 127.0.0.4:15672",
   [{rabbitmq_web_mqtt,