Merge remote-tracking branch 'origin/master' into stream-timestamp-offsetstream-timestamp-offset

1 files changed, 81 insertions, 0 deletions

diff --git a/deps/rabbit/src/code_server_cache.erl b/deps/rabbit/src/code_server_cache.erl
new file mode 100644
index 0000000000..b53f5dcee9
--- /dev/null
+++ b/deps/rabbit/src/code_server_cache.erl
@@ -0,0 +1,81 @@
+%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
+%% ex: ts=4 sw=4 et
+%% This Source Code Form is subject to the terms of the Mozilla Public
+%% License, v. 2.0. If a copy of the MPL was not distributed with this
+%% file, You can obtain one at https://mozilla.org/MPL/2.0/.
+%%
+%% Copyright (c) 2007-2020 VMware, Inc. or its affiliates.  All rights reserved.
+%%
+
+-module(code_server_cache).
+
+-behaviour(gen_server).
+
+%% API
+-export([start_link/0,
+         maybe_call_mfa/4]).
+
+%% gen_server callbacks
+-export([init/1,
+         handle_call/3,
+         handle_cast/2,
+         handle_info/2,
+         terminate/2,
+         code_change/3]).
+
+-record(state, {
+    modules = #{} :: #{atom() => boolean()}
+}).
+
+%% API
+start_link() ->
+    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
+maybe_call_mfa(Module, Function, Args, Default) ->
+    gen_server:call(?MODULE, {maybe_call_mfa, {Module, Function, Args, Default}}).
+
+%% gen_server callbacks
+
+init([]) ->
+    {ok, #state{}}.
+
+handle_call({maybe_call_mfa, {Mod, _F, _A, _D} = MFA}, _From, #state{modules = ModuleMap} = State0) ->
+    Value = maps:get(Mod, ModuleMap, true),
+    {ok, Reply, State1} = handle_maybe_call_mfa(Value, MFA, State0),
+    {reply, Reply, State1};
+handle_call(_Request, _From, State) ->
+    {reply, ignored, State}.
+
+handle_cast(_Msg, State) ->
+    {noreply, State}.
+
+handle_info(_Info, State) ->
+    {noreply, State}.
+
+terminate(_Reason, _State) ->
+    ok.
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
+
+%% Internal functions
+
+handle_maybe_call_mfa(false, {_M, _F, _A, Default}, State) ->
+    {ok, Default, State};
+handle_maybe_call_mfa(true, {Module, Function, Args, Default}, State) ->
+    try
+        Reply = erlang:apply(Module, Function, Args),
+        {ok, Reply, State}
+    catch
+        error:undef ->
+            handle_maybe_call_mfa_error(Module, Default, State);
+        Err:Reason ->
+            rabbit_log:error("Calling ~p:~p failed: ~p:~p~n",
+                             [Module, Function, Err, Reason]),
+            handle_maybe_call_mfa_error(Module, Default, State)
+    end.
+
+handle_maybe_call_mfa_error(Module, Default, #state{modules = ModuleMap0} = State0) ->
+    ModuleMap1 = maps:put(Module, false, ModuleMap0),
+    State1 = State0#state{modules = ModuleMap1},
+    {ok, Default, State1}.